Influence of beam crosssection, loading arrangement and aggregate type on shear strength

This paper describes 14 tests on simply supported and continuous reinforced concrete beams which were designed to investigate the influences of aggregate type, loading arrangement and shear reinforcement ratio on shear strength. The beams were rectangular in cross-section with a/d , 3.5 (where a is the shear span and d the effective depth). Marine dredged gravel was used in ten beams (two without shear reinforcement) and limestone in the remaining four (two without shear reinforcement). The cracks typically passed around the gravel aggregate but through the limestone aggregate. Aggregate fracture was found only to reduce the shear strength of the beams without shear reinforcement. The factors of safety for shear failure implicit in Eurocode 2, BS 8110 and CSA A.23.3-04 are examined with data from this project and elsewhere. Eurocode 2 is shown to provide the lowest factor of safety for most beams. This is particularly significant for rectangular sections where Eurocode 2 can give lower factor of safety for shear than flexural failure which is undesirable. An amendment is proposed to address this.