Application of an Improved Genetic Algorithm for Optimal Design of Planar Steel Frames

Genetic Algorithm (GA) is one of the most widely used optimization algorithms. This algorithm consists of five stages, namely population generation, crossover, mutation, evaluation, and selection. This study presents a modified version of GA called Improved Genetic Algorithm (IGA) for the optimization of steel frame designs. In the IGA, the rate of convergence to the optimal solution is increased by splitting the population generation process to two stages. In the first stage, the initial population is generated by random selection of members from among AISC W-shapes. The generated population is then evaluated in another stage, where the member that does not satisfy the design constraints are replaced with stronger members with larger cross sectional area. This process continues until all design constraints are satisfied. Through this process, the initial population will be improved intelligently so that the design constraints fall within the allowed range. For performance evaluation and comparison, the method was used to design and optimize 10-story and 24-story frames based on the LRFD method as per AISC regulations with the finite element method used for frame analysis. Structural analysis, design, and optimization were performed using a program written with MATLAB programming language. The results show that using the proposed method (IGA) for frame optimization reduces the volume of computations and increases the rate of convergence, thus allowing access to frame designs with near-optimal weights in only a few iterations. Using the IGA also limits the search space to the area of acceptable solutions

Determination of Behavior Coefficient of Prefabricated Concrete Frame ith Prefabricated Shear Walls

AbstractIncreasing population in recent decades has made the necessity of quick low cost construction unavoidable. Meanwhile the use of prefabricated concrete frame with prefabricated concrete shear walls due to better quality of performance and reduction of manufacturing time is a good option for public multiple floor buildings. These structures in addition to resistance to seismic loads have more flexibility in methods of construction. There is little information about the exact behavior of prefabricated concrete frame with shear walls under earthquake and dynamic loads. Hence much research has been done by various researchers on the seismic behavior of these structures in the form of experimental and analytical models. Today, the main section of the seismic design of buildings is done based on equivalent static force method and calculating earthquake force of design from earthquake linear spectrum by applying a reduction coefficient called behavior coefficient of structure that embrace philosophy of design. So the necessity of determining behavior coefficient with respect to its importance in seismic design of structures seems essential. The behavior coefficient of structure is a coefficient that includes inflexible function of structure and indicates strength and hidden ductility of structure in inflexible stage. In this study various types of pre-fabricated concrete frames together with pre-fabricated 4 and 8-storey shear walls with 1 and 3 bays are studied. The effect of two kinds of uniform and triangular loading on behavior factor has also been taken into consideration. Non-linear static analysis method (Push-over) has been used in order to determine the behavior factor. On the whole, the results have shown that by increasing the bays and building storeys the structural behavior coefficient was increased