| The corrugated steel box girder with corrugated steel web PC instead of the traditional thick concrete box girder web plate is a new steel- mixed composite structure, because of thin steel web, it can not be arranged in the body of tendons in the web, but with plenty of external tendons to replace tendons in the body. Therefore, researching dynamic characteristics of externally prestressed on the impact of PC combination box girder with corrugated steel webs is very necessary. Based on the model test beam test, theoretical formula calculation and ANSYS finite element analysis, this paper make a systematical study of the impact of external prestressing on single cross-sectional corrugated steel webs PC combination of dynamic characteristics of simple box girders. The main conclusion of the study and to complete the work as follows:(1) Referring classic structural dynamics, considering the effect of corrugated steel web box girder shear and shear lag effect and the loss of external prestressing, and consider the influence of prestress on the bending stiffness of the beam body, expanding and revising externally prestressed formula of natural vibration characteristics of traditional concrete box girder web, then deducing corrugated steel webs PC combination simply supported box girder external tendons natural frequency of the beam which is calculated in the linear, single fold and double fold linear arrangement of linear equations.(2) The uniform section simply supported model test beam 5m with corrugated steel web is designed and produced, and the first order natural frequency of the model test beam under external tendons in eight different working conditions of the initial tension is tested, the test results of model beam show that:The first order natural frequency of model test beam will increase with the increase of the external tendons initial tension.(3) For the production of corrugated steel web model test beam, the derivation formula is applied in simply supported box girder with corrugated steel webs PC combination vibration frequency to calculate the first order natural frequency of model test beam under external tendons in eight different working conditions of the initial tension. The results show that the first order natural frequency of the beam will increase with the increase of effective tensile force of external tendons.The results with the test beam for the first order natural frequency of vibration test values maintained a consistent growth trend, and the value is closer, which prove the theoretical derivation can correctly calculate the natural frequency of corrugated steel web PC combination of simple box girders.(4) Model test of beam ANSYS finite element calculation model is set up, which calculate the first order natural frequency of the model test beam under external tendons in eight different working conditions, the results show that: Finite element calculation results with experimental beam test results are a consistent trend and the values are close, the relative error is about 3%, which proves that vibration characteristics of ANSYS finite element model established in this paper can correctly simulate the model test beams.(5) Different external tendons layout parameters(initial eccentricity of external tendons, cross-sectional area of external tendons and the deflection angle of external tendons) are analysed to study the law on corrugated steel web PC combination simply supported box vibration frequency through the theoretical formulas and ANSYS finite element. The results show that: The different external tendon layout parameters have a certain impact on the first order natural frequency of simply supported box girder with corrugated steel webs PC combination.(6) Through analysis of the vibration characteristics of the external tendons, this paper obtain that the free length of external tendons should be controlled at less than 12 m, Which makes the external tendons frequency and bridges frequency and external load frequency stagger to each other, then very well solves the resonance problem of the external tendons and the beam body. And by the frequency method can anti calculate out the effective tension stress in vitro tendons, whether for the construction or late reinforcement of corrugated steel box girder has a great sense of conservation. |
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