SHEAR DUCTILITY OF REINFORCED-CONCRETE BEAMS OF NORMAL AND HIGH-STRENGTH CONCRETE

An experimental investigation was conducted to study the ductility of shear critical reinforced 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, and the amount of shear reinforcement. Concrete strength (f(c)') was varied between 5760 and 15,760 psi (40 and 109 MPa). The shear span-to-depth ratio a/d was varied between 1 and 4, and the shear reinforcement ratio gamma(w) was varied between 0 and 0.784 percent. For the range of variables tested, the results indicate that shear (web) reinforcement improves the shear ductility index of reinforced concrete beams of normal as well as high-strength concrete. High-strength reinforced concrete beams with a/d of 3 exhibit a plastic post-peak response, when shear reinforcement provided is about twice the minimum recommended by the ACI Building Code. Furthermore, for beams with shear reinforcement, the shear ductility index for beams with a/d of 1 decreases with an increase in concrete strength, whereas for beams with a/d of 2 and 3 there is an insignificant change in the shear ductility index due to an increase in the concrete strength.