三道湖中桥无粘结预应力混凝土主梁设计

对直线配索无粘结预应力混凝土梁截面应变进行了分析,根据极限状态下截面受压边缘混凝土应变分布形式及无粘结预应力钢束高度处的混凝土应变分析,得出无粘结预应力钢束极限应力增量的积分表达式,编制了计算程序进行求解,并与21片两集中力三分点加载实验梁的实验结果进行了对比,结果较为吻合;不计梁体弹性区段的混凝土应变时,极限应力增量计算值减少7.5～15.1MPa,占极限应力增量的1.9%～4.5%,可偏安全地予以忽略.根据理论和实验结果,对标准跨径25m的三道湖中桥上部结构预应力混凝土箱形主梁进行了设计.

Design of the prestressed concrete girders in sandaohu middle bridge

Strain analysis was performed to the cross sections of prestressed concrete beams with straight line unbonded tendons.Based on the strain distribution calculation of the compression concrete fiber in ultimate state,the concrete strain at the location of the unbonded tendons was integrated to establish an equation group to calculate the ultimate stress increment.A computer program was assembled to solve the equations.To verify the accuracy of the computational method,21 specimens with straight line unbonded tendons were tested to failure by two concentrated loads at 1/3 span.Comparison indicates that the calculated ultimate stress increment had shown excellent consistency with the tested results.When the strain in the elastic area of the beam was neglected,the ultimate stress increment decreased 7.5 to 15.1 MPa,accounting for only 1.9% to 4.5% of the total stress increment,which indicates that the strain in elastic area can be safely neglected.Based on the theoretical and experimental research,the unbonded tendons of the prestressed concrete box-girders in Sandaohu middle bridge were designed.