# AutoCalcs Documentation > AutoCalcs is a browser-based structural analysis tool with integrated steel design checks for beams, frames, plates, and trusses. Build 3D finite element models with members and quadrilateral or triangular plate elements, apply loads and supports, and analyse structures for internal forces, reactions, and deflections — no installation or signup required. --- ## Free Section Properties Library Source: https://autocalcs.com/section-library Use the free AutoCalcs Section Library to look up catalogue section properties for steel, timber, aluminium and cold-formed structural sections. Search by designation or browse by country/design standard, material and shape family. No sign-in is required for lookup. The page shows cross-section diagrams with local axes, dimensions, cross-sectional area, moments of inertia (second moments of area), section moduli and torsion constants where supplied by the selected record. Metric and imperial catalogue display conventions are supported. Available strength and source information depend on the record. This is a catalogue lookup; use the Custom Section Builder or Section Properties Calculator to calculate properties for custom geometry. "Analyse Section in 3D FEA Free" opens the selected record as Section 1 on a 6 m beam along global X, with both endpoints fixed in all six degrees of freedom. The app asks before replacing current work. Material selection and assignment, and loads, are required before analysis; no demonstration loads or automatic analysis are added. Catalogue section strength data is not a complete material definition or a member design-code check. Normal Structural FEA free-tier limits apply when running analysis. --- ## Documentation: Structural FEA --- ### Getting Started Source: https://autocalcs.com/documentation/structuralfea/getting-started This guide will walk you through creating your first structural model in AutoCalcs. #### Creating a New Project 1. Navigate to https://autocalcs.com/structuralfea 2. You'll start with a blank canvas #### Basic Workflow A typical workflow in AutoCalcs follows these steps: 1. **Create Geometry** — Draw nodes and connect them with members 2. **Define Supports** — Add boundary conditions to nodes 3. **Assign Properties** — Set materials and cross-sections for members 4. **Apply Loads** — Add forces, moments, and distributed loads 5. **Run Analysis** — Execute the structural analysis 6. **View Results** — Examine displacements, reactions, and internal forces #### Your First Model **Step 1: Draw a Simple Beam** 1. Press `Ctrl+D` or click the Draw tool to enter Draw mode 2. Click at the origin (0, 0, 0) to place the first node 3. Click at (5, 0, 0) to place the second node and create a member - After placing your first point, move your mouse in the positive X direction — it should snap to this vector. - Type in the distance "5" and hit Enter. 4. Press `Escape` to finish drawing **Step 2: Add Supports** 1. Press `Escape` or `Ctrl+S` or click the Select tool to enter Select mode 2. Click on the first node (at origin), or hold `Shift` and drag to box select - The Properties panel should automatically appear — ensure only the node is selected. 3. In the Properties panel, set the support to "Fixed" by clicking the Fixed support icon - This will automatically set the Degrees of Freedom to `FFFFFF`. 4. Click on the second node and set it to "Pinned" by clicking the Pinned support icon - This will set the Degrees of Freedom to `FFFRRR` (translations fixed, rotations free). **Step 3: Assign Section and Material** 1. Select the member by clicking on it 2. In the Properties panel, assign a section by clicking on the book icon in the Section row - Section Library/Australia/STEEL/UB Universal Beams/UB 200x18.2 3. Assign a material by clicking on the book icon in the Material row - Material Library/Australia/Steel/STEEL **Step 4: Apply a Load** 1. With the member selected, right-click on the member to open the context menu 2. Select "Member Distributed Loads" 3. This opens the Loads dialog, adding a distributed load for member 1. However we get a warning as we haven't defined any load cases 4. Select "Manage Load Cases" 5. For this example, make a load case with ID "1" and Title "Dead Load" then press "Apply and Close" 6. Back in the Loads dialog, set the load magnitude in the "Start Y (kN/m)" to "-2" kN/m (negative for downward) **Step 5: Run Analysis** 1. Click the "Render Style" button and select the Rendered option to confirm beam orientation 2. Click the "Run Analysis" button in the top ribbon — by default this is a Linear analysis 3. Wait for the analysis to complete - Note: Anonymous users are limited to 2 analysis runs per day. Sign up for free for 5 runs per day. **Step 6: View Results** Use the result toggles in the left sidebar to visualize analysis results: - **Deflection** — Shows the deformed shape (hold `D`+scroll to scale) - **Reactions** — Shows support reactions (hold `R`+scroll to scale) - **Moments** — Bending moment diagram (hold `M`+scroll to scale) - **Shear** — Shear force diagram (hold `S`+scroll to scale) - **Axial** — Axial force diagram (hold `A`+scroll to scale) - **Torsion** — Torsion diagram (hold `T`+scroll to scale) Use these buttons to control what's shown on the canvas: - **Loads** — Toggle load arrows on/off (hold `L` to scale distributed or `C` for concentrated loads) - **Labels** — Toggle labels on/off (right-click for label options) - Label options include: Show node ID, Show member ID, Show section ID, Show section names, Show load values, Show result values, Other annotations, and Font size slider (8px-20px) --- ### Interface Overview Source: https://autocalcs.com/documentation/structuralfea/interface-overview A comprehensive guide to the AutoCalcs structural analysis interface, detailing every tool, button, and control. #### Top Toolbar (Ribbon) The ribbon provides access to file operations, geometry dialogs, analysis controls, and global settings. **File & Edit Operations** - **File Manager** `Ctrl+O` — Open and manage saved projects. - **Save Project** `Ctrl+S` — Save the current project state. - **Undo / Redo** — Revert or re-apply changes. `Ctrl+Z` / `Ctrl+Y` - **Reports** — Configure PDF or Excel analysis reports; downloading either format requires Pro. - **Focus View** `Ctrl+F` — Center the camera on the model geometry. **Geometry & Data** - **Self Weight** — Open self-weight dialog to configure gravity loads. - **Load Selector** — Switch active load case/combination. Use `PgUp`/`PgDn`. - **Data Dialogs** — Open tables for Nodes and Members. - **Properties & Loads** — Manage section properties, materials, and applied loads. **Analysis & Settings** - **Health Check** — Run automated model validation to catch stability and connectivity issues. - **Run Analysis** — Execute Linear, P-Delta (2nd order), Buckling, or Modal analysis. - **Snapping** — Toggle Node, Midpoint, Axis, and Angle snapping. - **Settings** — Configure units, hotkeys, and application preferences. - **Documentation** — Open this help guide. - **Feedback** — Send comments, bug reports, or feature requests to the developers. #### Left Sidebar The left sidebar contains the primary modeling tools and display controls. **Modeling Tools** - **Select Mode** `Esc` — Select nodes and members. - **Draw Members** `Ctrl+D` — Click to place nodes and members. - **Copy / Array** `Ctrl+C` — Copy selected nodes or members with a drawn vector offset. - **Extrude** `Ctrl+E` — Copies selected nodes or members with a linking member. - **Mirror** `Ctrl+M` — Mirror selected geometry across a plane. - **Move** `W` — Move selected nodes with a drawn vector offset. - **Split Member** `B` — Split selected members at midpoint. - **Intersect Members** `X` — Create nodes where selected members cross. **Display Controls** - **Render Mode** — Toggle between Wireframe, Outlined, and Rendered views. - Toggle visibility of supports, member fixities, labels, and loads. - Tip: Right-click Labels or Loads for detailed options (e.g., Node IDs, Load Values). - Toggle visibility of global axes, origin point, nodes, and members. **Result Views** - **Displacement**, **Moment**, **Shear**, **Torsion**, **Axial**, **Reactions** - Visualize analysis results. Hold the corresponding hotkey + Scroll to scale the diagrams: - `D` + Scroll (Disp) - `M` + Scroll (Moment) - `S` + Scroll (Shear) - `T` + Scroll (Torsion) - `A` + Scroll (Axial) - `R` + Scroll (React) #### Right Sidebar (Properties) The properties panel is context-sensitive, showing details for the currently selected nodes or members. **Member Properties** - **Member Type:** Normal, Tension/Compression Only. - **Section:** Assign cross-sections from the library. - **Material:** Assign materials from the library. - **Fixity:** Define fixity to each node for all DOF (Fixed/Pinned). - **Sideways:** Turn the section 90 deg. **Node Properties** - **Position:** X, Y, Z coordinates. - **Restraint:** Define supports (Fixed, Pinned, Roller, etc.). #### Bottom Status Bar Displays active command prompts (e.g., drawing instructions). --- ### Drawing Source: https://autocalcs.com/documentation/structuralfea/drawing Learn how to draw your structural members. #### Entering Draw Mode & Creating Nodes Press `Ctrl+D` or click the Draw tool in the toolbar to enter Draw mode. 1. Click anywhere on the canvas to place a node 2. Click again to place another node — a member is automatically created between them 3. Continue clicking to create connected members 4. Press `Escape` to finish the current chain 5. Click on an existing node to start a new chain from that point #### Snapping Precision is key in structural modeling. AutoCalcs uses a tiered snapping system to ensure your nodes and members are placed exactly where you intend. **Snapping Priority** 1. **Nodes:** Highest priority. Snaps to existing node points. 2. **Members:** Snaps to midpoints and perpendicular points of members. 3. **Alignment:** Snaps to X, Y, or Z axes relative to existing nodes. 4. **Construction Grid:** Snaps to major grid lines and elevations. 5. **Fine Grid:** Fallback 10mm precision snap for all other cases. Key snapping features include: - **Node Snap** — Snap to existing nodes - **Midpoint Snap** — Snap to member midpoints - **Axis Snap** — Snap to X, Y, or Z axes from the last point - **Angle Snap** — Snap to 30 or 45 degree increments - Note: This only works when drawing in a 2D plane. Toggle snapping options using the Snapping button in the top ribbon. #### Modeling Aids To help with large scale layouts, you can enable visual reference systems in Settings > Visual: **Construction Grids** — A horizontal reference system (XY plane). You can set independent X and Z spacings (e.g., 5.0m) to match your primary column lines. **Elevations** — Horizontal planes at specific vertical heights (Y-axis), helpful for multi-story floor levels or roof heights. #### Coordinate Input For precise placement, you can type coordinates directly into the input fields at the top right of the screen while drawing: - **Absolute Coordinates (X, Y, Z):** After entering Draw mode, type the X, Y, and Z coordinates separated by pressing `Tab` (e.g., `5` `Tab` `0` `Tab` `3`) to place the starting node at that exact global position. You can navigate between these input fields using the arrow keys. - **Distance:** Once the first node is placed, a distance input field appears in the top right. Move your mouse to define the direction, then type the desired length and press `Enter` to draw the member. - **Distance & Angle:** When drawing in a 2D plane (such as Top or Front view), an additional angle input field appears. You can specify both the length and the angle (e.g., length `5` and angle `45`) to draw the member precisely. #### Drawing Tips - Use standard views (1-9 keys) for drawing in specific planes (e.g., Top, Front). - Zoom in for more precise node placement when not using coordinates. - Use the coordinate input for exact dimensions to ensure accuracy. --- ### Editing Source: https://autocalcs.com/documentation/structuralfea/editing Modify your structural model with these editing operations. #### Undo/Redo - `Ctrl+Z` — Undo the last action - `Ctrl+Y` — Redo the last undone action The undo history is preserved until you close or reload the page. You can also use the Undo and Redo buttons located in the top left corner of the screen. #### Delete Select items and press `Delete` to remove them: - Deleting a node also deletes all connected members - Deleting a member leaves the nodes intact Alternatively, right-click on the selected items and choose **Delete** from the context menu. #### Move 1. Select the items you want to move 2. Press `W` to enter Move mode 3. Click to set the base point 4. Click again to set the destination, or enter coordinates You can also activate the Move tool by clicking the **Move** button in the left toolbar. #### Intersect Members If two or more members intersect, we can select them and create nodes where they cross: - First, select the members that are intersecting - Press `X` - You can also right-click and select **Intersect** from the context menu. Any loads applied to the affected members will be removed. Section, material, and design properties are inherited by the new segments. #### Split Member Split a member at its centre point, creating a new node: 1. Select the member(s) to split 2. Press `B` 3. You can also right-click and select **Split at Midpoint** from the context menu. Any loads applied to the affected members will be removed. Section, material, and design properties are inherited by the new segments. #### Divide into Segments Divide a member into equal-length segments: 1. Select a member 2. Right-click and select **Divide into Segments** from the context menu 3. Enter the number of segments Any loads applied to the divided members will be removed. Section, material, and design properties are inherited by the new segments. #### Edit Properties Select items and use the Properties panel to modify: - **Nodes**: Edit support conditions - **Members**: Edit section, material, node fixities --- ### Selection Source: https://autocalcs.com/documentation/structuralfea/selection Selecting objects is fundamental to editing your model. #### Entering Select Mode & Single Selection Press `Esc` or click the Select tool in the toolbar. Click on any node or member to select it. The previous selection is cleared. #### Box Selection Since mouse dragging is reserved for 3D navigation (panning and orbiting), you must hold a modifier key to initiate a selection box: - **Hold Shift + Drag**: Initiates a selection box. - **Hold Ctrl + Drag**: Initiates a selection box. The direction of the box determines the selection mode: - **Left-to-Right (Window)**: Selects only objects fully contained within the box. - **Right-to-Left (Crossing)**: Selects all objects that are either inside or touched by the box. #### Selection Shortcuts - `Ctrl+A` — Select all nodes and members - `Ctrl+I` — Invert selection - `Ctrl+R` — Restore previous selection - `Escape` — Return to Select tool / Cancel active operation #### Selection Filtering The Properties panel shows different options based on what's selected: - **Single node**: Position, supports - **Single member**: Section, material, node fixity --- ### Copy, Extrude & Mirror Source: https://autocalcs.com/documentation/structuralfea/copy-extrude-mirror Efficiently create repetitive geometry with these duplication tools. #### Copy Create copies of selected geometry at a specified offset. **Quick Copy Mode** 1. Select the geometry to copy 2. Press `Ctrl+C` to enter Copy mode 3. Draw a line to define the copy direction and distance **Copy Dialog** Press `Shift+C` for more options: - **Offset Direction**: Specify X, Y, Z distances - **Number of Copies**: Specify the number of arrayed copies #### Extrude Model geometry fast by extruding selected nodes or members. **Quick Extrude Mode** 1. Select nodes or members 2. Press `Ctrl+E` to enter Extrude mode 3. Draw a line to define the extrusion direction and distance **Extrude Dialog** Press `Shift+E` for more options: - **Extrude Direction**: Specify X, Y, Z distances - **Number of segments**: Array extrusion into multiple segments **Extrude behavior:** - Extruding nodes creates new nodes and connecting members - Extruding members creates a frame (new members