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Seismic loads are assumed to act in both directions, and just one set of loads is generated for both directions. Manually input loads are usually applied to just one building face for each orientation, representing the building mass between that face and the opposite one. If applied to opposite faces, the forces generated by these loads are added.
Seismic loads are generated or input as line line loads along the chord at the edge of the diaphragm at that building level, and can be uniform, triangular, triangular or trapezoidal loads. Seismic area loads are not permitted. Generated seismic point loads represent wall mass parallel to the force direction. It is also possible to enter seismic point loads, representing concentrated mass such as a chimney.
Note that seismic loads you enter directly are added to those created using the load generation procedure, and thus do not contribute to the base shear shown in the load generation section of the Seismic Load Generation Details, or to the story shear or diaphragm force shown in the Seismic Information table. As many seismic design provisions are contingent on aspects of the load generation procedure, like base shear distribution to levels and seismic ground motion parameters, user-entered seismic loads may create invalid designs without the program being able to detect it.
It is therefore not recommended to enter your own seismic loads as well as generating them. If you want to model seismic loads from elements not included in the Shearwalls model, then use manually entered building masses and generate loads from them. Forces from adjoining structures should be modeled as shear line forces entered directly in load input view, rather than seismic loads.