Test Method On Steeve Stretching Force And Dynamic Characteristics Of Steeve Arch

With the development of design theory and construction technology, steel concrete steeve arch bridge has a rapid development and application. The bridge of this kind is not only beautiful in the structural form; compatible with the advantages of the reinforced concrete and steel material in material properties; in terms of the mechanical behavior, the bridge of this kind is also compatible with the advantages of arch and beam bridges.With a wide range of applications of the new bridge structure, through theoretical analysis and real bridge load test method, it is essential to master the static and dynamic mechanical properties of the bridge structure. Only if the static and dynamic mechanical properties of the bridge are full clear, it ensures the safe operation of the bridge.Steeve cable force state directly determines the stress state of the overall steeve arch stress state and deformation state, therefore, the steeve cable force state is one of the key factors which could determine the safe operation. In the process of using the bridge, as relaxation and stress inherent loss in steeves, coupled with the traffic load cycles, the steeve cable force will change with the process of using. Engineering practice shows that, the degradation of steeve cable force is a random, non-linear process. Therefore, the monitoring of steeve cable force is necessary.In the process of the monitoring of steeve cable force, two aspects must be taken into account. On the one hand is the single state of the steeve cable force; the other hand, the overall status of full-bridge steeve cable force.At present, a number of tests on cable force method based on vibration testing has been formed, but the accuracy of existing calculation model for the long and soft cable is acceptable. However,the errors are great for short steeve. Influence factor analysis of short steeve tensile force based on frequency calculation has been carried out. And the concept of correction coefficient of influencing factors is proposed, in order to meet the engineering application. However, as the calculation influencing factors of steeve tension based on the natural frequency. It needs further study about calculation model.As for assessment of steeve cable force state for the full-bridge,the assessment of cable force state is multivariate analysis problem. The commonly used multivariate analysis method is regression method. However, the multiple regression analysis needs a large enough sample. And it's not only with large calculating, complex processing, but also the error is difficult to control.Northeast is located in the cold regions, the temperature difference between day and night and between summer and winter are great. The temperature change has a great influence on the cable tension. Therefore,the temperature influence should be considered in the full bridge steeve cable force state assessment.Therefore, the research on cable force testing methods of a single steeve and prediction methods of full-bridge steeve force state assessment is carried out.It is of great significance of ensuring the safe operation of steeve arch bridge to do research on the dynamic characteristics of the steeve arch bridges. Based on the above, the research on steeve arch cable force and the test meshod of full-bridge dynamic characteristics are carried out in this paper, in order to build a theoretical basis of the wide application of the bridges.Firstly, the research on test methods of cable force of steeve arch bridge with single steeve is done in this paper. The steeve cable force test methods based on vibration test and neural network algorithm have been proposed. And then, prediction method of full-bridge steeve force state assessment is carried out.Prediction method of full-bridge force state assessment based on gray system theory is formed. Based on theoretical analysis, the test methods of dynamic characteristics of steeve arch full-bridge are formed, too. Finally, rely on a 22+55+22m in two-lane prestressed concrete arch continuous girder bridge of the Changchun Light Rail Transit Project Phase III (fourth line of the Southern Section), the methods formed have been verified. Main research work are as follows:1.Test method for steeve tension of single rootStarted from basic principles of steeve vibration, influence factors of steeve tension during testing process are analyzed. Based on the analysis, a test method with high precision for steeve tension basis on vibration test has been formed. This method can easily calculate the steeve tension, during cable force adjustment phase and operational phase of construction, and only needs to obtain the pre-tension datas once during cable adjustment phase.Then a cable monitoring method of steeve arch bridges during cable adjustment phase is proposed, based on neural network algorithm. Cable force is taken as output, and the strain and displacement on specific section of arch rib and stiffening beams are taken as input, in this method. The steeve tension can be calculated only by collecting the srtain and displacement on specific section at any time.2. Evaluation method for cable force state of the whole bridgeNortheast of china is seasonal freezing region, and the region has such characterisctis as large temperature difference between day and night and large temperature changes among different seasons.While ambient temperature has great influence on cable force state. Influence law of ambient temperature on cable force state has been analyzed, and the theoretical model rejecting the influence of ambient temperature is formed. Based on gray system theory correlation analysis, prediction model of cable force state of steeve arch bridge is established. The gray correlation of full-bridge cable force is usd as index of cable force state in this model. And the prediction method of cable force state can be applied to cold regions well.3. Dynamic characteristic test of the whole bridge The finite element model of the steeve arch bridge is established, and dynamic characteristics of the whole bridge are analyzed. By the actual situation at the scene combined with theoretical analysis results, test program of dynamic characteristics is done. And the random resonse of the measuring points under ambient excitation is collected. By using random decrement technique combined with eigensystem realization algorithm(ERA), the vertical vibration characteristics of steeve arch bridges are analyzed from random response.