Tutorial 5 of 7 · Intermediate · about 25 minutes

Plates and shells: slabs and walls

Beams and columns are members; slabs, walls, mats and tanks are surfaces. This tutorial adds a concrete slab and a shear wall to a frame as plate and shell elements, meshes them, loads the slab, and reads deflections, plate contours and the total forces across a section cut.

1. Draw the slab #

1. On the Home tab, pick the Plate tool.
2. Click the four corners of a bay at Level 2. A plate appears between the beams.
3. In the properties panel, give it a thickness (8 inches) and a concrete material (4,000 psi normal-weight concrete).
4. Choose the behavior: plate bending only, membrane only, or a full shell with both. A floor slab that also acts as a diaphragm is a shell.

2. Mesh it #

A plate is analysed as many smaller elements. Select the plate and set the mesh size, or the number of divisions along each side. The mesh is made so the plate's nodes meet the beams' nodes, so the slab and the frame work together.

Finer meshes give more accurate stresses at the cost of a longer run; the tutorial model is small enough for a fine mesh. Large models run on the server's graphics processor automatically when that is faster.

3. Draw a shear wall #

1. Pick the Plate tool again and click the four corners of a wall between two columns, from the base to Level 2.
2. Give it a thickness of 10 inches and the same concrete, as a shell.
3. Fix the nodes along the base of the wall with the Support tool.

4. Load the slab #

Select the slab and apply an Area load directly to its plates: 100 psf of dead load and 50 psf of live load, each in its own case. A pressure on plates acts on the plates themselves, rather than being spread to the beams.

5. Run and read the plate results #

1. Run the analysis.
2. Deformed shape shows the slab sagging between the beams.
3. Plate contours colors the plates by the result you pick: deflection, bending moments in each direction, membrane forces, or stresses at the top or bottom face. Hover the slab for the value at any point.
4. The contour legend shows the range and the units.

6. Total forces in the wall: section cuts #

For the wall, the useful numbers are the total shear, axial force and moment it carries:

1. On the Results tab, click Section cut.
2. Draw the cut across the base of the wall.
3. ILX Structures adds up the forces of every element crossing the cut and reports the wall's total shear, axial force and in-plane moment for each case and combination: the forces you design the wall for.

7. Design the wall #

On the Design tab, define the wall panel from its plates and design it to ACI 318-19 with the forces from its section cut: shear strength, axial load and moment, and the reinforcement ratios.

Going further #

• Solids: thick parts and local stress studies, with the solid elements under Solid FEM, axisymmetric, thermal on the Advanced tab.
• Imported meshes: Gmsh, Abaqus and UNV meshes from Contact, material NL, GPU, import mesh.

Screens in the app may differ slightly from the words here as the app gains features; the steps stay the same. Questions: services@ilxstudio.com.