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实际工程施工中,竖向预应力钢筋及锚垫板的定位都存在误差,导致锚垫板顶面和锚固螺母底面之间产生初始夹角θ,该夹角使竖向预应力钢筋在锚固时回缩量增加,竖向预应力损失增大,本研究通过现场测试分析夹角θ对竖向预应力损失的影响。在某预应力连续刚构桥施工过程中,利用SDC620三维电子寻北仪对该初始夹角θ进行测试,收集400个样本,采用皮尔逊Ⅲ曲线假设、矩估计法及皮尔逊2χ拟合检验法对样本分布规律进行分析,结果表明:初始夹角θ服从皮尔逊Ⅲ曲线分布。利用JMZX-3108AT型锚索计对竖向预应力瞬时锚固损失进行测试,结果分析表明:瞬时锚固损失F与钢筋长度l呈反比,与夹角θ呈线性关系,夹角θ对竖向预应力损失影响很大。本研究中初始夹角θ的测试方法和瞬时锚固损失的计算公式为首次提出,以期对竖向预应力设计及施工有所帮助。
In actual engineering construction, there are errors in the positioning of vertical prestressed steel bars and anchor plates, resulting in an initial angle θ between the top of the anchor plate and the bottom of the anchor nuts, which makes the vertical prestressing steel tend The amount of shrinkage increases and the loss of vertical prestress increases. In this study, the effect of the included angle θ on the loss of vertical prestressing was analyzed through on-site testing. During the construction of a prestressed continuous rigid frame bridge, the initial angle θ was measured by using the SDC620 3D electronic north-finding instrument and 400 samples were collected. The Pearson Ⅲ curve assumption, the moment estimation method and the Pearson 2 × fitting test The results show that the initial angle θ obeys Pearson Ⅲ curve distribution. The instantaneous anchorage loss of vertical prestressing was tested by JMZX-3108AT anchor cable. The results show that the instantaneous anchoring loss F is inversely proportional to the length of steel bar l and is linear with the included angle θ, and the angle θ has no effect on the vertical prestressing force Losses have a great impact. The calculation method of the initial angle θ and the calculation formula of instantaneous anchorage loss are presented in this study for the first time in order to be helpful to the design and construction of vertical prestress.