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TECHNICAL PAPERS

# Moving Axle Load From Multi-Span Continuous Bridge: Laboratory Study

[+] Author and Article Information
Tommy H.T. Chan

Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. C.cetommy@polyu.edu.hk

Demeke B. Ashebo

Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. C.

J. Vib. Acoust 128(4), 521-526 (Feb 12, 2006) (6 pages) doi:10.1115/1.2202154 History: Received September 10, 2004; Revised February 12, 2006

## Abstract

Laboratory study on the identification of moving vehicle axle loads on a multi-span continuous bridge from the measured bending moment responses is presented. A bridge-vehicle system model was fabricated in the laboratory. The bridge was modeled as a three span continuous beam and the car was modeled as a vehicle model with two-axle loads. A number of strain gauges were adhered to the bottom surface of the beam to measure the bending moment responses. Using measured bending moment responses as an input, the corresponding inverse problem was solved to identify moving loads. The moving forces were identified when considering bending moment responses from all spans of the beam. In order to avoid the lower identification accuracy around the inner supports of continuous bridge and to improve the computation efficiency, the moving force identification from the target (one selected) span of the continuous bridge was studied. The rebuilt responses were reconstructed from the identified loads as a forward problem. To study the accuracy of the method the relative percentage errors were calculated with respect to the measured and the rebuilt bending moment responses. The rebuilt bending moment responses obtained from the identified forces are in good agreement with the measured bending moment responses. This indirectly shows that the method is capable of identifying moving loads on continuous supported bridges.

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## Figures

Figure 1

Group of moving forces over the continuous beam

Figure 2

Experimental setup

Figure 3

Sensors arrangement on the main beam

Figure 4

Output of photoelectric sensors and strain gauge

Figure 5

Identified axle loads for multi-span continuous case

Figure 6

The measured and rebuilt bending moment responses for continuous beam case at midpoint of each span

Figure 7

Identified and static forces for target (middle) span case

Figure 8

The measured and rebuilt bending moment responses at midpoint of target span (for middle span case)

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