Inelastic earthquake response of single‐story asymmetric buildings: an assessment of simplified shear‐beam models

Abstract

SUMMARYThe inelastic seismic torsional response of simple structures is examined by means of shear-beam type models as well as with plastic hinge idealization of one-story buildings. Using mean values of ductility factors, obtained for groups of ten earthquake motions, as the basic index of post-elastic response, the following topics are examined with the shear-beam type model: mass eccentric versus sti ness eccentric systems, e ects of di erent types of motions and e ects of double eccentricities. Subsequently, comparisons are made with results obtained using a more realistic, plastic hinge type model of singlestory reinforced concrete frame buildings designed according to a modern Code. The consequences of designing for di erent levels of accidental eccentricity are also examined for the aforementioned frame buildings.

An answer to an important controversy and the need for caution when using simple models to predict inelastic earthquake response of buildings with torsion

“…For asymmetric frame buildings like those designed for this study following the EC8 dynamic procedure, the critical elements are the frames at the flexible edges of the building. This is predicted both by the detailed, realistic, MDOF, models, as well as by the simplified models having the correct element strengths (SIMP1 and SIMP2) and confirms similar findings for one-story buildings reported in [26]. 2.…”

“…Subject to the limitations imposed by the underlying assumptions, the results in this paper confirm earlier findings pointing to inadequacies of the simplified, one-story, shear-beam-type systems, 538 S. A. ANAGNOSTOPOULOS, C. ALEXOPOULOU AND K. G. STATHOPOULOS for predicting the inelastic response of real, asymmetric, multistory frame buildings, subjected to torsion due to earthquake motions and consequently for deriving general conclusions about torsional provisions of the codes [25,26,28,31]. Using as the basis for comparison, the predictions of such response by detailed, multistory models of the PH type, it was found that:…”

“…We must also note that the basic finding herein, i.e., that the critical elements in code-designed buildings, as derived using detailed PH models, are the flexible edge frames, not the stiff edge elements indicated by the analyses with the SIMP3-type models, have been first reported in References [25] and [26]. In Reference [26] the comparisons of ductility demands were for onestory buildings, idealized both with the PH-type model and also with the SIMP3 type of simplified model (design for earthquake only).…”

“…The basic goal here is to see how well and under what conditions is the inelastic response of simplified, one-story, shear-beam type, asymmetric systems comparable with the inelastic response of realistic multistory buildings and hence how valid are code assessments made on the basis of such simplified models. This is a continuation of work presented in [25,26,31] and to the best of the author's knowledge, it is one of the first, if not the first attempt to address this issue. It must also be pointed out that pushover analyses to determine properties of SDOF systems, as well as story properties of equivalent, shear-beam type, MDOF systems for approximating the nonlinear dynamic response of symmetric buildings, were used by Pique in the mid 70s [35].…”

Inelastic Parametric Analysis of Seismic Responses of Multistorey Bidirectional Eccentric Structure

“…By adopting a 3D plastic hinge model, which closely approximates actual frame structures, Stathopoulos et al [20] conducted inelastic dynamic time history analysis of multistorey bidirectional eccentric structures. In contrast to related noneccentric systems, the so-called flexible side frames had more ductility requirements than that of stiff side frames; this finding was also different from previous results using the simplified one-storey model [21]. Rizwan et al [22] utilized the SAP2000 to construct a plastic hinge model of a 3D frame structure and conducted nonlinear dynamic history analysis on two kinds of asymmetric structures.…”