and connecting members) #### Mirror Create mirrored copies of geometry about a plane. **Mirror Mode** 1. Select the geometry to mirror 2. Press `Ctrl+M` to enter Mirror mode 3. Choose a mirror plane by pressing `X`, `Y`, or `Z` (YZ, ZX, or XY) 4. Click a point on the canvas to define the mirror location 5. Confirm to delete the original geometry or keep it --- ### Nodes Source: https://autocalcs.com/documentation/structuralfea/nodes Nodes are the fundamental building blocks of any structural model. Think of them as the "joints" or "points" that define where structural members connect and where the structure interacts with the world. #### What are Nodes? In structural analysis, a node is simply a point in 3D space defined by X, Y, and Z coordinates. While members (beams, columns, braces) carry loads between points, nodes are those points themselves. Nodes serve several critical purposes: - **Connection points** — Where two or more members meet and transfer forces between each other - **Support locations** — Where the structure connects to the ground or other fixed points (foundations, walls, etc.) - **Load application points** — Where point loads and moments are applied to the structure - **Result locations** — Where displacements, reactions, and other results are calculated Every member in your model connects two nodes — a start node and an end node. Without nodes, members would have nowhere to begin or end. #### Creating Nodes Nodes are created automatically when you: - Click in Draw mode - Import geometry - Split members - Intersect members - Use Copy, Extrude, or Mirror tools #### Node Properties Select a node to view/edit its properties: **Position** - **X, Y, Z**: Coordinates in the global system **Support Conditions** Each node has 6 degrees of freedom (DOFs): - **DX, DY, DZ**: Translations in X, Y, Z - **RX, RY, RZ**: Rotations about X, Y, Z Common support types: - **Free**: No restraints (all DOFs free) - **Pinned**: Translations restrained, rotations free - **Fixed**: All DOFs restrained - **Roller**: One translation restrained #### Quick Support Assignment The Properties panel provides preset support icons for quick assignment: - **Fixed** (FFFFFF) — All 6 DOFs restrained - **Pinned** (FFFRRR) — Translations fixed, all rotations free - **Roller** variants — One translation free, others fixed Click on any icon to apply that support condition to selected nodes. You can also toggle individual DOFs using the 6-character code (F = Fixed, R = Released, S = Spring). #### Spring Supports Set any DOF to **S** and enter a stiffness value to model an elastic support — soil springs, flexible foundations, or soil-structure interaction — instead of a perfectly rigid restraint. #### Support Settlement (Prescribed Displacement) A support settlement moves a restrained node by a known amount instead of holding it exactly where it was drawn — used for differential foundation settlement or other imposed support movement. Enter a signed value for any restrained (**F**) DOF; it is enforced under every load combination and is supported in linear static, P-Delta, and buckling analyses. #### Nodes Table Click the **Nodes** button in the ribbon to open the Nodes table. This provides a spreadsheet view of all nodes in your model where you can: - Set support conditions in bulk - Export node data #### Node Labels Toggle node labels in the Display panel (left sidebar). Right-click the Labels button to choose what to display: node IDs, member IDs, section IDs, section names, load values, result values, or other annotations. --- ### Members Source: https://autocalcs.com/documentation/structuralfea/members Members are the structural elements that connect nodes. They represent beams, columns, braces, and any linear structural element in your model. #### What are Members? Each member is defined by: - **Start and end nodes** — The two points the member connects - **Section** — The cross-sectional shape and properties - **Material** — The material properties (steel, timber, etc.) - **End releases** — How the member connects to its nodes (rigid or pinned) - **End eccentricities** (optional) — Rigid offsets between each joint node and the member's true structural endpoint, producing a textbook M = N x e moment from axial force (local or global reference axes) #### Creating Members Members are created automatically in Draw mode: 1. Press `D` or click the Draw tool to enter Draw mode 2. Click to place the start node 3. Click again to place the end node — a member is created between them 4. Continue clicking to create connected members 5. Press `Escape` to finish the chain Click on an existing node to start a new chain from that point. #### Member Properties Select a member to view and edit its properties in the Properties panel: **Section** — The cross-sectional shape determines structural behaviour. Select from the dropdown or click the book icon to open the Section Library. **Material** — The material defines stiffness (Young's Modulus) and density for self-weight. Select from the dropdown or click the book icon to open the Material Library. **End Releases (Member Fixity)** — Control how the member connects at each end. The Properties panel shows i-end and j-end fixity controls with preset options: - **Fixed** (FFFFFF) — Fully rigid connection (default) - **Pinned** — Rotations released at that end The 6-character code represents: Dx, Dy, Dz, Rx, Ry, Rz (F = Fixed, R = Released). #### Member Orientation Each member has a local coordinate system: - **Local x-axis** — Along the member length (from i-node to j-node) - **Local y-axis** — Minor bending axis (typically vertical for horizontal members, but represents the direction of vertical load) - **Local z-axis** — Major bending axis (typically horizontal, axis of rotation for primary bending) Results like bending moments and shear forces are reported in the local coordinate system. #### Tension/Compression Only Members can be set to carry only tension or only compression. This is useful for modelling cables (tension-only) or struts that buckle (compression-only). Set this property in the Properties panel when a member is selected. --- ### Rigid Diaphragms Source: https://autocalcs.com/documentation/structuralfea/rigid-diaphragms A rigid diaphragm constrains selected nodes to move as one rigid body in the diaphragm plane. Use it for frame models where a floor deck or wall panel is assumed rigid in-plane but is not modelled with shell elements — for example, distributing seismic lateral forces to vertical elements by stiffness. **Creating a diaphragm** — Select structural nodes, right-click **Add Rigid Diaphragm**, or use **Constraints** in the Properties panel. Choose the diaphragm normal axis, DOF mode (in-plane 3 DOF for floors/walls, or full 6 DOF for inclined surfaces), slave nodes, and master method. **Master node** — A phantom master at the centroid (recommended) or an existing structural node. The master carries the in-plane translations and twist; out-of-plane DOFs remain free for standard horizontal floors. **Seismic integration** — The seismic load wizard can apply per-floor lateral forces through rigid diaphragms at each floor mass centre. Do not add a rigid diaphragm on top of a floor already modelled with plate elements — the slab membrane already provides in-plane stiffness. --- ### Sections Source: https://autocalcs.com/documentation/structuralfea/sections Sections define the cross-sectional geometry of structural members. The section properties determine how a member resists bending, shear, and torsion. #### Opening the Section Library Click the **Sections** button in the ribbon, or click the book icon next to the Section field in the Properties panel when a member is selected. #### Section Library The built-in library includes sections organised by region: - **Australia** — Steel, cold-formed steel, aluminium, and timber - **Canada** — Steel and timber - **Europe** — Steel and timber - **United Kingdom** — Steel and timber - **United States** — Steel and timber #### Section Properties Each section requires these geometric properties for analysis: - **Area (A)** — Cross-sectional area, affects axial stiffness - **Moment of Inertia (Iyy, Izz)** — Resistance to bending about each axis - **Torsional Constant (J)** — Resistance to twisting #### Adding Sections Two ways to add sections: - **From Library** — Browse sections organised by region and select to add to your model - **Custom** — Click **Create Custom** in the library to define a parametric section with your own dimensions (sign-in required) #### Custom Sections Define custom sections by specifying dimensions. Available shapes: - **I-Shape** — Universal beam profile - **Channel** — C-section profile - **Tee** — T-section profile - **Angle** — L-section profile - **Solid Rectangle** — Rectangular bar - **Solid Circle** — Round bar - **Circular Hollow** — Pipe / CHS - **Rectangular Hollow** — RHS / SHS Section properties are calculated automatically from your dimensions. #### Assigning Sections 1. Select one or more members 2. In the Properties panel, click the Section dropdown 3. Select the desired section All selected members will be updated to use the chosen section. #### Section Colours Each section has an assigned colour for visualisation. Click the colour swatch in the Section Library to change it using the colour picker or preset palette. Members are displayed in their section's colour unless selected. #### 3D Rendering Switch to "Rendered" view mode (in the Display panel) to see members displayed with their actual cross-section shape extruded along the member length. This helps verify section assignments visually. --- ### Materials Source: https://autocalcs.com/documentation/structuralfea/materials Materials define the physical properties that determine how structural members behave under load. Each member must have a material assigned for analysis. #### Opening the Material Library Click the **Materials** button in the ribbon, or click the book icon next to the Material field in the Properties panel when a member is selected. #### Material Library The built-in library includes materials organised by region (Australia, Metric, Imperial): - **Steel** — Standard structural steel properties - **Stainless Steel** — Stainless steel grades - **Aluminium** — Standard aluminium properties - **Timber** — Sawn, glulam, LVL, and engineered timber from various regions #### Material Properties Each material defines: - **Young's Modulus (E)** — Stiffness of the material, determines deflection under load - **Poisson's Ratio (v)** — Lateral strain ratio (typically 0.3 for steel) - **Mass Density (p)** — Mass per unit volume, used for self-weight calculations - **Thermal Coefficient** — Coefficient of thermal expansion #### Adding Materials Two ways to add materials: - **From Library** — Browse materials organised by region and select to add to your model - **Custom** — Click **Create Custom** in the library to define a material with your own properties (sign-in required) #### Assigning Materials 1. Select one or more members 2. In the Properties panel, click the Material dropdown 3. Select the desired material All selected members will be updated to use the chosen material. --- ### File Management Source: https://autocalcs.com/documentation/structuralfea/file-management Save, load, and manage your structural models in AutoCalcs. Your work is preserved between sessions, and signed-in users get cloud sync across devices. #### Opening the File Manager Click the folder icon in the top-left corner of the ribbon, or press `Ctrl+O` to open the File Manager dialog. #### Saving Your Work AutoCalcs automatically saves your current model to browser local storage as you work. To save a named project: 1. Click the save icon in the ribbon or press `Ctrl+S` 2. Enter a name for your project 3. Click **Save** The project name appears in the top ribbon. An asterisk (*) indicates unsaved changes. #### New Project To start fresh with an empty model: 1. Open the File Manager 2. Click **New Project** 3. Confirm to clear the current model #### Loading Models To open a previously saved model: 1. Open the File Manager (`Ctrl+O`) 2. Select from your list of saved projects 3. Click **Open** or double-click the project #### Local vs Cloud Storage Projects can be stored locally in your browser or in the cloud: **Local Storage** - Local files are marked with an orange **Local** tag in the File Manager - Stored in your browser's localStorage — clearing browser data will delete them - Only accessible on the device and browser where they were created - No account required **Cloud Storage (Sign In Required)** - **Cross-device access** — Access your projects from any computer - **Persistent storage** — Projects won't be lost if you clear browser data - **Secure** — Your work is stored safely in the cloud Sign in to save projects to the cloud. Remember to save regularly — cloud projects are updated when you click Save. #### File Manager Toolbar The File Manager includes a toolbar with additional features: - **New / Folder** — Create a new project or folder to organise your files - **Copy / Cut / Paste** — Duplicate or move projects between folders - **Import / Export** — Import projects from JSON files or export for backup and sharing - **Delete** — Remove selected projects or folders - **Search** — Filter projects by name - **Sort** — Order files by name or date - **View modes** — Switch between list, grid, and thumbnail views #### Keyboard Shortcuts - `Ctrl+S` — Save current project - `Ctrl+O` — Open File Manager --- ### Load Cases Source: https://autocalcs.com/documentation/structuralfea/load-cases Load cases are named groups that organize your structural loads into logical categories. Each load in your model belongs to exactly one load case, allowing you to analyze different loading scenarios separately and combine them later. #### What are Load Cases? In structural engineering, loads are typically grouped by their nature and source. Common load case types include: - **Dead Load (D or G)** — Permanent loads from the structure's own weight, fixed equipment, and finishes - **Live Load (L or Q)** — Variable loads from occupancy, furniture, and movable equipment - **Wind Load (W)** — Loads from wind pressure on the structure - **Snow Load (S)** — Loads from snow accumulation on roofs - **Seismic (E)** — Earthquake-induced loads - **Roof Live (Lr)** — Maintenance and temporary loads on roofs This organization allows you to apply different load factors and create load combinations as required by design codes. #### Opening the Load Cases Dialog Access the Load Cases dialog by clicking the **Load Cases** button in the ribbon toolbar. This opens a spreadsheet-style interface where you can manage all your load cases. #### Managing Load Cases The Load Cases dialog presents a table with the following columns: - **ID** — A unique identifier for referencing the load case (e.g., "1", "2", "DL") - **Title** — A descriptive name (e.g., "Dead Load", "Live Load") - **Notes** — Optional notes or descriptions for documentation - **Color** — The display color for loads in this case (click to customize) **Adding Load Cases** — Simply type in an empty row to create a new load case. At minimum, provide an ID to make the load case valid. **Editing Load Cases** — Click any cell to edit its value. Changes are tracked but not applied until you click **Apply** or **Apply and Close**. **Deleting Load Cases** — Clear the ID field to mark a row for deletion. When you apply changes, empty rows are removed. Note: Deleting a load case will also delete all loads assigned to that case. #### Dialog Actions The dialog toolbar provides several actions: - **Download CSV** — Export load cases to a spreadsheet file - **Copy** — Copy table data to clipboard - **Save as Preset** — Save your load case setup for reuse in other projects - **Reload** — Discard changes and reload from model or from saved presets #### Load Case Colors Each load case has an assigned color that determines how loads are displayed on the model: - Click the color swatch in the table to open the color picker - Choose from the preset palette or select a custom color - Loads are displayed in their load case's color, making it easy to identify which loads belong to which case - Default colors are automatically assigned from a