Simple formulae for damage estimation of composite steel/concrete moment resisting frames

Simple empirical expressions to estimate maximum seismic damage on the basis of three well known damage indices for planar regular steel/concrete composite moment resisting frames are presented. They are based on the results of extensive parametric studies concerning the inelastic response of a large number of frames to a large number of ordinary far-field type ground motions. Thousands of nonlinear dynamic analyses are performed by scaling the seismic records to different intensities in order to drive the structures to different levels of inelastic deformation. The statistical analysis of the created response databank indicates that the number of stories, beam strength ratio, material strength and the ground motion characteristics affect structural damage. Nonlinear regression analysis is employed in order to derive simple formulae, which offer a direct estimation of the damage indices used in this study. More specifically, given the characteristics of the structure and the ground motion, one can calculate the maximum damage observed in column bases and beams. Finally, one example serves to illustrate the use of the proposed expressions and demonstrates their efficiency and accuracy.