Seismic performance of cover-plate strengthened frames

Abstract

This paper summarizes results and conclusions of a case study of cover-plate strengthened frames with two, five and ten stories. The study begins with the comparison of a test results from a cover-plate connection assembly specimen with results using a detailed nonlinear finite element analysis (FEA) model. With a strong correlation to the test specimen, more FEA models are generated and analysed in order to (a) examine the local behavior of cover-plate profiles; various and (b) compare their performance to the simplified structural models that will be used in the static and time history analysis of those of the frames. With the reliable simple structural model of the cover-plate connection assemblies capturing both elastic and inelastic behavior, such a model is incorporated into frames to perform nonlinear static and time history analyses. Nine frames (two-, five- and ten-story steel moment frames with and without a cover plate) are the designed for the study. For comparative purposes, the 1940 Imperial Valley (El Centro station, 0·32g PGA) and the 1994 Northridge (Newhall station, 0·59g PGA) ground motions factored to 0·3 and 0·6g are used in time-history analyses. Global and local performance of frames are discussed in terms of plastic deformation distribution, story shear force and inelastic drift ratio. Copyright © 1999 John Wiley & Sons, Ltd.