Study On Evaluation Technique Of Security Performance For Cable Of Bridge

Cable stated bridge is becoming one of the popular styles in the modern bridge construction especially in the long-span bridge due to its distinguished advantages such as single framework, well aerodynamic stability and relative light weight with a long span and so on. As the important load-bearing members of the cable-stated bridge, the stayed cable and its durability have direct effect on security performance and service life of the bridge. But, the bridge would catch fire easily because of thunder and lightning, self-ignition of vehicle, traffic accident, human activity, ageing or short circuiting of electromechanical system of bridge, etc, it certainly will be a threat to stay cable.Once the stay catch the fire,it would raise temperature of material, and seriously decrease sectional area of stay cable, furthermore change material properties, sectional characteristic and carrying capacity, have an unfavorable influence on structural performance. And even cause major safety accident and economic loss. Thus, studing on durability of bured stay cable and according to research result, making pertinent repairement, protection or replancement of stay cable have an important significance in aspect of safe and economy.Making an example of study in durability for stay cable of Hedong large bridge, this paper have detected and evaluated the safty of stay cable in some aspects as follows:(1) Detection for damage of stay cable:Evaluate the condition of stay cable by visual examination for stay cable, visual examination for anchorage zone mainly, and nondestructive testing for interior of cable with ultrasonic guided waves system.(2) Test for cable tension and measurement for lineshape of deck:the temperature would be changed while the cable catch fire, it had an influence on material properties and sectional characteristic, so as to change the cable tension.And furthermore, it would have an influence on lineshape of deck. Therefore, having an decection for cable tension and lineshape of deck, and comparing with the data before fire, we can know the effect degree from fire.(3) Simulation experiment for material under fire:Because we could't get samples from damaged cable, in this paper,we carried simulation experiment for material under fire. By static load test, fatigue test, salt spray test, we have detection and evaluation for bearing capacity, mechanical properties, and corrosion resistance of stay cable.(4) Finite element analysis:With the result of inspection for sectional area of stay cable and data from simulation experiment for material properties under fire, building finite element model. By finite element analysis, we determine the stress distribution and deformation situation, and evaluate the security performance for bridge from global aspect.According to the results of test, detection and investigation, we can evaluate the durability and security of stay cable and the whole bridge, so as to provide the reliable scientific foundation aeffective, reasonable and economical treatment measures, and ensure that the bridge is in secure and unlocked state.