Compurers & Srrucrures Vol. 58. No. 3, pp. 487-498. 1996 Elswier Science Ltd Printed in Great Britain > Pergamon 0045-794!MSMKI166-2 w . _ 0045.7949/96 $9.50 + 0.00 DYNAMIC ANALYSIS OF A TEN-STORY REINFORCED CONCRETE BUILDING USING A CONTINUUM MODEL M. J. Chajes, W. W. Finch Jr and J. T. Kirby Department of Civil Engineering, University of Delaware, 137 DuPont Hall, Newark, DE 19716, U.S.A. (Received 18 November 1994) Abstract-During the 1989 Loma Prieta earthquake, accelerometers maintained by the California Division of Mines and Geology Strong Motion Instrumentation Program (CSMIP) recorded the response of a IO-story, reinforced-concrete building located in San Jose, California. In this paper, a computationally efficient, approximate, dynamic analysis of the building is conducted utilizing a reduced-order continuum model. Continuum methodology makes use of the repetitive nature of lattice framing systems to generate finite element models having significantly fewer degrees of freedom than models generated using classical discrete finite element techniques. The vibrational characteristics of the continuum model, as well as the results of dynamic analyses, are compared to information gained from the recorded response of the building. The continuum model proves to be quite accurate, both in capturing the dominant periods of vibration of the structure and in predicting the time-history response. As a result, the method shows promise as a tool for use in the analysis and design of large lattice structures subjected to earthquake loads. zyxwvutsrqpon INTRODUCTION On October 17, 1989, a M, = 7.1 (surface wave magnitude) earthquake occurred along the San An- dreas Fault in Northern California with its epicenter located under a mountain called Loma Prieta. The earthquake triggered a large number of strong- motion accelerometers deployed throughout the San Francisco Bay area by both the California Division of Mines and Geology [l] and the U.S. Geological Survey [2]. These instruments recorded a great deal of valuable seismic response data for a variety of struc- tures including buildings, bridges, dams and tunnels. These data provide the opportunity to evaluate the accuracy of either existing or newly developed com- puter analysis techniques. Classical discrete finite element methods for pre- dicting linear response of large structures to even simple static loading may involve the solution of thousands of linear simultaneous equations. Adding time-varying dynamic loadings, along with material and geometric nonlinearities, can lead to thousands of coupled simultaneous nonlinear equations which must be solved at very small time increments. Even with modern high-speed computers, the compu- tational effort, storage requirements and associated cost of solving such equations can prohibit the use of full-scale dynamic analysis in everyday design. As a result, approximate yet accurate methods for con- ducting dynamic analyses of large structural frame- works are needed. Various researchers have investigated the use of continuum models for conducting both linear and nonlinear analyses of lattice structures [3-241. Finite element models resulting from continuum method- ology have significantly fewer degrees of freedom than discrete finite element models, which individu- ally model each of the beam and column elements. Hence, the use of continuum models can result in a considerable reduction incomputational effort with a corresponding savings in cost. This paper focuses on the seismic response of a lo-story, reinforced-concrete building located in San Jose, California, to the Loma Prieta earthquake. In particular, the paper investigates the use of a reduced- order continuum model to predict the dynamic re- sponse of the structure. The accuracy of the analysis is evaluated by comparing the computed results to the actual building response recorded during the earth- quake. To the author’s knowledge, this is the first attempt to compare the dynamic continuum analysis of a large building to its recorded structural response during an earthquake. CONTINUUM METHODOLOGY During the past 20 years, continuum models of large truss and frame structures have been used to study vibrational characteristics, static and dynamic response, and buckling behavior. Among the most prominent works are those by Noor et al. [3-71, who studied the static and dynamic response of beamlike lattice structures and predicted their buckling charac- teristics; Abdel-Ghaffar [%-lo], who used continuum models to find frequencies and mode shapes of suspension bridges; Sun et al. [l l] and Abrate and Sun [12], who used a beam element developed by Yang [13] to conduct vibrational analyses of planar truss systems; Sun and Juang [14], who incorporated 487