A Simplified Procedure to Assess the Seismic Response of Nonlinear Structures

The paper presents an improvement of the iterative procedure proposed in the ATC 40 document to evaluate seismic response of nonlinear structures in terms of maximum displacement and acceleration, given the structural initial elastic period, the yielding acceleration and the hardening ratio in the plastic range. As a second issue the results of the procedure are compared with nonlinear step by step dynamic integration, with the bilinear and Takeda model, and with the assumptions of equal energy and equal displacement. Two case studies of existing reinforced concrete buildings are further examined. For the cases examined, the ATC 40 procedure is overall as or less precise than the simpler equal energy and equal displacement principles.