Cost Optimum Design of Prestressed Concrete Bridge Decks Based on Bridge Loading Iranian Code using Genetic Algorithm

Among the concrete bridge deck sections، single-cell box girder is one of the most common sections. Single box arrangements are efficient for both longitudinal and transverse designs، and they produce an economic solution for most medium and long span bridges. Design of prestressed concrete bridges involves many variables which are related to each other. So it leads to a wide variety of acceptable designs. Since bridge designers conventionally use trial and error method along their experiences، optimality of the design depends significantly on designers'' experiences. Thus these structures have significant potential of cost optimization. In this study، optimization of simply supported، post-tensioned prestressed concrete box girder bridges using Genetic Algorithm (GA) is presented. Genetic algorithm is an iterative procedure maintaining a population of structures that are candidate solutions to specific domain challenges. During each temporal increment (called a generation)، the structures in the current population are rated for their effectiveness as domain solutions، and on the basis of these evaluations، a new population of candidate solutions is formed using specific genetic operators such as reproduction، crossover، and mutation. They efficiently exploit historical information to speculate on new search points with expected improved performance. Iran bridge loading code is considered for loading the bridge and AASHTO standard specifications for highway bridges are used for designing the bridge. Various variables considered are cross-sectional dimensions of the girder، number of tendons، number of strands per tendon، tendons arrangement، reinforcements of slabs and prestressing force. Constant design parameters are bridge width، span length and material properties. It is concluded that optimization using new algorithms like GA is an appropriate alternative for traditional bridge design process which will result in saving in time، cost and human effort.