Optimum Design of Reinforced Concrete Cantilever Retaining Walls according Eurocode 2 (EC2)

Abstract

This study investigates optimum design in terms of minimum cost of reinforced concrete cantilever retaining walls. For the optimization process, the evolutionary method which is a combination of genetic algorithm and local search techniques was implemented. Evolutionary method was adopted in this study because it can effectively solve highly nonlinear problems and problems that feature discontinuous functions as demonstrated by several works available in the literature. The popularity of the evolutionary method may also be attributed to its availability as one of the solving methods in Solver add-in tool of Microsoft Excel. This implies that it is freely available and no need to pay for extra license to run any optimization problem. The design variables of the problem are thickness of stem wall, thickness of base slab, width of the heel, width of the toe, area of steel reinforcement for the stem wall and base slab. The objective function was to minimise the total cost of the wall, which includes costs of concrete, steel, forming, and excavation. The constrained functions were set to satisfy provisions and requirements of Eurocode 2 (EC2). Material strength and soil characteristics are treated as design parameters where they are kept constants during solution of the problem. Various material cost ratios were considered. Consequently, optimum design charts were developed for a wide range of wall height, coefficient of friction and surcharge load. Following a comprehensive investigation of the minimum cost problems carried out for different cases, one can conclude that the total cost of the retaining wall is directly proportional to the wall height and surcharge load values, whereas, the cost is almost independent of coefficient of friction.