Evaluation of Overturning Forces On Shear Wall Buildings

by William E. Gates, Gary S. Hart, Sunil Gupta and Mukund Srinivasan

Gates, William E., Gary S. Hart, Sunil Gupta and Mukund Srinivasan (1994). Evaluation of Overturning Forces On Shear Wall Buildings. SMIP94 Seminar on Seismological and Engineering Implications of Recent Strong-Motion Data, p. 1 - 20.

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Abstract

The strong motion instrumentation program (SMIP) of the California Division of Mines & Geology (CDMG) has been designed to instrument specific building types in specific areas of California where strong ground motion records may be readily obtained from active seismic sources. The records are intended for use by structural engineers and researchers in developing analytical and design procedures that more accurately represent the building's behavior in earthquakes. Recent California earthquakes have provided significant data on a series of instrumented shear wall buildings along with observable data on their earthquake performance.

This paper presents a detailed investigation of three high-rise shear wall buildings in the nine- to ten- story range with three different shear wall configurations: perimeter walls, core walls and distributed walls. The dynamic earthquake response of these buildings is assessed to evaluate overturning forces in the shear walls under three recent northern California earthquakes: 1984 Morgan Hill, 1986 Mt. Lewis; and 1989 Loma Prieta. Two methods of data reduction and analysis are employed in the investigation to assess the significance of soil- structure interaction on building overturning forces. These include: simplified data analysis procedures using recorded motions, mode shapes and building weights to assess dynamic performance and three dimensional hear elastic dynamic analyses using soil-structure models for the shear walls and foundation systems.

Realistic three-dimensional models of the structures refined through system identification techniques are used to study the response to the three earthquakes. These analyses indicated that under the larger earthquakes structural softening occurred that was associated both with soil strain levels as well as shear wall cracking. The analytical results are compared with code procedures for predicting the periods of the structures as well as the distribution of overturning forces.