Form: {Code-Specific} Seismic Loading
Use the Seismic Loading form to the input the parameters and coefficients for the specified seismic load, including load direction and diaphragm eccentricity, seismic coefficients, time period, lateral load elevation range, near source factors, and additional code-specific factors. Code-specific program defaults are provided.
Note: Options to specify your own factors are available when the User Coefficients or User Load option is selected in the Auto Lateral Load drop-down list on the Define Load Patterns form.
The diaphragm eccentricity options have meaning only if the model has diaphragms. SAP2000 ignores eccentricities where diaphragms are not present.
Where diaphragms are present, SAP2000 calculates a maximum width of the diaphragm perpendicular to the direction of the seismic loading. This width is calculated by finding the maximum and minimum X or Y coordinates (depending on direction of load considered) of the points that are part of the diaphragm constraint and determining the distance between these maximum and minimum values.
After the appropriate diaphragm width has been determined, SAP2000 applies a moment that is equal to the specified percent eccentricity times the maximum width of the diaphragm perpendicular to the direction of the seismic loading times the total lateral force applied to the diaphragm. This moment is applied about the diaphragm center of mass to account for the eccentricity.
Click the Override button to modify eccentricities on a diaphragm-by-diaphragm basis.
See Also
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Access the {Code-Specific} Seismic Loading form as follows:
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