Test Study Of Prestress Monitoring On First Simply Supported Then Continuous T-beam Bridge

For modern prestressed concrete structure, the value of prestress loss affects directly the degree of crack resistance of structure. In the tension period,the loss of prestress is the main part; therefore, analyzing prestress loss in the tension period becomes one of the important research projects in prestressed concrete field. The friction loss is the main part of prestress loss in the tension period, and the difference between theoretical calculation and practical calculation is large, so it is a very complicated work to determinate accuratly the value of prestress loss in the tension period. The actual prestressed loss value is greater or less than the calculated value, which can affect the structure properties under loading action(such as deformation, anti-arch and cracking load), it is adverse to estimate loss values too high or low under working load.In the paper,the discipline of prestress loss of simply supported-to-continuous prestress T-beam is studied based on the test method that measuring stress of prestressed concrete T-beam by burring sensor in prestressed T-beam. Burring the sensor in eight beams and four wet juncture places of two simply supported-to-continuous bridges, the measured variation value of beam stress in each construction step of simply supported-to-continuous bridge can be got. Analysising the relationship between measured variation value and theoretical calculation variation value of beam stress ,the results are got as follows:â‘ Comparing measured data and theoretical calculation data,we can know that the overall chang trend of measured stress and theoretical stress is anastomosing,which provide the guiding significance to construction control.â‘¡Prestressed concrete Tbeam can not shrink freely because of the contact of the bottom plate of the beam and pedestal after concrete pouring,and the temperature of beam decreased with time changed,so tension stress is produced inside the beam.â‘¢The boundary condition of prestressed concrete Tbeam changed into simply supported after the stretching the prestressed force of single beam,and the tension stress in concrete pouring released partially,so the accumulated value of stress 7days after concrete pouring can reflect better the variation of stress of prestress concrete compared the increased value of stress of single beam when the pre and post stretching prestressed,and it is necessary to measure the stress before single beam stretching prestressed,and it is appropriate to select the 1st day after concrete pouring as measured zreo point.