Introducing a plastic analysis formula for braced frames and its optimization using genetic algorithm to predict the collapse of steel braced frames

Plastic analysis method is one of the most effective and most used methods in this field. Analysis of moment frames has been carried out with the aid of simple plastic analysis by many researchers. However, the analysis of braced frames due to the buckling of braces and the presence of axial and shear forces simultaneously in the frame members is very complex and therefore, little research has been done in this area. In this research, a special theory based on combination of mechanisms method for the plastic analysis of steel braced frames has been presented. Using the genetic algorithm, a program has been proposed to determine the failure mechanism and collapse load of the steel braced frames based on this methodology. The comparison of the results shows that the proposed formula is very accurate and can accurately determine the failure mode and its corresponding load. According to this, three arbitrary frames with different in number of stories is investigated. The collapse mechanism corresponding to the critical load factor is obtained by means of Genetic optimization algorithm and the virtual work theory. For Verification, a pushover analysis is performed for determination of collapse mode of each frame. In examples one and two which the frames are low-rise, the solution is the same, while in the third example, a slight difference is observed in the location of hinge formations. However, this error had been observed in moment frames due to the difference of the principals in the two applied analysis.