Experimental Study On Two-Way Concrete Slab Subjected To Punching Shear

As is well-known,corrosion of steel bars is a chief factor to affect the durability of reinforced concrete structure.In recent years, fiber reinforced polymer (FRP) composites have been widely used in bridges, civil buildings, offshore structures and underground engineering infrastructures due to their superior properties such as high strength, light weight, good corrosion resistance etc. For solving the problem of corrosion of steel bars in concrete structures, the investigation on feasibility of reinforced concrete structure with FRP rebars instead of steel reinforcement will be important and necessary. In this paper,the Seven specimens were reinforced with BFRP bars but the concrete strength, reinforcement ratio of BFRP bars and the aspect ratio of specimens varied in different specimens, the other two specimens were respectively reinforced with partial or all steel bars as control specimens.A series of the test data, such as the occuring and development of crack, BFRP tendons strain, concrete strain, load-deflection curve, cracking load, ultimate load and so on, were measured. And the punching behavior of two-way concrete slabs reinforced with basalt fiber reinforced polymer(BFRP)bars under punching shear loading is studied based on the test results. The main works include:(1)the characteristics of punching shear deformation of the two-way concrete slabs reinforced with BFRP bars under punching shear are analyzed. The results show that load-center deflection curve of BFRP reinforced concrete slab can be roughly divided into three stages, namely before cracking, after cracking, and punching shear failure.(2)The punching shear failure characteristics of two-way concrete slabs reinforced with BFRP bars are investigated. Compared with the reinforced concrete two-way plate, cracks of BFRP reinforced concrete slab develop faster, and the deflection is relatively larger in the same loading level, but the punching failure exhibites as brittle characteristic.(3)The effects of some factors, such as strength of concrete, BFRP reinforcement ratio, aspect ratio of specimens, etc.on the punching shear capacity of BFRP reinforced concrete two-way are analyzed. The results show that the ultimate punching capacity of BFRP reinforced concrete two-way slab enhances with the increase of concrete strength grade and BFRP reinforcement ratio.(4)The punching shear failure mechanism of BFRP reinforced concrete two-way slabs are analyzed. The results show that the punching-resistance mechanism of BFRP rebars is similar to steel rebars in concrete two-way slabs.(5)Based on the test studing and the theoretical analysis, referring to the previous research results and considering the inherent characteristics of BFRP Tendon, the calculating formula on punching shear capacity of concrete two-way slabs reinforced with BFRP rebars under mid concentrated loading are proposed.