| Post-tensioned prestressed concrete T-beam bridges are widely used in the construction of modern highway bridges.Prestressed steel bundles play a vital role in them.At present,the research on pre-stressed steel beams of precast beams is also hot.After the prestressing force is applied to the steel beam,the T beam will be deformed under the action of pre-energizing,and the longitudinal bridge will be arched upward,and the transverse bridge will be deformed by side bending.The longitudinal deformation of t-beam affects the setting of precambidity,and the quadratic polynomial linear form with the inverse of the mid-span deflection value as the vertex is usually adopted,but the rationality and correctness of choosing the quadratic polynomial as the precambidity linear form is not explained in the design and construction.At present,the analysis of the influencing factors and control measures of side bending deformation is becoming more and more mature,but the research on the calculation of side bending deformation is not sufficient.The allowable deviation of the vertical direction of the prestressed hole during the construction process is given in "Technical Specifications for Construction of Highway Bridges and Culverts",but the deviation of the transverse crossbridge direction which has a great influence on the amount of lateral bending deformation is not clearly defined.In calculating the theoretical elongation of the prestressed steel bundle,in order to simplify the calculation,the canonical calculation formula uses the projection length of the member on the vertical axis instead of the actual length of the steel bundle.This simplification makes the calculation formula not change due to the change of the linear shape of the steel beam caused by the deformation of the straight section bellows,which brings errors to the calculation result.Based on this background,the main research contents and conclusions of this paper are as follows:(1)Analyze and study the factors affecting the lateral bending of prefabricated T-beams,and propose effective measures to control the lateral bending deformation of prefabricated Tbeams.Based on the consideration of the deviation of the cross-cross bridge,the allowable value of the transverse bridge deviation of the beam hole in the prefabricated T beam is determined to be 10 mm by the limit of the lateral bending deformation determined by the specification,the lateral beam tolerance of the side beam hole is 8 mm.(2)After the prestressed concrete T beam is tensioned,the beam body will be longitudinally deformed.The static balance method is used to derive the differential equation of deformation curve,the deformation data of the engineering example and the numerical simulation data are collected,and the mathematical fitting is used to verify the prestressed concrete T-beam bridge with continuous support and continuous construction.The reasonable pre-camber curve equation is obtained.It is a fourth degree polynomial.(3)The formula for calculating the theoretical elongation of prestressed steel bundles given in "Technical Specifications for Highway Bridges and Culverts" is analyzed to determine the source of error in straight strips.By determining the change of the length of the steel bundle before and after the deformation of the bellows,it is found that the difference in the elongation before and after the improvement has a maximum impact of 7.2% of the fluctuation range allowed by the specification of up to 48.72%.Therefore,when performing the prestressed tension check,The actual elongation error is not within 6% of the theoretical elongation error range,and there is also a calculation simplification problem of the formula itself.Finally,by summarizing the main work of this paper and combing the conclusions,the shortcomings of the full text are prospected. |
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