Research On Corrosion Damage Of Steel Strand Under Different Damage Types Of Sheath

Cable-stayed bridges have been widely used at home and abroad due to their huge spanning ability and relatively good aerodynamic stability.As the lifeline of the entire structural system,the stay cables play the role of connecting and supporting the bridge deck main beam and the cable tower.However,the material properties of the stay cable itself and the long-term exposure of the stay cable system to the natural environment cause the stay cable to be easily broken by corrosion.In response to this problem,the characteristics of corrosion behavior and the law of corrosion degree with time of steel strands were obtained through electrochemical accelerated corrosion test and uniaxial tensile test.Compared with three evaluation methods of corrosion damage rate of steel strands,the applicability of three calculation methods to different damage forms of steel strands is summarized.Finally,the working conditions of different damage forms,different damage degrees and different damage positions of steel strands are simulated by ABAQUS,and then the corrosion fracture characteristics and the law of stressstrain changes of steel strands after corrosion are obtained.The main conclusions of this paper are as follows:(1)The damage form of PE sheath determines the corrosion behavior of steel strands.In the case of circumferential damage,uniform corrosion occurs in the section of steel strands along the circumferential direction.In the case of longitudinal damage,the steel strand corrodes along the radial direction on one side of the longitudinal breakage;With the time increased of accelerated corrosion,the corrosion depth,corrosion product volume and damage wound expansion range of steel strands increase,but the corrosion rate of steel strands decreases gradually.(2)The weight loss method can be used to compare the degree of corrosion damage and corrosion rate of steel strands with different damage forms,and the section loss method and depth method can accurately evaluate the corrosion rate of sheath damaged steel strands.(3)The tensile curve of longitudinally damaged steel strand is close to that of un-corroded steel strand,and there is an obvious plastic stage,while the tensile curve of circumferential damaged steel strand has no yield platform.(4)The nominal elastic modulus and tensile strength of corroded steel strands generally decrease as the corrosion damage rate increases.With the increase of corrosion damage rate,the decreasing range of nominal elastic modulus and tensile strength of circumferential corrosion damaged steel strands gradually weakens.There is a good linear relationship between the nominal elastic modulus and tensile strength of steel strands damaged by longitudinal corrosion and the corrosion damage rate of steel strands.(5)The numerical simulation results show that the fracture form and fracture process of steel strands are different under different forms of corrosion damage.Steel strands damaged by circumferential corrosion occurred overall fracture at the damage wound.The corrosion side wire of the longitudinally corrosion damaged steel strand first breaks,then the center wire and the un-corroded side wire break.Among them,the fracture form and the change of stress and strain of the steel strand damaged by circumferential corrosion are related to the distance from the damage wound to the near end of the steel strand.