Modal Parameters Estimation of Building Structures from Vibration Test Data Using Observability Measurement

Jae-Seung Hwang,Hongjin Kim,Bong-Ho Cho

doi:10.1155/2015/627852

Abstract

The load distribution to each mode of a structure under seismic loading depends on the modal participation factors and mode shapes and thus the exact estimation of modal participation factors and mode shapes is essential to analyze the seismic response of a structure. In this study, an identification procedure for modal participation factors and mode shapes from a vibration test is proposed. The modal participation factors and mode shapes are obtained from the relationship between observability matrices realized from the system identification. Using the observability matrices, it is possible to transform an arbitrarily identified state space model obtained from the experimental data into a state space model which is defined in a domain with physical meaning. Then, the modal participation factor can be estimated based on the transformation matrix between two state space models. The numerical simulation is performed to evaluate the proposed procedure, and the results show that the modal participation factor and mode shapes are estimated from the structural responses accurately. The procedure is also applied to the experimental data obtained from the shaking table test of a three-story shear building model.

Highlights

The modal participation factors and mode shapes are coefficients that represent how the ground acceleration is distributed to each mode of a building structure
The ground acceleration is used as an input to the single-input single-output (SISO) system and the first floor acceleration is used as an output
The numerical simulation is performed using threeand eight-story shear buildings, and the results show that the modal participation factor and mode shapes are estimated from the structural responses accurately compared to those of the analytical model

Summary

Introduction

The modal participation factors and mode shapes are coefficients that represent how the ground acceleration is distributed to each mode of a building structure. Ground vibrations can be affected by natural processes like earthquakes as well as by human events such as transportation [1], civil work [2], blasting [3], and industrial activities For this reason, the method to calculate the modal participation factor and mode shape is presented in many references in the area of dynamics of building structures [4, 5]. Due. Shock and Vibration to the discrepancies between an idealized shear building model and a real structure, the modal participation factors and mode shapes may be calculated with errors resulting in incorrect estimation of structural behavior. Because the observability matrices can be constructed without knowledge of mass, stiffness, and damping matrices of the structure, it is possible to identify the modal participation factor directly from the measured response using the proposed method. The numerical simulation is performed to evaluate the proposed procedure, and the procedure is applied to the experimental data obtained from the shaking table test of a three-story shear building model

Modal Parameters Estimation

Numerical Verification

Experimental Verification

Conclusion