OPTIMIZATION OF TAPERED FRAMES BY MULTI-SEARCH METHOD AND APPLYING PRESTRESSING FORCE IN MEMBERS

In recent years, the application of tapered frames has increased in industry. In this regard, many researchers investigate different approaches to optimizing the design procedure of the industrial tapered frame. In this paper, optimization of tapered frames by applying prestressing force has been demonstrated to minimize the weight of the whole structure. Multi-Search Method (M.S.M) based on GA has been selected as the approach to optimization. Therefore, steel tapered frame has been optimized using M.S.M on the base of AISC code. The results of the process in each step, including analysis, design, and optimization, have been verified by comparing it with analytical solution. In the aforementioned process, each member of frame has 5 optimized design variables including height of web at the end of member, thickness of web, thickness of flange, and width of flange. In addition, the optimal prestressing force is provided by the code. The place of the applied prestressing force has been determined at the bottom and the top of column. The prestressed cable is one of the practical methods for applying force. The location and amount of prestressing force are the variables of optimization. Regarding the practical approach to applying prestressing in the steel structure, the prestressing force has been applied in three locations. In the first, second, and third cases, the force has been applied to the bottom of the column, the top of the column, and the top and bottom of the column, respectively. In each case, the prestressing force as a variable will be optimized. The efficiency of applying prestressing force has been evaluated by means of examples with different geometries and spans. The obtained results indicate the effect of applying presressing force to the tapered frames. The effectiveness of this method is dependent on the location of the force applied to the span or the frame. The results show the effectiveness of this approach, particularly in the third case.