predefined palette #### Active Load Case When viewing your model, you can select which load case to display. The active load case affects: - Which loads are visible on the canvas - Which load case new loads are assigned to when created via context menu Use the load case selector dropdown in the ribbon to change the active load case. #### Self-Weight Self-weight is a special automatic load calculated from member sections and materials. It is controlled per load case — see the Self Weight documentation for details. #### Analysis with Load Cases When you run analysis: 1. Each load case is analyzed independently 2. Results are stored separately for each load case 3. You can view results for individual load cases 4. Load combinations can then combine results from multiple cases using factors #### Best Practices - Use clear, descriptive names that indicate the load type (e.g., "Dead Load" rather than "LC1") - Keep load case IDs short for easy reference in load combinations - Use consistent naming conventions across projects - Document assumptions in the Notes field - Create separate load cases for loads that may need different factors in combinations --- ### Node Loads Source: https://autocalcs.com/documentation/structuralfea/node-loads Node loads are concentrated forces or moments applied directly at nodes (points) in your structural model. They represent point loads such as column reactions, equipment loads, or applied torques. #### Types of Node Loads Each node load can include up to six components (3 forces, 3 moments): **Forces** - **Fx** — Force in the global X direction - **Fy** — Force in the global Y direction - **Fz** — Force in the global Z direction **Moments** - **Mx** — Moment about the global X axis - **My** — Moment about the global Y axis - **Mz** — Moment about the global Z axis #### Adding Node Loads **Method 1: Context Menu** 1. Select one or more nodes 2. Right-click to open the context menu 3. Select **"Node Loads"** 4. This opens the Loads dialog with the Node Loads tab active and the selected node(s) pre-filled 5. Enter the force and/or moment values 6. Click **Apply** **Method 2: Loads Dialog** 1. Click **Loads** in the ribbon to open the Loads dialog 2. Select the **Node Loads** tab 3. In an empty row, enter: - **Case** — The load case ID this load belongs to - **Node** — The node ID(s) to apply the load to - **Forces (Fx, Fy, Fz)** — Force values in global directions - **Moments (Mx, My, Mz)** — Moment values about global axes 4. Click **Apply** to add the loads to your model #### Sign Convention Node loads use the global coordinate system. Positive directions are: **Forces** - **+Fx** — Force pointing in the +X direction (right) - **+Fy** — Force pointing in the +Y direction (up) - **+Fz** — Force pointing in the +Z direction (out of screen) For gravity loads (downward forces), use **negative Fy** values. **Moments** — Moments follow the **Right-Hand Rule**. Point your right thumb in the positive axis direction (+X, +Y, or +Z), and your curled fingers indicate the positive moment direction. #### Load Case Assignment Every node load must be assigned to a load case: - Specify the load case ID in the "Case" column - If no load cases exist, you'll be prompted to create one first - Loads inherit the display color of their assigned load case #### Applying to Multiple Nodes The Node column supports multiple nodes in a single row: - **Ranges**: `1-5` applies to nodes 1, 2, 3, 4, and 5 - **Lists**: `1,3,7` applies to nodes 1, 3, and 7 The same load values are applied to all specified nodes. #### Editing Node Loads To modify existing node loads: 1. Open the Loads dialog 2. Find the load in the Node Loads table 3. Edit the values directly in the cells 4. Click **Apply** to save changes #### Deleting Node Loads To remove a node load: - Clear the Case or Node field to mark the row for deletion - Or select the row and press `Delete` - Click **Apply** to confirm the deletion #### Load Visualization Node loads are displayed on the model as arrows when the Loads display is enabled: - **Forces** — Single-headed arrows pointing in the force direction - **Moments** — Double-headed arrows indicating the axis of rotation (Right-Hand Rule applies) - **Scale** — Arrow length is proportional to magnitude - **Color** — Matches the load case color Toggle load visibility using the **Loads** button in the left sidebar. Hold `C` and scroll to adjust the concentrated load arrow scale (`L` + scroll for distributed loads). #### Units Force and Moment values use the current unit system: - **Forces**: kN, N, lbf, kip - **Moments**: kN-m, N-m, kip-ft, lb-ft Units can be changed in Settings > Units. --- ### Member Loads Source: https://autocalcs.com/documentation/structuralfea/member-loads Member loads are effects applied along structural members. They include distributed loads, concentrated forces and moments at specific stations, and thermal loads. #### Types of Member Loads You can apply three main types of loads to members: **1. Distributed Loads** — Loads laid out continuously along part or all of the member's length. Common examples: - **Uniform Distributed Load (UDL)** — Constant magnitude, like a floor slab resting on a beam. - **Trapezoidal Load** — Magnitude varies linearly from start to end (e.g., wind pressure varying with height). - **Partial Loads** — Loads that only apply to a specific segment of the member. **2. Concentrated Loads** — Point forces applied at a specific location along the member, such as a secondary beam framing into a main girder. **3. Thermal Loads** — Temperature effects applied to the whole member: a uniform temperature change that drives axial expansion (or restrained axial force), plus two independent through-section temperature gradients (along the member's local-y and local-z axes) that drive bending curvature. An optional per-member thermal-expansion-coefficient override lets a member use a value different from its material — useful for an aluminium or stainless member in a steel frame. Concentrated member rows may contain force, moment, or both. Global components stay aligned with model axes. Local components follow the displayed member axes; positive moments follow the right-hand rule, Local Mx is Saint-Venant torsion, and Local My/Mz are bending couples. Moments add no translational modal or seismic mass. Local Mx uses J only: no Iw, warping DOF, warping normal stress, or complete lateral-torsional buckling capability is implied. #### Adding Member Loads You can add loads via the **Loads Dialog** or the context menu. **Using the Loads Dialog** 1. Click the **Loads** button in the ribbon. 2. Select the **Member Distributed Loads**, **Member Concentrated Loads**, or **Member Thermal Loads** tab. 3. Enter data in the spreadsheet grid. **Using Context Menu** 1. Select specific members in the 3D view. 2. Right-click and choose **Member Distributed Loads** or **Concentrated Loads**. 3. The dialog will open with the selected member IDs pre-filled. #### Distributed Load Properties When defining distributed loads, you specify: - **Case:** The load case ID (e.g., "1" or "DL"). - **Member:** The ID(s) of the members to load. Supports ranges (e.g., "1-5, 8"). - **Axis:** The coordinate system for the load direction (Global or Local). - **Units:** The unit used for position (% or Length unit like m). - **Start/Finish Position:** Where the load begins and ends. - For %: Use 0 to 100 (0 = start node, 100 = end node). - For Length: Use distance from the start node (e.g., 2.5m). - **Start/Finish Force (X, Y, Z):** The magnitude of force per unit length at the start and end positions. **Examples:** - **Full Length UDL:** Start Pos = 0, Finish Pos = 100 (%), Start Force = -5, Finish Force = -5. - **Triangular Load:** Start Force = -10, Finish Force = 0. #### Concentrated Load Properties For point loads on members: - **Position:** The location of the point load along the member (% or Length). - **Force (Fx, Fy, Fz):** The concentrated force components along the selected Local or Global axes. Positive values act toward the corresponding positive selected axis. - **Moment (Mx, My, Mz):** The concentrated couple in the selected moment unit. For example, Local Mz = 20 kN·m at 50% applies a positive midspan bending couple following the right-hand rule. #### Coordinate Systems **Global Axis** — Directions align with the global X, Y, Z axes of the model. Directions do not change as the member rotates. - **Global Y (-):** Gravity loads (downward). - **Global X/Z:** Lateral loads like wind (if defined globally). **Local Axis** — Input and canvas directions align with the displayed geometric member orientation: - **Local x:** Along the member axis. - **Local y:** Perpendicular to the member; vertical for a typical horizontal beam. - **Local z:** Perpendicular to x and y, completing the right-handed frame. Sideways rolls the displayed y/z axes by 90 degrees. Section Alpha does not rotate an authored Local load or its glyph; the transformer decomposes the geometric Local components onto the principal solver axes. Internal-force results may be reported in that principal frame. Useful for loads applied normal to inclined members, such as wind on a sloped roof rafter. #### Sign Convention - **Global:** Follows the global axes (Y is up, so -Y is down). - **Local y/z:** Positive is in the positive local axis direction. #### Tips - You can copy/paste data to and from Excel directly into the loads grid. - Use the % unit for positions if you want the load to automatically adjust when member length changes. - To apply a load to all floor beams, select them first using "Select by Section", then use the context menu. --- ### Self Weight Source: https://autocalcs.com/documentation/structuralfea/self-weight The Self Weight feature automatically calculates the weight of structural members based on their material density and cross-sectional area. This ensures you don't have to manually calculate and apply gravity loads for the structure itself. #### How it Works Self weight is calculated using the formula: ``` Weight = Area x Density x Gravity Multiplier x Length ``` Where: - **Area:** Cross-sectional area from the assigned Section. - **Density:** Material density from the assigned Material. - **Gravity Multiplier:** A factor defining the direction and magnitude of gravity (typically -1 in Y). #### Enabling Self Weight Self weight is managed via the **Self-Weight Settings** dialog, accessible from the Ribbon. 1. Click the **Self-Weight** button (weight icon) in the Ribbon. 2. In the dialog, you will see a list of your Load Cases. 3. For each Load Case where you want self-weight applied, enter the **Gravity Multipliers** (g's). **Gravity Multipliers** You can define the acceleration due to gravity as a vector (X, Y, Z) for each load case: - **Standard Gravity (Vertical Down):** Set Y = -1, X = 0, Z = 0. - **Horizontal Acceleration (Seismic approximation):** Set X or Z to a non-zero value (e.g., 0.1). - **No Self Weight:** Set all values to 0 or leave the row empty/disabled. Usually, you only apply self-weight to a specific "Dead Load" or "Self Weight" load case. #### Requirements For self weight to be calculated correctly, every member must have: - A valid **Section Property** (defines Area) - A valid **Material Property** (defines Density) If a member is missing either of these, its self weight will be zero. #### Visual Validation When self weight is enabled for the active load case, you won't see explicit arrows on every member (to avoid clutter), but the analysis will include these forces. To verify: 1. Run the analysis with only self weight enabled. 2. Check the **Reaction Y** forces. They should equal the total weight of your structure. --- ### Load Combinations Source: https://autocalcs.com/documentation/structuralfea/load-combinations Load combinations apply factors to load case results and sum them together, as required by structural design codes. This allows you to determine the worst-case design forces under various loading scenarios. #### What are Load Combinations? A load combination multiplies the results from each load case by a specified factor and sums them: ``` Combination Result = f1 x LC1 + f2 x LC2 + f3 x LC3 + ... ``` For example, the ASCE 7 combination `1.2D + 1.6L` means: - Multiply Dead Load results by 1.2 - Multiply Live Load results by 1.6 - Add them together The factored results represent the design forces that structural members must resist. #### Opening the Load Combinations Dialog Click the **Load Combos** button in the ribbon toolbar to open the Load Combinations dialog. #### Creating Load Combinations The dialog displays a spreadsheet with: - **ID** — A unique identifier for the combination - **Title** — A descriptive name (e.g., "1.4D", "1.2D + 1.6L") - **Factor columns** — One column for each defined load case, where you enter the multiplier **Adding a Combination** 1. Type an ID and Title in an empty row 2. Enter factors for each load case you want to include 3. Leave factor cells empty or set to 0 for load cases not included 4. Click **Apply & Close** to save your changes **Example Combinations** | ID | Title | Dead | Live | Wind | |----|-------|------|------|------| | 1 | 1.4D | 1.4 | | | | 2 | 1.2D + 1.6L | 1.2 | 1.6 | | | 3 | 1.2D + 1.0W + L | 1.2 | 1.0 | 1.0 | | 4 | 0.9D + 1.0W | 0.9 | | 1.0 | #### Common Load Combinations (ASCE 7 LRFD) | Combination | Formula | Description | |-------------|---------|-------------| | 1 | 1.4D | Dead load only | | 2 | 1.2D + 1.6L + 0.5(Lr or S) | Dead + Live + Roof/Snow | | 3 | 1.2D + 1.6(Lr or S) + (L or 0.5W) | Roof/Snow dominant | | 4 | 1.2D + 1.0W + L + 0.5(Lr or S) | Wind included | | 5 | 1.2D + 1.0E + L + 0.2S | Seismic included | | 6 | 0.9D + 1.0W | Uplift — Wind | | 7 | 0.9D + 1.0E | Uplift — Seismic | #### Common Load Combinations (AS/NZS 1170) For Australian/New Zealand standards (ULS, Section 4.2): | Combination | Formula | Description | |-------------|---------|-------------| | 1 | 1.35G | Dead load only | | 2 | 1.2G + 1.5Q | Dead + Live | | 3 | 1.2G + Wu + 0.4Q | Wind with companion live | | 4 | 0.9G + Wu | Uplift — Wind | | 5 | G + Eu + 0.3Q | Earthquake with companion live | | 6 | 0.9G + Eu | Uplift — Earthquake | #### Auto-Generate Combinations Pro users can automatically generate all required load combinations for a given design code. Click **Auto-Generate** in the toolbar to open the wizard. **How it Works** 1. Select a design code (e.g., ASCE 7 or AS/NZS 1170) 2. Map your load cases to standard categories (Dead, Live, Wind, etc.). For directional categories like Wind and Seismic, you can select multiple cases simultaneously. 3. Configure Mirroring for directional cases if required. 