| Cables are the main bearing components of large-span bridges (cable-stayed bridges, suspension bridges), which are manufactured by high strength steel wires or steel strands. The cables are always in high stress state and bear the repeated action from live load like vehicles and wind, additionally, affected by the surrounding corrosive media. High stress, fatigue load and corrosion effect increase the risk of cable collapse, and reduce the service life of the cables to only 20 to 30 years. Therefore, a comprehensive study on the bearing capacity after corrosion and corrosion fatigue performance of the high-strength steel wire is of great importance, which can contribute to providing an appropriate time to carry out maintenance and replacement, reducing economic losses and extending the work life of the structure. Under the support of the national basic project (973 project) "The fundamental research of extra large-span bridge safety design and evaluation" topic 3 "Extra large-span bridge performance evolution characteristics under the action of various factors" (2015 CB057703), corrosion and fatigue properties of high-strength galvanized steel wires are studied in this paper. The main contents and conclusions are summarized as follows:(1) Acid salt spray tests of steel wires were carried out for seven periods of 10d,20d,30d, 40d,50d,60d and 90d. By using hemispherical notch to simulate the corrosion pit, static tensile tests of corroded wires and wires with notch were performed. The results show that elastic modulus and yield strength are not sensitive to the degree of corrosion and the depth of notch, while the ultimate strength and strain have a downward trend with the increase of degree of corrosion and the depth of the notch, the ultimate strain of the corroded wires decreases sharply. It is also indicated that the fracture of the notched wire is brittle.(2) Two million cycles with different stress amplitude were applied to the new wires and wires with acid salt spray exposure 10d and 60d. Then, the static tensile tests were performed. The results show that fatigue damage have a little influence on elastic modulus, while the situation is totally different for the strength of steel wires with relatively high degree of corrosion. It is also found that ultimate strain is most sensitive to fatigue damage.(3) Continuous acid salt spray tests and copper accelerated salt spray tests were conducted to get steel wires with different degrees of corrosion, which were used for the subsequently fatigue tests. The results show that both zinc coating corrosion and uniform corrosion have little effect on the fatigue life of the wires, and the presence of corrosion pit will significantly reduce the fatigue life of steel wires with the increase of the degree of corrosion, but the trend is slow descending in the subsequent time. It is also indicated that the wire fracture in fatigue test is brittle.(4) Prefabricated crack was manufactured on the wire surface, after which the corrosion fatigue test of presplit wires and its influence factors (i.e. environment media, temperature, loading frequency and stress amplitude) were studied. The results show that the fatigue life of steel wires in air environment is the largest, followed by in wet environment, while in salt spray environment is the shortest under the equal stress amplitude. Under equal stress amplitude, the fatigue life in salt spray environment increases with the increase of loading frequency, while fatigue life in damp environment decreases with the increase of temperature. It is also shown that S-N curves of corrosion fatigue tests are well linearly related in double logarithmic coordinates. |
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