The Research Of The Fatigue Reliability Of Bridge Cables Under Corrosive Environment

Bridge cable is the main bearing and power transmission components of a cable-stayed bridge. It is vulnerable to corrosion damage caused by environmental and mechanical factors, corrosion pits emerging on the surface of wires, leading to deterioration of mechanical and fatigue properties in the design reference period of bridge. By finite element analysis, mechanical tensile tests, fatigue performance tests and reliability index estimation of wires under different pit distributions, the impact of pit distribution on the surface of cable wires on the mechanical properties and fatigue properties of wires is researched in the text. The main research process and results are described as follows:1) Firstly, the impact of distribution parameters of cable wires on the maximum von mises stress and yield load of the bottom of the pit is researched by finite element calculation. The parameters include depth, length when only one pit exists, clear distance between pits, depth when two pits exist on the same side of wires and distance between center lines of pits, depth when two pits exist on the opposite side of wires. The functional relationship between maximum von mises stress and the parameters above is established. To research the impact of two pits on the stress distribution of wires, the maximum von mises stress of wires with two pits is compared to that of wires with one pit.2) Secondly, the impact of distribution parameters of cable wires on the nominal tensile strength has been researched by mechanical tensile tests. The relationship between yield load and nominal tensile strength is analyzed. The parameters include depth, length when only one pit exists, clear distance between pits, depth when two pits exist on the same side of wires and distance between center lines of pits when two pits exist on the opposite side of wires. The trend of yield load and the nominal tensile strength is compared with each other, the results are explained from the perspective of stress distribution.3) Thirdly, the impact of the parameters on the fatigue life of wires is researched by fatigue tests and theoretical prediction method respectively. The parameters include depth, length, stress amplitude when only one pit exists, clear distance between pits, when two pits exist on the same side of wires. By comparing the results, theoretical predictions are proved to be correct. The impact of other parameters such as depth when two pits exist on the same side of wires and distance between center lines of pits, depth, stress amplitude when two pits exist on the opposite side of wires on the fatigue life is researched further by theoretical prediction method. The results are compared to that of wires with one pit and the relation between them is analyzed.4) Fourthly, based on the fatigue life predicted above, the functional relationship between fatigue life of wires and stress amplitude is established. Combining with previous achievements about fatigue resistance variability, fatigue reliability index under different amplitude and different cycles is calculated. The relationship between fatigue reliability index and amplitude and cycles is analyzed, providing a basis for fatigue property evaluation of cable wires.