Nonlinear Earthquake Behavior of Tall Buildings

A digital-computer study was made on the response of typical high-rise buildings to strong earthquake motions. Frame components were assumed to have bilinear moment-curvature properties, with yield strengths provided by normal seismic-design procedures. The structures were subjected to the ground motions recorded in the 1940 El Centro earthquake, and the resulting maximum displacements and ductility factors were evaluated for a wide range of the basic parameters, period of vibration and variations of yield strengths. The results indicate that nonlinear deformations tend to be concentrated in the girders of buildings designed by normal procedures, with ductility factors of about 4 to 6 in the critical members. However, they also demonstrate that strengthening the girders may force the yielding into the columns, making distribution of strength between the various elements a critical factor.