Research In Bridge Rapid Diagnosis Based On Dynamic Test

The existing bridge structure detection methods are mainly divided into static-load test method and dynamic-test method. Although the static-load test method has mature theory and reliable data, the testing process must be interrupted traffic and a lot of time will be wasted.The dynamic-testing method, in most cases, obtains the modal information of the bridge structure to evaluate its performance. But its theory is not mature enough, and the testing data is not sensitive to the structural damage. The quasi static load test is a kind of test method which is based on the strain or deflection influence lines to evaluate the carrying-capacity of bridge structure. The quasi static load test has high requirement for the test method and equipment precision, so it has not been applied in a wide range in our country.In Hebei traffic science foundation funding, the bridge rapid diagnosis technology which is based on dynamic test is proposed in this subject. The dynamic test includes dynamic modal test and dynamic loading test. Fourier transforming is used to analyze the acceleration signal to obtain the information of the bridge, such as frequency, mode of vibration, damping ratio, stiffness, etc. In the dynamic load, the strain or deflection influence lines of each measuring point in the bridge structure could be collected while the standard-load car is driving through the bridge at the specified path. The information of the testing bridge obtained from the above two kinds of test is used to modify the initial finite element of the bridge. The finite element model of bridge structure is built using parameter. The design variables, state variables and objective function requires to select reasonably and effectively in the process of model optimization. Using the optimization module of the large finite element software ANSYS, adjust the design variable values time and again until the finite element calculation results and the measured structural alignment is highly consistent. And then the bridge structure finite element updating is regarded as same as the real bridge structure. Use the static load test method theory to valuate the bridge health condition fleetly on basis of the static-load test data on revised bridge finite element modelSeveral aspects of research has been made as follow for the rapid diagnostic technology which is based on dynamic test. 1.Considering the bridge damage that may occur, the research which is about the change of the dynamic-test data caused by the transverse connectiondamage and the beam crack is made in the indoor bridge finite element model, in order to provide the theoretical support to bridge detection and testing program. 2.Researched the influence and the influence degree of the reinforcement ratio, elastic modulus, cross section moment of inertia on the strain or the influence lines, which provides the basis for the reasonable selection of design variables. 3.The objective function is established based on the calibration technology for the finite element model of bridge structure utilizing the dynamic modal parameters and the testing strain influence lines. Select objective function reasonably to guarantee the convergence and effectiveness of the model optimization and provide a basis for the finite element model for bridge structure optimization. 4.Applied the rapid detection method, which is put forward in this subject, to two bridge detection engineering. By means of the two bridge detecting process, detailed introduced the whole process of bridge structure detection, which included the testing-data acquisition of the dynamic modal test and dynamic loading test, testing-data analysis, optimization of the model, simulation of the static load test and evaluation of the testing bridge in the end.