Development of an Improved Capability for Predicting the Response of Highway Bridges: Final Report

About the report:

This study compared experimental and analytical stress and deflection response of a simply-supported highway bridge as measured from a field test and as predicted from a finite-element analysis. The field test was conducted on one span of a six-span highway bridge in Virginia using a loaded dump truck as the applied loading. Deflection and strain measurements were recorded at the quarter point and midspan of two adjacent spans with the test vehicle in various positions. A finite-element model of the bridge was then developed in which the bridge deck was represented using quadrilateral shell elements and the girders were represented by beam elements. Two different versions of the finite element model were utilized, one assuming simply-supported ends, and one in which continuity was included. Nodes were located such that stresses and deflections in the finite-element model could be predicted at locations corresponding to those where experimental data was recorded. It was found that the measured response and predicted response from the finite element model with simply-supported boundaries did not compare favorably. Differences on the order of 50% or more were typical. Experimental data from the field test had, however, indicated a degree of restraint at the supports corresponding to approximately 10% fixity. When this degree of restraint was included in the finite element model of the bridge, comparison between measured and predicted response improved markedly. In fact, the difference between measured and predicted deflections were generally less than 5%. Comparison of measured and predicted stresses indicated somewhat larger differences although the agreement was still satisfactory. Results of this study indicate that the overall response of a relatively simple bridge structure can be satisfactorily predicted from rationally developed finite element models. In the formulation of these models, however, considerable attention should be devoted to a realistic representation of the longitudinal and transverse stiffness and particularly to the support conditions of the structure.

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