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制作一混凝土台阶梁模拟PC箱梁桥变高度腹板,在梁内安装10根不同长度竖向预应力筋及YGM锚具,测试了竖向预应力各项损失值;同时通过在螺母下放置不同倾角的垫板以模拟锚具安装误差,测试安装倾角误差与预应力瞬时锚固损失的关系;通过改变张拉锚固过程中拧紧螺母施加的扭矩值,得出扭矩、倾角与瞬时锚固损失的关系。测试结果分析表明:除长期损失外,竖向预应力各项损失测试值均大于规范JTGD62-2004计算值。管道摩阻损失与混凝土弹性压缩损失占比重很小,竖向预应力损失主要是由钢筋回缩损失与长期损失组成,其中回缩损失又占绝大部分比例。钢筋的回缩损失与锚具安装误差,螺母拧紧程度存在明显对应关系。施加较大的拧紧扭矩并不能完全消除因锚具安装误差引起的预应力损失,为了减小竖向预应力损失,必须提高锚垫板的安装精度。
A concrete step beam was made to simulate the height of the PC box girder bridge. Ten vertical prestressing tendons and YGM anchors were installed in the beam to test the vertical prestress loss values. At the same time, Different inclination of the plate in order to simulate the installation error of the anchor to test the installation of tilt angle and the relationship between the prestressed anchorage loss; by changing the tightening torque applied to the nut during tensioning and drawing, the relationship between torque, angle and instantaneous anchoring loss . Test results show that: In addition to long-term losses, the vertical prestressed loss test values are greater than the standard JTGD62-2004 calculated value. The friction loss of the pipe and the elastic compression loss of the concrete account for a very small proportion. The loss of the vertical prestress mainly consists of the contraction loss and the long-term loss of the steel, and the retraction loss accounts for the vast majority of the loss. Reinforcement retraction loss and anchor installation error, there is a clear correspondence between the degree of nut tightening. Applying a large tightening torque can not completely eliminate the prestress loss caused by the installation error of the anchor. In order to reduce the vertical prestress loss, the installation precision of the anchor plate must be increased.