Analysis Of Load Response And Bearing Capacity Influence Of Damaged Prestressed Concrete Cylinder Pipe

Prestressed Concrete Cylinder Pipe is a new type of composite pipe with superior performance,which is widely used in long-distance water conveyance projects at home and abroad.However,during service,PC CP is affected by such factors as corrosion,hydrogen brittleness and material defects.The pre-stressed steel wire in the pipeline may rust or even break,which affects the pipeline carrying capacity.When the damaged PCCP is impacted by rock fall,the bearing capacity of the pipe will be severely tested,and even the pipe burst accident will cause serious impact on the national life.Based on the research of predecessors,this paper established and improved the three-dimensional finite element model of PCCPs,studied the loading mechanism and damage process of buried PCCPs in damaged state,and further studied the dynamic response of the system composed of rock-soil-PCCPs under impact load,in order to provide reference basis for operation management and structural safety evaluation of in-service PCCPs.The main research contents of this paper include the following aspects:(1)Test study on load-carrying capacity of broken PCCP.According to the prototype test,a three-dimensional non-linear finite element numerical model of wire-breaking PCCP considering the gripping force of mortar was established,and the internal pressure loading test of wirebreaking pipeline was simulated numerically.By comparing and analyzing the numerical simulation results of ANSYS software with the measured data of prototype pipeline test,the rationality of the broken wire PCCP numerical model is verified.Based on the prototype test and considering the interaction between pipe and soil,the influence of wire breakage on the stressstrain response of PCCP in service was studied by changing the number of wire breaks and the internal water pressure in the numerical model(2)Study on the bearing capacity of corroded PCCP.According to the corrosion characteristics of the pre-stressed steel wire,the buried PCCP model considering the loss of prestress,the change of cross-section area of steel wire and the bond-slip relationship between steel wire and concrete and the buried PCCPmodel considering only the change of cross-section area of steel wire and the relationship of bond-slip are established.By changing the numerical model,the corrosion area,corrosion degree and internal water pressure of the PCCP wire were changed.The influence of corrosion of pre-stressed steel wire on the bearing capacity of buried PCCP was studied,and its bearing mechanism and failure process were summarized.(3)Response analysis of damaged PCCP under impact load.Applying APDL module in ANSYS software and LS-DYNA explicit dynamic analysis software,a three-dimensional finite element model of buried PCCP line under impact load of collapsed rocks was established,which changed the quality(diameter),height and buried depth of the pipeline etc.Based on the above consideration of damage conditions of pipeline such as wire breakage and corrosion,the influence rule of impact load on mechanical response of PCCP line was further considered.Based on the above research,this paper summarized the impact of damage factors such as corrosion and fracture of prestressed steel wires and falling rock impact loads on the bearing capacity of PCCP,and put forward reasonable suggestions to prevent the above risks in engineering practice,hoping to provide some reference for practical projects.