CARRYING-CAPACITIES OF RC SLABS WITH FULLY-FIXED SUPPORTS BASED ON THE COMPRESSIVE-TENSILE MEMBRANE EFFECT

It is important to estimate the carrying-capacities of beams and slab members under large deformation condition in the engineering design. The carrying-capacities of reinforced concrete (RC) slabs are conventionally obtained by the compressive-membrane effect under small deformation condition. However, it is extremely important to estimate the carrying-capacities of RC slabs by taking the compressive-tensile membrane effect into account due to most of catastrophic fractures of the members occur in the large deflection stage. The whole process from loading to fracture of RC slabs is divided into the compression of the slab end, the descending branch of concrete cracking and the ascending branch of reinforcement yielding. The load-deflection curve with membrane effect is obtained according to the elastic-perfectly plastic model of reinforced concrete member under bending moment. The carrying-capacities of RC slabs based on the tensile-membrane effect under large deformation condition are derived and the full load-deflection curves by taking the compressive-tensile membrane effect into account are further obtained by using the classical deflection differential equation and the energy principle, in which the softening coefficient of flexural rigidity is used to correct the deflection. The results show that the full load-deflection relationships of RC slab can be predicted reasonably based on the carrying-capacity assessment including the compressive-tensile membrane effect. It is indicated that the analytical results are in good agreement with the test data and can be employed to predict the carrying-capacities of RC slabs.