How do I run a pseudo-static lateral analysis?

Extended Question: I need to run a pseudo-static lateral analysis in which structural inertia represents the earthquake load. I would like to apply a seismic coefficient to inertia such that lateral force is a fraction of g, and not an acceleration function similar to response spectra or time history. How is this done?

Answer: Pseudo-static seismic load may be assigned by applying a gravity load in the lateral direction. This is done as follows:

  1. Define a separate load pattern, perhaps named Inertia.
  2. Select Assign > Frame Loads or Area Loads or Solid Loads > Gravity, then assign the load pattern with gravity multipliers in the Global X or Y direction.
  3. Specify a self-weight multiplier of 0 such that the self-weight of the structure is not included in this load pattern. You may always check base reactions in the output tables for a given case or combination to ensure that self-weight is applied correctly.

An alternative is to use the seismic auto lateral load pattern to calculate and assign the load according to specific requirements. This procedure is documented in the Lateral Loads Manual, available in the Manuals directory of the software installation directory.