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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
UNDERSTANDING OF THE SEISMIC PERFORMANCE OF
ASYMMETRIC R/C BUILDING STRUCTURES
Junwu DAI 1 Yuk-Lung WONG 2 and Minzheng ZHANG 1
1 Institute of Engineering Mechanics, China Seismological Bureau, China
Department of CSE, The Hong Kong Polytechnic University, Hong Kong
ABSTRACT
This paper is composed by the following investigations: 1) Using the time-history response of the base
shear-torque of 3 asymmetric RC single-story-building systems under a set of earthquake simulation
tests on shake table, both of the advantages and shortcomings of the base shear-torque (BST) surface
(1C. De La Llera and A.K. Chopra) established on the assumption of idealized force-displacement
relationship are checked. 2) Based on the experimental results and the assumption of the bi-linear
force-displacement relationship, a more reasonable and effective analytical model, the state space of
base shear-torque is developed for estimation of the seismic performance particularly the torsional
effects of the RC asymmetric structures.
KEYWORDS
earthquake simulation test, torsional, asymmetric, seismic response, inelastic, shear-torque relationship
BACKGROUND AND OBJECTIVES
It has been observed repeatedly in strong earthquakes that the presence of asymmetry in the plan of a
structure makes it more vulnerable to seismic damages. There are reports of extensive damages to
buildings that are attributed to excessive torsional responses caused by asymmetry in earthquakes such
as the 1972 Managua earthquake, the 1989 Loma Prieta earthquake, the 1995 Kobe earthquake and the
1999 Chi-Chi earthquake. Although torsion has been recognized as a major reason for poor seismic
performance of asymmetric buildings and many studies have been done on this topic, the analytical and
experimental studies on the inelastic seismic response of asymmetric buildings do not have a long
history. Recently, De La Llera and Chopra (1995) developed a simple model for analysis and design of
asymmetric buildings based on the assumption of idealized elasto-plastic force-displacement
relationship. Each story of the building is represented by a single super-element in the simplified model.
In this method, the story shear and torque interaction surface (Kan and Chopra 198L Palazzo and
Fraternali 1988, De La Llera and Chopra 1995) is used as an important component. The story shear and
torque (SST) surface is basically the yield surface of the story due to the interaction between story shear
and torque. Each point inside the surface represents a combination of story shear and torque that the
story remains elastic. On the other hand, each point on the surface represent a combination of shear and
torque that leads to the yielding of the story. How realistic is such a model to represent the behavior of
ductile buildings in seismic regions is a subject that requires further investigation.