Plate Loads
Plate pressures are surface loads on quadrilateral or triangular plate elements: slab area loads, wall and tank pressures, roof pressures and similar.
Uniform and Linear Pressure
Uniform pressure applies one magnitude to a plate group or to individual plate elements. Linear ramp varies from a start pressure to an end pressure across a plate group.
Linear ramps require a Plate Group because the group geometry defines the variation axes. Individual elements take Uniform pressure only.
Adding plate loads
- Open the Applied Loads dialog on the Plate Pressure tab: click Loads in the ribbon, or select plates and right-click Plate Pressure Loads (or use Plate Pressure in the Loads section of the Properties panel) to pre-fill the selected elements.
- Select a load case and either a Plate Group or individual Element(s).
- Choose Uniform and enter Magnitude, or choose Linear ramp and enter Start pressure, End pressure and Varies along.
- Select the Direction.
Properties
| Field | Description |
|---|---|
| Case | Load case ID, e.g. 1 |
| Plate Group | A meshed plate group; the pressure is applied to every tile in it |
| Element(s) | Individual plate element IDs, as a range or list (12-20, 12,15,18). Disabled when a Plate Group is selected. |
| Distribution | Uniform, or Linear ramp (Plate Group only) |
| Magnitude | Uniform pressure in the current pressure unit (e.g. kPa, psf) |
| Start / End pressure | Pressures at the two ends of a Linear ramp |
| Varies along | Group local x or local y axis along which the ramp varies |
| Direction | Local z (normal), Global X, Global Y or Global Z |
Use a Plate Group to load a whole slab, wall, tank or panel, or for any ramp; use Element(s) for uniform pressure on selected tiles only.
Ramp axes
A Linear ramp follows q(s) = q_start + (q_end − q_start)s, where q is pressure intensity in the current pressure unit, q_start and q_end are the Start pressure and End pressure, and s runs from 0 to 1 along the selected group axis. The axis sets magnitude only and is independent of load Direction.
- Planar groups: Local x and local y follow the shell-axis arrows displayed on the model. The ramp runs from Start pressure on the negative side of the selected axis to End pressure on its positive side.
- Cylinder walls: local x runs circumferentially from the start-angle seam in the increasing-angle direction; local y runs base to top.
- Cylinder floor/roof caps: local y runs centre to rim. Local x uses the increasing-angle direction on the floor and decreasing-angle direction on the roof.
- Circular/annular plates: local x runs clockwise from the start-angle seam; local y runs from the centre or inner edge to the outer rim.
- Cone/frustum shells: local x runs from the seam in the increasing-angle direction; local y runs from base to top along the sloping meridian.
On any closed circumferential group, a local-x ramp is not periodic: there is a step at the closing seam from the End pressure back to the Start pressure.
Mesh-Stepped Ramp and Validation
Each tile carries its area-averaged pressure, so a Linear ramp is applied and displayed as uniform bands stepped at the mesh, not as an exact gradient within each element.
- One tile band along the ramp axis cannot represent a ramp and blocks analysis.
- Two or three bands are allowed with a coarse-ramp warning.
Use at least four bands along the ramp axis, and check mesh convergence where the pressure gradient matters.
Direction
- Local z (normal): acts perpendicular to the plate. Positive pressure acts along local +z; on curved surfaces it follows each tile's own normal.
- Global X / Y / Z: acts along the global axis, positive toward the positive axis, per unit of actual (not projected) plate surface area. It is resolved into normal and in-plane components on each plate. Gravity is −Y, so a downward floor load is a negative Global Y pressure.
See Sign Conventions for axis and sign details.
Display, analysis and units
- Pressures display in the load case colour when the Loads display is on with the Distributed load type ticked, at the distributed-load scale (hold
Land scroll to resize). - They act as applied loads in static analysis. Gravity-direction pressures can also contribute mass in modal analysis, according to the selected mass/load pattern.
- Values use the current pressure unit (kPa, Pa, ksf or psf), set in Settings.