SHEAR-STRENGTH OF REINFORCED LIGHTWEIGHT CONCRETE BEAMS OF NORMAL ANDHIGH-STRENGTH CONCRETE

An experimental investigation was conducted to study the ultimate shea r strength and the load-deformation characteristics of shear critical reinforced lightweight concrete beams of normal as well as high streng th concrete. A total of 15 shear critical reinforced concrete beams wi thout and with shear (web) reinforcement were tested in a 'stiff' test ing facility and complete load-mid-span deflection curves including th e post-peak portion were obtained. The experimental variables were the concrete compressive strength, shear span to depth ratio (ald) and th e amount of shear reinforcement. Concrete cylinder strength (f(c)) was varied between 30.5 MPa (4430 psi) and 89.3 MPa (12950 psi). The shea r span to depth ratio was varied between 1 and 4 and the shear reinfor cement ratio (gamma(w)) was varied between 0 and 0.784 percent. For th e range of variables tested, the results indicate that the predicted u ltimate shear capacities in accordance with the ACI Code and the BS 81 10 Code provide an adequate margin of safety when compared with the ob served values for normal as well as high strength lightweight concrete beams using different types of lightweight aggregates such as stalite , lytag, pellite and pumice. Furthermore, the results indicate that th e restriction imposed by the BS 8110 Code on the strength of concrete not to exceed 40 MPa for shear strength computations may be overly res trictive. The presence of shear (web) reinforcement improves the post- peak deformation characteristics of reinforced lightweight concrete be ams of normal as well as high strength concrete.