4. Choose ULS, SLS, or both 5. Click Generate — the wizard creates every required combination permutation. The wizard auto-detects category mappings from your load case names. Categories left unmapped are silently skipped. **Directional & Mirroring Support** - **Multi-Directional Selection**: If you have `Wind X` and `Wind Z`, select both in the Wind category dropdown. The generator will loop through both, creating a full set of combinations for each direction. - **+/- Mirror Pattern**: Enabling the +/- Mirror toggle automatically generates both positive and negative variations of the load (e.g., `1.2D + 1.0Wx` and `1.2D - 1.0Wx`). **Supported Design Codes** | Code | Region | Types | |------|--------|-------| | AS/NZS 1170 | Australia / New Zealand | ULS + SLS | | ASCE 7 (LRFD) | USA | ULS | | ASCE 7 (ASD) | USA | ULS | | Eurocode 0 (EN 1990) | Europe | ULS + SLS | | NBCC 2020 | Canada | ULS + SLS | Generated combinations can be appended to your existing entries or replace them entirely. #### Dialog Actions The toolbar provides: - **Auto-Generate** — Generate combinations from a design code - **Download CSV** — Export combinations to spreadsheet - **Copy** — Copy to clipboard - **Save as Preset** — Save for reuse - **Reload** — Reload from model or presets #### Viewing Combination Results After running analysis, you can view factored combination results: 1. Enable a result view (Moment, Shear, etc.) in the left sidebar 2. Use the result selector dropdown in the left sidebar to choose a load combination 3. The displayed diagram shows the factored, combined results You can switch between individual load case results and combined results at any time. #### Best Practices - Name combinations clearly using the factor notation (e.g., "1.2D + 1.6L") - Include all combinations required by your governing design code - Consider both strength (ultimate) and serviceability combinations - For wind and seismic, remember to include both positive and negative directions - Use presets to maintain consistent combinations across projects --- ### Running Analysis Source: https://autocalcs.com/documentation/structuralfea/running-analysis Once your structural model is complete, you can execute the finite element analysis to calculate displacements, reactions, and internal forces. #### Before Running Analysis Ensure your model meets these requirements for a successful analysis: **Checklist** - All members have sections assigned — Members without sections have undefined stiffness - All members have materials assigned — Materials provide the elastic modulus - Sufficient supports — The structure must be stable (no rigid body motion) - At least one load case with loads — Either applied loads or self-weight enabled - No disconnected parts — All members should be connected **Minimum Support Requirements** For a stable 3D structure, you need to restrain: - 3 translations (prevent movement in X, Y, Z) - 3 rotations (prevent spinning about X, Y, Z) A single fixed support provides all 6 restraints. For pinned supports, you typically need at least 3 non-collinear supports. #### Model Health Check Before running an analysis, it is recommended to use the **Health Check** tool. This automated system scans your model for common issues that could lead to analysis failure or inaccurate results. To run a health check, click the **Health Check** button in the ribbon. The dialog will categorize issues into: - **Errors (Red):** Critical issues that prevent the analysis from running. These must be resolved first. - **Warnings (Yellow):** Potential issues that may affect accuracy or stability but won't block the analysis. Note: If you attempt to run an analysis while your model has critical errors, the Health Check dialog will open automatically to show you what needs to be fixed. #### Running the Analysis **Quick Run** 1. Click the **Linear** button in the ribbon — the button label shows the currently selected analysis type 2. Wait for the analysis to complete (a loading spinner appears) 3. Check the status message **Changing Analysis Type** 1. Click the dropdown arrow next to the button 2. Select the analysis type: - **Linear** — Standard first-order analysis (default) - **P-Delta** — Second-order analysis with geometric nonlinearity - **Buckling** — Elastic buckling analysis to find critical load factors and mode shapes (Classic for general models; Wittrick-Williams exact-member checks for eligible beam, frame, and truss models) - **Modal** — Eigenvalue analysis for natural frequencies, mode shapes, and mass participation factors (requires self-weight on at least one load case) The button label updates to reflect your selection. Next time you click it, it runs that analysis type. #### Analysis Status After running the analysis, you'll see one of these outcomes: **Success** — The analysis completed successfully. Results are now available: result toggles in the left sidebar become active, you can view displacements, reactions, and force diagrams. **Warning** — The analysis completed but with warnings. Results are available but should be reviewed carefully. **Error** — The analysis failed. Check the error message for details. No results are available until the issue is resolved. #### Common Errors **Unstable Structure (Mechanism)** — The structure can move freely without developing internal forces. Causes: Missing or insufficient supports, too many member releases creating a mechanism, disconnected parts. Solutions: Add more supports or restrain additional degrees of freedom, check that all nodes are connected to at least one member, review member end releases. **Missing Section or Material** — One or more members don't have required properties assigned. Solutions: Select all members without sections, assign sections and materials via the Properties panel, use the Members table to review all member properties at once. **Singular Stiffness Matrix** — A mathematical error indicating the stiffness matrix cannot be inverted. Common causes: Collinear nodes with pin connections, zero-length members, members with zero stiffness properties, insufficient global restraints. Solutions: Check for overlapping or duplicate nodes, verify member connectivity at joints, ensure supports prevent all rigid body motion. **Analysis Did Not Converge** — For iterative analyses, the solution didn't stabilize. Common causes: Structure is at or near buckling load, very large deflections relative to member lengths, numerical instability from extreme stiffness ratios. Solutions: Try Linear analysis first to understand the behavior, reduce applied loads to check if the structure is overloaded, review structure for stability issues. #### Results Become Stale After a successful analysis, results may become "stale" if you modify the model (adding/moving/deleting nodes or members, changing properties, modifying loads, or changing supports). Stale results remain viewable but may not reflect the current model. Re-run the analysis to update results. #### Usage Limits - **Anonymous Users:** Limited to 2 analysis runs per day. Sign up for a free account to increase this to 5 runs per day. - **Free Accounts:** 5 analysis runs per day, models limited to 8 nodes. Unchanged official sample models are exempt. - For larger models (unlimited nodes), upgrade to the Pro plan. #### What Happens During Analysis When you click Run: 1. **Model preparation** — Your model data is packaged for the solver 2. **Server transfer** — Data is sent to our analysis server 3. **FEA solution** — The finite element equations are solved 4. **Results transfer** — Results are sent back to your browser 5. **Visualization** — Results are displayed on your model The entire process typically takes a few seconds for typical models. --- ### Analysis Types Source: https://autocalcs.com/documentation/structuralfea/analysis-types AutoCalcs offers different analysis methods to suit various structural problems. Choosing the right analysis type is crucial for obtaining accurate results. #### Linear Analysis **Best for:** Most standard structures, beams, frames, plates, and trusses where deformations are small. This is the default analysis type. It assumes: - **Small Displacements:** The structure's deformed shape does not significantly affect the equilibrium equations. - **Linear Material Behavior:** Materials follow Hooke's Law (stress is proportional to strain). **Tension/Compression Only Support** — Although termed "Linear", this solver handles tension-only and compression-only members and supports with an active-set process. Elements can activate or deactivate over successive passes, and inactive elements are checked using their trial elastic force until the active set is sign-consistent. #### P-Delta Analysis (Second Order) **Best for:** Tall buildings, slender columns, and flexible structures where sway is significant. P-Delta analysis accounts for geometric nonlinearity. It considers the additional forces and moments created when vertical loads (P) act on the laterally displaced (Delta) position of the structure. Key effects captured: - **P-delta (small delta):** Effect of axial loads on the bending stiffness of individual members (beam-column effect). - **P-Delta (large Delta):** Effect of vertical resultants acting on the sway of the entire frame. Formulation: this is a bounded two-pass, linearised second-order analysis. The first pass solves [K]{D0} = {F} and recovers the reference force state P0. The second pass solves [K + Kg(P0)]{D1} = {F}. It does not repeatedly update element geometry or provide a large-rotation solution. When one-way elements are present, the two-pass sequence repeats only as needed to converge their active set. #### Buckling Analysis (Elastic) **Best for:** Determining critical buckling loads and identifying instability modes. Elastic buckling analysis solves a generalised eigenvalue problem to find the load factors at which the structure becomes unstable. It returns critical load factors (eigenvalues) and the corresponding buckling mode shapes (eigenvectors). Key outputs: - **Critical load factor:** The multiplier on the applied loads at which buckling occurs. - **Mode shapes:** The deformed shape the structure would adopt at buckling. - **Effective length factors (K):** Computed per member from the governing eigenvalue. Two eigenvalue solvers are available. **Classic** is the general-purpose option and supports 3D frames, plates and shells, constraints, member offsets, and changing axial force. **Wittrick-Williams (exact member)** is a Pro cross-check for member-only beam, frame, and truss models, including 3D space frames. Its member solution is exact when axial force is constant. When axial force changes along an ordinary member, Refine members must be enabled; refinement is limited to models with 20 nodes or fewer and no result is returned unless the refinements agree. Use Classic for plates or shells, rigid diaphragms or node links, member offsets, and changing-force tension-only or compression-only members. Open-section torsional and flexural-torsional buckling require a separate design check. Note: This is a linearised buckling analysis — it assumes the pre-buckling behaviour is linear. #### FEA Solver Verification Source: https://autocalcs.com/fea-verification The public FEA verification tables contain 82 published, analytical, and independently checked benchmark results with a displayed average difference of 0.20%. Buckling coverage comprises 10 Wittrick-Williams cases and 11 Classic cases, including analytical Euler and textbook frame problems, an independently assembled 3D truss tangent-stiffness comparison, independent changing-axial-force solutions, and an independently checked Classic 3D non-uniform-axial frame comparison. #### Modal Analysis (Eigenvalue) **Best for:** Determining natural frequencies, mode shapes, and mass participation factors for seismic design, floor vibration checks, and dynamic feasibility. Modal analysis solves the generalised eigenvalue problem [K]φ = ω²[M]φ to extract the natural vibration characteristics of the structure. Results depend only on mass distribution, stiffness, and boundary conditions — no applied dynamic load is needed. Key outputs: - **Natural frequencies** (Hz) for each mode, sorted ascending. - **Mode shapes** — normalised eigenvectors, rendered with within-member bowing curves. - **Mass participation factors** per direction (X, Y, Z), used for modal combination and the 90% participation check in seismic codes. - **Effective modal mass** per mode per direction. Mass source: Before running modal analysis, select a reference load pattern (load case or combination) containing self-weight. Self-weight provides positive physical mass. Applied loads are netted at each node, member position, or loaded plate; only the local net force acting with gravity becomes mass. Locally net-upward load is omitted with a warning, and loads at different locations do not cancel each other. Moment loads and non-gravity-direction forces do not contribute. Physical mass: extra mass is not added to massless degrees of freedom. Those coordinates still move with the structure through stiffness and are omitted from the reported frequency list. A 0 Hz result means the model can translate or rotate as a rigid body while still carrying mass, usually from a missing support; those modes have no period. A direction with neither stiffness nor mass is a mechanism and needs a model correction. The requested mode count is a maximum; fewer finite-frequency modes may be returned, and that does not prove the rest of the spectrum has been searched. Reported total mass includes mass at supported nodes, and participation percentages use that complete physical mass. Formulation: distributed member and material mass use consistent element mass matrices with automatic h-refinement (4 sub-elements per physical member). Concentrated mass remains at its application location. The eigenproblem is solved through sparse ARPACK extraction with torsional and invalid-mode filtering. Known limitations: - Open sections (I-sections, channels, tees, angles): torsional and lateral-torsional modes are underestimated (6-DOF element without warping DOF). Pure horizontal sway modes in X and Z (Y is vertical) — which govern seismic design — are unaffected. - Tension-only and compression-only physical members are linearised as ordinary two-way elastic members because the eigenvalue solve requires a constant stiffness matrix. Nodal P/N support springs are preconverged at the selected mass-combination operating point and then held fixed. - Response Spectrum Analysis (RSA) combination is not yet exposed; modal outputs feed code-based equivalent-lateral-force calculations and floor vibration checks. Tier limits: Free up to 12 modes; Pro up to 30 modes. #### Comparison Guide | Feature | Linear | P-Delta | Buckling | Modal | |---|---|---|---|---| | Equilibrium Formulation | On undeformed shape | Linearised second pass with Kg(P0) | Eigenvalue ([K]+λKg) | Eigenvalue ([K]−ω²[M]) | | Stiffness Matrix | Constant | Two-pass: K, then K + Kg(P0) | Geometric stiffness matrix | Constant (cubic Hermite) | | Mass Matrix | — | — | — | Consistent distributed mass, localized concentrated mass, h-refined | | Load Input | Forces / moments | Forces / moments | Load combination (for Kg) | Mass-source pattern only | | Output | Forces, displacements | Forces, displacements (amplified) | Critical load factors, mode shapes, K-factors | Natural frequencies, mode shapes, participation factors | | Use Case | Standard steel/concrete frames | Slender structures, drift-sensitive designs | Critical load and stability assessment | Seismic design, floor vibration, dynamic feasibility | #### Which one should I use? **Start with Linear Analysis.