Retrofitting of Deficient Connections in Frame-Shape Piles of RC Bridges using Fiber Cementitious Composites and Steel Angles

Beam-column connections are vulnerable areas of reinforced concrete moment frames-shapes of bridge piles and damaging of this area under the earthquake loads results in decreasing of seismic performance of frame and increasing of frame drift and eventually destruction of members and even the entire bridge structure. Due to the importance of connection zones in these frames, correct implementation based on regulations has significant impact on seismic performance of the frame. In this paper, the influence of stirrup of panel zone in a concrete connection of bridge piles with a scale of one-half has been conducted experimentally and numerically under cyclic seismic loading and then another deficient connection without any stirrup in the panel zone has been reinforced by high-performance fiber-reinforced cementitious composites (HPFRCC), and its effect on connection performance and compensation of the lack of stirrup of the panel zone has been studied. Also, to evaluate different states of connection strengthening of bridge piles, seven different analytical samples have been presented and the influence of different panels of HPFRCC on connection improvement and in strengthening the weak concrete connection by prestressed steel angels has been studied and compared. In this study, the hysteresis curves of load-displacement and their envelope curves and also energy dissipation, stiffness and stiffness loss curves of the connections have been studied. Results indicated that increasing the flexural capacity and ductility and rapid decreasing in stiffness-loss of connection in primary cycles of connection retrofitted with HPFRCC were more than those of the connection without stirrup in connection zone of bridge frame-shape piles. Maximum capacity of deficient connection of RC bridge piles was increased by 17-48% using high performance fiber reinforced cementitious composite (HPFRCC) panels.