| Prestressed Concrete Cylinder Pipe (PCCP) was introduced to China in late1980s, and it had been widely applied in many fieids of hydraulic, municipal and electric power because of its special structure and excellent performence. Recently, the research on combined bearing capacity of PCCP has not been mature, especially, cracks and broken wires resulted from influence of manufacturing process, curing, placing and performence environment will be found on the structure of PCCP. These problems not only affect the bearing capacity of structure, but also resuit in engineering failure. Thus it has significant theoretical meaning and practical necessity to investigate the affects of cracks and broken wires on safety of structure.This paper summaried the research status and theoretical and design methods, based on finite element nonlinear analysis and failure criterion,using ABAQUS, researching affects of cracks and break wires on safety of PCCP is performed, and some achievements has summaried below:1. According to categories and causes of cracks, reseaching affects of cracks on safety of PCCP by using prototype tests and finite element methods is performed.(1) According to the results of three-edge bearing load tests, researching the failure rules of pipe of2m diameter and4m diameter with longitudinal cracks in the outer core under the loads was performed. The results showed that there were no visible cracks in the2m diameter pipe during the process of being applied loads to1.4times of design anti-cracking loads, and visible cracks were found in the4m diameter pipe when being applied1.3times of design anti-cracking loads.(2) Based on the longitudinal cracks placement of2m diameter and4m diameter pipe in the prototype tests, finite element models for2m diameter and4m diameter pipe are simulated using ABAQUS. The behaviors of PCCP applied different loads are investigated. The results of numerical simulation show that varieties of stresses near cracks tip are obvious, especially for concrete and mortar. The mainbody of pipe transform to cylinder and wires from concrete resulted from crackings continue expansion and redistributed of moments to prevent early failure of pipe. For the larger diameter PCCP, the stresses changes are obvious and agree with the results of prototype tests.(3) The results of hydrostatic tests show that the first crack is found at the end of pipe, and extending with increase of internal loads. This paper presents the process of researching this phonomenon by establishing finite element models using ABAQUS, the results show that the stresses of mortar have larger change.2. Based on analysis for failures and affect factors of broken wires in PCCP,4m diameter PCCP are simulated by using ABAQUS. Researching the affects of break wires on structural safty is presented for different wires broken number and area.(1) Analysing stress statement of PCCP is performenced in single area of broken wires for broken wires rates of5%,10%,15%,20%. Under the loads applied the bearing capacity of PCCP decreases with the increase of wires broken rates. The easiest to cracks occur on the top and bottom of pipe and outer surface of broken wires areas. It is more obvious of affects of broken wires on mortar, which againsts to control of outer cracks and corrision. Otherwise, the cylinder has increasingly nonuniform force with increasing of broken wires rates, easily resulting in separating between sylinder and concrete surface, finally resulting in failure of PCCP.(2) When the wires broken rate is20%, setting two broken areas at the1/3and2/3respectively, analysing and comparing stress states in the different broken wires areas. Multi-broken wires areas are more dangerous than single break wires area because of its larger influence on bearing capacity of pipe and the nonuniform stresses of pipe. Focus stresses and larger stresses are found near the break wires areas. A wide range of broken wires area wound result in structure failures of PCCP.Based on the characteristics of PCCP, to some extent, the affects of cracks and broken wires on structure safty of PCCP are not significant. Broken wires wound accelerate failure of pipe, and more cracking followed. Effective engineering measures should be made to control the development of cracks and broken wires. |
