Seismic analysis
Use Seismic analysis to perform response spectrum analysis based on predefined static shapes or modal combinations.
Press Setup… to open the seismic analysis settings.
Seismic analysis, setup
The Seismic analysis, setup dialogue contains two tabs: Method and Options.
Method tab
Choose the method used to generate seismic forces. Three alternative methods are available.
Static, linear shape
- α – rotation angle of the horizontal seismic direction
- λ x′, λ y′ – scaling factors for local directions
- Tx, Ty – translational factors in global directions
- The table lists the calculated periods and effective mass ratios
- Select – choose which shape(s) to include
Static, mode shape
- α – rotation angle of the seismic direction
- Set – apply manual selection of mode shapes
- Auto – automatic mode selection
- λ x′, λ y′ – scaling factors for local directions
- The table lists available mode shapes with periods and effective mass ratios
- Select / Clear – choose or clear selected shapes
Modal analysis
- α – rotation angle of the seismic direction
- Set – apply manual selection of mode shapes
- Auto – automatic mode selection
- The table lists mode shapes and effective mass ratios for x, y, and z directions
- Select all / Select / Clear – modify selection
- Dominant sh. – Select / Clear – choose dominant shapes used for direction-dependent evaluation
- Summation rule by directions – drop-down menu to select the rule for combining modal results. The available rules are:
- SRSS – Square Root of Sum of Squares
- CQC – Complete Quadratic Combination
Options tab
- Combination rule – select which formula to use for directional combination of seismic effects
- Signed results – preserve sign information when combining results
- Torsional effect for buildings – numeric field defining additional torsional amplification for building-type structures
- Add to documentation – exports the seismic setup and tables into the documentation module