Background

Prestressed concrete cylinder pipe (PCCP) consists of a concrete core, a steel cylinder, prestressed steel wires and a mortar coating, and damages and defects of this composite structure mainly include longitudinal cracking of concrete core, corrosion of steel cylinder, corrosion and fracture of prestressed steel wires and the cracking and delamination of mortar coating. Based on CFRP's characteristics, this study researches and develops the carbon fiber reinforced polymer strengthening technology of PCCP with independent intellectual property through a large-scale prototype test, indoor experiments and numerical simulations, which fills the gaps of domestic researches and applications.

Contents

    · Performing the prototype tests with interior loads and external loads according to different layers, layout types of carbon fibers and loads combination, at the same time,  conducting the indoor experiments on impaired CFRP samples;

    · Numerically simulating the whole  process  of  PCCP  failure before and after reinforcement and comparing the results with prototype test results in order to understand the post-reinforcement PCCP stress status, bearing mechanism and failure process and to establish the design principle of PCCP reinforcement;

    · Developing CFRP protective materials and based on experiments, suggesting the performance indicators and major technical indicators for YEC surface protective materials suitable for long-term immersion conditions; and

    · Establishing a complete set of construction processes and quality control standards through field tests, which takes into account the low temperature and high humidity within PCCP.

Achievements

    · The prototype tests have been made for the first time at home and abroad, which fully reflects the mechanical properties of PCCP and CFRP strengthening of PCCP, indicates the changes in the mechanical properties of damaged CFRP, and produces rich and extremely valuable test data;                                  

    · The constitutive relation, interlayer relationship, calculation method and mechanical parameters of CFRP strengthening of PCCP have been clarified. And the structural models and design principles of CFRP have been proposed;

    · YEC surface protective materials suitable for long-term immersion conditions have been developed, greatly improving the durability of CFRP; and

    · A complete set of construction processes and quality control standards has been established to ensure construction quality under the circumstances of low temperature and high humidity within PCCP.

Application

The achievements have been successfully applied to PCCP pipeline reinforcement of major water conservancy projects, such as the South-to-North Water Transfer Project and the Irtysh-Karamay-Urumqi Canal Project in Xinjiang. These applications produce direct economic benefits of 150 million yuan by preventing PCCP pipelines from catastrophic damage.

PCCP repair design section

Prototype tests with internal loads

Prototype tests with external loads

Fiber bragg grating sensing net analyzer

The process of CFRP construction

The overall picture of reinforced PCCP

Numerical simulation of the whole process of PCCP failure