ASSESSING STRENGTH AND DRIFT LIMITATIONS FOR SEISMIC DESIGN OF FLAT SLAB BUILDINGS

This paper quantifies the relative contribution of minimum stiffness i.e., code drift limit versus minimum strength requirements to an economic and reliable design of low- to mid-rise flat slab buildings located in moderate seismic zones 0.25g. two building schemes are considered: columns-only and columns-shear walls flat slab buildings. three versions of each type, namely 4-, 8- and 12-story are investigated with a theme layout representative of typical office building construction. the procedure starts by designing the buildings for gravity only loadings. then, each building is checked for compliance to code seismic design requirements for strength no-collapse limitation and stiffness damage limitation through bi- directional multi-mode response spectrum analysis perfonned on three dimensional computer models of the structure. re-dimensioning of lateral resisting structural members is applied in order to achieve code-compliant structures under the code estimated seismic demand. the design is revisited again and members are once more re-dimensioned to satisfy strength requirements only while ignoring code drift limitation. all building versions are then compared to estimate 1) the benefit of adding shear walls to somehow inherently flexible flat slab buildings; and 2) the penalty which stringent design code analysis constraints may impose on the design economy of such building systems.