Ultimate behaviour of composite steel concrete bridges with rigid and simple diaphragm connections.

In the design of composite bridges, the North American practice either ignores or minimizes the contribution of transverse diaphragms to the transverse load distribution; this results, among other disadvantages, in heavier longitudinal steel girders than necessary as well as in the loss of headroom. In this thesis, parametric and experimental studies were carried out to investigate the influence of simply and rigidly connected diaphragms on the structural response of composite bridges. In the analyses, both the yield line theory and the finite element method were used. Formulae based on yield line theory are developed to predict the ultimate load capacity of composite bridges. These formulae were based on both the parametric study as well as on laboratory test results on composite bridges. The developed formulae can be used to predict the ultimate load capacity or the required ultimate moment of resistance for the design of simple span and continuous span composite bridges. On the other hand, the finite element method is used to conduct a parametric study of the response of composite bridges under elastic and post-elastic loading ranges. The experimental study was conducted on four composite bridge models in two groups. Group A consists of two simply-supported single span bridge models and Group B consists of two continuous two-span bridge models. The test results were used to verify the assumption made in the theoretical analyses and to substantiate the results from such analyses. Good correspondence between the theoretical and experimental results is found. Both the analytical and experimental results demonstrated that the response of rigidly connected diaphragm composite bridges is superior to that of the simply connected diaphragm bridges. Rigidly connected diaphragm composite bridges are stiffer and stronger than simply connected diaphragm bridges. Furthermore, they have a better ability to distribute the load over the bridge under both service and ultimate loadings. The concrete deck slab also plays an important role in the transverse load distribution over the bridge. The results also revealed that there is an optimum number of the rigidly connected diaphragms in composite bridges beyond which no improvement in the load distribution should be expected. Connection types, load locations, aspect ratio of the bridge, sectional moment capacities, and the number of transverse diaphragms used influence the ultimate load capacity and the load distribution characteristics of composite bridges under service and ultimate loads. Comparison of the load distribution factors obtained from the finite element results and those of the Ontario Highway Bridge Design Code showed the code factors to be overly conservative.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1992 .S654. Source: Dissertation Abstracts International, Volume: 54-05, Section: B, page: 2643. Thesis (Ph.D.)--University of Windsor (Canada), 1992