USE OF NEW EQUIVALENT NONLINEAR SDF SYSTEM OF PLANAR MULTI-STOREY R/C FRAMES IN STATIC PUSHOVER PROCEDURE

摘要

In the present paper, the issue of the approximate definition of a new equivalent Non-Linear Single Degree of Freedom (NLSDF) system on planar reinforced concrete (r/c) multistory frames is presented. It is known that, in order to estimate the demand seismic inelastic floor displacements the application on non-linear response history analysis (NLRHA) is suggested for accuracy reasons. However, due to its high computational cost the use of the simplified static pushover analysis is often preferred. Also, in the NLRHA there are difficulties in the qualitative comprehension, while in the static pushover procedure there is more natural inspection of the results of analysis. In order to perform the static pushover analysis an equivalent non-linear single degree of freedom system that represents the initial planar frame must be defined. In the present paper, the characteristics of an improved new equivalent non-linear single degree of freedom system are given and a suitable numerical example is presented. The definition of the NLSDF system has mathematically derived recently, considering suitable dynamic loadings on the masses of each r/c system and using simplified assumptions. The new equivalent NLSDF system in combination with the inelastic design spectra can give in many cases an approximate evaluation of the required seismic floor displacements for a known design earthquake. The present methodology is suitable for all types of planar frames that possess the required normality by the contemporary Seismic Codes in elevation, as well as in planar r/c frames where is impossible to appear soft-storey (yielding mechanism at all columns -top & bottom- of someone floor).