A 3-story office building is to be designed and constructed…

A 3-story office building is to be designed and constructed in downtown San Francisco (where the short period spectral acceleration, Ss, is 1.5g and spectral response acceleration at one second, S1, is 0.6g).  The building will reside on a dense soil with soft rock (Site Class C).  Long period is 12 sec.  The structural system consists of special concentrically braced frames (SCBF) – see the following figure.  The dead loads are 70 psf at the roof and 100 psf at the floor levels.  At each floor level, the partition load is 20 psf (note that no partition load exists at the roof).  Do not factor these loads and ignore live loads when calculating the floor weights.   Seismic design category is