Experimental and Analytical Studies on the Seismic Response of Freestanding and Anchored Laboratory Equipment, PEER Report 2005-07


This report presents the results of a comprehensive experimental program investigating the seismic response of freestanding and anchored laboratory equipment. The study is part of a broader study on the UC Science Laborator y facility that implements the performance-based earthquake engineering (PBEE) methodology proposed by the PEER Center.

In this study, quasi-static experiments were conducted in order to examine the mechanical behavior of the contact interface between laboratory equipment and the floors on which the equipment is situated. Based on the results of these experiments, the report presents two idealized contact friction models that were constructed: (a) an elastoplastic model and (b) a classical Coulomb friction model.

The report presents shake table test results of freestanding equipment subjected to ground and floor motions with 50% and 10% in 50 ye ars hazard levels. For the equipment tested, although some rocking was observed, sliding was the predominant mode of response, with sliding displacements reaching up to 2 ft. Numerical simulations with the elastoplastic model using MATLAB and with the Coulomb model using the software Working Model 2D were performed. When the friction coefficient values obtained from the quasi-static tests were used, the simulations yielded time-history results that were in fair agreement with the experimental data. The predicted responses were appreciably improved for both models when reduced values of the friction coefficients were used.

Following the PEER methodology, the report identifies a representative Intensity Measure, IM, and the associated Engineering Demand Parameter, EDP. The proposed lognormal distribution of the EDP is tested against the shake table experimental results, and simple linear relationships for the mean and standard deviation of the EDP in terms of the IM are offered. The report presents generated fragility curves and an example that illustrates how to use them.

Results of shake table tests done on wooden scale models of the equipment confirm Working Model’s ability to capture the overturning potential of equipment and provide confidence in its use to analyze the seismic response of equipment. Working Model was used to compute the responses of equipment subjected to 2% in 50 years motions (which were not tested on the shake table due to its displacement limitations). The report presents these responses together with generated fragility curves.

The report finally presents results of shake table tests performed on anchored equipment which indicate that recorded peak equipment accelerations are
significantly larger than those recorded during the freestanding equipment tests, on several occasions 7 or more times larger. Such high accelerations may pose a threat to the sensitive contents of laboratory equipment.

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Dimitrios Konstantinidis
Nicos Makris
Publication date: 
July 3, 2005
Publication type: 
Technical Report
Konstantinidis, D., & Makris, N. (2005). Experimental and Analytical Studies on the Seismic Response of Freestanding and Anchored Laboratory Equipment, PEER Report 2005-07. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA.