The Contact Analysis Method Of Unbonded Prestressed Concrete Structure Calculation

The Unbonded Prestressed Technology is widely applied in the Civil Engineering, especially in a section highly smaller Component and in the Long-Span Prestressed Structure, having the superiority which the ordinary Prestressed Structure is unable to compare. As an important branch of Post-Tensioned Prestressed, it has a obvious difference to the ordinary Post-tensioned Prestressed structure. However, at present, the computational method of Unbonded Prestressed Concrete Structure is still based on the ordinary Bonded Prestressed Technology, neglected uncoordinated characteristic of distorting between Unbonded Tendon and Concrete Walled in the actual structure. The non- authenticity of the Calculation Models will cause the computed result inaccurate or the precision reduced, also will be unable to carry on the computation of Detailed Structure. Therefore, establishing the struture calculation models of reflecting really the reciprocity between Unbounded Prestressed Reinforced Steel and Concrete has a stronger practical significance to consummate the design and calculation method of the Unbonded Prestressed Structure.In view of the non- Deformation Compatibility between Unbonded Tendon and Concrete are due to the relatively skids of two, Takeing the contact analysis theory as foundation, with the aid of Finite Element Methods and Large Finite Element Analyse Software Tool, establishes analysis models of Unbonded Prestressed Structure based on the Contact Element Method. Use Three Dimensional Point-to-Point contacts to simulate the Face-to-Face contact between Unbonded Tendon and Concrete walled in the actual, but Normal Stiffness between the contact point is determined by contact material Young's Modulus and the size of the contact face, while Tangential Stiffness is considered synthetically according to the value of Normal Stiffness and the Friction Coefficient between Prestressed Reinforced Steel and Concrete. In order to confirm the accuracy of the model, on the basis of correlation experiment reference material data, establishes corresponding Finite Element Analysis Model of the Structure, uses the Contact Element Method and the Freedom Couple Method of original reference, separately carries on The Numerical Simulation And Calculation to test beam, then carries on the contrast analysis with the test results. The result indicated that, before the concrete cracked, the Contact Element Method may simulate the actual structure well, but the compressive stress and deflection deformation is somewhat lower after cracking. For further explores of the applicationg of Contact Element Method in the practical engineering design, in view of three types of the computation of the Unbonded Prestressed Structural at Serviceability limit-State, the Structure stressful condition of the ordinary Bonded Prestressed Concrete in tension period and the Strengthening Reinforced Concrete Beams by External Prestressing, the paper establishes the analysis model of Contact Element Method separately, carries on the detailed Numerical Simulation and Calculation, and carries on the result contrast to the conventional method. The result indicated that, speaking of these three kinds of situations,using the Contact Element Method has the better computation precision.It is more real of using Contact Analysis Model to simulate the characteristic of non Deformation Compatibility between Unbounded Prestressed Reinforced Steel and Concrete. Using the Contact Element Method on the basis of Contact Analysis Theory to compute the structure of the Unbonded Prestressed Structure before cracking ,the result is more accurate than the other methods, It can be a reasonable method of Structural Design and Computation of Unbonded Prestressed Concrete,But its applicability and computational efficiency are still waiting for further improvements.