| The box girder with corrugated steel webs is an improved form of steel-concrete composite box girder structures and its static and dynamic mechanical behavior is different from the common pre stressed concrete box girder. The paper is based on the Chang Zhuang Reservoir Bridge, which is on the overhead line viaduct of Long Hai Road Express Line project in Zhengzhou City. The vibration characteristics of the corrugated steel webs continuous box girder bridge are studied using the analytic method and finite element method. The specific research contents and conclusions are as follows:(1) Relying on Chang Zhuang Reservoir Bridge which is on Zhengzhou City LongHai Road Express Line project main line viaduct, the finite element software ANSYS is used to establish the finite element model of three span continuous structure. When the model is established, fully attention should be paid to the details of the structure. The box girder chamfer, twists and turns and webs of prestressed reinforcement should be accurately simulated, which will be a model for analysis of the subsequent natural vibration characteristics.(2) In order to make a comparison, according to the equivalent principle of the static bending stiffness of the section, the common concrete continuous box girder is established and the concrete continuous box girder is established on the basis of the design guideline of the highway prestressed concrete box girder meanwhile. Then the modal analysis of continuous box girder with corrugated steel webs and two continuous box girders are carried out to determine the difference of the inherent vibration characteristics. The results show that the vibration frequency of continuous box girder with corrugated steel webs is improved to a certain extent compared with the vibration frequency of the ordinary concrete continuous box girder and the dead weight will be reduced. Due to the weakening of the cross section of the framing effect, the box girder of the torsional stiffness decreases. With the increase of the thickness of concrete webs and concrete box girder of high-order mode order will change, the torsion of delayed emergence, which shows that the shear stiffness of box girder with corrugated steel webs is small and it is necessary to take measures to reinforce it.(3) On the based of considering both the shear deformation of corrugated steel webs and externally prestressed tendons, the self-vibration frequency calculation formulas of two kinds of simple supported beam with corrugated steel web plate and single span beam with corrugated steel webs (a simple support and a consolidation) are derived and the results are compared with the finite element calculation results. Then the effects of internal and external prestressed tendons on the frequency of the continuous box girder bridge with corrugated steel webs are discussed. The results show that the analytical results of the natural frequencies are decreased with the application of external prestressing, which is consistent with the traditional understanding; When the elastic modulus variation caused by prestress is included in the body, the application of external prestressing force increases the natural frequency of the continuous box girder with corrugated steel webs, which is consistent with the changing trend of the test results.(4) Considering the size of both external and internal prestressed tendons, wave-form structure (the angle of twists and turns, the single plate width and the thickness of the web) as well as the number of middle partition. Then the corresponding finite element model is established. The influence of the above factors on the vibration characteristics of the corrugated steel webs continuous box girder bridge is explored, and some conclusions are drawn:Considering the change of stiffness caused by "structural softening" and the change of elastic modulus caused by compression of concrete, the increase the" size of both external and internal prestressed tendons will increase the natural frequency of the bridge. When the angle of the corrugated steel web plate is about 30 degrees, the maximum frequency of the box girder is reached; with the increase of the width of the single plate, the frequency of each direction increases and then decreases, the value of the single plate width has its optimal range. Increasing the thickness of corrugated steel web can improve the bending stiffness of box girder to a certain extent, which can improve the torsional stiffness of corrugated steel web plate. When the thickness increases to a certain value, the influence of bending rigidity and torsional rigidity will be gradually reduced.(5) The torsion frequency of continuous box girder with corrugated steel webs can be obviously improved by adding middle partitions. However, with the increase of the number of middle partitions, the frequency increase rate becomes slow. This shows that the number of the transverse partition plate should be integrated with the change of the torsional stiffness and the weight of the box girder. |
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