DYNAMIC RESPONSE OF NONLINEAR STRUCTURES

Abstract

The current practice in earthquake resist-nt design is to allot: structures to behave elastically for moderate sized earthquakes and, during severe earthquakes, structures are permitted to undergo deformations which extend into the post=-elastic range. This indicates the desirability of a limit design approach for structures which are called upon to resist strong'mot.ion earthquakes. Behaviour of single degree of freedom elasto-plastic and bilinear systems have already been investigated in detail. But, in practice 9 very few structures will have such idealized load-deflection curves. As such, the elasto-plastic and bilinear systems are not a true representation of actual behaviour.. In this investigation, a more general type of nonline_;rity has been assumed. The response has been obtained for two actual recorded earthquake excittions namely Elcentro and Taft earthquakes. In particular, nonlinear systems have been related with the linear systems through a concept of 'REDUCTION FACTOR' 9 so that the design of n nonlinear system may be based on the knowledge of an equivalent linear system. Reduction factors are presented for ductility ratio varying from 2 to 6 for two earthquake excitations which cn.n be used for design purposes.