عنوان مقاله [English]
Carbon nano-materials, especially Carbon nanotubes (CNTs) is the most prospective advanced materials for application in cement based products for the construction industry, due to their excellent material properties. An appropriate design for beam-column joints structures is needed to meet the requirements of strength and ductility to prevent any sudden failure. Under seismic action, these beam-column joint zone is considered as the most sensitive zone that undergoes different shear stresses in various deflection. The seismic performance of beam-column connections and joints can be enhanced by using improved details in the joints ensuring a strong connection behavior. However, the use of dense reinforcements brings about executive problems such as lack of concrete condensation. This paper investigates the effect of engineering cementitious composites containing carbon nanotubes (CNT-ECC) on the behavior of RC exterior beam-column joint under reversed cyclic loading. In this study, three beam-column concrete joints were tested, one of the joints as reference specimen, and in two other joints of the critical area of beam-column connection, with the engineering cementitious composite (ECC) and CNT-ECC were replaced. The main parameters considered include the moment-deflection relationship, the energy absorption capacity, hysteresis curve and the crack propagation. The specimen was subjected to a reverse cyclic loading under control deformation at the tip of the beam. Loading was continued until the load dropped to more than 30-40% of the maximum load. Also, to simulate the actual sample, the compressive load of fifteen tons continuously entered the column. The mixing technique for producing highly dispersed nano material in cement mortar is crucial as it directly affects the mechanical properties of the cementitious composite. In this study, a surfactant (plasticizer) and Arabic Gum was used in order to get a homogenous dispersion of CNT in water. According to the results in the sample containing CNT in the plastic joint, it absorbs the highest amount of energy at the end of loading, which was 28% and 55% higher than ECC and NC, respectively. Also results indicate that the use of ECC-CNT in the plastic bonding zone has a significant effect on the energy absorption and relative deformation of the joints.