Experimental Investigation of the Structural Performance of Existing and RC or CFRP Jacket-Strengthened Prestressed Cylindrical Concrete Pipes (PCCP)—Part A

Abstract

A popular water pipe system used in many countries is one formed by prestressed cylindrical concrete pipes (PCCPs) formed by identical precast moduli joined together in situ. This technology was and still is quite popular in many water supply systems internationally. This technology was mainly selected at the time due to its cost-based comparative advantage. However, over the years, numerous incidents of structural failures have been reported for this type of pipeline, causing, in some cases, serious disruption of the water supply. This study summarizes the results of an experimental investigation on ten (10) PCCP specimens taken from an existing water pipeline with the objective of investigating their bearing capacity under either three-edge bending or internal hydraulic pressure loads. Moreover, there is a need to check the capability of specific retrofitting/strengthening schemes to upgrade this bearing capacity and thus enhance the operational period. Provided that the prestressing wires are fully active according to design specifications, the original specimen performed satisfactorily for the set internal hydraulic pressure limit of 8.5 bar. Specimens retrofitted with either internal or external CFRP or RC jacketing performed satisfactorily for internal hydraulic pressure levels well above this 8.5 bar limit. A critical factor is, as expected, the loss of prestress.

Numerical Study of the Performance of Existing Prestressed Cylindrical Concrete Pipes Strengthened with Reinforced Concrete or Carbon-Reinforced Fiber Polymer Jackets—Part B

“…It was the decision of the owner of this pipeline to apply specific retrofitting schemes after 70 years of operation. Part A [1] of the study detailed tested specimens representing the modulus of the pipe in situ, which was almost identical to the modulus that makes up the actual pipeline that is in operation. By comparing the bearing capacity of the retrofitted specimens with that of the one without any retrofit, the effectiveness of the retrofitting scheme could be evaluated in a comparative manner.…”

“…Therefore, the numerical simulation is also a step towards proving the validity of such a numerical approach to realistically approximate the observed behavior. Among the tested specimens, one represented the prototype pipeline whereas three specimens represented three different retrofitting schemes; two of these retrofitting schemes employed carbon reinforcing fiber polymer (CFRP) jackets (either internally or externally for the pipe) and the third retrofitting scheme employed an external reinforced concrete (RC) jacket [1]. Because such pipelines have been in operation for many decades, it is of interest to be able to examine their current safe performance as well as to investigate the effectiveness of specific retrofitting schemes to ensure their desired performance in the future.…”

“…Chapter 2 includes a summary description of the tested samples and the loading conditions and how they were numerically simulated. The full description is given by Manos et al [1]. Chapter 3 includes a comparison of the measured response and the corresponding numerical predictions for each specimen tested.…”

“…10 and spec. 7, [1]) subjected to hydraulic internal pressure are numerically simulated. The numerical simulation was then extended to include the retrofitted specimens with three different retrofitting schemes (spec.…”

“…3 and spec. 1, [1]). The validity of each numerical simulation is based on comparing the overall measured and numerically predicted response of the internal hydraulic pressure amplitude versus the corresponding radial expansion for each of the five specimens.…”