【作者】 王静；

【导师】 刘小会；

【作者基本信息】 重庆交通大学 ， 桥梁与隧道工程， 2023， 硕士

【摘要】 钢绞线作为重要受力构件被广泛应用于斜拉索、预应力混凝土和空间网架结构中,对该构件的力学性能研究具有重要意义。钢绞线具有复杂的空间几何结构和接触特征,工程设计时通常简化了这些因素的影响。为此本文对捻角、摩擦和接触状况等因素对钢绞线力学性能的影响进行了评估,并选取了对钢绞线应用广泛的斜拉索,以频率法和垂度法两种索力计算方法为理论依据,讨论了某斜拉桥三根不同长度平行钢绞线斜拉索（15.2-61）和平行钢绞线斜拉索中钢绞线的细部构造对整体结构力学性能和张力计算的影响。最后基于BP神经网络对斜拉索进行了多参数索力预测。本文主要研究内容如下:（1）为分析钢绞线细部构造其弯曲刚度的影响,以平行钢绞线斜拉索中单根钢绞线为研究对象,构建七丝钢绞线精细化接触有限元模型,对有捻角和无捻角钢绞线在不同细部构造下的弯曲力学性能进行分析,得到拉索的抗弯刚度与其内部钢丝之间的绞捻特性、钢丝间的摩擦相互作用以及所受张力有关。研究表明,对于无捻角平行钢丝束,其跨中位移与两端施加的弯矩载荷呈线性关系,抗弯刚度与其长度无关,可近似取1.16EI_equ。（2）对于有捻角七丝钢绞线,钢绞线细部构造的不同对其弯曲性能的影响不同。研究表明,钢绞线抗弯刚度随捻距和摩擦系数的增大而增大、随长度L的增大而减小,在无张力条件下其抗弯刚度可近似取EI_min;此外,钢绞线初始接触状态的改变对其抗弯刚度有较大影响,当钢绞线股间非相互接触时,抗弯刚度会发生一定的折减;HDPE护套弹性模量远低于钢丝的弹性模量,不能提供给钢绞线较大的抗弯作用,对钢绞线抗弯刚度影响不显著;钢绞线抗弯刚度与其初始张力呈正相关关系,相关系数约为0.984。（3）为精确分析钢绞线细部构造对斜拉索力学性能的影响,提高索力计算的精确性,减小其它外界因素对索力计算的影响,基于频率法和垂度法的相关研究,选取了工程索力计算的常用公式,并对两种索力计算方法的影响因素进行分析,得到减振器、抗弯刚度、边界条件以及张拉力等因素对斜拉索索力的影响。研究表明,在进行索力分析时,计算索力误差随拉索抗弯刚度以及拉索主频阶次n的增大而增大,但这种影响随拉索长度的增加而减小;此外,斜拉索减振器的安装以及边界条件的设置也会对索力造成工程允许之外的误差。（4）为研究钢绞线钢丝之间复杂的组合构造特性与斜拉索频率以及垂度之间的关系,基于频率法和垂度法两种索力计算方法以及钢绞线弯曲刚度的分析,对钢绞线在不同细部构造下斜拉索振动频率以及垂度进行理论模拟分析。研究表明,钢绞线捻距对斜拉索频率以及垂度影响显著,在规范规定捻距范围内,对于短索与中索,钢绞线捻距长度分别采用约218～265mm与大于205mm时,索力计算精度更接近理论值;而对于长索,钢绞线捻距的改变对其索力影响并不显著。斜拉索频率以及垂度在钢绞线节径比变化时比较敏感,在规范规定节径比范围内,当其小于约22时,索力计算超过工程允许误差,这种影响随着钢绞线节径比的增加而减小;钢绞线初始接触状态对斜拉索索力影响较小,但均为在钢绞线各根钢丝相互接触的情况下索力计算误差达到最小;HDPE护套能够较大降低短索的振动频率以及垂度,而对中长索影响较小;当斜拉索耦合间距为其总长度的1/16到1/32时,斜拉索整体性能较好,在进行索力计算时,能够进一步提高索力检测精度。（5）为解决理论公式的局限性,利用Matlab搭建BP神经网络模型,以钢绞线在不同细部构造下的斜拉索索力预测精度为指标,对斜拉索进行多参数索力预测。研究表明,BP神经网络可以对斜拉索索力进行精确的预测,表明该索力预测方法的可行性;此外,在已知斜拉索相关具体参数时,可以根据神经网络对斜拉索索力进行预测,并与索力理论计算结果对比验证,该方法可为实际工程中斜拉索索力检测提供一定的参考。更多还原

