Experimental Study On Aggregate Size Role In Shear Strength Of Reinforced Concrete Beams Without Shear Reinforcement

Reinforced concrete members without shear reinforcement are mainly used insome large or mass structures, the shear capacity of which is mainly provided by theconcrete. Unlike flexural failures, shear failures of concrete structure s are rapid,brittle and without obvious warning.Once happened, it will cause greater economiclosses and casualties. So in addition to the flexural design, it is important to calculatethe shear capacity of these members. Only under the clear understanding of theessence on the shear failure mechanism, can we effectively avoid the occurrence ofsuch damage.However, shear failure mechanism of beams without shear reinforcement is avery complicated problem. Since the beginning of the20th century, scholars fromdifferent countries have made extensive study on these problems, but failed toestablish a unified theory and design method. Especially in terms of the aggregateinterlock mechanism, there is still much controversy. Therefore, in order to gain newcognitive in mechanism level, further related theoretical analysis and experimentalresearch are needed.As a kind of composite material, the mechanics performance of concrete dependson the mechanical properties of the combined area between aggregate and hardeningcement. While accounted for about70%~80%of concrete’s volume, aggregate makesa great influence on the mechanical properties of concrete. In order to investigate theinfluence of the maximum aggregate size on the shear behavior of beams withoutshear reinforcement,16reinforced concrete beams subjected to concentrated loadingwere tested. The major parameters are the maximum aggregate size and span-to-depthratio. The experimental phenomena and test results, mainly including the material testresults of concrete and reinforcement, crack process and failure mode of test beams,the ultimate shear capacity, the load-middle deflection curves and the load-straincurves, were observed and collected. On the analysis of the surface roughness ofcrack, the relative displacement between crack lips, the influence of aggregate size onthe test results, and the calculation of shear carried by the uncracked concretecompression zone, it was concluded that the aggregate interlock is the mainmechanism of shear transfer in beams without shear reinforcement, and that sheardesign methods should be established on the basis of accounting the criti cal influence of aggregate interlock on the beam-shear behavior of reinforced concrete members.This thesis collected and described some general theories and computationalmodels about shear failure of reinforced concrete beams without shear reinforcement,such as the compressive force path concept, the splitting failure theory, the modifiedcompression field theory(MCFT),the critical shear-crack theory (CSCT) and thestatistical analysis formula proposed by Zsutty,and made a compariton of the testedshear capacity and the predicted value of different theories and v aried codes, whilecollected79historical test data for shear failure of reinforced concrete beams withoutshear reinforcement, taking into account the effect of the aggregate size on onnominal ultimate shear stress of reinforced concrete beams without stirrups.