Load Cases

A load case defines how loads are to be applied to the structure (e.g., statically or dynamically), how the structure responds (e.g., linearly or nonlinearly), and how the analysis is to be performed (e.g., modally or by direct-integration).

Any load case type can be used when analyzing a bridge model. For seismic analysis, static, response spectrum, and time history load case types are useful. Pushover analysis can be performed using a nonlinear static load case. Stage construction analysis is also performed using nonlinear static load cases.

There are serval analysis options that are specialized for analysis of vehicle live loads. Moving load load cases compute influences line for various quantities and solve all permutations of lane loading to obtain the maximum and minimum response quantities.

Multi-step static and multi-step dynamic (direct integration time history) load cases can be used to analyze one or more vehicles moving across the bridge at a specified speed. These multi-step load cases are defined using special bridge live load patterns that define the direction, starting time, and speed of vehicles moving along lanes (see Step 11).

Use the Analysis > Type > New command, or on the Bridge Wizard select the Load Cases item and click the Define/Show Load Cases button, to access the Define Load Cases form and add, modify, or delete cases.