Research On Structural Improvement Test In Negative Moment Section With The Change From Simple Supporting To Continuous Of The Prestressed Concrete T-beam

Prestressed concrete simply supported by continuous structure due to prefabricated construction convenience,high comfort advantages,in the highway bridge has been widely used.However,with the increase of the service period,the simply-connected continuous beam bridge has different degree of cracking in the negative moment section of the pier,which affects its service life.The analysis shows that the effective prestressing caused by the construction quality is the main reason leading to its cracking.The current negative bending moment zone structure design using additional tooth plate way to implement prestressed,need to set up hanging basket high-altitude operations,narrow construction surface to high-quality construction has brought objective difficulties,the urgent need to improve.Aiming at the above problems,a new type of negative moment section structure is proposed in Chongqing traffic construction science and technology project.By reducing the difficulty of construction,simplifying the construction process,reducing the effective pre-stress caused by difficult construction,and then reducing the negative moment section of the crack disease,to extend the service life of the bridge.Aiming at the above problems,a new type of negative moment section structure is proposed in Chongqing Municipal Science and Technology Project.By reducing the difficulty of construction,simplifying the construction process,reducing the effective pre-stress caused by difficult construction,and then reducing the negative moment Section of the crack disease,to extend the service life of the bridge.In order to verify the reliability of the new negative bending section,this paper analyzes the mechanical behavior of the new negative moment section by means of the scale model test,and improves the negative bending section of the simply-changing continuous T-beam bridge Of the promotion and application to provide strong support,the main research content and conclusions are as follows:(1)Based on the review of the status quo of the research on the simple and continuous girder bridge technology,the improved structure of the new type of prestressed concrete T-beam simply modified variable negative bending moment is proposed.Mechanical properties of the test program,and application of ABAQUS finite element analysis software for theoretical calculation and analysis.(2)Five pairs of spans,such as prestressed concrete T-beam simply supported by continuous beam test beam,and carried out a period of six months of key mechanical indicators monitoring.The results show that the improved structure of the new negative bending section greatly reduces the difficulty of construction compared with the traditional negative bending section.At the same time,the mechanical properties are close to each other,and the trend of the index changes with time is also the same,which proves the improved structure of the new negative moment section works.(3)The development trend of key measuring points of test beam under different negative moment section prestressed tension control stress is observed.The results show that the compressive stress of the negative moment section will be reduced at a greater rate with the decrease of the prestressing tension control stress,so the prestressed tension control stress should be strictly controlled during the construction process.(4)The experimental results show that the effect of single bearing and double support on the improved structure of new negative bending section is completed.The experimental results show that the tensile stress of the cast-in-place part of the pier is reduced under the "clipping effect" of the double bearing,and the structural force is better than that of the single bearing.(5)The simulation results show that the new negative bending moment section and the new structure can be used to simulate the test beam by means of FEA numerical simulation platform and predict the development trend of prestressed cable force in the next ten years.The results show that the structural prestress loss of the new negative bending moment section is slightly smaller than that of the traditional negative bending moment,and there is little difference in structural mechanical properties.Finally,through the finite element for single and double bearing simulation,the bearing voiding disease has a great influence on the structure,and finally the single seat form is recommended.(6)Combined with the test and the actual bridge test results,summed up the new negative bending section to improve the structural advantages and shortcomings.The advantage is that the improved structure of the new negative bending section can effectively improve the safety of the construction personnel and improve the controllability of the prestressed tension in the negative moment section and shorten the construction time by 57% and save the time cost.However,the tension tank structure to cut off the stirups,affecting the reinforcement within the beam.