** It is faster and sufficient for the vast majority of low-rise structures. Consider P-Delta if: - You are designing a Moment Resisting Frame (MRF) - Your structure has slender columns - Lateral drift is a governing design criteria - Axial loads are a significant fraction of the buckling load Use Buckling Analysis to inspect elastic critical load factors and instability mode shapes. Reported effective length factors are diagnostic equivalents; review member participation, restraint assumptions, and the selected material standard before using them in design checks. No universal load-factor threshold by itself proves design adequacy or classifies a frame as braced or sway. Use Modal Analysis to determine fundamental natural frequencies for seismic design (ASCE 7 §12.8, AS 1170.4, EC8, NBCC), extract mass participation factors for the 90% participation requirement, check floor vibration acceptability for occupant comfort, and identify soft storeys or torsional irregularities by mode shape inspection. --- ### Result Types Source: https://autocalcs.com/documentation/structuralfea/result-types AutoCalcs provides a comprehensive set of analysis results to help you understand your structure's behavior under load. #### Displacement Shows how the structure moves from its original position: - **Translation (Dx, Dy, Dz)** — Movement in X, Y, Z directions - **Rotation (Rx, Ry, Rz)** — Rotation about X, Y, Z axes The visual display shows the deformed shape of the structure, usually magnified so you can see the behavior patterns. #### Reactions Forces and moments that the supports exert on the structure to maintain equilibrium: - **Forces (Fx, Fy, Fz)** — Reaction forces in global directions - **Moments (Mx, My, Mz)** — Reaction moments (for fixed supports) Displayed as arrows at support nodes. #### Axial Force The force stretching or compressing a member: - **Positive (+)** — Tension (stretching) - **Negative (-)** — Compression (squashing) Important for designing trusses, columns, and bracing. #### Shear Force Forces trying to slice the member: - **Vy (Major Shear)** — Shear force in the local y-direction (typically vertical shear for beams) - **Vz (Minor Shear)** — Shear force in the local z-direction (typically horizontal shear) #### Bending Moment The moment causing the member to bend: - **Mz (Major Moment)** — Moment about the local z-axis (typically causing vertical bending). This is the primary moment for floor beams. - **My (Minor Moment)** — Moment about the local y-axis (causing sideways bending). Displayed as a filled diagram. The diagram is drawn on the tension side or compression side depending on your convention settings. #### Torsion The moment twisting the member about its own axis (Mx). Important for beams loaded eccentrically or curved members. #### Member Stress Colours members by elastic beam-theory stress recovered from solved 1D member forces and section geometry. Rendered and outlined views show per-fibre quantities across the member surface; wireframe uses a station gradient along the member. This is member-level post-processing, not local shell/solid stress analysis of web/flange junctions, support/load-introduction regions, welds, bolts, or connections. Right-click the Member Stress button to choose the quantity: - **Total Normal Stress σx (N + M)** (default): signed elastic normal stress from axial force plus biaxial bending at the governing fibre; it excludes shear and torsion - **Axial Normal Stress σx,N**: signed uniform axial normal stress, P/A - **Bending Normal Stress |σx,M|**: absolute bending-only normal-stress component at the governing fibre - **Torsional Shear Stress τT**: Saint-Venant torsional shear from T and J (nominal; no warping torsion) - **Total Shear Stress τ**: combined transverse and torsional shear at the worst cross-section point - **Max Principal Stress σ1**: maximum in-plane principal stress - **Min Principal Stress σ2**: minimum in-plane principal stress - **von Mises Equivalent Stress**: distortion-energy equivalent stress for ductile metals - **Tresca Equivalent Stress**: maximum-shear equivalent stress for ductile metals - **Rankine Stress (Max Principal Tension)**: maximum tensile principal stress for brittle materials such as concrete and masonry Von Mises and Tresca are greyed out on concrete and timber members (Rankine is the brittle-material criterion). Signed quantities follow the model tension/compression colour convention, and values are shown in your unit system (MPa or ksi). Concrete member stress contours show the gross-section elastic stress field from the concrete shape geometry and section properties only; they do not include reinforcing bars, cracked-section behaviour, transformed-section properties, strain compatibility, or code stress-block design. #### Units **Metric (SI)** - Displacement: mm or m - Force (Axial, Shear, Reactions): kN - Moment (Bending, Torsion): kN-m **Imperial (US)** - Displacement: in or ft - Force: kip or lbf - Moment: kip-ft or lb-ft #### Result Sign Conventions **Member Internal Forces** — Follow the member's local coordinate system: - Axial: Tension is positive - Shear: Positive shear acts in positive local y/z direction on a positive face - Moment: Positive moment acts counter-clockwise about local axis (Right Hand Rule) **Reactions** — Follow the global coordinate system: - +Fy: Upward reaction force - +Fx: Reaction to the right --- ### Viewing Results Source: https://autocalcs.com/documentation/structuralfea/viewing-results After running a successful analysis, you can visualize and explore the results directly on your 3D model. #### Result Toggles The left sidebar contains toggle buttons to control which results are displayed: - **Displacement** — Shows the deformed shape - **Reactions** — Shows support reaction arrows - **Moments** — Shows bending moment diagrams - **Shear** — Shows shear force diagrams - **Axial** — Shows axial force diagrams - **Torsion** — Shows torsion diagrams #### Selecting Results to Display Use the dropdowns in the left sidebar to filter the results: **Load Case / Combination** — Select a specific Load Case or Load Combination to see results for just that case or combined, factored results. **Component Direction** — For diagrams like Shear and Moment, you can choose which axis to display: - Shear: y (Major) or z (Minor) - Moment: z (Major) or y (Minor) #### Adjusting Scales Hold one of the following keys and use your mouse wheel (scrolling) to adjust the size of that specific diagram: - `D` — Displacement (Deformation) - `R` — Reactions - `M` — Moment Diagrams - `S` — Shear Diagrams - `A` — Axial Diagrams - `T` — Torsion Diagrams - `L` — Distributed Loads (visual size) - `C` — Concentrated Loads (visual size) #### Reading Values **Tooltips** — Hover your mouse over any result diagram to see a tooltip with the exact value at that location. **Annotations** — Toggle Show Annotations in the display options to show maximum and minimum values on each member, and values at member ends. #### Result Colors - Displacement: Purple/Violet - Reactions: Amber/Orange - Moment: Blue - Shear: Green - Axial: Red - Torsion: Pink #### Exporting Results - **Screenshots** — Use your computer's screenshot tool to capture the visualized results - **Reports** — Configure PDF or Excel reports via the Ribbon; downloading either format requires Pro --- ### Sign Conventions Source: https://autocalcs.com/documentation/structuralfea/sign-conventions Understanding the coordinate systems and positive directions used in AutoCalcs is essential for accurate modeling and result interpretation. **Key Principle: Right-Hand Rule** — AutoCalcs consistently uses the Right-Hand Rule for all coordinate systems and rotations. #### Global Coordinate System The global system defines the position of all nodes in 3D space. It is a strictly Y-Up system: - **X-Axis**: Horizontal (Red) — Positive to the Right - **Y-Axis**: Vertical (Green) — Positive Upwards (Elevation) - **Z-Axis**: Depth (Blue) — Positive Outwards/Forwards ``` +Y (Up) ^ | | | +----------> +X (Right) / / v +Z (Forward/Out) ``` #### Member Local Axes Each member has its own local coordinate system (x, y, z) that moves and rotates with the member. **Local x-axis (Longitudinal)** — Defined by the line connecting Node A (Start) to Node B (End). Positive direction is from Node A to Node B. **Local y-axis (geometric input/display axis)** — Perpendicular to the x-axis. For horizontal members, this points Up vertically. **Local z-axis (geometric input/display axis)** — Perpendicular to both x and y, defined by the Right-Hand Rule (z = x x y). For typical horizontal beams, this axis is horizontal. Sideways rolls these displayed geometric y/z axes by 90 degrees. Alpha does not rotate authored Local loads. The solver decomposes geometric Local components onto the section's principal axes, and internal-force diagrams may use that principal frame. #### Positive Sign Conventions **Analysis Results** - Displacements (Dx, Dy, Dz): Follow Global Axes (+X Right, +Y Up, +Z Forward) - Rotations (Rx, Ry, Rz): Follow Right-Hand Rule about Global Axes - Reactions: Forces acting ON the structure from supports. Follow Global Axes. **Internal Forces** - Axial Force (Fx): Tension is Positive (+), Compression is Negative (-) - Shear Force (Fy, Fz): Positive when acting in positive local axis direction on a positive face - Bending Moment (My, Mz): Follows Right-Hand Rule about local axes. Default displays moment on the Tension Side. #### Load Inputs - **Force Loads (Fx, Fy, Fz)**: Follow Global Axes direction. (e.g., -10kN Fy is a downward gravity load). - **Moment Loads (Mx, My, Mz)**: Follow Right-Hand Rule about the axis. - **Distributed Loads**: Specified in Global or Local axes. Downward gravity load on a beam is typically Global -Y or Local -y. --- ### Settings Source: https://autocalcs.com/documentation/structuralfea/settings Customise AutoCalcs to match your workflow and preferences. #### Visual Settings - **Theme** — Choose between Light, Dark, or System (follows your OS preference) - **Node Size** — Adjust the diameter of nodes in the viewport - **Line Thickness** — Adjust the width of member lines in pixels #### Hotkeys Customise keyboard shortcuts for tools and actions. Shortcuts are organised into categories: - **Modes** — Switch between draw, select, move, mirror, copy, extrude, and focus modes - **Commands & Actions** — Undo, redo, and delete operations - **Dialogs** — Open copy and extrude dialogs - **Selection** — Select all, invert selection, and select last created elements - **View** — Preset camera angles (front, back, left, right, top, bottom, isometric) To reassign a shortcut, click on the current key and press your desired key combination. **Diagram Scales** — Hold a designated key and scroll the mousewheel to adjust the visual scale of loads, results diagrams, displacements, and reactions in the viewport. #### Units Configure your preferred unit system: - **Metric** — Millimetres, metres, kilonewtons, megapascals - **Imperial** — Inches, feet, kips, ksi Within each system, you can customise individual unit types: - **Length** — For geometry dimensions - **Force** — For loads and reactions - **Moment** — For bending moments and torques - **Displacement** — For deflection results Internal data remains metric. Display and input values are converted. Section and material library units are based on the country of origin and do not change. #### Profile Settings When signed in, you can customise your profile: - **User Logo** — Upload your company or personal logo to appear on PDF reports Supported formats: PNG, JPG, WebP, SVG. Maximum upload size is 5MB. #### Reset to Defaults To restore all settings to their default values, click the **Reset to Defaults** button at the bottom of the Settings dialog. --- ### Keyboard Shortcuts Source: https://autocalcs.com/documentation/structuralfea/keyboard-shortcuts Master these shortcuts to speed up your workflow. #### Tool Modes | Shortcut | Action | |---|---| | `Ctrl+D` | Draw mode | | `Esc` | Select mode | | `W` | Move mode | | `Ctrl+F` | Focus on selection | #### Drawing Operations | Shortcut | Action | |---|---| | `Ctrl+C` | Copy mode | | `Ctrl+E` | Extrude mode | | `Ctrl+M` | Mirror mode | | `Shift+C` | Open Copy dialog | | `Shift+E` | Open Extrude dialog | #### Selection | Shortcut | Action | |---|---| | `Ctrl+A` | Select all | | `Ctrl+I` | Invert selection | | `Ctrl+R` | Restore previous selection | | `Escape` | Return to Select mode / Cancel operation | | `Delete` | Delete selected | #### Editing | Shortcut | Action | |---|---| | `Ctrl+Z` | Undo | | `Ctrl+Y` | Redo | | `X` | Intersect members | | `B` | Split member at point | #### Views | Shortcut | Action | |---|---| | `1` | Front view | | `9` | Back view | | `3` | Right view | | `7` | Left view | | `5` | Top view | | `2` | Bottom view | | `4`, `6`, `8` | Isometric views | All keyboard shortcuts can be customized in Settings > Hotkeys. --- ## Educational Guides --- ### How to Build a 3D FEA Model: Step-by-Step Guide Source: https://autocalcs.com/build-3d-fea-model Finite element analysis doesn't have to be complicated. This guide walks you through building a complete 3D structural model in six simple steps — from placing your first node to viewing bending moment diagrams. No download or signup required. #### Build Your First Model in 6 Steps **1. Draw Your Structure** — Start by placing nodes in 3D space and connecting them with members or plate elements. Click to place nodes, draw members between them, or add quadrilateral and triangular plates to define your structural geometry. You can create beams, frames, plates, trusses, or any combination. **2. Add Supports** — Define how your structure connects to the ground by assigning support conditions to nodes. Choose from fixed, pinned, or roller supports — or create custom restraints by locking individual degrees of freedom. **3. Assign Sections and Materials** — Select cross-sections from a library of thousands of real profiles — steel W shapes, HSS tubes, timber, aluminium, and more. Each section comes with pre-calculated properties like area, moment of inertia, and section modulus. **4. Apply Loads** — Add point loads, distributed loads, or moments to your members and nodes. Organise loads into separate load cases (dead, live, wind, etc.) to analyse different scenarios independently. **5. Run the Analysis** — Hit the Run Analysis button and the solver computes your model using the Direct Stiffness Method. The FEA engine assembles element stiffness matrices, applies boundary conditions, and solves the global system in seconds. **6. View Results** — Explore your results interactively in 3D. Visualise deflected shapes, bending moment diagrams, shear force diagrams, axial force, torsion, and stress distributions. Check reactions at supports. PDF and Excel analysis report downloads are a Pro feature. #### Why Use AutoCalcs for FEA? Most FEA software requires expensive licenses, lengthy installations, and a steep learning curve. AutoCalcs runs entirely in your browser and is designed to get you from zero to results as fast as possible. - **Free tier** — Core analysis types are available without a licence fee, subject to daily-run and model-size limits - **Browser-based** — Works on any computer, no installation or IT approval needed - **Real section libraries** — Thousands of steel, timber, and aluminium profiles with properties - **Full 3D analysis** — Not limited to 2D; model space frames, trusses, and complex geometry - **Instant results** — Moment, shear, axial, torsion, deflection, and stress diagrams - **P-Delta & Buckling capable** — Run second-order and elastic buckling analysis when needed --- ### Linear vs Nonlinear Structural Analysis Source: https://autocalcs.com/linear-vs-nonlinear-analysis Choosing the right analysis type is fundamental to accurate structural design. Linear analysis is faster and simpler, but nonlinear analysis captures effects that linear methods miss entirely. #### What is Linear Analysis? Linear (first-order) structural analysis makes two key assumptions: - **Small displacements** — The structure deflects so little that we can ignore the change in geometry when calculating forces - **Linear material behaviour** — Stress is proportional to strain (Hooke's Law), and the material returns to its original state when unloaded Under these assumptions, doubling the load doubles the displacement. The principle of superposition applies — you can add load cases together. For most everyday structures — residential buildings, small commercial frames, typical beams and columns — linear analysis provides accurate results. #### What is Nonlinear Analysis? Nonlinear analysis relaxes one or both of these assumptions: **Geometric Nonlinearity** — Accounts for changes in geometry as the structure deforms. Equilibrium is calculated on the deformed shape, not the original. Includes P-Delta effects, large displacement theory, cable and membrane structures. **Material Nonlinearity** — Accounts for non-elastic material behaviour such as yielding, plasticity, cracking, or creep. Includes steel yielding and plastic hinges, concrete cracking and crushing, pushover and collapse analysis. The most common nonlinear analysis in practice is P-Delta analysis — a form of geometric nonlinearity that captures second-order effects while still assuming elastic material behaviour. #### Side-by-Side Comparison | Aspect | Linear (First-Order) | Nonlinear (Second-Order) | |---|---|---| | Equilibrium | On original geometry | On deformed geometry | | Superposition | Yes | No | | Solution Method | Single step (direct) | Iterative | | Computation Speed | Fast | Slower (iterations) | | P-Delta Effects | No | Yes | | Stability Detection | Not captured | Divergence indicates instability | | Results Accuracy | Conservative for stiff structures | More accurate for flexible structures | #### When is Linear Analysis Sufficient? - Stiff structures — Braced frames, shear wall buildings, stocky columns - Small displacements — Deflections are small relative to member lengths (typically <1%) - Low axial loads — Gravity loads are modest relative to buckling capacity - Service load analysis — Checking deflections and stresses under working loads - Preliminary design — Quick sizing before detailed analysis For these cases, the error from ignoring second-order effects is typically less than 5%. #### When Do You Need Nonlinear Analysis? - Tall buildings — Multi-storey structures where drift amplification matters - Slender members — Columns with high slenderness ratios - Unbraced frames — Moment frames relying