在桥梁连续梁T构悬臂施工中，纵向预应力钢绞线的伸长值的影响因素有哪些？

What are the factors affecting the elongation of the longitudinal prestressed steel strand during the cantilever construction of the bridge continuous beam T structure?

张拉时是否有一段钢绞线被卡住，部分区段未达到张拉应力,或者穿素时，一组钢绞线互相纠缠了。孔道摩阻，混凝土的弹模对其影响较大ΔL=ΔL2-ΔL1=544mm。钢绞线在1.05δk时的量测伸长值:  ΔL=ΔL3-ΔL1=575mm

Whether a section of steel strand is stuck at the time of tensioning, part of the section does not reach tensile stress, or when it is worn, a group of strands entangled with each other. The influence of the elastic modulus of the concrete is greater than that of the delta L= Delta L2- Delta L1=544mm. The measurement and elongation value of the steel strand at 1.05 delta K: Delta L= Delta L3- Delta L1=575mm

小心钢绞线夹片会啃钢绞线，那会大幅降低拉应力，虽然油表读数显示到了设计应力，但实际传递到钢绞线上的并没有那么多。我们试过很多次,在拉应力达到设计值时，一般凡是伸长值不够的钢束，大部分是因为夹片啃钢绞线。

Be careful that the steel strands will gnaw the steel strand, which will greatly reduce the tensile stress. Although the oil meter reading shows the design stress, there is not much that is actually delivered to the steel strand. We have tried many times when the tensile stress reaches the design value, usually the steel bundles that have not been stretched enough, mostly because the clip is gnawing at the steel strand.

所以在张拉之前，一定要检查一下限位板的空隙是否满足钢绞线夹片在张拉中的自由伸缩量，但空隙也不能太大，否则钢绞线夹片回缩引起的应力损失会增大，一般要留2mm左右。

So before tensioning, we must check whether the gap of the limit plate meets the free expansion of the steel strands in the tension, but the gap is not too large. Otherwise, the stress loss caused by the shrinkage of the steel strand will increase, and generally it should remain 2mm or so.

还有钢绞线在使用前要送检，钢绞线伸长量要根据检测报告上的弹性模量计算。

The steel strand should be checked before use, and the elongation of the steel strand should be calculated according to the modulus of elasticity on the test report.

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