Soil-Structure Interaction Effect on the Optimal Design of Low-, Mid- and High-Rise Reinforced Concrete Frames

In procedure for analysis, design and optimization of reinforced concrete buildings, for most or maybe all regular buildings, different parts of the procedure for different parts of the building, including main structure and its foundation, are usually carried out independently. This means that these structures are mainly analyzed and designed by supposing a fixed-base, and then, forces at the foot of columns are obtained and used to analyze and design the foundation. Thereby, no attention is paid to the effects of foundation settlements on the distribution of forces in structural elements. Interaction between the structure, the foundation and its subsoil (flexible-base), changes the actual behavior of the structure compared to the method in which the structure is investigated alone (fixed-base). In this paper, various RC buildings, including low-, mid- and high-rise types, with foundations and soil under their foundations in three different layers, with a depth of each layer equal to ten meters, are modeled using SAP2000. Also, all the frames are optimized using Artificial-Bee-Colony algorithm in MATLAB, subject to stress and drift constraints. The results show that, since in a structure with optimal design the values of stress in elements and drift of stories are usually very close to the maximum allowable limits, hence, a slight increase in structural response, induced by soil-structure interaction effects, may lead to the violation of optimal design constraints. Therefore, taking not into account such effects in design optimization of structure, may lead to not only a non-optimal but also an infeasible design.