Since construction of structures has high costs for their creators, designers and specialists are concerned about options that are economically feasible and appropriate, and also meet the preset goals of the structure. The optimal use of materials in building structures is considered as the main objective of each structure. On the other hand, among buildings used by humans, buildings as the most common and most important structures for the most general use, are prioritized in terms of optimization. For this purpose, in this paper, optimization of steel, three, six, and nine steel folding frames for reducing the structure weight, which is a criterion of cost of construction, is investigated by observing the principles and constraints of the structure against earthquake forces. Since the classical algorithms can not effectively find the optimal answer in the search space with a large number of variables, in this study a number of fuzzy algorithms were used for optimization, which include Monte Carlo NVE, Genetic Algorithm (GA), Particle Swarm Algorithm (PSO) and Gravity Search Algorithm (GSA). In order to compare the accuracy of the presented algorithms, the results of them were compared in terms of run time, optimal response and number of replications.