Loads and combinations
Load cases #
Loads ▸ Load cases adds, renames and deletes cases. Each case has a type (Dead, Live, Roof Live, Snow, Rain, Wind, Seismic, Earth, Fluid, Other) and a short code (D, L, Lr, S, R, W, E, H, F, T, SW). The combination generator uses the type, so set it correctly. The active case (Loads tab) receives the loads you apply and is drawn in the view.
Applying loads #
| Load | How |
|---|---|
| Nodal load | Fx, Fy, Fz, Mx, My, Mz on the selected nodes. |
| Distributed load | Uniform or trapezoidal (w1, w2) on the selected members, full length or from a to b, in global X / Y / Z or member local x / y / z, optionally per projected length. |
| Point load on member | P at distance a from end i, global or local direction. |
| Area load | A pressure on plates (normal or global direction) or on members with a tributary width. |
| Self-weight | Member (and plate) weight from the material density × factor, in a Dead case. |
The Loads table lists every load with how it reaches the engine. Gravity is −Z: a downward load is a negative Fz or wz.
Environmental load generators #
Loads ▸ Environment and the Seismic tab generate ASCE 7-22 loads onto the story levels:
- Wind (Ch. 26 and 27, directional procedure): V, exposure, Kd, Kzt, Ke, enclosure / GCpi, G, plan dimensions, roof slope; story forces and the Fig. 27.3-8 load cases.
- Snow (Ch. 7): ground snow load, exposure, thermal and importance factors, slope; balanced, unbalanced, drift and sliding snow.
- Seismic ELF (Ch. 11 and 12): Ss, S1, site class, R, Ie, Cd, Ω0, period, seismic weight, vertical distribution, irregularities and ρ.
Combinations #
Loads ▸ Generate ASCE 7-22 LRFD (§2.3) or ASD (§2.4) builds the combinations from the model's case types, with the options of §2.3.1 (companion live factor f1 0.5 or 1.0), Ev = 0.2SDS·D, ρ and reversed lateral loads. The Combinations editor adds, edits and deletes rows (one factor per case). Each combination carries its method (LRFD or ASD); the steel design uses the LRFD combinations.
Results are shown per load case (unfactored), per combination, or as the envelope of all combinations.