Experimental Study On Reinforced Concrete Slabs With Discontinuous Support

With the diversification of structure style of building, the wide application of reinforced concrete slabs with discontinuous support increases obviously, but the related investigation is very limited. Considering this situation, a series of specimens of reinforced concrete slabs with discontinuous support is designed, and the bearing capacity and deformation behavior of specimens are investigated according to their testing results. A calculation method for one-way slab's ultimate load capacity under compressive membrane action is proposed, an experiment of a group of one-way slab specimens supported by shear-wall is conducted, and the influence on bearing capacity of cantilever slab and continuous slab with different depth of reinforcement cover is also discussed by test. Based on above testing results and investigations, six reinforced concrete slabs with discontinuous support of case engineering are analyzed.The principle contents are summarized as follows:(1) A series of one-way slabs, two-way slabs and L-shaped slabs with discontinuous support is tested, the testing results show that the bearing capacity and deformation behavior are both varied with the transformation of the length of fixing edge, and the influence on specimens'deformation behaviors of the arrangement of fixing edge is also investigated. Based on the testing results of two-way slab specimens with free edge, the regularity of distribution of their yielding line patterns is proposed. According to the analysis of L-shaped slabs'testing results and ultimate states, the disturbance on yielding line pattern of local reinforcement enhancing is validated, and the improved reinforcement at the top of slab angle is presented. The ultimate load capacity of these specimens are calculated by yielding line method, based on the analysis of the errors between calculations and testing results, it is proposed that neglecting the discontinuous support's influence on the ultimate states of specimens, yielding line method can be used to predict the ultimate load capacity of reinforced concrete slabs with discontinuous support.(2) Based on the assumption of additional three-hinge arching action, an analytical method was proposed to predict the ultimate load of lateral restraint one-way slab under compressive membrane action. An experiment of a set of reinforced concrete one-way slabs supported by shear-wall is carried out, and the calculations of this proposed method are contrasted to the testing results. The influences on specimens'bearing capacity of some design parameters are also investigated by the analysis of testing results, such as the vertical load on ending shear-walls, lateral restraint stiffness of horizontal support, and the span-height ratio and steel percentage of central slab. According to the equilibrium relationship under compressive membrane action, the negative interval of additional capacity is proven in the late of this stage. According to specimens'deformation condition, a three-stage model is presented to simulate the additional load-deflection relationship, and by superposing to the deformation behavior of bending action, it can be used to predict the deflection of one-way slab under compressive membrane action.(3) Based on the situation that upper-deep negative reinforcement cover in reinforced concrete slab is usually discovered, a series of cantilever slabs and continuous slabs with different-depth reinforcement cover is designed, and the influence on their loading capacity of reinforcement cover depth is investigated by tests. According to testing results and theoretical analysis, it is pointed out that the cantilever slab belongs to determinate structure, its bearing capacity decreases obviously with the increasing of reinforcement cover depth, and its reinforcement cover should be restricted strictly; continuous slab belongs to indeterminate structure, the effect on its bearing capacity of upper-deep negative reinforcement cover is very limited, considering the advantageous influence on their bearing capacity of compressive membrane action, so its requirement can be relaxed.(4) Six slabs with discontinuous support of case engineering are chosen to be tested nondestructively, and their ultimate load capacities can be calculated by the testing results. Accounting the additional load capacity of compressive membrane action, their load capacities can also be calculated by yielding line method, and a calculating approach to reinforced concrete slabs with discontinuous support in case engineering is proposed by the comparison between the projection and the calculation.