NDTnet 1998 Aug, Vol.3 No.8

Abstract

Figure 1 General arrangement of an arch bridge test

This paper reports results studying the possibility of using a non-destructive testing method as a tool for the integrity assessment of flat arch bridges. Staged non-destructive testing was carried out on a brickwork masonry arch bridge, both with and without granular backfill material, using a transient impact dynamic excitation test method. The arch was then loaded statically and monotonically until collapse. At each loading increment the arch was nondestructively tested to establish its modal characteristics, its time and frequency domain responses, and its structural integrity. Figure 1 shows the general arrangement for one such test on a single ring, circular segmental arch with a span:rise ratio of 10. The static load was applied to the backfill's surface above the 1/4-span point. An impact hammer and dual channel spectrum analyser were used for the modal testing. The effect of loading on the arch's modal characteristics was isolated. The subsequent degradation of the arch's frequency response function (FRF) was related to its serviceability limit state. Events such as cracking to form the failure mechanism's hinges were categorised by their effect on the FRF.

The arch's resonant frequency sharply decreased when collapse was imminent. The results were compared to those previously obtained using a dynamic 3-D finite element analysis of the arch response in both time and frequency domains (1). The results showed that the model adopted was capable of predicting the experimental observations.The method is offered for further exploration and field trialing as tool for engineers involved in either condition based maintenance or assessment of such structures which are facing urgent reassessment in light of EU transport policy harmonization on axle loads by 1999.

1. Bensalem, A., Fairfield, CA. & Sibhald, A. Proc. ICE, J. Struct. & Bldgs, 1997,122:69-82.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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