Shear resistance strengthening of novel castellated key with embedded steel plates for dry joints in precast bridges

The shear performance of the precast segment concrete bridge depends largely on the shear resistance of joints between adjacent segments. However, the current joint structures have the limitation of shear resistance strengthening and the inconvenience of construction. To improve the shear capacity of the joints and achieve quick construction, a novel castellated shear key incorporating embedded steel plates is proposed. A total of fifteen single-keyed dry joints were designed, including two reference joints with a plain concrete key and a reinforced key and thirteen novel keys with embedded steel plates. Monotonic push-off tests of joints with or without shear keys were carried out. The influence of design parameters of the novel shear key, including heightto-thickness ratio, strength, steel ratio of the steel plates and bonding methods between concrete and steel plates on the shear performance of the joints were investigated comprehensively. The results indicated that the reinforcement of the shear capacity of the joints with the novel keys was 8.5%-33.9% higher than that of the joints with plain concrete keys due to the yielding of the steel plates. As expected, the embedded steel plates in shear keys could reach a shear-yielding state when the height-to-thickness ratio was larger than 25 or the yield strength of steel plates was lower than 355 MPa. A prediction formula of shear resistance capacity for the joints with novel shear keys was proposed considering the contribution of concrete and steel plates. It showed good prediction accuracy with an average value of 0.98 for the ratio of predicted to experimental values.