ABSTRACTS

A box girder bridge is a special case of folded plate with closed cross section. Box girder bridges have proved to be very efficient structural solution for medium and long span bridges. Thin-walled box girder bridges are most economical. There are three box girder configurations commonly used in practice. Box girders can be constructed as Single cell (one box), multi-spine cell (separate boxes) or multi-cell (contiguous boxes or cellular shape). Analytically, however, the box girder bridge is a complex indeterminate problem. Several researches have been carried out on advanced analytical methods of analyzing thin-walled box girder bridge for many years in order to better understand the behavior of all types of box-girder bridges, the results of these different research works are dispersed and undervalued. Therefore, existing methods for analyzing box girder bridges need to be improved; such improvements will either seek to simplify existing methods or attempt to improve results accuracy. The present work introduced the structural analysis of box girder bridges using Higher Order (HO4) Finite Strip which is an improvement to the existing higher order HO3 type. On account of its complexity, a MATLAB Computer program for determining structural response of thin-walled box girder bridges was developed using Higher Order (HO4) Flat Shell Strip. A simply supported thin-walled multi-cell box girder bridge was be adopted as the analytical structure. Validation of the theoretical formulations, which is synthesized in the proposed higher order (H04) finite strip computer program, was carried out by comparing the results obtained using the developed program with beam theory solution and the theoretical analysis results in published literature. Using three prototype models of simply supported thin-walled multi-cell box girder bridge i.e. model 1 (two-cell), model 2 (three-cell) and model 3 (four-cell) a numerical study of displacement and stress distributions was carried out to demonstrate the application of the theoretical formulations and developed computer program to the analysis of a typical simply supported thin-walled multi-cell box girder bridge subjected to vehicular loads. The analysis results were compared to the beam theory solution which does not include the effects of shear deformation. Results of analysis showed, among other findings that the effect of shear deformation were more in deflection than in stresses. Based on the results of analysis, distribution of stresses were studied, it was observed that the bending moments are resisted mainly by flanges whereas the shear stresses are resisted mainly by the webs. Investigating the effect of number of cells in a reinforced concrete box girder bridge using the developed model, the analysis results as presented in Tables (4.4, 4.5, 4.6, 4.11 - 4.19) and Figs.(4.4 – 4.12) showed that the Model 3 (four-cell) is the most efficient of the three prototype model in terms of strength properties – deflection and stress distribution. However, it will be more costly in construction than the other two. Therefore, the principles and programs developed in this research could be used in practice for the analysis of simply supported thin-walled multi-cell box girder bridge, box beam and folded plate structures.