TSINGHUA SCIENCE AND TECHNOLOGY ISSN 1007-0214 20/21 pp124-130 Volume11,Number1,February2006

Push-Over Analysis of the Seismic Behavior of a Concrete-Filled

Rectangular Tubular Frame Structure*

NIE Jianguo (聂建国) **, QIN Kai (秦 凯), XIAO Yan (肖 岩)

Department of Civil Engineering, Tsinghua University, Beijing 100084, China;

Department of Civil Engineering, University of Southern California, Los Angeles, CA 90089, USA

Abstract: To investigate the seismic behavior of concrete-filled rectangular steel tube (CFRT) structures, a push-over analysis of a 10-story moment resisting frame (MRF) composed of CFRT columns and steel beams was conducted. The results show that push-over analysis is sensitive to the lateral load patterns, so the use of at least two load patterns that are expected to bound the inertia force distributions is recom-mended. The M-φ curves and N-M interaction surfaces of the CFRT columns calculated either by Han’s formulae or by the USC-RC program (reinforced concrete program put forward by University of Southern Califonia) are suitable for future push-over analyses of CFRT structures. The P- effect affects the MRF seismic behavior seriously, and so should be taken into account in MRF seismic analysis. In addition, three kinds of RC structures were analyzed to allow a comparison of the earthquake resistance behavior of CFRT structures and RC structures. The results show that the ductility and seismic performance of CFRT struc-tures are superior to those of RC structures. Consequently, CFRT structures are recommended in seismic regions.

Key words: concrete-filled rectangular steel tube; push-over analysis; capacity curve; reinforced concrete

Introduction

Over the past twenty years the static push-over proce-dure has been presented and developed by several au-thors, including Saiidi and Sozen[1], Fajfar and Gasper-sic[2], Bracci et al.[3], amongst others. This method is also described and recommended as a tool for design and assessment purposes for the seismic rehabilitation of existing buildings[4]. The purpose of push-over analysis is to evaluate the expected performance of a structural system by estimating its strength and defor-mation demands in design earthquakes by means of a Received: 2004-06-30; revised: 2004-11-07

Supported by the Overseas Youth Cooperative Foundation of the ﹡

To whom correspondence should be addressed. ﹡﹡

National Natural Science Foundation of China (No. 50128807) E-mail: niejg@mail.tsinghua.edu.cn; Tel: 86-10-62772457

static inelastic analysis, and by comparing these de-mands to available capacities at the performance levels.

Push-over analysis is basically a nonlinear static analysis that is performed by imposing an assumed dis-tribution of lateral loads over the height of a structure and increasing the lateral loads monotonically from zero to the ultimate level corresponding to the incipient collapse of the structure. The gravity load remains con-stant during the analysis. Push-over analysis is very useful in estimating the following characteristics of a structure: 1) the capacity of the structure as represented by the base shear versus top displacement graph; 2) the maximum rotation and ductility of critical members; 3) the distribution of plastic hinges at the ultimate load; and 4) the distribution of damage in the structure, as expressed in the form of local damage indices at the ul-timate load. Although push-over analyses of reinforced