INFLUENCE OF REINFORCEMENT DETAILING ON DUCTILE BEHAVIOUR OF RC FRAME

Abstract

Most of the important requirements of an earthquake resistant structure are related to its strength and ductility. Ductility of RC framed structures can be achieved by proper detailing of critical regions. Experimental evaluation is necessary to check the effectiveness of the detailing provisions. The primary objective of this investigation is to study the hysteretic behaviour and the available ductility of a conventionally designed and detailed RC frame as per IS: 456-1978 by conducting a quasi-static test. The initial stiffness of the system was found to be less than the analytical predictions due to the flexibility of beam-column joints and at the base of the column. It was observed that the energy was dissipated through stable hysteretic behaviour of RC frame with inelastic activities concentrated in beam-column joints and column-footing intersection. A failure mechanism was formed by failure of beam-column joints due to small volume of joint panel which can be attributed to excessive compressive stresses in the joint concrete and spalling of concrete at the outside ace of the column. Premature failure of joint and spalling of joint cover made the reinforcing bars ineffective in transferring the tensile forces and the full strength of the frame was not achieved. Therefore joints must be made capable of resisting the compressive forces and high shear by providing the transverse reinforcement in the form of stirrups and increasing the volume of joint panel. Eventhough an undesirable failure mechanism was formed, the available ductility was about 10.