PCCP Rehabilitation using Advanced Hybrid FRP Composite Liner

This paper presents the design approach and results for full-scale hydrostatic tests performed on prestressed concrete cylinder pipe (PCCP) sections strengthened with the StrongPIPE Hybrid FRP system. The system is a trenchless technology for PCCP rehabilitation that consists of continuous, high-strength steel wires wrapped inside a pipe and sandwiched between two layers of fiber-reinforced polymer (FRP) composites. Installation of the system is automated which improves the quality of the final product and expedites production. The system combines the durability of FRP composites with the ductility, stiffness, and lower cost of steel. It can be used for the rehabilitation of short and long runs of pipes. Three full-scale pressure tests were performed on two 66-in (1676-mm) diameter, 20-ft. (6.1-m) -long PCCP sections (one benchmark and one strengthened with StrongPIPE system). The original unstrengthened pipe had a design bursting pressure 291 psi (2 MPa). However, original pipe section failed at a pressure of 140 psi (0.97 MPa) after only 25% of the original prestressing wires were cut. Testing of the pipe section strengthened with StrongPIPE system was conducted in two phases. In Phase I, all of the existing prestressing wires were cut in four stages (25% cut in each stage) to simulate progressive damaged condition of the pipe. In each stage, the pipe was pressurized to 300 psi (2.07 MPa) after the wires were cut. After all the wires were cut, the pipe was pressurized to 450 psi (3.1 MPa) and no failure occurred. In Phase II, the outer concrete core of the host pipe was completely removed in the test region to mimic further damage to the host pipe and was again pressurized to 450 psi (3.1 MPa). The overall performance of the system was excellent. The high stiffness of new steel wires prevented excessive deformation and dilation of the system at higher pressures, which resulted in more pressure resisted by the system and less pressure transferring to the host pipe. The hybrid FRP system provides a cost effective and durable solution for repair and strengthening of PCCP.