Sensitivity of the Optimum Design of Reinforced Concrete Flat Slab Buildings to the Unit Cost Components and Characteristic Material Strengths

In this paper the influence of the unit cost of steel, concrete and formwork and thecharacteristic strengths of steel and concrete on the optimum design of reinforced concrete flat slab buildings is investigated. Size optimization of flat slab buildings according to the British Code of Practice is carried out. The objective function is the total cost of the building including the cost of floors, columns and foundations. The total cost of the building includes the cost of material and labour for concrete, reinforcement and formwork. Excavation cost is also considered in the cost of foundations the optimization process is handled in two levels.In the first level the optimum cross-sectional dimensions of reinforced concrete elements isdetermined using a hybrid algorithm based on genetic algorithm. In the second level anexhaustive search is applied to seek the optimum size and number of steel bars for eachindividual type of structural elements. A practical example is given to demonstrate theachieved cost saving and sensitivity of the optimum design to unit cost items and thecharacteristic strengths of steel and concrete.