Analyzing the Structural Implications of Redundancy in Truss Bridge Design

Abstract

The extensive national infrastructure of the United States is gradually deteriorating due to lower investment and infrequent maintenance and repair. With a growing population and increased movement of goods, the question arises of whether or not the bridges of our infrastructure network will be able to handle even larger traffic loads. One aspect of bridge design that is relevant to this issue is redundancy, the characteristic of a damaged bridge to continue to carry load and to avoid collapse. Do the nation’s bridges, many of which are truss bridges, exhibit sufficient redundancy? This thesis research analyzed redundancy in truss bridges by utilizing and adapting a formerly proposed methodology for measuring redundancy. The objectives of the research were to demonstrate that this methodology could be successfully applied to truss bridges and to use that methodology to examine possible solutions to improve truss redundancy. Nonlinear analysis was performed on a computer model of a steel truss bridge under truck loading conditions. The results of this analysis were used to calculate redundancy, which was determined to be insufficient. Adjustments to the model, including additional truss members and rotational springs, were made and redundancy was evaluated. The proposed modifications were discussed within the context of the legal standard of care. Results suggested that new standards for truss design should be implemented into official bridge design specifications in order to enhance redundancy.