accuracy evaluation of fema440 modified coefficient equivalent nonlinear procedure for irregular steel moment resisting frames

one of well-established procedures for the equivalent nonlinear static procedure is fema440 modified coefficient method (mcm) utilizing a displacement modification procedure in which several empirically derived factors are used to modify the response of a single-degree-of freedom model of the structure assuming that it remains elastic. this paper presents a detailed investigation on performance of fema440 mcm for estimating frame maximum roof displacement, base shear, and median story drifts of steel moment resisting frames with irregularities in elevation. results of nonlinear dynamic analyses of 44irregular frames subjected to a family of 14 ground motions and nonlinear equivalent static analyses of all frames up to the target roof displacement computed by mcm are compared to evaluate the accuracy and conservatism of fema440 mcm.