Experimental study of the effect of engineering cementitious composites containing carbon nanofibers on concrete-beam-column joint

Concrete beam-column joint perform an important role in structural ductility, energy absorption and delaying breakdown. In this study, the effect of engineered cementitious composites containing carbon nanofibers (CNF-ECC) on the behavior of T-shaped concrete beam-column connections under cyclic loading is investigated. The tensile strain hardening behavior of ECCs has made a powerful material with high energy absorption and high cracking potential before failure. Since ECC is a relatively new material, much of the research has focused on understanding the nature of these materials, their different constituents, different mixing ratios, the stress-strain curve relationships, the invention of new composites. Research has also been done on its practical applications in structures. But these studies are not as extensive as research on the behavior of materials themselves, and require a great deal of analytical ad laboratory work. In this study, three concrete joints were tested, one of which was replaced as a reference specimen and the other two joints were replaced with ECC and CNF-ECC. The main parameters considered include hysteresis Moment curves - relative drift, energy absorption capacity, and crack distribution. Experimental models were subjected to cyclic loading at the end of the beam with displacement control. The loading continued until the load reduction reached more than 30-40% of the maximum load. The results show that by using these high- performance materials, the ductility and energy absorption of these joints are effectively improved. The results showed that using these powerful materials, the ductility and energy absorption of these joints were effectively improved and the cracks created in the connection spring as a dense network of micro-cracks with very shallow depth and width. respectively.