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U.S. Geological Survey Open-File Report 2012–1058

In cooperation with the University of California Berkeley

Evaluation of Fault-Normal/Fault-Parallel Directions Rotated Ground Motions for Response History Analysis of an Instrumented Six-Story Building

By Erol Kalkan and Neal S. Kwong

Thumbnail of and link to report PDF (3.2 MB)Abstract

According to regulatory building codes in United States (for example, 2010 California Building Code), at least two horizontal ground-motion components are required for three-dimensional (3D) response history analysis (RHA) of buildings. For sites within 5 km of an active fault, these records should be rotated to fault-normal/fault-parallel (FN/FP) directions, and two RHA analyses should be performed separately (when FN and then FP are aligned with the transverse direction of the structural axes). It is assumed that this approach will lead to two sets of responses that envelope the range of possible responses over all nonredundant rotation angles. This assumption is examined here using a 3D computer model of a six-story reinforced-concrete instrumented building subjected to an ensemble of bidirectional near-fault ground motions. Peak responses of engineering demand parameters (EDPs) were obtained for rotation angles ranging from 0° through 180° for evaluating the FN/FP directions. It is demonstrated that rotating ground motions to FN/FP directions (1) does not always lead to the maximum responses over all angles, (2) does not always envelope the range of possible responses, and (3) does not provide maximum responses for all EDPs simultaneously even if it provides a maximum response for a specific EDP.

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Suggested citation:

Kalkan, E., and Kwong, N.S., 2012, Evaluation of fault-normal/fault-parallel directions rotated ground motions for response history analysis of an instrumented six-story building: U.S. Geological Survey Open-File Report 2012–1058, 30 p., available at http://pubs.usgs.gov/of/2012/1058/.



Contents

Abstract

Introduction

Description of Structural System and Computer Model

Ground-Motions Selected

Methodology for Evaluation of Fault-Normal/Fault-Parallel Directions

Structural Response Variability with Rotation Angle

Evaluation of Fault-Normal/Fault-Parallel Directions Rotated Ground Motions

Conclusions

Acknowledgments

References Cited


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