Effect of the soil slope on the cost-efficient optimum discrete design of reinforced concrete isolated footings

Abstract

The primary aim of this study was to investigate the impact of the soil slope on the cost-efficient optimum design of reinforced concrete isolated footings. In contrast to previous studies, the magnitude of the soil-bearing capacity was considered dynamically related to the foundation size and embedment depth. Thus, the principal objective of the optimization process was to attain an optimal reinforced concrete isolated footing design on sloped soil at the lowest possible cost. The length and width of the foundation, thickness of the footing, embedment depth, and diameter of the steel longitudinal rebars were considered as design variables. To achieve optimum designs, the principles of the Turkish Requirements for Design and Construction of Reinforced Concrete Structures (TS500 2000) and the Turkish Building Earthquake Code (TBEC 2018) were utilized to determine the practical structural design constraints of the optimization problem. The well-known Hansen and Vesic methods were used independently to compute soil load-bearing capacities. Thus, reinforced concrete isolated footings were cost-effectively optimized in four different load cases and four different soil slope cases, considering the Hansen and Vesic approaches as two different computation methods for the soil load-bearing capacity. As a robust and up-to-date algorithm, the grey wolf optimizer was utilized as an optimization tool. 32 optimum designs were then optimally evaluated with respect to cost efficiency, considering the soil slope, load case, and load-bearing capacity computation effects. As a result, increments in the soil slope were found to increase the cost of reinforced concrete isolated footings nonlinearly. The maximum cost differences between the 0° and 45° soil slopes evaluated in the design examples analyzed using the Hansen and Vesic soil load-bearing capacity methods were 116.36% and 148.05%, respectively.