Optimization of Reinforced Concrete Frames

The optimization of three-dimensional (3D) reinforced concrete frames is discussed. The validity of the assumption that optimum concrete-section dimensions are insensitive to the number, diameter, and longitudinal distribution (topology) of reinforcing bars is examined. The validity of this assumption is examined by comparing optimum results from a multilevel method that simultaneously optimizes concrete-section dimensions and the number, diameter, and topology of the reinforcing bars to a traditional method that represents the number, diameter, and topology of the reinforcing bars through the single design variable, As, the total area of steel. Based on results from the comparison, a new method, referred to as the simplified method, is presented and recommended as the most efficient method for the optimization of reinforced concrete frames. The methods are applied to 3D one-, two-, and four-story frames subjected to load combinations involving dead, live, snow, and seismic loads.