Seismic Loading

The Seismic Loading tab is only available when the project name is selected in the Job Tree. The properties here affect every level and every member in the job.

Here you can set structure and region specific settings that will cascade to any member that allows for seismic overstrength loads (beams). If you find that you are most likely to reuse the same settings for every job, simply click the Save as Default button in the upper right corner of the window and the software will keep these settings for every job moving forward. If you are not designing members that will utilize the overstrength seismic load combinations, you can skip this step.

IBC Building Code

There are two approaches to seismic design in the software.

For all IBC building codes, and when the option to apply seismic overstrength design on the Member Info tab is not selected, the Seismic Loading tab is not utilized. The value entered for Seismic on the Loads tab is expected to be E=f(E_v,E_h) as specified by ASCE/SEI 7-16 Sec. 12.4.2.

For IBC 2018 and newer, the software will provide an option to apply seismic overstrength design on the Member Info tab. If the option is selected, the software will use the inputs provided on the Seismic Loading tab (Overstrength Factor (Ω₀), Spectral Response Acceleration Parameter at a Period of 1 second (S_DS), and Seismic Design Category) and the Q_E value entered on the Loads tab to calculate the seismic load effect with overstrength, E_m=f(E_v,E_mh), specified by ASCE/SEI 7-16 Sec.12.4.3. Software does not consider axial load effects due to seismic forces.

Note: There are upper and lower limits for the two input fields. The input for Overstrength Factor (Ω₀) must be greater than 0 but not greater than 3. The input for Design Parameter at Short Periods (S_DS) must be greater than 0 but not greater than 2. If the value entered is less than or greater than the ranges specified, the default (either system or user) will appear instead of the invalid input.

Only Structural Composite Lumber is valid for Seismic Overstrength Analysis.

NBCC Building Code

For NBCC, software will not utilize this tab and the member info tab will not have the option to apply seismic overstrengh design.