二次张拉钢绞线箱梁腹板竖向预应力损失研究

为了研究二次张拉钢绞线竖向预应力损失,进行了二次张拉钢绞线的矩形板试验,同时测试了采用二次张拉技术的实桥箱梁腹板竖向预应力的应力损失,并与传统的精轧螺纹钢竖向预应力体系进行比较.测试结果表明,采用二次张拉钢绞线技术后,箱梁腹板的即时竖向预应力损失基本上可以降低至10%以内,远小于精轧螺纹钢体系的竖向预应力损失率,可有效地提高箱梁腹板竖向预应力效率和抗剪可靠性.最后结合试验结果,探讨了管道摩阻、接缝压缩、锚具变形及回缩、弹性压缩、钢绞线松弛和混凝土收缩徐变等二次张拉竖向预应力各项损失的影响因素,并对各项二次张拉竖向预应力损失的设计取值方法提出了建议.     

Load compensation research on twicetension for loop anchor cable of inner lining in Yellow River-crossing tunnel

The load compensation equipment for anchor cable named low retraction prestressed anchorage system with twice-tension （referred to as twice-tension anchorage system） is proposed in the paper. Calculation results of loop anchorage prestressing loss （PL） values of inner lining （IL）in Yellow River-crossing tunnel under two anchorage systems, including twice-tension anchorage system and HM （Chinese transliteration is huanmao） anchorage system, are introduced. The software ANSYS is selected to realize the three-dimensional （3D） finite element modeling to accomplish simulation and calculation works under the two anchorage systems, respectively. Stress processes of IL under the two working conditions, of which one is completed cable tensioning （CCT） and the other is water in the tunnel with the designed water pressure （DWP）, are contrasted and analyzed. Impacts of prestressing forces of anchor cables on structural safety under the two anchorage systems are contrasted. The calculation results show that the twice-tension anchorage system can reduce PL effectively and then increase prestresses of wall concrete （WC）. Meanwhile, the anchorage system has the advantages of improving security and stability of tunnel structure, reducing project costs and saving steel consumption. The research work is available to related design and construction of anchor cable, and is worthy of promotion and application.