Opti̇mum desi̇gn of prestressed concrete bri̇dge beams based on di̇fferenti̇al development algori̇thm

Bridges are constructions built on highways and railways that provide transportation of people and vehicles over the valleys. When these structures are designed, they are divided into classes according to the intended use and the material to be used (wood, reinforced concrete, steel construction, prestressed concrete etc.). Nowadays, prefabricated beams which are used frequently have gained considerable importance due to their advantages to cross large spans. Prestressed concrete is a technique which is aimed to reduce or eliminate the tensile stresses generated by the service loads to a certain level by giving the prestressing force to concrete in order to economically reach the effective span in reinforced concrete structure instead of increasing the sectional dimensions. For this reason, bridges are the most widespread manufacture where this method is used among all prestressed structures. The purpose of using prestressed concrete is to cross large spans more safely and with lower cost by reducing the tensile stresses generated in the concrete section. This can be considered as an optimization problem which is commonly encountered in engineering applications. In this study; optimum cost determination was made with "differential development algorithm" by considering prestressed concrete and reinforcement of bridge structures which consist of prefabricated prestressed concrete bridge beams (I Profile). This optimization process consists of topology and shape optimization. In the design of optimization, it is aimed to define the design problem considering two important criteria as safety and cost. Optimum design is consist of purpose of function, design variables and constraints. Constraints are calculated in accordance with Standard Specifications for Highway Bridges (AASHTO). In this study, the number of prestressed beams, beams with of cross-section dimensions, depth of beam upper flange, depth of beam bottom flange, width of stem, width of bottom flange, the height of upper gusset plate, the height of bottom gusset plate will be calculated as design variables during the design stage.Another variable affecting the design and the number of reinforcements sellected formerly will be determined as aresult of optimum design. The other fixed values are determined depending on the properties of the bridge. Thus, there are 9 design variables to be considered in order to achieve solution in optimum design problem. Additionally, bending, handling, shear safety stresses and deflection constraints are also calculated in accordance with AASHTO specifications. In this study, while the optimal values of the design variables are calculated, the differential development algorithm which has recently been used in many fields has been used. The success of the proposed method has proved with the obtained results.