PC箱梁腹板竖向预应力扩散效应测试分析

为了研究箱梁腹板在竖向预应力作用下的应力扩散效应,将箱梁腹板视作狭长矩形薄板,以多对力作用在该薄板模拟腹板在竖向预应力作用下的应力场,导出竖向正应力的解析解,并采用最小二乘法原理得其数值解。引入应力均匀度参数λ和应力水平系数κ,计算得相应截面的λ值和κ值,表明λ值和κ值对竖向预应力筋间距s较为敏感;在保证λ值和κ值大于0.95的前提下计算得适合工程精度的腹板竖向预应力扩散角α,并进行多项式拟合。通过实桥测试腹板竖向应力扩散效应,同时采用有限元软件模拟计算,结果表明在竖向预应力筋作用下,腹板应力扩散效应明显,在腹板的上部和下部,两根竖向预应力筋之间存在应力空白区,在腹板中部竖向应力都比较均匀。

Analysis on PC Box Beam Webs by Vertical Prestress in Consideration of Stress Diffusion

In order to study the stress distribution effect of the webs which is under the action of vertical prestress,pairs of forces were acted on a long and narrow rectangular thin plate,and the webs stress field under the effect of vertical prestressing was simulated,with analytical solution of vertical normal stress derived and the numerical solution obtained by the Least-square method.The parameters,λ and κ,were introduced and calculated to describe vertical stress uniformity and stress level,which shows that λand κ value are more sensitive to webs vertical reinforcement spacing.On the premise of uniformity of vertical prestress and stress level,the fitting diffusion angle of vertical prestress acting on the webs is obtained and fitted by polynomial.Vertical prestress diffusion effect of the webs was tested in bridge site and analyzed by the finite element software.The results show that the webs stress diffusion is obvious,and the stress has a good uniformity at the section of H/2 but a bad uniformity at axillary and shore up.