施工期钢绞线锚下有效预应力测试技术

为准确检测锚下预应力大小,研发了预应力钢绞线锚下有效预应力测试系统,基于等效刚度理论揭示了系统的工作机理,针对两类情况分别提出了张拉力的判别准则,解释了张拉力与延伸量关系的特征曲线.研究结果表明:张拉力与延伸量的关系曲线分为消除非弹性变形阶段、反拉段弹性变形阶段及反拉段和锚固段协同受力阶段;根据张拉力-延伸量曲线出现"拐点"和未出现"拐点"两种情况分别提出判别准则,"拐点识别法"可用于锚下有效预应力测试,实际工作张拉力与测试张拉力误差不超过3%;锚下有效预应力测试评定标准需考虑预应力损失.

Testing Technology of Under-Anchorage Effective Prestress of Steel Strand in Construction Period

To accurately detect under-anchorage effective prestress， a test system for prestressed steel strand was developed and its working mechanism was revealed based on the equivalent stiffness theory. A specific criterion of tension for two kinds of situations was given and the tension-elongation characteristic curve was explained. Results show that tension-elongation curve can be divided into inelastic deformation eliminating section， elastic deformation of the reverse stretching section and co-work of both reverse stretching section and anchorage section. Specific tension criterion can be given according to whether there exists an inflection point in the tension-elongation curve， which can be used for detecting under-anchorage effective prestress. The error between actual working tension and the tested tension is less than 3%. It is suggested that the prestress loss should be considered in the evaluation standard of under-anchorage effective prestress.