Estimation of Inelastic Deformation Demands of SDOF Systems

Abstract

Two recently proposed and closely related approximate methods to estimate the maximum lateral inelastic deformations demands of single-degree-of-freedom (SDOF) systems subjected to earthquake ground motions are investigated. In both methods, maximum inelastic displacements are estimated from maximum elastic displacements through the use of parameters that relate the response of elastic and inelastic SDOF systems. In the first method, the maximum inelastic displacement is estimated from the maximum elastic displacement through mean strength reduction factors derived from statistical studies. In the second method, the maximum inelastic displacement is estimated from the maximum elastic displacement through inelastic displacement ratios also derived from statistical studies. It is shown that the first method is actually a first-order approximation of the second method and that only in the absence of variability the two methods provide the same result. Furthermore, it is shown that the systematic error introduced by the first method leads to underestimations of maximum inelastic displacement demands. The error is evaluated and examples using results from statistical results of the seismic response of SDOF systems are presented.