Mechanical Properties of Double-gasketed Steel Joints for Bar-wrapped Cylinder Concrete Pressure Pipe Using Experimental and Numerical Methods

Differential settlements of foundation can result in the excessive relative rotation angles between bar-wrapped cylinder concrete pressure pipes (BCCP), which may cause the failure of joint structures. This paper presents experimental and numerical methods for investigating mechanical properties of pipe joints under different relative rotation angles. Four hydraulic jacks were installed below two DN1400 BCCP specimens to induce controlled relative rotation during the experiment. Three types of loading modes were designed to test the structure performance of joints under different loading conditions. Concrete damaged plasticity model (CDPM) and cohesive elements are used in finite element method to simulate the mechanical response of concrete under complex loading, and fracture in bonded interface between concrete and steel cylinder. The results show that the whole failure process of joints can be divided into four stages, that is, the debonding of bell end interface layer, the cracking of spigot end inner concrete core, the debonding of spigot end interface layer and the yielding of steel spigot ring, arranged in the order of failure occurrence. The limit values of different failure stages are variable with the change of prestress loss value, insertion depth, loading modes, pipe types and inner water pressure. All the factors need to be considered in determining the limit values of different stages using experimental and numerical methods to evaluate the failure state of BCCP joint structures in engineering.