The Research On The Condition Assessment Of JiuJiang Cable-stayed Bridge

Load test is an important testing method, which can provide advantageousa nd direct bases for administrators to evaluate carrying capacity of bridge. Especially for the new structure, bridge design theory and working technics it can provide valid actual datum. Jiujiang Bridge is a consolidation system of tower-girder-fursta with 81 meters high. Based on the method of modern bridge design, infinite element, random vibration, and vibration testing and analysis technology this paper studies and designs the load test plan of Jiujiang Cable-stayed Bridge by summarizing the load test plans of some concerned bridges.Through the the oretical analys is of Jiujiang bridge, this paper makes sure the controlling load and loading case under the condition of ensuring the load test efficiency. According to the results of comparison between the actual value and the theoretical value of the controlling section this paper makes clear the actual carrying capacity of bridge.The problem of bridge vibration is very complicated and the analysis in theory still can not meet the requirement of the engineering application. In order to test the actual condition when the bridge is forced by dynamical load, running test, braking test and jumping test are carried out respectively. According to the time-travel curve under the cases above-mentioned, the actual figure of impact coefficient comes out. At the same time this paper compares it with that in theory and brings forward beneficial advices for the road managing and maintaining department.Theoretical mode analysis is made by establishing the dimensional infinite element model of Jiujiang Bridge with ANSYS software, thus natural vibration frequency and mode shape of Jiujiang Bridge theoretically are concluded. With pulsation measurement method this paper tests the actual mode parameters (including mode shape, natural vibration frequency andd ampingr atio). The comparison between actual results and those in theory indicatesth at this bridge is qualified with satisfactory dynamical peculiarity. Furthermore, this paper analyses the causes that these mode shape lie in according to the structure characteristic of Jiujiang Bridge.Mode analysis is also made before and after ranging cables and the condition of Jiujiang Bridge are summarized further by comparing the testing results.