Effect of Design Parameters on the Dynamic Response of Bridges

About the report:

Engineers and researchers have long recognized the importance of vehicle-induced vibration with regard to the response and service life of bridges. In spite of the recognition of the importance and role of dynamic response in deterioration and fatigue damage, the use of current design practices can still result in bridges with undesirable dynamic response characteristics. The primary objective of this study was to develop a procedure for representing moving loads on a bridge model within the context of a commercially available computer code. Such an evaluation might reveal ways to improve design procedures to mitigate unacceptable dynamic response. To achieve this goal, it was necessary to employ a moving load, and, thus, a secondary objective was to develop a procedure for representing moving loads on a bridge model within the context of a commercially available computer code. A third objective was to evaluate the relative effects of various parameters that have a substantial effect on dynamic response. Finite element models of typical bridge structures were developed using ANSYS, a commercially available computer code. A feature of this program, the ANSYS Parametric Design Language (APDL), was employed to represent moving loads with various characteristics. The algorithm developed to represent transient loads in the finite element beam model solution provided results essentially identical with those determined from theory. The relative influence of various design and load parameters was investigated using a finite element model of a section of an actual bridge. Midspan displacements of the bridge were calculated and normalized with respect to the static displacement. Changes in displacement attributable to modifications of the bridge characteristics and to loading parameters were determined.

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