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You are able to specify the self-weight density per unit of surface area for all of the actual and inferred building elements in Shearwalls – exterior walls, interior walls, floor diaphragms, roof diaphragms, and ceiling diaphragms. The self-weights are combined with the geometry of the element to create building mass loads.
You can specify whether to include the self-weight for a type of element, i.e. whether you want each type of building element included in the building mass generation process.
These self-weights apply to all building elements on a specified range of levels of the building. By selecting a single level or a range of levels, and generating loads more than once, it is possible to use different self-weights to generate building masses on different levels of the building, for example to model a concrete floor on one level of the structure, or more massive walls at the base.
If am individual level is composed of radically different materials, you can handle this by modifying the building masses after they are generated or by adding custom building masses.
Default values for all the self-weights are specified in the Default Settings.
Walls
Wall self-weights are entered as psf area densities, the area being in the vertical plane. Separate self-weights are entered for interior and exterior walls to account for greater thickness and possibly heavy cladding of the exterior walls.You may want to exclude interior walls if a partition weight has been included in the floor self-weight.
The program identifies generated dead loads from wall self-weight for use in hold-down effect factor Jhd calculations. If you wish to include these dead load loads for that purpose, but rely on a floor partition weight for interior wall building masses, then we recommend generating both dead loads and building masses from wall self-weight, then deleting the building masses before generating seismic loads.
Floors and Ceilings
Self-weights are specified as area densities in the horizontal plane. Separate self-weights can be specified before generating loads for each floor, if desired, and for the ceiling of the uppermost level. Note that storage loads and equipment loads must be included in this amount, or entered as a separate building mass.
Roof Panels
You can choose to add self-weights as psf area densities in the inclined plane of roof panels or as a horizontally projected area load.
Snow Loads
You input the the snow load as a self-weight, which is considered to extend over the entire projected area of the roof, as if it were a flat-roof load.
NBC 4.1.9.1.(2), requires 25% of the snow load to be included as building mass for seismic calculation, so the program includes only 25% of the load as building mass. .