基于螺纹联接的预应力精轧螺纹钢筋张拉力识别原理与技术

Tension identification principle and technology for prestressing fine-rolling screw-thread steel bars based on a threaded connection model

为了防止预应力混凝土箱梁桥腹板开裂,以混凝土箱梁桥预应力精轧螺纹钢筋张拉力测试,并修订相关规程。视预应力精轧螺纹钢筋锚固螺母与锚垫板为弹簧联接,联接弹簧的刚度为其接触面法向接触刚度。放弃精轧螺纹钢筋与锚固螺母固结假定,视其钢筋、螺母螺纹为弹簧联接,视螺纹为悬臂结构,并基于图乘法计算联接弹簧刚度,建立预应力精轧螺纹钢筋锚固系统弯曲振动动力学模型。考虑到精轧螺纹钢筋联接传力过程中,每圈螺纹传力大小的不均匀性,越远离接触面传力越小,导致精轧螺纹钢筋的外露长度发生相对变化,影响测试结果的正确性,提出其法向接触刚度的修正方程。最后,开展了室内模型试验和多座桥梁的现场试验。研究结果表明:该方法解决了预应力精轧螺纹钢筋锚固系统因外露长度不同引起的张拉力测试误差,获得了锚固螺母与锚垫板法向接触刚度与张拉力关系式,该关系式符合接触面法向刚度与法向力关系的一般规律;模型试验和现场试验均表明其法向接触刚度与张拉力关系具有稳定性,其原理可应用于现场桥梁测试和相关规范修订。规范的实施对彻底解决竖向预应力损失过大和失效的问题具有重要意义,该研究结果对于土木工程类似结构的张拉力、机械结构类似的紧固力测试与分析具有参考意义。

To prevent web cracking of a pretensioned concrete box girder bridge,this study aimed to provide a more efficient accurate test technique for effective tensile force of prestressing fine-rolling screw-thread steel bars and revised the relevant regulations.It was considered that the anchorage nut and the anchor plate of prestressing fine-rolling screw-thread steel bars were connected by springs and the stiffness of the coupling spring was the normal contact stiffness of the contact surface.Dismissing the fixation assumption of the steel bars and anchorage nut,the connection between the steel bar and nut threads were considered as a cantilever structure and the stiffness of springs was calculated using the graphic multiplication method.The dynamic model of the bending vibration of the prestressing fine-rolling screw-thread steel bars was established.During the process of joint force transmission of fine-rolling screw-thread steel bars,the force transmission in each lap of thread was non-uniform,and the farther away from the contact surface,the smaller the force transmission.This may change the length of the exposed segment of the steel bars and affect the accuracy of the test results.Based on the thread characteristics,a modified equation of the normal contact stiffness of the contact surface was proposed.Finally,model tests and field tests of multiple bridges were conducted.The results show that the problem of the tension test error caused by the different exposed segment lengths of the anchor system of the prestressing fine-rolling screw-thread steel bars is solved using this method.The relationship between the normal contact stiffness and tension of the anchorage nut and anchor plate is obtained and which conforms to the general rule of the relationship between the normal contact stiffness and force.The results of the model and field tests show that the relationship between the normal contact stiffness and tension is stable and effective and can be used to conduct field tests and revise the current test specifications.The implementation of this code is of great significance to thoroughly solve the problem of excessive loss and failure of vertical prestress.It can be extended to other structures with a similar anchorage system.6 tabs,11 figs,21 refs.