Analytical and experimental study of a skew bridge model

0141-0296/$ - see front matter # 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.engstruct.2004.03.013
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J. Meng et al. / Engineering Structures 26 (2004) 1127–1142
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Received 2 January 2003; received in revised form 1 November 2003; accepted 16 March 2004
Abstract This paper describes an experimental study of a skew bridge model conducted at the Federal Highway Administration TurnerFairbank Highway Research Center. The objectives of the experiment are: (1) to perform a pilot study on the design, construction, instrumentation, testing and data processing of a skew bridge model, (2) to provide experimental data to validate a 3D finite element model developed for the skew bridge, and (3) to confirm the applicability of a simplified bridge model (the dual-beam stick model) developed for the dynamic analysis of skew bridges. Details of the design, construction, instrumentation, testing and data processing of the model bridge are described. Results for static displacements, natural frequencies, mode shapes and damping of the model bridge will be presented. A comparison of the results obtained from these tests with those obtained numerically from a finite element analysis and analytically from the dual stick bridge model shows that good correlation is obtained. # 2004 Elsevier Ltd. All rights reserved.
frequencies, mode shapes and damping that were required in a dynamic analysis. In what follows, the design, construction, instrumentation, testing and data processing of the bridge model are discussed. 2. Design and construction of the bridge model Generally, a dynamic experiment involves three constituent phases: test preparation, dynamic response measurements and modal parameter identification. Test preparation may include model selection, model design, model construction, instrumentation and data acquisition system setup. Details of the test preparation will be discussed in this section. 2.1. Model selection Skew bridges are often used for overpasses. Modern overpasses are typically continuous over two or three spans and designed for two to four lanes of traffic. Including medians, shoulders and guard rails, the width of a typical skew bridge often lies in the range of 36 ft (11 m) to 60 ft (22 m), and the length of each span is in the range of 40 ft (12 m) to 100 ft (30.5 m) [3]. Ideally, a full-scale model should be used for the tests. However, due to limitations on experimental expenses and other lab conditions, a scaled model was used instead. The size of the scaled model was determined primarily by the size of the NDE laboratory in the Federal Highway Administration’s Turner-Fairbank Highway Research Center in McLean, Virginia. Based on the feasibility of setting up the largest possible size skew bridge model in the given lab space and proper considerations given to similitude [17–20], a two-span continuous bridge with a span length and deck width of 12 ft (3.6 m) and 7 ft (2 m), respectively, was designed. This represented a scale factor of
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Bryant Associates, Syracuse, NY 13202, USA Federal Highway Administration, 6300 Georgetown Pike, McLean, VA 22101-2296, USA Department of Civil and Environmental Engineering, Syracuse University, 220 Hinds Hall, Syracuse, NY 13244-1190, USA
Keywords: Skew bridge; Dynamic analysis; Experimental study
1. Introduction The experimental study of the vibration characteristics of structural systems is an important element in our efforts to understand and control the many vibration phenomena encountered in design. Very often, tests are performed on a complex structure with the objective of obtaining an empirical description of its dynamic behavior, or providing verification for an analytiel. To quantify the dynamic response of a given structure, the determination of its intrinsic dynamic properties such as natural frequencies, vibration modes and damping, etc., is of particular importance. These structural characteristics can be determined using a modal test [6,8]. Performing a modal test on a structure allows an analyst to validate results generated using a finite element (or other analytical or numerical) model, and so more confidence can be placed on the structural model to provide meaningful analysis results.
à Corresponding author. Tel.: +1-315-443-2311; fax: +1-315-4431243. E-mail address: emlui@ (E.M. Lui).