【Abstract】 As an important mechanical component,steel strand is widely used in stay cables,prestressed concrete and space grid structures.It is of great significance to study the mechanical properties of this component.Steel strands have complex spatial geometry and contact characteristics,and the influence of these factors is usually simplified in engineering design.In this paper,the effects of twist angle,friction and contact conditions on the mechanical properties of steel strands are evaluated,and the stay cables widely used in steel strands are selected.Based on the two cable force calculation methods of frequency method and sag method,the effects of three parallel steel strand stay cables（15.2-61）with different lengths and the geometric structure of steel strands in parallel steel strand stay cables on the mechanical properties and tension calculation of the overall structure of a cable-stayed bridge are discussed.Finally,based on BP neural network,the multi-parameter cable force prediction is carried out.The main contents of this paper are as follows:（1）In order to analyze the influence of the detail structure of steel strand on its bending stiffness,a single steel strand in the stay cable of parallel steel strand is taken as the research object,and a refined contact finite element model of seven-wire steel strand is constructed.The bending mechanical properties of steel strands with twist angle and without twist angle under different detail structures are analyzed.It is concluded that the bending stiffness of the cable is related to the twist characteristics between the internal steel wires,the friction interaction between the steel wires and the tension.Research has shown that for non twisted angle parallel steel wire bundles,the mid span displacement is linearly related to the bending moment load applied at both ends,and the bending stiffness is independent of its length,which can be approximated as 1.16EI_equ.（2）For seven-wire steel strand with twist angle,the influence of different details of steel strand on its bending performance is different.Research has shown that the bending stiffness of steel strands increases with the increase of lay distance and friction coefficient,and decreases with the increase of length L.Under tension free conditions,its bending stiffness can be approximately taken asEI_min In addition,the change in the initial contact state of the steel strand has a significant impact on its bending stiffness.When the steel strand strands are not in contact with each other,the bending stiffness will undergo a certain reduction The elastic modulus of HDPE sheath is much lower than that of steel wire,which cannot provide significant bending resistance to steel strands and has no significant impact on the bending stiffness of steel strands The bending stiffness of steel strands is positively correlated with their initial tension,with a correlation coefficient of approximately 0.984.（3）In order to accurately analyze the influence of the detailed structure of the steel strand on the mechanical properties of the stay cable,improve the accuracy of the cable force calculation,and reduce the influence of other external factors on the cable force calculation,based on the related research of the frequency method and the sag method,the common formulas for the calculation of the engineering cable force are selected,and the influencing factors of the two cable force test methods are analyzed.The influence of shock absorber,bending stiffness,boundary conditions and tension on the cable force test is obtained.The results show that the cable force test error increases with the increase of the bending stiffness and the main frequency order of the cable,but this effect decreases with the increase of the cable length.In addition,the installation of the cable-stayed shock absorber and the setting of the boundary conditions will also cause errors beyond the engineering permission for the cable force test.（4）In order to study the relationship between the complex combined structural characteristics of steel strands and the frequency and sag of stay cables,based on the two cable force test methods of frequency method and sag method and the analysis of bending stiffness of steel strands,the vibration frequency and sag of stay cables under different detailed structures of steel strands are theoretically simulated and analyzed.Research has shown that during cable force testing,the lay length of steel strands has a significant impact on the frequency and sag of stay cables.Within the specified lay length range,for short and medium cables,when the lay length of steel strands is approximately 218-265mm and greater than 205mm,the accuracy of cable force testing is closer to theoretical values For long cables,the change in the twist length of the steel strand has no significant impact on the cable force test.The frequency and sag of stay cables are sensitive to changes in the pitch diameter ratio of steel strands.Within the range of pitch diameter ratio specified in the specifications,when it is less than about 22,the cable force test exceeds the engineering allowable error.This impact decreases with the increase of the pitch diameter ratio of steel strands The initial contact state of the steel strand has little effect on the cable force test of the stay cable,but the calculation error of the cable force reaches the minimum when the steel strands are in contact with each other HDPE sheath can significantly reduce the vibration frequency and sag of short cables,but has little impact on medium and long cables When the coupling distance of the stay cable is 1/16to 1/32 of its total length,the overall performance of the stay cable is good,which can further improve the accuracy of cable force detection when conducting cable force testing.（5）The BP neural network model is built in Matlab,and the multi-parameter cable force prediction is carried out for the stay cable with the prediction accuracy of the cable force of the steel strand under different stranding modes as the index.The research shows that the BP neural network can accurately predict the cable force of the stay cable,which proves the feasibility of this cable force prediction method.In addition,when specific parameters related to stay cables are known,the cable force of stay cables can be predicted based on neural networks,and compared with the results of theoretical calculation of cable force,which can provide a certain reference for the detection of cable force in practical projects.更多还原