Towards bridge optimization: evaluation of optimal parameters at critical response states

Abstract

The paper is assigned to development of optimization techniques for load carrying structure of a bridge, constructed from standard steel profiles. Statement of a problem, involving constraints due to relationships of codified regulations in concert of an employment of elastoplastic response of structure ensures an obtaining an optimal structure compatible with actual engineering design. These techniques allows to employ a significant strength resource versus usual elastic design, id est result the significant material savings. Solution of such optimization problem is rather difficult even applying an iterative approach due to peculiarities of development of plastic deformations, yield conditions, involving several components of internal forces, stiffness constraints, evaluation of load combinations due to code regulations, finally, the problem size. Computational efficiency and successful iterative optimization (convergence) of structures, involving stiffness constraints (full optimization problem) highly depend on choosing starting point and that of an application of rational limitations for minimum values of designed parameters and that for extreme displacements. This separate problem by itself is difficult to solve also. The above mentioned values are identified by solving the limit equilibrium optimization and analysis problems. Then the full optimization problem can be solved. Such an optimization approach was successfully employed by authors for simpler structures.