The aim of this research is to obtain the optimum spacing between columns in both directions for multi story buildings through the optimization of reinforced concrete required to construct them. This will help the designer in determining the economic spacing in the preliminary design stage, to predict the cross section sizes of members for these spans and to determine the most influenced structural members. A four story (ground + 3 floors ) virtual reinforced concrete building was analyzed and designed for three cases of columns spacing ( 3.0 m , 6.0 m , 9.0 m ) using reinforced concrete frame structures for the same working load conditions. A detailed estimation and comparison for reinforced concrete quantities was carried out for the structural members and the average per square meter was calculated.
The results showed that the foundation was the most influenced members due to increase in the span of columns, 3.72 m was the optimum spacing concerning the quantity of Concrete required for construction (0.965 m3/m2) while the span of 4.23 m was the optimum span for reinforcing steel (86.64 kg/m2).