Railway Bridge State Diagnostic Test Research

Bridge structures may be partly damaged or prematurely aging when they continuously bear various effects such as vehicle loads,impact actions,temperature changes,fresh gale strong winds and so on. Though the forenamed phenomena will not entirely damage the structure immediately, it brings potential danger to the security of the structure. Time going, partly damage will be continuously enlarged under the effect of stress intensity,fatigue. Bearing capacity of the bridge will descend successively and the structure will be failed in the end.In order to ensure the security of the running trains, the state of partly damaged bridge must be estimated in a short time so as to judge that if the train can run in term of original speed or not. what means that whether the train should be slowed down or not, and whether the traffic need to be closed down to do reinforced treatment for the bridge.Against the forenamed problems, a set of diagnostic technology for railway concrete bridges has been put forward to the structural experiment,the diagnose of operation state and the mode testing.(1) With the help of railway bridge load test, the actual active state of the structure under load can be known, so we can judge the carrying capacity synthetically and constitute the qualification for safe exertion.(2) The major factor of lateral vibration in span center of beam has been summarized in the case of strong-beam and weak-pier or weak-beam and strong-pier by the analysis of test data.(3) The operation state of the bridge can be judged by natural frequency of lateral vibration and lateral amplitude; natural frequency of lateral vibration and other mode parameter of pier and beam can be received exactly by mode testing, which are the data foundation of subsequent curvature mode analysis for structure damage;(4) With the help of energy-accumulating hammer and Varied-Time-Base Sampling technology, large structures can be excited effectively and the former order modes of the structure can be received exactly. (5)The effect of noise has not been considered in the numerical calculation. Environment noise and the other problems will be come up in actual applications, so some measures must be adopted to reduce the effect of noise and improve the detecting precision.(6) Database of the first order natural frequency of lateral vibration of bridge structures which belongs to Guangzhou Railway Co. has been established. So the operation state of bridge can be judged by the variety of natural frequency of lateral vibration.(7) Using the rapid diagnose technology of railway concrete bridges, the disease of number 3 bridge in the east has been diagnosed exactly. Corresponding reinforce measure has been presented, and the disease has been punished successfully. Speed limit has been cancelled.