11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) E. Oñate, J. Oliver and A. Huerta (Eds) OPTIMIZATION OF RC FRAME STRUCTURES SUBJECTED TO STATIC LOADING GEBRAİL BEKDAŞ * AND SİNAN MELİH NİGDELİ † * Department of Civil Engineering, Faculty of Engineering Istanbul University Avcılar, 34320 Istanbul, Turkey e-mail: bekdas@istanbul.edu.tr † Department of Civil Engineering, Faculty of Engineering Istanbul University Avcılar, 34320 Istanbul, Turkey e-mail: melihnig@istanbul.edu.tr Key Words: Harmony Search, Optimization, Reinforced Concrete, Cost Optimization, ACI- 318. Abstract. Generally, the initial design of reinforced concrete cross-sections are assumed by a designer and amount of reinforcements are calculated. Economy, which is the main goal of engineers, is only provided if the engineer is expert. Optimization techniques can be employed to find best design variable. In this study, reinforced concrete (RC) frame structures are optimally designed by using harmony search algorithm. The design constraints given in ACI-318: Building Code Requirements for Structural Concrete are taken into consideration. Optimum cross-sections and detailed reinforcements of a single-bay single-story frame structure are found for minimum material cost of the structure. The results showed that the proposed method is effective to find optimum design variable with minimum costs. 1 INTRODUCTION In the design of reinforced concrete (RC) structures, procedure of analyses and constraints given in several design codes are considered by the design engineers. Cross sectional dimensions are assumed according to experience of the engineer and requirements reinforcements are calculated. The area of the reinforcements is never exactly placed in the corresponding section because of reinforcement bars with constant diameter sizes. Also, reinforcements with special sizes (reinforcements providing the exact required area) cannot be used because of economy in production and practice in construction. Since RC is a composite of steel and concrete, the cost of the design cannot be foreseen. Although several experienced engineers know approximate cost and economical design, prices of the concrete and steel may show great differences according to region of the construction. For that reason, optimization of RC frames is an important subject. Optimum design of several RC members has been proposed by several researchers. Since