Optimization of steel frame building systems in terms of parameters and reliability requirements

The problem of ensuring safety and reliability of building structures in modern socio-economic conditions is especially urgent. An important aspect of this issue is to determine the rational costs of manufacturing the load-bearing systems. This should take into account the possible emergency situations and their consequences. The purpose of the present studies is to create a methodology for the optimal design of normally operated steel frames considering material and social losses from the possible failure of structural elements. A method for parametric optimization of steel frame systems during selection of rod cross-sections and structure reliability levels is developed. The problem is to minimize structure manufacturing costs and recover damage caused by any material and social losses in the event of possible malfunctions and damage. Constraints on the strength, stiffness, and stability of the frame have all been taken into consideration. A two-stage optimization scheme is proposed. The first stage includes several parametric optimization processes using a genetic algorithm with minimization of construction costs for various system load levels. Then the structure's reliability is assessed within a probabilistic formulation for each of the obtained parameter combinations. Eventually variant of the frame is selected based on the minimum sum of the manufacturing cost and the expected value of material and social losses possible during operation period of the structure, expressed in monetary terms. An example of optimum design of a spatial frame with personnel present in the areas of possible damage is considered. The presented method allows implementing a comprehensive approach to optimum designing, while taking into account both the manufacturing cost and the possible failures of the constructive system.