TOWARDS SIMPLIFIED COMPUTER-BASED ANALYSIS OF SKEWED-BRIDGES

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Author

Presented To

Department of Engineering

ABSTRACT
Needs for aesthetics, protection of abutments, and safety requirements of greater speeds on highways, demand better alignment. In order to achieve these, skew bridges are frequently built. The analysis of such structures poses specific difficulties to bridge designers, for example, response to torsional motions when the skew angle is greater than 20°. In this study the structural behavior of skew bridge decks of various configurations and loading conditions is presented. Element models of the structure are discussed through the matrix displacement method. In addition, discretisation of the deck through its representation as a plane grillage of discrete interconnected elements is fully discussed. Loadings to BS5400 and load cases and combinations at both ultimate and serviceability limit states are provided. Special attention is given to the formulation of the problem in a systematic manner, which makes it suitable for computerized analysis of any bridge deck that is represented as an assemblage of discrete interconnected elements. Further, an attempt has been made to provide a simplified approach to the use of these tools, so that their fruits may be made available to the designer without the need to perform complicated analysis in the design office. Having preselected a structure, the engineer can then identify a particular chart viii and read directly the value of the structural response concerned without performing any rigorous analysis. Clearly, a great economy of time and effort is achieved, if for many structures such as highway skew bridges that might not be analysed conventionally, much detailed analysis can be replaced by the use of suitable charts. Finally, a FORTRAN 77 computer program, GRID, is presented for the transverse analysis of bridge decks. It allows reinforcement to be proportioned for transverse as well as stirrups to be proportioned for longitudinal shear and torsion. Documentation, sample input and output, and a source listing as well as analysis aid charts are provided. It is hoped that bridge designers would find it convenient to use these charts.