Research On Prestressed Concrete Cylinder Pipe Bearing Capacity Assessment

Prestressed Concrete Cylinder Pipe(PCCP)is a kind of composite pipeline,which is widely used in various water transfer projects.Due to the complex working environment,the structure of PCCP might generate cracks and broken wires in operation,thus degrade the performance and even result to engineering accident such as pipeline explosion in severe cases.Therefore,it is necessary to analyze the effects of cracks and broken wires on the bearing capacity of PCCP and assess the bearing capacity of pipeline.This paper refers to PCCP pipeline engineerings and ABAQUS finite element software is used to performing numerical simulation.Comparing the numerical simulation result with the test result,the validity of the numerical simulation model can be verified,so as to research the bearing capacity of PCCP.This paper comprehensively analyzes the cause of cracks of PCCP and researches the influence of the inner annular cracks,which are resulted from the drying shrinkage effect of concrete,on the bearing capacity of PCCP.Extending the welding position of the steel cylinder and the root of spigot ring inwardly to analyze the effect of this change on the circumferential cracks of the inner wall of spigot,it can be concluded that this measure could reduce the axial tensile stress of concrete core after wire wrapping and help reducing the circumferential cracks of the inner wall of spigot.Taking the influence of bond stress of mortar coating on the steel wire into consideration,establishing a more practical wire broken model of PCCP,and studying the effect of the quantity and location of wire broken on bearing capacity of PCCP,it can be concluded that wire stress will completely release at the fracture when the wire has broken.However,due to the effect of the adhesive force of mortar coating,the stress of the broken wire will not lose but will be unaffected along the circumference of the pipe about 2750 mm.Wire broken will increase the stress on the unbroken wires on both sides,and along the length of the pipe,its influence range increases with the number of broken wires,and eventually degrade the bearing capacity of PCCP.The more the quantity of wire broken is,the greater the performance of bearing capacity will degrade;with same amount of wire broken,the effect of it generated on the side of pipeline is greater than that in the middle.Estimating broken wire development speed and assessing the bearing capacity of PCCP on the basis of actual broken wire detection data,it can be concluded that an undamaged PCCP will not break under the pressure of both internal and external.10% of wire broken,the concrete core will generate tensile damage;40% of wire broken,the concrete core will generate penetrating crack underthe pressure of both internal and external,and the pipe should not be carried on;while 60% of wire broken,the steel cylinder will yield and PCCP may burst.