混凝土箱梁支座位移实验及有效温度计算

SUPPORT DISPLACEMENT TEST AND EFFECTIVE TEMPERATURE CALCULATION OF CONCRETE BOX GIRDER

为计算非线性温度分布下桥梁的支座位移,基于单位荷载法基本原理,建立了连续梁支座位移的计算方法和截面有效温度的计算公式。在此基础上,提出了有效温度的5种简化计算方法。为检验计算方法的精度和合理性,以西安沣河大桥这座单箱三室7跨变截面的连续箱梁桥为研究对象,现场实测了箱梁截面的温度和支座位移。实验研究和数值计算结果表明,截面的有效温度与截面的温度分布和截面的形状有关,对于变截面箱梁而言,即使具有相同的温度分布,不同截面的有效温度也是不同的。考虑混凝土的热传导效应,假定混凝土板内温度变化为指数衰减模式计算截面有效温度的加权平均值,所得支座位移误差较小,且偏安全。随后,有限元方法的计算结果进一步表明这种算法的合理性。

In order to calculate the displacement of the bridge under the nonlinear temperature distribution, the method on support displacement estimation of continuous beam and effective temperature calculation of cross section are proposed based on unit-load method. Then five simplified calculation methods on effective temperatures are established. In order to investigate the accuracies of those simplified methods, the temperature and displacement of the box girder section were measured based on the seven-span variable cross section girder of Fenghe Bridge with a single box 3 rooms located in Xi＇an. Experimental and numerical results show that the effective temperature of the cross section is related to the temperature distribution and the shape of the section. For the non-uniform cross section box girder, the effective temperature of different cross section is different even in the same temperature distribution. If the weighted average value of the effective temperature of cross section is calculated by the exponential decay temperature variation across concrete slab for the heat conduction effect, the estimated support displacement would and be relatively conservative with small errors. The numerical results of the finite element method show that the simplified algorithm is reasonable.