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Uncertainty analysis of strain modal parameters by Bayesian method using frequency response function

Xu Li (徐 丽)1,2, Yi Weijian (易伟建)3 and Zhihua Yi (易志华)4

  1. Beijing University of Technology, Beijing 100022, China
  2. Guangzhou University, Guangzhou 510405, China
  3. Hunan University , Changsha 410082, China
  4. City College of New York, NY 10031, USA

Abstract: Structural strain modes are able to detect changes in local structural performance, but errors are inevitably intermixed in the measured data. In this paper, strain modal parameters are considered as random variables, and their uncertainty is analyzed by a Bayesian method based on the structural frequency response function (FRF). The estimates of strain modal parameters with maximal posterior probability are determined. Several independent measurements of the FRF of a four-story reinforced concrete frame structural model were performed in the laboratory. The ability to identify the stiffness change in a concrete column using the strain mode was verified. It is shown that the uncertainty of the natural frequency is very small. Compared with the displacement mode shape, the variations of strain mode shapes at each point are quite different. The damping ratios are more affected by the types of test systems. Except for the case where a high order strain mode does not identify local damage, the first order strain mode can provide an exact indication of the damage location.

Keywords: frequency response function; uncertainty; strain mode; Bayesian method; local damage; damage detection; concrete frame

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Copyright 2009 IEM. Journal of Earthquake Engineering and Engineering Vibration. All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as described below, without written permission from the Publisher. Copying of articles is not permitted except for personal and internal use, to the extent permitted by national copyright law, or under the terms of a license issued by the National Reproduction Rights Organization of China.