Determining the Optimal Cost of Concrete Ribbed Slabs Based on Load and Beam Span

To optimize the cost of a reinforced concrete ribbed slab, the cost of concrete and steel used in it should be reduced. In other words, the cross section area of concrete and steel of structure should be reduced. To calculate the cross section area of concrete and steel of concrete ribbed slab, six design variables are defined that are related to slab thickness, bar diameter and ribs dimensions. The floor system of a structure made of reinforced concrete requires the efficient transfer of floor loads to vertical systems through the capacity of resistance to shear, bending and torsion. In addition to the need for strength, floors must meet the deformation criteria with a low crack width and deflection. The combination of these factors constitutes the constraints of slab cost optimization. To solve this optimization problem in this paper, the colliding bodies optimization (CBO) algorithm is used. The CBO algorithm is a new metaheuristic algorithm that has been developed in recent years and its main difference with other metaheuristic algorithms is that it does not require input parameters and their adjusting and requires less computational effort and time. In order to evaluate the effect of loading and beam span parameters on the optimal cost of concrete slabs, three different cases are defined. In each case, one loading state and four different beam spans are considered. In each state, due to the change of input parameters, the optimal design problem is executed independently and the value of the objective function and the corresponding value of the design variables are determined. In this way, the sensitivity of the optimal cost of concrete slabs to the loading and beam span parameters is analyzed. The results of this study Shows the effect of changes in beam span on the cost of ribbed concrete slab is much greater than the effect of load changes on the cost of slab. By increasing the beam span by 50%, the cost of the slab becomes more than doubles. In other words, the least change in the objective function due to changes in the length of the beam span in a certain loading case, has resulted in an increase of about 100% in the objective function, but the effect of loading on changing the cost of ribbed slab is much less. The greatest effect of loading was to change the value of the objective function by about 13%