Inelastic response of RC frame buildings with seismic isolation

Abstract

A comprehensive parametric study on the inelastic seismic response of seismically isolated RC frame buildings, designed for gravity loads only, is presented. Four building prototypes, with 23 m by 10 m floor plan dimensions and number of storeys ranging from 2 to 8, are considered. All the buildings present internal resistant frames in one direction only, identified as the strong direction of the building. In the orthogonal weak direction, the buildings present outer resistant frames only, with infilled masonry panels. This structural configuration is typical of many existing RC buildings, realized in Italy and other European countries in the 60s and 70s. The parametric study is based on the results of extensive nonlinear response-time history analyses of 2-DOF systems, using a set of seven artificial and natural seismic ground motions. In the parametric study, buildings with strength ratio (Fy/W) ranging from 0.03 to 0.15 and post-yield stiffness ratio ranging from 0% to 6% are examined. Three different types of isolation systems are considered, that is, high damping rubber bearings, lead rubber bearings and friction pendulum bearings. The isolation systems have been designed accepting the occurrence of plastic hinges in the superstructure during the design earthquake. The nonlinear response-time history analyses results show that structures with seismic isolation experience fewer inelastic cycles compared with fixed-base structures. As a consequence, although limited plastic deformations can be accepted, the collapse limit state of seismically isolated structures should be based on the lateral capacity of the superstructure without significant reliance on its inherent hysteretic damping or ductility capacity

Principles of Energy Efficient Construction and their Influence on the Seismic Resistance of Light-weight Buildings

“…The behaviour of buildings founded on TI, when subjected to earthquake ground motions, is to a certain extent similar to the problems of nonlinear dynamic SSI and therefore a similar level of accuracy is presumed for the results obtained in this paper. The findings of previous researches [23][24][25][26][27][28][29][30][31][32][33][34][35][36] performed on simplified building models indicate that the results between the MDOF and equivalent SDOF models are in good agreement regarding buildings' top displacement response, whereas the simplified methods could lead to conservative estimates of the ductility demands for high rise structures. These facts are taken into consideration in this paper, where the results are mainly focused on low to mid-rise structures and on the distinction between the response of the FB and BI models.…”

“…Only a part of these results pointing out the performance of light-weight energy efficient buildings were presented in this paper. Similar simplified models for the superstructure have already been used for extensive parametric studies of fixed based structures [23][24][25][26], seismic isolation systems [27][28][29], soil structure interaction (SSI) phenomena [30][31][32][33][34] or to determine the probabilistic characteristics of seismic ductility demand [35,36]. The behaviour of buildings founded on TI, when subjected to earthquake ground motions, is to a certain extent similar to the problems of nonlinear dynamic SSI and therefore a similar level of accuracy is presumed for the results obtained in this paper.…”

Rintc Project: Nonlinear Analyses of Italian Code-Conforming Base-Isolated Buildings for Risk of Collapse Assessment

“…The choice of representing the superstructure with a nonlinear model is justified by the results of recent studies on this topic [10], which pointed out the effects of the inelastic behaviour of the superstructure on the seismic response of base isolated structures. The model also includes the staircase structure (inclined beams and cantilever steps) as well as masonry infill panels.…”

Estimation of inelastic displacement ratio for base‐isolated structures

“…Moreover, the inelastic behavior of superstructure under pulse‐like NF ground motions at the maximum considered earthquake level was reported by Calugaru and Panagiotou . Cardone et al investigated inelastic seismic response of seismically isolated RC frame buildings. They recommended a global strength reduction ratio ( R = 2) for BI buildings featuring a weak‐beam/strong‐column inelastic mechanism .…”