on frame action for stability - Heavy gravity loads — High axial loads combined with lateral forces - Code requirements — Most modern codes require second-order analysis for certain structure types - Stability-sensitive structures — Arches, domes, shells, cable structures #### The 10% Rule A practical check: run both linear and P-Delta analysis on your structure. If the second-order results differ by more than 10%, you should use the nonlinear results for design. --- ### P-Delta Analysis: A Complete Guide to Second-Order Effects Source: https://autocalcs.com/p-delta-analysis P-Delta analysis accounts for the additional forces and moments caused by structural deformation under load. When a structure deflects, gravity loads create secondary effects that first-order analysis ignores. #### What is P-Delta Analysis? P-Delta analysis is a type of second-order structural analysis that considers how axial loads (P) interact with lateral displacements (Delta, or delta) to create additional moments and forces in a structure. Unlike first-order (linear) analysis, which assumes the structure remains in its original geometry, P-Delta analysis accounts for equilibrium on the deformed shape. The additional moment equals the axial force (P) multiplied by the displacement (delta). #### Two Types of P-Delta Effects **P-Delta (Big Delta)** — The effect of axial load acting through the relative lateral displacement between member ends. This is the "sway" effect in frames. Includes storey drift in multi-storey frames, lateral displacement of column tops, and global frame instability. **P-delta (Small Delta)** — The effect of axial load acting through the deflection along the member length. This is the "member curvature" effect. Includes bowing of individual members, amplification of member moments, and member buckling behaviour. Both effects reduce the effective stiffness of the structure and amplify internal forces. #### When Do You Need P-Delta Analysis? Consider P-Delta Analysis When: - Tall or slender structures — Multi-storey buildings, towers, masts - High axial loads — Heavy gravity loads combined with lateral forces - Flexible lateral systems — Moment frames without bracing - Slender columns — High slenderness ratios (L/r) - Code requirements — Many design codes mandate second-order analysis for certain structure types A common rule of thumb: if second-order effects increase forces by more than 10% compared to first-order analysis, they should not be ignored. #### How P-Delta Analysis Works 1. **Initial analysis** — Perform first-order analysis to get initial displacements 2. **Geometric stiffness** — Calculate additional stiffness terms based on axial loads and displacements 3. **Modified stiffness** — Subtract geometric stiffness from elastic stiffness (reducing overall stiffness) 4. **Re-analyse** — Solve with modified stiffness to get updated displacements 5. **Check convergence** — Repeat until displacements converge (or diverge, indicating instability) If the iteration diverges, the structure is unstable under the applied loads. #### Practical Example: Portal Frame Consider a simple portal frame with a horizontal load at the top. In first-order analysis, the frame deflects laterally, and we calculate moments based on the original geometry. With P-Delta analysis, the vertical load on the columns now acts at an eccentricity (the lateral displacement). This creates additional overturning moment: P x delta. The structure deflects more, which increases the eccentricity, which increases the moment, until equilibrium is reached. For a typical steel portal frame, second-order effects might increase moments by 5-15%. For a slender multi-storey frame, the increase could be 20-30% or more. --- ### AutoCalcs for Engineering Students Source: https://autocalcs.com/for-students Learning structural analysis shouldn't require expensive software. AutoCalcs provides a free tier with core FEA capabilities for understanding concepts, verifying hand calculations, and completing assignments. #### Why Students Love AutoCalcs - **Free tier for everyone** — Core analysis types are available without a student discount or time-limited trial, subject to the published usage and model-size limits. - **Learn by Doing** — Build models, apply loads, and see results instantly. Understanding comes from experimentation, not just reading textbooks. - **Verify Your Work** — Check your hand calculations against FEA results. Understand where approximations break down and why. - **No Barriers** — Works in your browser on any computer. No installation, no IT department approval, no license servers. #### Perfect for Your Coursework **Structural Mechanics** - Visualise shear force and bending moment diagrams - Understand how loads transfer through structures - See deflected shapes under different loads - Verify textbook examples and problem sets **Steel & Concrete Design** - Access real section libraries (W shapes, HSS, angles, etc.) - Calculate section properties accurately - Get member forces for design checks - Model realistic frame behaviour **Finite Element Analysis** - Understand the Direct Stiffness Method hands-on - See how element stiffness matrices combine - Experiment with mesh refinement effects - Build intuition for FEA behaviour #### What You Can Do The free tier gives you everything you need for learning: - Up to 8 nodes per model (plenty for learning) - Full 3D frame analysis - Linear static, P-Delta, and buckling analysis - Thousands of real sections (steel, timber, aluminium) - Save projects locally or to the cloud - Interactive 3D visualisation #### From Classroom to Career The skills you develop with AutoCalcs translate directly to industry software. Understanding structural behaviour, load paths, and FEA fundamentals is universal — the concepts work the same whether you're using AutoCalcs, SAP2000, ETABS, or STAAD. --- ### Why AutoCalcs? The 80/20 Rule of Structural Analysis Source: https://autocalcs.com/why-autocalcs Why pay thousands for features you rarely use? AutoCalcs provides the essential 80% of structural analysis tools for a fraction of the price, with a free tier for smaller models. #### The Problem with Traditional Software For decades, structural engineering software has been dominated by a few giant companies. Their business model: build a massive, all-encompassing suite that can handle every conceivable scenario. The result? Bloated software packages that cost thousands of dollars per year. But the reality is: most engineers only use about 20% of those features. For the vast majority of day-to-day work — designing beams, checking frames, meshing plates, verifying trusses — you don't need a spectral response analyser or a wind tunnel simulator. #### AutoCalcs Approach We built AutoCalcs with a different philosophy. Instead of trying to do everything, we focused on doing the essentials perfectly. | Feature | AutoCalcs | Traditional Software | |---|---|---| | Cost per Year | $0 - $360 | $1,200 - $3,000+ | | Account Required | No Signup | Required | | 3D Frame Modelling | Yes | Yes | | Linear Static Analysis | Yes | Yes | | P-Delta (2nd Order) | Yes | Yes | | Tension/Compression-Only | Yes | Yes | | Buckling / Frequency | No | Yes | | Response Spectrum | No | Yes | #### Zero Friction, Maximum Efficiency You open the URL, and you're modelling. No signup is required to use the full analysis engine. We believe that if the tool is good enough, you'll want to sign up to save your projects — but we won't force you. --- ## Free Calculators & Tools --- ### Free Online Beam Calculator Source: https://autocalcs.com/free-beam-calculator Analyse beams instantly with our free structural analysis tool. Get shear force diagrams, bending moment diagrams, and deflection results in seconds — no signup or download required. #### What Can You Calculate? **Beam Types** — Simply supported beams, cantilever beams, continuous beams, propped cantilevers. **Load Types** — Point loads, distributed loads (UDL), applied moments, multiple load combinations. **Results** — Shear force diagrams, bending moment diagrams, deflection curves, support reactions. **Features** — Real section library, material database, unit conversion, save & share projects. #### How It Works AutoCalcs uses the Direct Stiffness Method (finite element analysis) to solve your beam problems. This means you get accurate results for any configuration — not just the simple cases covered by textbook formulas. 1. Create nodes — Define the points along your beam 2. Add members — Connect nodes with beam elements 3. Apply supports — Pin, roller, or fixed supports 4. Add loads — Point loads, distributed loads, moments 5. Run analysis — Get instant results with diagrams #### Why Choose AutoCalcs? - **Free to use** — Full analysis capabilities at no cost - **No signup required** — Start calculating immediately - **Beyond 1D formulas** — Model beams within full 3D structures - **Professional accuracy** — FEA-based solver, not simplified formulas - **Access anywhere** — Not tied to one computer, just open the web app --- ### Free Online Frame Analysis Software Source: https://autocalcs.com/free-frame-analysis Analyse portal frames, rigid frames, and multi-storey structures with our free structural analysis tool. Full 2D and 3D capability with P-Delta (second-order) effects — no signup or download required. #### Frame Types You Can Analyse **Frame Configurations** — Portal frames (single & multi-bay), multi-storey rigid frames, moment-resisting frames, braced frames. **Analysis Types** — Linear static analysis, P-Delta (2nd order) effects, elastic buckling, sway analysis, multiple load combinations. **Results** — Bending moment diagrams, shear force diagrams, axial force diagrams, deflected shape & sway. **Modelling Features** — Pin & fixed connections, member end releases, real section library, copy & extrude tools. #### 2D and 3D Frame Analysis While many online calculators only handle simple 2D frames, AutoCalcs gives you full 3D capability. Model frames in any orientation, apply loads in any direction, and capture true structural behaviour including out-of-plane effects. #### P-Delta Analysis for Frames Second-order (P-Delta) effects are critical for frames, especially tall or slender structures. AutoCalcs includes P-Delta analysis to capture the additional moments and forces caused by gravity loads acting on the deflected shape. This is included free — no premium tier required. --- ### Free Online Plate Analysis Software Source: https://autocalcs.com/free-plate-analysis Analyse slabs, walls, panels, diaphragms, and mat-style surfaces with browser-based shell finite element analysis. AutoCalcs supports quadrilateral and triangular shell elements, surface pressure loads, plate result contours, and mixed frame-and-plate models - no signup or download required. #### Plate and Shell Elements AutoCalcs uses flat Mindlin-Reissner shell elements with six degrees of freedom at each node. Four-node MITC4 quadrilateral shells and three-node MITC3 triangular shells can be mixed in the same model, so regular slab regions can use quads while irregular areas can use triangles. #### Plate Modelling Features **Shell Elements** - MITC4 quads, MITC3 triangles, membrane action, plate bending, and transverse shear. **Loads and Analysis** - Local normal pressure, global X/Y/Z area loads per plate surface area, plate self-weight from material density, and linear static analysis plus supported modal and buckling workflows. **Results** - Resultant and global displacement contours; bending and twisting moments; transverse shear; membrane normal/shear stresses and forces; maximum/minimum principal moments and membrane stresses; top/bottom-fibre von Mises, Tresca, Bach, and Rankine equivalent stresses; and Wood-Armer concrete design moments. #### Engineering Interpretation Plate FEA gives analysis demands, not automatic final slab detailing. Peaks near columns, supports, openings, re-entrant corners, and beam tie-ins are mesh-sensitive, so design should use engineering judgement, mesh refinement, section-averaged values, or code-specific checks where local punching, one-way shear, or reinforcement detailing governs. --- ### Free Online Truss Calculator Source: https://autocalcs.com/free-truss-calculator Analyse roof trusses, bridge trusses, and structural trusses with our free structural analysis tool. Get member forces, reactions, and deflections in seconds — no signup or download required. #### Truss Types You Can Analyse **Truss Configurations** — Roof trusses (pitched, flat), Warren, Pratt, Howe trusses, bridge trusses, custom truss geometries. **Analysis Features** — Tension/compression-only members, pin-jointed analysis, self-weight calculation, multiple load combinations. **Results** — Axial forces (tension/compression), support reactions, node deflections, deflected shape visualisation. **Modelling Tools** — Quick node placement, copy & mirror tools, section library, member end releases. #### Pin-Jointed Truss Analysis For true truss behaviour where members carry only axial forces, use member end releases to create pin connections at joints. AutoCalcs also supports rigid connections if you need to analyse trusses with moment-carrying joints or check secondary bending effects. #### Tension-Only and Compression-Only Members Real trusses often include members that can only carry tension (cables, rods) or compression (struts that buckle in tension). AutoCalcs supports tension-only and compression-only members, automatically iterating to find which members are active. --- ### Beam Deflection Formulas Source: https://autocalcs.com/beam-deflection-formulas Quick reference for beam deflection equations with an interactive calculator for instant results. #### Understanding Beam Deflection When a beam is loaded, it bends and deflects from its original position. The amount of deflection depends on four factors: - **Load magnitude** — More load means more deflection - **Span length** — Deflection increases dramatically with span (to the 3rd or 4th power) - **Material stiffness (E)** — Higher modulus means less deflection - **Section stiffness (I)** — Higher moment of inertia means less deflection The product EI is called the flexural rigidity and appears in the denominator of all deflection formulas. #### Simply Supported Beam Formulas **Uniformly Distributed Load (UDL)** ``` delta_max = 5wL^4 / (384EI) ``` Maximum deflection occurs at midspan. The coefficient 5/384 is approximately 0.013. **Point Load at Center** ``` delta_max = PL^3 / (48EI) ``` Maximum deflection at midspan under the load. The coefficient 1/48 is approximately 0.021. **Point Load at Any Position** ``` delta_max = Pa^2*b^2 / (3EIL) (at load position) where a + b = L ``` #### Cantilever Beam Formulas **UDL Along Full Length** ``` delta_max = wL^4 / (8EI) ``` Maximum deflection at the free end. Cantilevers deflect about 10x more than simply supported beams for the same load and span. **Point Load at Free End** ``` delta_max = PL^3 / (3EI) ``` Maximum deflection at the free end under the load. #### Fixed-End Beam Formulas **UDL Along Full Length** ``` delta_max = wL^4 / (384EI) ``` Maximum deflection at midspan. 5x smaller than the simply supported case. **Point Load at Center** ``` delta_max = PL^3 / (192EI) ``` Maximum deflection at midspan. 