| Concave slab is being widely used to build a toilet in residential buildings. In order to meet architectural requirements and make the beams around the slab unexposed, the structure with concave slab is used in engineering practice. However, the failure mode and transfer mechanism is quite different from normal ones. Also the current codes have no specification for this structural system and there is the lack of the experimental research and knowledge about the behavior of this slab. Therefore, it is significant theoretically and practically to make the investigation on local concave slab.Based on the engineering practice, two types of reduced scale models (1:0.7, 1:0.75) of cold-rolled deformed bar reinforced concave slab have been tested under short term static load till failure. Experimental studies are taken to learn the failure modes, distribution of plasticity line, deformations, bearing behavior and the details of the specimens.The experiments indicate that the overall deformation behavior of the floors are similar to RC two-way slabs, but complex stress regions and weak parts appear at the conjunctions of ribbon beam and that of the lifting beam and the ribbon beams. Before each specimen reached to the ultimate limit state, deflections and widths of cracks of all the specimens have reached to the service limit. Significant'X'plastic hinge lines appears at the bottom of the slabs, which indicates the slabs fail in two-way bending, and the ultimate load can be determined by plasticity theory. The cracking loads of the specimens are much higher than the possible characteristic combinations of engineering practice, which makes the slab keep elastic property under service loads.Finally, a finite element model ABAQUS is adpoted to analyze such structural systerm. Because the simulation results are similar to test results, ABAQUS can be used to make the finite element analysis on the deformation and bearing behavior of concave slab. The factors such as dimensions of the slab and the yield stress of the bars are carefully investigated. RC two-way slab with the same dimension is also discussed. The results show that the influence of the ribbed beams is to increases the stiffness and the deformation of concave slabs under uniform loads is much smaller than normal slabs. Mechanical characteristics of the end of the ribbed beam becomes complex, Deformation concentration makes the crack more broadening. |
