偏轴应变法测试预应力钢绞线拉力的修正

Correction for Tension Measurement of Prestressed Steel Strand with Slant Axial Strain Method

为使偏轴应变法能准确测试钢绞线所受拉力的大小,通过考虑钢绞线形状、泊松比效应等对偏轴应变与轴向应变的关系进行理论推导,并对4根7.5m长、20根0.8m长钢绞线进行张拉试验,采集了952个有效数据,基于理论推导及试验数据对钢绞线偏轴应变与轴心应变之间的关系进行了研究。结果表明:经理论推导由偏轴应变法得到的1×7Φ15.2钢绞线内力比其实际内力偏小5.73%;对于长、短钢绞线由偏轴应变法得到的拉力修正系数较为一致,通过Lorentz及Gauss函数拟合得出利用偏轴应变乘以名义弹性模量得到的计算应力比实测应力偏小约6.5%;综合理论推导及试验结果建议采用偏轴应变法测试钢绞线拉力时应乘以修正系数1.06。

In order to measure the tension of steel strand accurately with slant axial strain method, the theoretical formula considering the steel strand shape and Poisson＇s ratio effect for the relationship between slant axial strain and axial strain was deduced. 952 valid test data were collected from the tension tests on four 7.5 m steel strands and twenty 0.8 m steel strands. The relationship between slant axial strain and axial strain was studied based on theoretical derivation and test data. The results show that the internal force of 1 × 7Ф15. 9, steel strand measured by slant axial strain is 5.73% smaller than the actual internal force; the correction coefficient with slant axial strain method is the same for long and short steel strand; with Lorentz and Gauss statistical analysis, the stress calculated with slant axial strain method is 6.5 % smaller than the measured stress. Combining theoretical analysis and experimental results, the internal force calculated by slant axial strain method should be multiplied by correction coefficient of 1.06.