SMIP 1990 Seminar

Proceedings of SMIP 1990 Seminar on Seismological and Engineering Implications of Recent Strong-Motion Data (PDF)

June 8, 1990

Sacramento, California


Table of Contents

    1-1 The Strong Motion Instrumentation Program and Data Recorded During the Loma Prieta Earthquake by A.F. Shakal and M.J. Huang


    The purpose of the Strong Motion Instrumentation Program (SMIP) is to improve methods to protect California citizens and property from earthquake-induced structural hazards. Toward this end, the program records strong earthquake shaking in structures and at ground response sites to obtain the data necessary for the improvement of seismic design codes. SMIP also promotes and facilitates the improvement of seismic codes through data utilization projects. The SMIP 1990 Research Review Seminar is a component of that effort. Several sets of data recorded during the Loma Prieta earthquake are the first measurements of the performance of several standard construction types during moderate and strong earthquake shaking, and these records will be the subject of data utilization studies in 1990.

    2-1 Directional Site Resonances Observed From the 1 October 1987 Whittier Narrows, California Earthquake and the 4 October Aftershock by J. Vidale, 0. Bonamassa and H. Houston


    We present evidence that sites often resonate preferentially in a particular compass direction. The 1 October 1987 mainshock and 4 October 1987 aftershock in the Whittier Narrows, California, sequence had very different mechanisms. Nevertheless, at 8 of 11 strong motion stations for which digitized records of both events are available, the direction of strongest shaking in the two events was much more similar than would be expected from their different focal mechanisms. The coincidence of the polarizations from the two events was greatest for the frequencies at peaks in the spectra, suggesting that site amplification and directional resonances are linked. Knowledge of directional site resonances may aid in predicting the directions of damaging earthquake motions.

    3-1 Strength and Ductility Demands for SDOF and MDOF Systems Subjected To Whittier Narrows Earthquake Ground by H. Krawinkler and A. Nassar


    This paper summarizes parts of a project that is concerned with an evaluation of the damage potential of the October 1, 1987 Whittier Narrows ground motions. The discussion focuses on strength and ductility demands imposed by these ground motions on single degree of freedom (SDOF) and multi-degree of freedom (MDOF) systems. In the SDOF study, bilinear as well as stiffness degrading models are evaluated. A procedure is presented that permits the evaluation of strength demands for MDOF systems based on inelastic strength demand spectra of SDOF systems.

    4-1 An Evaluation of Unreinforced Masonry Wall Performance by J.D. Raggett and C. Rojahn


    The objective of this study is to evaluate the assumption that there is no amplification of ground motion at the top of unreinforced masonry walls. Strong-motion records at the top and bottom of shear walls for one unreinforced masonry building, and four reinforced concrete buildings were analyzed. Accelerations at the top of reinforced concrete shear walls typically did not exceed 1.31 times ground accelerations. The unreinforced masonry building was damaged during the motions analyzed making results unreliable for predicting future motions.

    5-1 Interpretation of Painter Street Overcrossing Records to Define Input Motions to the Bridge Superstructure K. Romstad and B. Maroney


    This paper discusses portions of a study utilizing the strong motion data obtained from twenty sensors on and near the Painter Street Overcrossing in Rio Dell, California. Particular attention is paid to the influence abutment behavior has on measured response in the three directions of motion of the bridge superstructure. Previous studies have shown that transverse modes of vibration predicted by ambient testing may not reflect behavior during seismic events. The study also focuses on the influence of direction of input boundary motions to be used in analytical models to predict bridge response.

    6-1 Evaluation of Lateral Force Procedures for Buildings by G. Fenves


    The recent edition of building codes for earthquake resistant design specify a dynamic analysis procedure for computing lateral forces on buildings with irregular plan or vertical irregularities. This paper presents the use of the instrumented response of two buildings to strong ground motion for determining vibration properties and distribution of lateral forces. The two buildings were selected for the irregular features in their configuration, and the results illustrate the difference in lateral force distribution for type of building and amplitude of earthquake response.

    7-1 Investigation of Design and Analysis Methods for Steel Framed Buildings by A. Astaneh, S.A. Mahin, J.H. Shen and R. Boroschek


    The Strong Motion Instrumentation Program (SMIP) of the California Department of Mines and Geology has obtained significant records in a number of steel structures. The objective of this research was to conduct comparative studies of the response of two modern steel structures as predicted by current analytical methods and the response recorded by SMIP. Realistic models of the structures were developed and were subjected to 3-dimensional dynamic analyses. The analyses indicated that proper modeling of connections, and floor diaphragms can lead to accurate predictions of the response. Also, current code procedures predict a period that usually is significantly smaller than actual period of vibration.

    8-1 Seismic Response and Analytical Modeling of the CSULA Administration Building Subjected to the Whitter Narros Earthquake R.R. Lui, S. Mahin and J. Moehle


    This study examines the measured seismic response behavior of the CSULA Administration Building during the October 1, 1987 Whittier Narrows Earthquake. The shear forces and interstory drifts calculated from measured seismic responses are compared with UBC design requirements to ascertain the validity of UBC requirements. A three dimensional elastic model was constructed and subjected to the recorded base accelerations to study the correlation of analytical modeling predictions with measured seismic responses.