Semi-Basement Building Projects

When a project has a semi-basement (i.e., some of the walls at the ground floor continue down into the basement level while others rest on the foundation directly below the ground floor), the semi-basement building project option must be checked in the general project settings.

If this option is not checked, the program assigns supports only to the base of the basement-level walls. In this case, no support is assigned to the walls at the ground floor that rest directly on the foundation, so those walls — which have no support below them and no continuation downward — act as cantilevers and do not carry shear forces during an earthquake. Only the walls with full continuity take the seismic forces, which means the analysis produces incorrect results.

When the option is checked, supports are also assigned beneath the walls at ground floor level that do not continue to the lower storey, so the force distribution is performed as it should be.