Numerical Analysis Of Mechanical Characteristics For Concrete Cap And Its Influence On Buried Pipelines

Cap is a critical component of the pile group foundation for the upper load passing down. To study mechanical characteristics of cap based on pile-soil interaction could understand the true state of the cap better. So the research has theoretical significance and a very important value in engineering application.This dissertation in order to analysis the influence from cap on pipelines which 1.4m below the cap and both of them belong to the background of Shenyang 2nd ring road restruction. In order not to move buried pipelines and to ensure the safety of both cap and buried pipelines, the size of cap will be redesigned. ANSYS software has been used to do the nonlinear static analysis of the pile-soil-cap system. The new project meets requirements from bridge specification JTG_D62-2004, and the comparison revealed that the feasibility of using FEM analysis.In this dissertation, ANSYS has been used to create the 3D finite element model which studied increasing the thickness of cap can improve the crack load and ultimate load. Both of the punching-span ratio and the finite element result has revealed that the failure mode of the cap is punching failure. According to distribution of the first principal stress and the third principal stress of the cap, combined with the space truss model for concrete structure, space truss model of the six piles cap has been given. Comparatively analysis the mechanical characteristics of the cap both considering pile-soil interaction and no considering the interaction, and improvement for crack load and ultimate load of the cap has been revealed. According to the influence of the pile bridge structure to the buried pipeline, the new cap scheme would meet its strength requirements also ensure the safty of the buried pipelines.