【作者】 肜辉；

【导师】 邵旭东；

【作者基本信息】 湖南大学 ， 桥梁与隧道工程， 2010， 硕士

【摘要】 目前,我国对大跨径预应力混凝土箱梁桥腹板中的竖向预应力通常是采用张拉精轧螺纹钢的方式来实现,但精轧螺纹钢YGM锚固体系都存在锚具实际回缩损失大、安装的精度要求高、精轧螺纹钢筋易被拉断和压浆质量不够好等等缺陷。为此,湖南大学桥梁工程研究所和湖南湘潭欧之姆预应力锚具有限公司共同研制出一种“二次张拉低回缩钢绞线竖向预应力锚固系统”,使之得到有效的改善。为了验证这种新型锚具的工作性能,本文进行了以下几个方面的研究：1.从受力、施工现场的条件以及可靠度等方面考虑,本文确定螺母的最佳长度为25mm。2.单孔二次张拉低回缩预应力锚具螺母外侧最大应力位于与垫板相接触的受压端,往自由端逐渐减小,在自由端轴向应力转为拉应力、环向应力转为压应力。3.设计了采用二次张拉低回缩预应力锚具的矩形梁试验,将理论计算结果分别与传统夹片式锚具锚下应力场、新型二次张拉低回缩预应力锚具锚下应力场进行对比,发现在张拉过程中三者锚下应力场的变化规律一致,因此单孔二次张拉低回缩预应力锚具锚下构造可完全与传统夹片式锚具相同。4.通过实桥测试对低回缩二次张拉预应力锚具应用于腹板竖向预应力的预应力损失进行了测试,重点测试了其由于接缝压缩、锚具变形及回缩引起的预应力损失值、弹性压缩值、松弛损失值、收缩徐变损失值,并对影响预应力损失的因素进行了分析。在本文的最后,对新型二次张拉低回缩预应力锚具的发展和进一步研究提出了建议和注意的问题。更多还原

【Abstract】 At present, the vertical web’s pre-stress of the long-span prestressed concrete box-girder bridge is usually achieved through straining steel mills in China. However, steel mill YGM anchor system has so many deficiencies such as great back losses, high-demanding of precision in installation, possibility of pulling off the stell mill, inferiority of the mudjack and so on. To improve that effectively, the Institute of Bridge Engineering in Hunan University, together with Hunan Xiangtan OHM Prestressed Anchorage Company, has developed a "Twice Pre-stressed and Low Retracting Strand Vertical Web in Tension Anchorage System". In order to verify the performance of this new type of anchorage, this paper has made the following researches with the low retracting twice pre-stressed anchorage as subject of study:1. Considing the forces, the conditions in constructing site, and the reliability theory, it is suggested that 25mm is the best length of the nut in this paper.2. The single low retracting twice pre-stressed anchorage nut’s maximum stress is at the compressive end contact with the backing plate under the anchor. And the closer to the free end the smaller stress is. At the free end, the axial stress transforms to tensile stress and the hoop stress turns to pressure stress.3. A scaled test of rectangular beam using single low retracting pre-stress anchorage was constructed and experimented. Based on the strain measurements, the stress field under the traditional anchorage and the new low retracting pre-stressing anchorage system are obtained, and the results of the tests are consistent with the theoretical calculation ones. Therefore, compared with the traditional anchorage, the single low retracting pre-stress anchorage has the same contiguration under the anchor.4. Research on actual bridge has been made to measure pre-stress lose of vertical prestressing force in web which low retracting twice pre-stressed anchorage has been adopted. The emphases have been paid to the pre-stress lose induced by compression of joint, deformation and retraction of anchorage, elastic compression of concrete, lose through creep and shrinkage of concrete. And analysis has been made to study the factors influencing pre-stress lose.At last, this paper has put forward some advices and noticable problems for the new low retracting twice pre-stressed anchorage’s further development.更多还原