4x smaller than the simply supported case. #### Deflection Limits Ratios such as L/180, L/240, L/360, and L/500 are common references, not universal limits. The governing ratio, span definition, and load component depend on the applicable code, supported construction, and project criteria. Camber does not remove required live-, total-, or incremental-deflection checks. #### Units and Consistency | System | Span (L) | Material (E) | Section (I) | Result (delta) | |---|---|---|---|---| | Metric (mm) | mm | MPa | mm^4 | mm | | Imperial (in) | in | psi (or ksi/1000) | in^4 | in | --- ### Moment of Inertia Calculator Source: https://autocalcs.com/moment-of-inertia-calculator Calculate the second moment of area (moment of inertia) for common cross-sections. Supports solid rectangles, circles, hollow sections, and I-beams. #### What is Moment of Inertia? The moment of inertia (more precisely, the second moment of area) measures how a cross-section's area is distributed relative to an axis. It determines how much a beam will bend under load — the higher the moment of inertia, the stiffer the beam. Engineers use two main axes: the strong axis (typically z-z, giving I_zz) and the weak axis (typically y-y, giving I_yy). #### Formulas Used **Solid Rectangle** ``` I_zz = bh^3/12 I_yy = hb^3/12 A = bh ``` The moment of inertia increases with the cube of the dimension perpendicular to the bending axis — doubling the height increases I_zz by a factor of 8. **Solid Circle** ``` I = pi*d^4/64 A = pi*d^2/4 ``` Both axes have equal moment of inertia. **Hollow Rectangle (RHS/SHS)** ``` I_zz = (BH^3 - bh^3)/12 I_yy = (HB^3 - hb^3)/12 A = BH - bh ``` **Hollow Circle (CHS/Pipe)** ``` I = pi(D^4 - d^4)/64 A = pi(D^2 - d^2)/4 ``` **I-Beam / H-Section** ``` I_zz = (BH^3 - (B-t_w)h_w^3)/12 I_yy = (2*t_f*B^3 + h_w*t_w^3)/12 A = 2*B*t_f + h_w*t_w ``` Where h_w = H - 2*t_f is the web height. #### Why Moment of Inertia Matters The moment of inertia appears in two fundamental beam equations: ``` Bending stress: sigma = My/I Deflection: delta proportional to 1/(EI) ``` Higher I means lower stress for the same moment, and less deflection for the same load. --- ### Section Properties Calculator Source: https://autocalcs.com/section-properties-calculator Calculate geometric properties for common solid, hollow, I, channel, tee, and angle sections: area, centroid, second moments of area, elastic and plastic section moduli, and torsion properties where implemented. #### Section Properties Explained **Area (A)** — The cross-sectional area. Used to calculate axial stress (sigma = P/A) and self-weight. **Moment of Inertia (I_yy, I_zz)** — The second moment of area about the principal axes. I_zz is typically the strong axis, while I_yy is the weak axis. These determine bending stiffness and stress distribution. **Torsion Constant (J)** — The Saint-Venant torsion constant. Closed thin-walled sections generally have much larger J than comparable open sections. Open-section response may also require warping and member-stability checks; J alone is not a buckling resistance. **Section Modulus (S_yy, S_zz)** — The elastic section modulus, calculated as I/c where c is the distance to the extreme fibre. Used to find bending stress: sigma = M/S. **Centroid (C_y, C_z)** — The location of the geometric centre of the section. #### Supported Section Types **Open Sections** — I-Beam / H-Section (UB, UC, W), Channel (C, PFC, MC), Angle (L, EA, UA), Tee (T, cut from UB) **Closed & Solid Sections** — Hollow Rectangle (RHS, SHS), Hollow Circle (CHS, Pipe), Solid Rectangle (Flat bar), Solid Circle (Round bar) #### Notes on Accuracy This calculator uses closed-form geometry routines. Optional radii feed the implemented fillet contributions for I, channel, tee, and angle sections and the rounded-rectangle decomposition for hollow rectangles. Open-section J remains a thin-wall approximation; compare design-critical properties with a current supplier catalogue or validated section analysis. --- ### Von Mises Stress Calculator Source: https://autocalcs.com/von-mises-stress-calculator Free online calculator for von Mises equivalent stress from a 3D stress state (sigma_x, sigma_y, sigma_z, tau_xy, tau_yz, tau_zx) or from plane stress (sigma_x, sigma_y, tau_xy). Optionally enter a yield strength to get material-point yield utilisation and its inverse yield margin. Also reports Tresca equivalent stress and the three principal stresses. No signup required. #### When to Use Von Mises Use von Mises equivalent stress to compare a general 3D stress state at a point to a single yield strength for a suitable ductile material. It is widely used in FEA post-processing for combined normal and shear stresses, but this material-point comparison is not a complete member or code design check. #### Key Formulas (3D) ``` sigma_vm = sqrt(0.5 * [(sx-sy)^2 + (sy-sz)^2 + (sz-sx)^2 + 6*(txy^2 + tyz^2 + tzx^2)]) ``` For plane stress (sz = tyz = tzx = 0): ``` sigma_vm = sqrt(sx^2 - sx*sy + sy^2 + 3*txy^2) ``` Utilisation (if Fy given): sigma_vm / Fy. Inverse yield margin: Fy / sigma_vm. The latter is not an overall structural factor of safety. --- ### Principal Stress & Mohr's Circle Calculator Source: https://autocalcs.com/principal-stress-calculator Free plane-stress calculator. Enter sigma_x, sigma_y, and tau_xy to obtain principal stresses sigma_1 and sigma_2, maximum in-plane shear tau_max, principal angle theta_p, and a drawn Mohr's circle. Useful for stress transformation, interpreting suitable maximum-principal-stress criteria, and understanding combined normal and shear stress at a point. It does not perform a complete failure or code check. No signup required. #### Principal Stresses (2D) For a plane stress element: ``` sigma_1,2 = (sigma_x + sigma_y)/2 +/- sqrt(((sigma_x - sigma_y)/2)^2 + tau_xy^2) tau_max = (sigma_1 - sigma_2)/2 ``` The principal angle theta_p rotates the stress element so shear on the transformed faces is zero. #### Mohr's Circle Mohr's circle plots normal stress on the horizontal axis and shear stress on the vertical axis. The centre is at ((sigma_x + sigma_y)/2, 0) and the radius is tau_max. sigma_1 and sigma_2 are the circle intercepts on the normal-stress axis. --- ### Flat Plate Deflection & Stress Calculator Source: https://autocalcs.com/plate-deflection-calculator Free calculator for maximum deflection and a governing bending-stress magnitude in idealised thin rectangular and circular flat plates under uniform pressure, total load on the plate, or a central point load. Edge conditions include all edges simply supported, all edges fixed (clamped), and rectangular plates with two opposite edges fixed. The rectangular coefficient tables use Poisson's ratio nu = 0.3; circular and fixed-strip equations use the entered value. Metric (mm, MPa) and imperial (in, ksi) units. No signup required. #### Supported Cases **Rectangular plates** — Short span b, long span a, thickness t, elastic modulus E. Uniform pressure q or total load; central point load P. **Circular plates** — Radius a, thickness t. Uniform pressure or central point load. Simply supported or clamped boundary. #### Typical Deflection Form (Uniform Pressure, Rectangular SS) ``` w_max = alpha * q * b^4 / (E * t^3) ``` where alpha depends on aspect ratio a/b (Roark Table 11.4). Bending stress uses beta coefficients: sigma = beta * q * b^2 / t^2. #### Notes Results are for thin-plate theory (small deflection, linear elastic). Thick plates and large deflections are outside scope. For shells and plates in a full 3D model, use AutoCalcs Structural FEA. --- ### Beam Load Calculator (Preliminary) Source: https://autocalcs.com/beam-load-capacity-calculator Estimate a preliminary load limit for one idealised beam and load case. The result is the lower of a 0.6F_y elastic bending-stress screen and a user-selected deflection-ratio screen. It is not a code design capacity or safe working load. #### How the Screening Limit Is Calculated The page evaluates two simplified criteria: - **Bending-stress screen** — Elastic section stress reaches 0.6F_y - **Deflection screen** — Elastic deflection reaches the selected span ratio The lower value controls the calculator output. That does not establish adequacy of the member, restraints, connections, or load combinations. #### Bending-Stress Screen The maximum bending stress in a beam is: ``` sigma = M / S ``` Where M is the idealised bending moment and S is the elastic section modulus. For a simply supported beam with UDL, the corresponding screened load is: ``` w_screen = 8 * F_b * S / L^2 ``` #### Deflection Screen Working backwards from the deflection formula: ``` delta_max = 5wL^4 / (384EI) <= L/360 ``` Rearranging for the corresponding screened load: ``` w_screen = 384 * E * I / (5 * L^3 * 360) ``` #### Input Values **Section Modulus (S)** — The elastic section modulus. For symmetric sections, S = I / (h/2). **Yield Stress (F_y)** — Enter the specified, thickness-dependent value for the actual product. The calculator uses 0.6F_y only as a transparent yielding screen, not as a complete ASD, LRFD, or other code resistance. #### Important Limitations This calculator does not check lateral-torsional or local buckling, section slenderness, plasticity, shear, web crippling, connections, bearing, load combinations, or code factors. Do not use its output as an allowable load or design capacity. --- ### Tributary Width Calculator Source: https://autocalcs.com/tributary-width-calculator Convert floor, roof, wind, or snow area loads into equivalent beam line loads. Enter either a direct tributary width or the spacing to adjacent beams. #### Area Load to Line Load ``` line load = area load * tributary width ``` In metric units, kPa is kN/m^2, so multiplying by metres gives kN/m. In imperial units, psf multiplied by feet gives lb/ft. #### Scope The calculator is intended for simple one-way tributary loading checks. It can also calculate equivalent total load and simple-span reactions for uniform or tapered tributary widths. Complex framing, openings, two-way slab action, transfer systems, and diaphragm behaviour require engineering judgement and, where appropriate, a full structural analysis model. --- ### Load Combination Calculator Source: https://autocalcs.com/load-combination-generator Check scalar structural load-combination forms for AS/NZS 1170, ASCE 7-22, Eurocode 0, and NBCC from nominal dead, live, snow, wind, seismic, and related load effects. #### How It Works Enter unfactored load effects for each load type. Values can be forces, line loads, reactions, shears, or moments, provided every value uses a consistent unit family. The calculator evaluates the same scalar load-combination templates exposed by the AutoCalcs 3D FEA load-combination wizard. #### Scope This page is a standalone scalar combination helper, not a complete project-specific code engine. It does not resolve project-specific reductions, occupancy exceptions, notional loads, flood, construction-stage loads, overstrength combinations, serviceability drift combinations, or other special requirements. For a full frame or structure, individual load cases should be analysed in the model before combinations are enveloped. --- ### Structural Unit Converter Source: https://autocalcs.com/structural-unit-converter Convert between metric and imperial units used in structural engineering. Covers 11 categories: length, force, stress/pressure, moment, area, volume, moment of inertia, section modulus, distributed load, mass, and temperature. #### Why Unit Conversion Matters Metric/imperial confusion is a real source of engineering errors. Getting conversions wrong can lead to member mis-sizing, especially on international projects where drawings may mix unit systems. #### Common Structural Engineering Conversions | From | To | Factor | |---|---|---| | in | mm | 25.4 | | ft | m | 0.3048 | | kip | kN | 4.4482 | | ksi | MPa | 6.895 | | in² | mm² | 645.16 | | in⁴ | mm⁴ | 416,231 | | kip·ft | kN·m | 1.3558 | | lb/ft | kN/m | 0.01459 | | psi | kPa | 6.895 | | °F | °C | (°F − 32) × 5/9 | --- ### Young's Modulus Calculator Source: https://autocalcs.com/youngs-modulus-calculator Calculate Young's modulus (E) from experimental stress-strain data or force/deformation measurements. The nearest listed modulus is shown for comparison only; modulus alone cannot identify a material or grade. #### What is Young's Modulus? Young's modulus (E) measures a material's stiffness in the linear elastic region. It is the ratio of stress to strain: ``` E = σ / ε = (F/A) / (ΔL/L₀) ``` Higher E means less deflection under the same load. Deflection is inversely proportional to the flexural rigidity EI. #### Input Modes **Stress & Strain** — Enter stress (σ) and strain (ε) directly. **Force & Deformation** — Enter applied force (F), cross-sectional area (A), change in length (ΔL), and original length (L₀). The calculator converts to stress and strain internally. Supports metric (kN, mm², MPa) and imperial (kip, in², ksi) units. #### Common Values for Structural Materials | Material | E (GPa) | E (ksi) | Indicative Strength | Density (kg/m³) | |---|---|---|---|---| | Structural Steel | 200 | 29,000 | 250–450 MPa | 7,850 | | Stainless Steel | 193 | 28,000 | 170–1,000 MPa | 7,700–8,000 | | Aluminum (6061-T6) | 68.9 | 10,000 | 240–280 MPa | 2,700 | | Aluminum (general) | 70 | 10,153 | 35–500 MPa | 2,700 | | Concrete (normal) | 30 | 4,351 | 20–50 MPa (f'c) | 2,400 | | Concrete (high strength) | 40 | 5,802 | 50–100 MPa (f'c) | 2,500 | | Timber (softwood) | 11 | 1,595 | 20–40 MPa | 500 | | Timber (hardwood) | 16 | 2,321 | 40–80 MPa | 700 | | Cast Iron (gray) | 110 | 15,954 | 130–300 MPa | 7,200 | | Copper | 117 | 16,969 | 70–220 MPa | 8,940 | | Glass | 70 | 10,153 | 30–70 MPa (tensile) | 2,500 | | Carbon Fibre (CFRP) | 150 | 21,756 | 1,500–3,500 MPa | 1,600 | Strength bases vary by material and are broad context only; they are not directly comparable and cannot be inferred from E. --- ### Effective Length Factor (K) Calculator Source: https://autocalcs.com/effective-length-factor-calculator Calculate column effective length factor K using the alignment chart (nomograph) method. Supports both braced (non-sway) and sway (unbraced) frames. #### What is the Effective Length Factor? The effective length factor K relates a column's actual length to the length of an equivalent pin-ended column with the same buckling load: ``` P_cr = π²EI / (KL)² ``` K < 1 means the column is more restrained than a pin-ended column. K > 1 means it is less restrained. For braced frames K ranges from 0.5 to 1.0. For sway frames K ranges from 1.0 upwards. #### The Alignment Chart Method The stiffness ratio G at each end of the column is: ``` G = Σ(EI/L)_columns / Σ(EI/L)_beams ``` G = 0 represents a fixed end. G = ∞ represents a pinned end (AISC recommends G = 10 for practical pinned bases). The calculator solves the underlying transcendental equations numerically (bisection, 50 iterations) to give exact K values rather than graphical approximations. #### Input Modes **Direct G** — Enter G_A and G_B directly. Quick-set buttons for fixed (G = 0) and pinned (G = 10). **From Stiffness** — Input Σ(I/L) for columns and beams at each joint. The calculator computes G automatically. #### Braced vs Sway Frames **Braced frames** have lateral support from shear walls, bracing, or other stiff elements. Joints cannot translate laterally. K ≤ 1.0. **Sway frames** allow lateral translation at joints. No external lateral restraint. K ≥ 1.0. #### Code References - AISC Steel Construction Manual - Table C-A-7.1 - AS 4100:2020 - Clause 4.6 - Eurocode 3 - Annex E (informative) - CSA S16:19 - Clause 10.1.3 --- ### Euler Buckling Calculator (Column Critical Load) Source: https://autocalcs.com/column-buckling-calculator Client-side Euler critical-load calculator for one idealised, straight, prismatic column under concentric axial compression. Not a design-code capacity check and not a substitute for frame eigenvalue buckling in Structural FEA. #### Formula ``` Pcr = pi^2 * E * I / (K * L)^2 ``` Pass effective length KL into the standard Euler expression. Use Imin (governing weaker axis). Metric and imperial units are supported. #### Ideal theoretical K factors | End condition | Theoretical K | |---|---| | Fixed-fixed | 0.5 | | Fixed-pinned | 0.699 | | Pinned-pinned | 1.0 | | Fixed-free (cantilever) | 2.0 | | Custom | user value | These are ideal textbook restraints. Real frames need alignment-chart or FEA-based K factors. #### Optional screening - Radius of gyration r = sqrt(I/A) - Effective slenderness KL/r - Euler critical stress Fe = Pcr/A = pi^2 E / (KL/r)^2 - Comparison of Fe to Fy (flags when elastic Euler is not appropriate; does not compute inelastic capacity) - Applied load ratio P/Pcr as a neutral screening ratio (not pass/fail) #### Product boundary Does not perform eigenvalue/frame buckling, matrix stiffness analysis, Johnson/Perry/AISC/AS4100/EC3/CSA column curves, local or torsional buckling, or section-library integration. Use Structural FEA for multi-member frames, flexible restraints, critical load factors, and animated buckling modes. --- ### Steel Weight Calculator Source: https://autocalcs.com/steel-weight-calculator Calculate nominal steel mass from section unit mass, member length, and quantity. Supports kg/m with metre lengths or lb/ft with foot lengths, plus multiple-item totals. Reference