Direct Displacement-Based Design

Abstract

The direct displacement-based seismic design method as applied to steel framed buildings in accordance with the Model Code DBD12 is presented. Moment resisting, eccentrically braced and concentrically braced frames are mainly considered. The method employs displacements as the main design parameters of the problem and succeeds in effectively controlling damage. It is based on the construction of an equivalent linear single-degree-of-freedom system to the original nonlinear frame and a displacement design spectrum with high amounts of viscous dam**. Thus, by assuming a target interstorey drift ratio and determining the design displacement and the equivalent dam** of the single-degree-of freedom system, one can obtain from the displacement spectrum the required period and hence stiffness and design base shear necessary for the structure to achieve the assumed deformation. Using the computed design base shear, one can distribute it along the height of the frame and dimension beams and columns in conformity with the capacity design rule. Numerical examples involving steel moment resisting and braced (eccentrically and concentrically) frames are presented for illustration purposes and demonstration of the advantages of the method. New developments of the method pertaining to various improvements and further applications are also briefly discussed.