Performance evaluation and strengthening analysis on serving reinforced concrete poles with steel ring joint

In order to reveal the failure mechanism and load bearing capacity properties of serving Reinforced Concrete Poles (RCP), three poles with 4.2m length, three poles with 3.5m length and three RCP with steel ring joint strengthened CFRP (Carbon Fiber Reinforced Plastic) are conduct experiments of flexural capacities. According to the test, the whole process of forcing and failure mode is observed, and important indicators of load-deflection curves, stiffness degradation rule curves and ultimate bearing capacity are obtained. Results show that the failure models of majority of nonreinforced specimens are concrete creaking and not yield steel ring joint, and their failures are obviously brittle. The mean strains of specimen cross-sections meet the assumption of plane-section. The damage of reinforced specimens are mainly bonding failure between the interface of concrete and CFRP, and the damage process is very rapid. The characteristic of damage is brittleness. The bearing capacity of specimens with double layers is 32.8% higher than that of single layer. The mean strains of strengthened specimen cross-sections also meet the assumption of plane-section. Comparison of different specimens, the bearing capacity and initial elastic stiffness of the late stage of poles reinforced are improved 58.8% and three times, respectively, and their ductility properties are also improved. The energy dissipation abilities of strengthen poles and non-strengthen poles are almost the same.