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CFRP Renewal of Prestressed Concrete Cylinder Pipe (WaterRF Report 4352)
Citation:
Zarghamee, M., M. Engindeniz, AND N. Wang. CFRP Renewal of Prestressed Concrete Cylinder Pipe (WaterRF Report 4352). Water Research Foundation, Denver, CO, 2013.
Impact/Purpose:
The purpose of the study reported herein is to develop the requirements on materials, design, and installation of carbon fiber reinforced polymer (CFRP) renewal and strengthening of distressed prestressed concrete cylinder pipe (PCCP); so that the pipe, when subjected to the exposure environment, design working and transient pressures, gravity loads, and live loads, shall have the necessary strength, reliability, and durability to resist the loads throughout the design life as it continues to degrade in the exposure environment. CFRP liners adhered to the inner core can provide an effective means of internal repair and strengthening of PCCP. Water utilities have used this technology since the 1980s, and increasingly in recent years, when other methods such as post-tensioning or pipe replacement were not feasible or economical. However, a standard that can be used by the professional engineers and utilities for the design of CFRP liners to ensure adequate strength, durability, and reliability of the repaired pipe throughout its service life has been lacking. To develop a design standard, the Concrete Pressure Pipe Committee of the American Water Works Association (AWWA) has formed a subcommittee to draft a standard for CFRP Renewal and Strengthening of PCCP. Although the AWWA draft Standard produces a consensus document for the design of CFRP liners, the value of the standard is greatly increased if it is based on fundamental analytical data and experimental data. This study is aimed at producing such data.
Description:
The project completed and reported on multiple tasks, including: Review literature and data on degradation of CFRP to determine the material adjustment and time effect factors that should be used in design of CFRP liners for design lives of five and fifty years; Review literature and data on buckling resistance of CFRP liners in degrading PCCP; Perform two full-scale hydrostatic pressure tests and eight three-edge bearing tests to study the behavior of CFRP-lined distressed PCCP with regions of broken wires and cracked outer core; Perform detailed nonlinear finite element analysis (FEA) of ten representative CFRP-lined buried PCCP, simulating the degradation process of PCCP after CFRP installation; and verify critical design parameters; Determine the buckling equation that should be used in design of the CFRP liners; Perform reliability analysis and determine load and resistance factors for all design limit states of CFRP-lined PCCP. Failure modes were discovered that were not included among the initial list of failure modes of the CFRP liner, which prevented continuing to pressurize the pipe to the ultimate capacity of the CFRP-renewed and strengthened pipe. A design confirmation test is recommended in which the pressure in the CFRP-renewed and strengthened pipe is allowed to increase until either the CFRP is ruptured or the calculated ultimate capacity of the pipe is reached. The results of this research have been shared with the AWWA Standard Committee on Renewal and Strengthening of PCCP.
