A Study on Natural Periods and Modal Damping Ratios for Buildings in California

Undergraduate #330
Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering

Juan Manuel Alonso - University of California, Irvine
Co-Author(s): Farzin Zareian and Angie Harris, University of California, Irvine, CA

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The estimation of building modal parameters is an important and recurring topic of research in the Structural Engineering community. System identification has been chosen by many as the ideal method of estimating the natural period and damping ratio of existing buildings. The outcome of such system identification is used for the derivation of formulas for natural periods which are currently utilized in building codes. However, the prediction of damping ratios remains a difficult task due to the high variability of the identified data. This study provides a practical approach in calculating the natural period and damping ratio of buildings with which a more accurate estimation of these modal parameters becomes possible. To that end, we have utilized a database of instrumented buildings that have experienced ground shaking in past earthquakes in California– through California Strong Motion Instrumentation Program – and estimated their natural periods and damping ratios through system identification. Using this information, new formulas for natural periods and damping ratios have been derived. Our results show that the analysis of modal parameters, of buildings at all levels of excitation, provide the best environment for parameter estimation.

Funder Acknowledgement(s): UC Irvine LSAMP/CAMP office: 2015 Summer Research Scholars Program

Faculty Advisor: Farzin Zareian, zareian@uci.edu