Optimum design of composite steel I-girder bridges with heuristic algorithm techniques

In this study, an efficient optimum design approach consisting of two stages is presented to realize the design of composite steel I-Girder bridges. In the first step, the analysis methods adopted by the bridge designers are examined. Line-Girder analysis method is used to analyze the solutions under the influence lines and most unfavorable loading conditions. With the application of the moving load distribution coefficients to the line-girder analysis results, the results of CSiBridge and SAP2000 software are approached with sufficient precision. Fixed and moving load calculations are analyzed in detail in steel bridge systems. It was found that the error rate between Line-Girder and SAP2000-Bridge 3D exact analysis results is acceptable for the case of the Strength I. Composite steel I-Girder bridge superstructure is examined in three stages according to AASHTO LRFD Specification. In this way a realistic analysis and design is provided. In the second step of the thesis study, a general purpose software was developed on the VB.Net platform with the SAP2000 API functions for the optimum design algorithm. In order to realize the optimum design, the most effective harmony search method among the heuristic algorithms is adapted to the software. The best designs were obtained with the most appropriate harmony parameters determined in this study. With the effective limiters such as stress and deflection, optimum design problem has been established with harmony search technique considering the limiters of AASHTO LRFD specification. In order to demonstrate the suitability of the developed Harmony Search Algorithm, the problems were solved with the Nonlinear GRG and Evolutionary method available in MS-EXCEL SOLVER and the results obtained were compared with the results of the harmony search method. It was found that deflection limiter was effective determinant in optimum design of steel I-Girder bridges.