Load Test Research Of Gonghe Cable-stayed Bridge In Shenyang City

Load test is an important testing method, which can provide advantageous and 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. Gonghe bridge is a double deck structure with single tower and single cable plane ,which regrads the nether cantalever as non-mobile roadway. This idea fully using the lower space is a new experiment and it need verifying in practice. Based on the method of modern bridge design, infinite element, random vibration ,vibration testing and analysis technology this paper studies and designs the load test plan of Gonghe Cable-stayed bridge by summarizing the load test plans of some concerned bridges.Through the theoretical analysis of Gonghe 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 and verifies that this double-cantalever structure is viable.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 Gonghe bridge with ANSYS software, thus natural vibration frequency and mode shape of Gonghe bridge theoretically are concluded. With pulsation measurement method this paper tests the actual mode parameters (including mode shape, natural vibration frequency and damping ratio). The comparison between actual results and those in theory indicates that 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 Gonghe bridge.The damping factor of bridge structure is very complicated. By pulsation measurement with half power point method this paper gets the actual figures of damping ratio of 5 steps, which are between 2.4% ~5.9%. These figures are scattered and they have the descending tendency with the increment of natural vibration frequency.