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Xie X.,Zhejiang University | Sun L.,Zhejiang University | Wang Y.,Hangzhou Municipal Public Construction and Development Company | Li J.,Zhejiang University
Zhongguo Tiedao Kexue/China Railway Science

In order to determine the unknown parameters like flexural rigidity in tension identification of short hangers, a new method called additional mass method was proposed based on the significant effect of mass on the natural frequency of the hangers. Artificial Neural Network (ANN) was employed to solve the nonlinear relationship among frequencies, tension and flexural rigidity. The tension and flexural rigidity of hanger were randomly generated, and the natural frequencies before and after the attachment of the mass were calculated by finite element method, these parameters were used as training data in ANN, which was founded to identify the tension and flexural rigidity of hangers. A group of short hangers length from 2~10 m were studied, and field experiments were taken in an arch bridge under construction to validate the feasibility and effectivity of this approach. The identification errors are about 0.5‰ and 6% resepectivily, which were better than the string theory method obviously. Source

Wang T.,Zhejiang University | Xie X.,Zhejiang University | Wang Y.,Hangzhou Municipal Public Construction and Development Company | Shi P.-C.,Ningbo Communications Investment Holdings Ltd Company
Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science)

A new method for bending, torsion and distortion analysis of composite truss girders was proposed aiming at structural spatial analysis problems of prestressed composite truss girders that replace the web of concrete box girder with steel truss webs. The composite truss girder was converted into a thin-walled box girder based on shearing equivalence principle, and the deformation of top and bottom concrete flanges were represented by two independent displacement functions. The differential equilibrium equations and formulation for finite element analysis were derived based on the calculating method of regular box girders. Computing formulas of element stiffness matrix and formulation for prestressing tendons were also given. The precision of the method was validated by comparison with examples of three-dimensional finite element method. The method is practical for its fewer freedom, easy to use, definite deformation concept, and combination with existing analysis method of box girders. Source

Huang H.-Y.,Zhejiang University | Xie X.,Zhejiang University | Wu D.-Y.,Zhejiang University | Wang R.-F.,Hangzhou Municipal Public Construction and Development Company | Wang Y.,Hangzhou Municipal Public Construction and Development Company
Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science)

Taking a PC partial cable-stayed bridge with tower beam consolidation and pier beam separation system as an example, the damping characteristics of such structures was investigated in bridge vibration test. Based on non-orthogonal damping theory, the relationship between component damping and modal damping ratio was studied, and the assumption that the modal damping ratio can be obtained by superposition of component damping under small damping condition was verified. The characteristics of damping ratio which was calculated by strain energy proportional damping theory was discussed, and the component damping ratio was talked over by comparison of experimental and theoretical results. The results show that the damping ratios of vertical bending mode and torsional mode are about 1%, which is less than that of ordinary PC continuous beam bridge. The damping ratio can be obtained by linear superposition of component damping according to non-orthogonal damping theory. It also can be approximately estimated with strain energy proportional damping theory, while the material damping ratios of PC beam, concrete pier and tower and steel cable are around 1.0%, 1.2%, 0.1% and 4.0% respectively. Source

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