Shear strength of reinforced lightweight concrete beams of normal and high strength concrete

Abstract

An experimental investigation was conducted to study the ultimate shear strength and the load-deformation characteristics of shear critical reinforced lightweight concrete beams of normal as well as high strength concrete. A total of 15 shear critical reinforced concrete beams without and with shear (web) reinforcement were tested in a ‘stiff’ testing facility and complete load–midspan deflection curves including the post-peak portion were obtained. The experimental variables were the concrete compressive strength, shear span to depth ratio (a/d) and the amount of shear reinforcement. Concrete cylinder strength (f'c) was varied between 30·5 MPa (4430 psi) and 89·3 MPa (12950 psi). The shear span to depth ratio was varied between 1 and 4 and the shear reinforcement ratio (γw) was varied between 0 and 0·784 percent. For the range of variables tested, the results indicate that the predicted ultimate shear capacities in accordance with the ACI Code and the BS 8110 Code provide an adequate margin of safety when compared with the observed values for normal as well as high strength lightweight concrete beams using dlflerent types of lightweight aggregates such as stalite, lytag, pellite and pumice. Furthermore, the results indicate that the restriction imposed by the BS 81 10 Code on the strength of concrete not to exceed 40 MPa for shear strength computations may be overly restrictive. The presence of shear (web) reinforcement improves the post-peak deformation characteristics of reinforced lightweight concrete beams of normal as well as high strength concrete.