entries are separated by metric and US designation system. In every table row, kg/m and lb/ft are conversions of the same physical section; the calculator does not present unlike catalogue sections as equivalents. Custom mass and length inputs are converted and preserved when the unit system changes. Mass = Unit Mass × Length × Quantity Published section masses and delivered tolerances must be confirmed against the current supplier or project catalogue before design or procurement. --- ### Embodied Carbon Calculator (Structural Members) Source: https://autocalcs.com/embodied-carbon-calculator Estimate product-stage A1–A3 embodied carbon (kgCO₂e) from member length, unit mass, and generic or project-specific emission factors. This is a cradle-to-gate subtotal, not a whole-life carbon assessment. #### What is Embodied Carbon? Embodied carbon spans greenhouse-gas emissions associated with materials and construction across defined lifecycle modules. This calculator covers A1–A3 only: raw-material supply, transport to manufacturing, and manufacturing. #### How the Calculation Works ``` kgCO₂e = Length (m) × Unit Mass (kg/m) × Carbon Coefficient (kgCO₂e/kg) ``` For example, a 6 m long 610UB125 (125 kg/m) using global-average structural steel (1.58 kgCO₂e/kg): 6 × 125 × 1.58 = 1,185 kgCO₂e. #### Carbon Coefficients (A1–A3) Indicative dated reference factors from IStructE *How to Calculate Embodied Carbon* (2nd ed., 2022), Table 2.3, including regional defaults, product values, and the explicitly labelled UK EAF typical lower bound. IStructE published a third edition in 2025; the built-in numbers remain tied to the verified 2022 table and are for preliminary estimating only. Use current guidance and project EPDs for formal reporting: | Material | kgCO₂e/kg | Source | |---|---|---| | Structural steel — open sections, global avg | 1.58 | IStructE HTCEC Table 2.3 | | Structural steel — UK open sections (consumption avg) | 1.74 | IStructE HTCEC Table 2.3 | | Structural steel — UK EAF open sections, typical lower bound | 0.567 | IStructE HTCEC Table 2.3 | | Steel hollow / closed sections (RHS, SHS, CHS) | 2.50 | IStructE HTCEC Table 2.3 | | Steel plate | 2.45 | IStructE HTCEC Table 2.3 | | Concrete — C32/40 global avg | 0.175 | IStructE HTCEC Table 2.3 | | Timber — sawn softwood (excl. sequestration) | 0.263 | IStructE HTCEC Table 2.3 | | Timber — glulam, global (excl. sequestration) | 0.512 | IStructE HTCEC Table 2.3 | | Timber — LVL (excl. sequestration) | 0.390 | IStructE HTCEC Table 2.3 | | Aluminium — worldwide extruded (31% recycled) | 13.2 | IStructE HTCEC Table 2.3 | | Aluminium — European extruded (31% recycled) | 6.83 | IStructE HTCEC Table 2.3 | Custom coefficients can be entered for project-specific EPD data. #### Lifecycle Stages (EN 15978) | Stage | Description | Included? | |---|---|---| | A1–A3 | Raw material supply, transport, manufacturing | Yes | | A4–A5 | Transport to site, construction | No | | B1–B7 | Use, maintenance, repair, replacement | No | | C1–C4 | Demolition, transport, waste processing, disposal | No | | D | Benefits beyond system boundary (reuse/recycling) | No | #### Comparing with Project Targets The result is an A1–A3 member subtotal in kgCO₂e. It omits floor-area normalization, unentered building elements, A4 and later modules, and the rules behind any external benchmark. Compare only after matching lifecycle modules, element scope, area basis, geography, and the current framework version. Results are preliminary estimates only. Formal reporting (BREEAM, LEED, whole-life carbon assessments) requires project-specific EPDs reviewed by a sustainability engineer. --- ## FAQs --- ### Frequently Asked Questions Source: https://autocalcs.com/faqs #### General **What is AutoCalcs?** AutoCalcs is a free, browser-based structural analysis tool for beams, frames, plates, and trusses. It allows you to create 3D models with members and quadrilateral or triangular plate elements, apply loads and supports, and analyse structures for internal forces, reactions, and deflections — all from your browser with no installation required. **Do I need to install anything?** No. AutoCalcs is 100% cloud-based and runs entirely in your web browser. There's nothing to download or install, and you can access your projects from any device. You can optionally install AutoCalcs as a PWA (Progressive Web App) for a more native app-like experience. **What browsers are supported?** AutoCalcs works best on modern browsers including Chrome, Firefox, Safari, and Edge. We recommend using the latest version of your preferred browser. **Is my data secure?** Yes. Your data is stored securely on our servers with encryption. We use industry-standard security practices to protect your information and project data. #### Account **How do I create an account?** Click the "Get Started" or "Sign In" button on the homepage. You can create an account using your email address or sign in with Google or other supported providers. **Can I change my email address?** Yes. You can update your email address and other account details through your account settings after signing in. **How do I reset my password?** Click "Sign In" and then select "Forgot password?" to receive a password reset link via email. #### Pricing & Billing **Is AutoCalcs free?** Yes. You can use AutoCalcs completely for free without an account (up to 2 analysis runs per day). Sign up for a free account to get 5 runs per day, 20 cloud-saved projects, and settings sync. All free users are subject to an 8-node limit per model. Unchanged official sample models are exempt. Pro users get unlimited nodes, runs, cloud storage, and PDF and Excel analysis report exports. **What payment methods do you accept?** We accept all major credit cards including Visa, Mastercard, and American Express. Payments are processed securely through our payment provider. **Can I cancel my subscription?** Yes. You can cancel your subscription at any time from your account settings. You'll continue to have access until the end of your current billing period. **Do you offer refunds?** Refunds are handled on a case-by-case basis. Please contact us at admin@autocalcs.com if you have concerns about your subscription. #### Features & Usage **What types of analysis can I perform?** AutoCalcs supports linear static analysis, P-Delta (second-order) analysis, elastic buckling analysis, and tension/compression-only member analysis. You can view results including bending moments, shear forces, axial forces, torsion, reactions, and deflected shapes. **Can I import existing models?** Currently, models are created directly within AutoCalcs using our intuitive 3D modelling tools including draw, copy, extrude, and mirror commands. Import functionality for CAD files is planned for future releases. **How do I save my work?** Without an account, your projects are saved locally in your browser storage. When signed in, projects can be saved to the cloud so you can access them from any device. **Is there a limit on the number of projects?** Free users can save up to 20 projects in cloud storage, plus unlimited projects in local browser storage. Pro users have unlimited cloud storage. **Can I share my projects with others?** Yes. Save the model to the cloud, then use Share in the Structural FEA ribbon to create a link. Recipients open the link and clone a full independent copy into their workspace (sign-in required). The owner's project is unchanged. JSON export remains available for offline backup. #### Technical **What analysis engine does AutoCalcs Structural FEA use?** We use Pynite, an open-source finite element analysis library. **What element types are supported?** AutoCalcs supports 3D beam/frame elements for modelling beams, columns, braces, and truss members. You can assign materials, cross-sections from our library, and define member end releases for pin connections. **What modelling tools are available?** AutoCalcs provides comprehensive modelling tools including node and member creation, copy, extrude, mirror, and split commands. Smart snapping features (axis, grid, and inference snapping) help ensure accurate geometry. #### Troubleshooting **I've found an issue or something isn't working correctly** First, try refreshing the page. If that doesn't help, try a hard refresh (Ctrl+Shift+R on Windows/Linux, Cmd+Shift+R on Mac) to clear the cache. If the issue persists, please contact us at admin@autocalcs.com with details about the problem. --- ## RC Section Analyser Source: https://autocalcs.com/rc-section-analyser Documentation: https://autocalcs.com/documentation/rc-section-analyser The RC Section Analyser is a standalone reinforced-concrete section analysis tool for rectangular, tee, and solid circular sections with longitudinal reinforcement. Define section dimensions, clear cover, tie diameter, bar sizes and counts, concrete and steel material properties, axial force, and bending moments. Metric and imperial display units are independent of the reinforcement catalogue. Results include gross and transformed section properties, nominal axial force-moment (P-M) interaction, a biaxial response boundary at the entered axial force, elastic stress extrema, and nonlinear moment-curvature response. Selected moment-curvature points can be inspected for strain and stress distributions. Mx is bending about the horizontal x-x axis and My about the vertical y-y axis; positive Mx compresses the top and positive My compresses the right side. An optional neutral-axis angle is measured counter-clockwise from the horizontal axis. Results are nominal and unfactored. This is section analysis, not a member design-code check or compliance certificate. It does not establish member stability, shear or torsion resistance, or design-code detailing compliance. Nonlinear section response does not imply support for global material-nonlinear FEA. The cracked service-steel stress estimate assumes zero service axial force and a compatible primary-axis orientation; estimates beyond steel yield are explicitly warned as outside the elastic model. Analysis requires sign-in. Free accounts receive 2 RC solves per UTC day; Pro includes unlimited RC solves and PDF reporting. Selected-state inspections consume RC solves as well. Consult the guide for supported inputs, result availability, and scope limitations. ## Custom Section Builder Source: https://autocalcs.com/custom-section-builder Documentation: https://autocalcs.com/documentation/custom-section-builder AutoCalcs Custom Section Builder is a browser-based tool for creating and calculating custom structural cross-sections. Start from a blank canvas, a standard library section, or a DXF profile. ### Creating and Editing Sections - Draw freeform solid profiles by placing points. - Draw thin-walled profiles from a centreline, thickness, and inside radius. - Create solid circles and freeform or circular openings. - Join multiple shapes into one connected built-up section. - Import a standard section as editable geometry or import a closed 2D DXF profile. - Edit vertices, edges, dimensions, corner radii, orientation, and scale with undo and redo. ### Calculated Results For a valid closed and connected section, the builder calculates area, centroid, second moments of area, principal axes, section moduli, torsion, shear, and warping properties. The centroid is read-only because it is calculated from the geometry. Property calculation requires sign-in. Free accounts receive a limited number of calculations per day. Pro users can apply actions, inspect section stress contours, export a PDF report, and save editable sections to the cloud. ### Structural FEA Integration and Limits Saved drawn sections appear in the Structural FEA section library for Pro users and can be assigned to members for structural analysis. Drawn sections are not supported by design code checks. The builder models one homogeneous material rather than composite or multi-material construction, and its stress contours are section review results rather than design-code checks. --- ## Steel Design Calculators AutoCalcs provides free steel design calculators for major international design codes. Each calculator checks a steel member against the relevant standard for classification, axial capacity (tension/compression), bending (including lateral-torsional buckling), shear, and combined interaction checks. ### AISC 360-16 Design Calculator Source: https://autocalcs.com/aisc-360-16-design-calculator Steel member design per AISC 360-16 with LRFD and ASD methods. Supports W-shapes, HSS (rectangular and round), CHS, angles, channels, and tees. Checks include classification (Table B4.1), tension (Ch. D), compression with flexural and flexural-torsional buckling (Ch. E), flexure with LTB (Ch. F), shear (Ch. G), and combined interaction (Ch. H). Checked against 78 verification cases from AISC Design Examples v15.0 with 0.15% average difference. ### AISC 360-22 Design Calculator Source: https://autocalcs.com/aisc-360-22-design-calculator Steel member design per AISC 360-22 with LRFD and ASD methods. Supports W-shapes, HSS (rectangular and round), CHS, angles, channels, and tees. Checks include classification (Table B4.1), tension (Ch. D), compression with flexural and flexural-torsional buckling (Ch. E), flexure with LTB and 360-22 local buckling updates (Ch. F), shear (Ch. G), closed-HSS torsion, and combined interaction (Ch. H). Checked against 42 verification cases from AISC Manual Companion v16.0 with 0.35% average difference. ### EC3 Eurocode 3 Design Calculator Source: https://autocalcs.com/ec3-design-calculator Steel member design per EN 1993-1-1 (Eurocode 3). Supports I-shapes, channels, RHS, SHS, CHS, tees, and angles within family-specific applicability limits. Checks include station-based cross-section classification (Classes 1-4), resistance checks (6.2), flexural buckling (6.3.1), lateral-torsional buckling with Mcr (6.3.2), and combined stability via Annex B (6.3.3). For I/H, channels, and RHS/SHS, signed concurrent N, My, and Mz are evaluated at real stations; internal-part Class 3 limits use the elastic plate-edge stress ratio. Supported Class 4 component paths use EN 1993-1-5 pure-compression or pure-bending effective properties. When a Class 4 member has concurrent axial-flexural or biaxial demand and load-state-consistent effective properties are unavailable, the engine returns INCOMPLETE, retains independent component rows, and suppresses 6.2.9/6.3.3. Tee/angle compression may use effective area, but Class 4 tee/angle bending is not implemented and returns INCOMPLETE without gross-modulus bending, LTB, or dependent interaction results. Class 4 CHS shell resistance is OUT_OF_SCOPE. Verified against 126 benchmark cases from SCI P364, Designers' Guide to EN 1993-1-1, and EUR 22898 EN with 0.43% average difference. ### AS4100 Design Calculator Source: https://autocalcs.com/as4100-design-calculator Steel member design per AS 4100:2020 (Australian Standard). Supports UB, UC, CHS, SHS, RHS, angles, tees, and channels. Checks include section classification (compact/non-compact/slender), section moment capacity (Cl. 5.2), member moment capacity with LTB (Cl. 5.6), compression with flexural buckling (Cl. 6.3), tension (Cl. 7.2), shear (Cl. 5.11), local bearing (Cl. 5.13), and combined actions (Cl. 8). Verified against 60 benchmark cases from Steel Structures Sample Worked Problems, Kirke/Al-Jamel Design Manual, ASI/ATM Design Capacity Tables, and independent benchmark cases with 0.17% average difference. ### CSA S16-19 Design Calculator Source: https://autocalcs.com/csa-s16-design-calculator Steel member design per CSA S16:19 (Canadian Standard). Supports W-shapes, HSS, CHS, angles, channels, and tees. Checks include classification (Table 2, Classes 1-4), compression with flexural and flexural-torsional buckling (Cl. 13.3), tension with shear lag (Cl. 13.2), bending with LTB (Cl. 13.5/13.6), shear (Cl. 13.4), and combined axial + bending interaction (Cl. 13.8/13.9). Verified against 50 benchmark cases from S-FRAME, STAAD.Pro, and Kulak & Grondin textbook with 0.16% average difference. --- ## Pricing --- ### Pricing Source: https://autocalcs.com/pricing Choose the plan that works best for you. AutoCalcs offers free and Pro tiers. You can toggle between Monthly and Annual (25% discount) billing on the Pro plan. All prices are in USD.