Experimental Study On Shear Behaviour Of Self-compacting Concrete Beams Without Shear Reinforcement

The failure induced by shear in concrete structures is particularly dangerous and should be avoided in the design process.The shear performance of ordinary concrete members has been studied for more than 100 years,but so far has not formed a unified shear design method.The shear mechanism is not very clear,depending on the length,depth,cross-sectional shape of the component,and the type of the component(beam,plate,column),whether the load is static load or reciprocating load.The existing shear specification is not based on the formula of the shear failure mechanism analysis,but based on the experiment of half experience and half theory formula,The difference in shear strength for different shear codes can more than double.Self-consolidating concrete(SCC)is a highly workable concrete that can spread under its own weight without segregation and bleeding.Comprehensive research has been done on both fresh and hardened properties of SCC,but relatively little research have been performed on the structural behavior of SCC.It is generally believed that the shear behavior of self-compacting concrete structural members is the same as that of ordinary concrete members.Taylor reported that the shear strength is derived from the contributions of compression shear zone(ranging between 20%and 40%),aggregate interlock mechanism(ranging between 35%and 50%),and the dowel action of longitudinal reinforcement(ranging between 15%and 25%).Aggregate interlock mechanism plays an important role in the shear resistance.Although self-compacting concrete is developed on the basis of ordinary concrete,it is quite different from ordinary concrete:in order to achieve self-compacting properties,self-compacting concrete uses less coarse aggregate.smaller aggregate and more gelling material.Therefore,some researchers believe that scc mixes that rely on material-based changes may result in substantially reduced shear strength.An experimental investigation was conducted to study the shear strength and cracking behavior of beams made with self-consolidating concrete(SCC)as well as normal concrete(NC).A total of 12 flexurally reinforced concrete beams which consist of 8 beams with self-compacting concrete and 4 beams with normal concrete,with no shear reinforcement,were tested under mid-span concentrated load until shear failure occurred.The main variables in the test are concrete strength(C60、C40)and shear span to depth ratios(2.2、2.6、3.0、3.4).According to the test results,the propagation of the cracks,cracking load,diagonal cracking load,shear strength,failure mode,deflection-load curve of the SCC and NC beams are analyzed and compared.While,basing on the test data in this study,several shear strength models:plasticity theory、the compressive force path concept、the splitting failure theory、the modified compression field theory(MCFT)、the critical shear-crack theory(CSCT)、Zsutty’formula、GB50010-2010、ACI318-11、CSA23.3-04、EC2-02 were analyzed and compared.The shear experimental test data of 142 self-consolidating concrete and 798 normal concrete simply-supported rectangular cross-section beams withoutweb reinforcement were collected,the similarities and differences on shear capacity between SCC and NC beams without web reinforcement was found.