AS法主缆锚靴位置钢丝受力安全性能分析

Analysis of safety performance of steel wire at strand shoe of main cable erected by AS method

空中纺线(AS)法主缆纺丝时,钢丝通过绕过锚靴进行锚固,锚靴的半径通常较小,此时钢丝会产生较大的弯曲应力。为了对锚靴位置钢丝的受力安全性能进行分析,首先,采用单根无应力钢丝进行弯曲试验,验证钢丝绕小半径锚靴的弯曲应力与理论计算值。通过钢丝的拉伸试验得到钢丝实测的应力-应变曲线,将钢丝的本构关系简化为双折线的强化模型。将绕过锚靴表面的钢丝受力状态视为拉弯构件,计入材料非线性并采用条分法对设计索力下截面应变状态进行迭代求解。考虑钢丝对锚靴的径向压力会产生摩擦力阻碍钢丝的自由伸长,通过实体有限元模型分析钢丝与锚靴间的滑移状态,讨论不同摩擦因数对钢丝应变的影响。最后,考虑钢丝间的挤压引起钢丝截面的法向应变,采用修正本构关系的分层有限元模型讨论钢丝径向力作用下的应变。研究结果表明:根据条分法分析得到5、7 mm直径钢丝绕400 mm半径锚靴时截面的最大应变分别为1.315%和1.831%,当钢丝的极限应变为4%,锚靴位置钢丝的安全系数分别为3.04和2.19;考虑摩擦作用后钢丝的最终应变降低130×10^(-6)~390×10^(-6),考虑钢丝互相挤压作用引起钢丝截面法向应变的增加量为140×10^(-6),径向力对钢丝的应变影响相对较小。

When the air-spinning method was adopted to build the main cable,the steel wires will be wound on the strand shoe.Due to the small radius of strand shoe,the steel wires around the strand shoe may generate considerable bending stress.In order to assess the safety performance of the steel wire at strand shoe,a single steel wire was used for bending test to verify the theoretical bending stress of the steel wire around the small radius anchor shoe.The stress-strain curve of the steel wire was simplified as the bilinear hardening model through the measured stress-strain curve of the steel wire.The stress state of steel wire in anchor shoe was regarded as tension bending member.Considering material nonlinearity,the sectional strain state was solved iteratively by the stripe method.Then the influence of different friction coefficient on the steel wire strain was discussed by solid finite element method.Finally,considering the normal strain of steel wire section caused by the extrusion between wires,the layered finite element model with modified constitutive relation was used to analyze the strain of steel wire under radial force.The results show that the maximum strain of 5 and 7 mm diameter steel wire around 400 mm radius anchor shoe is 1.315%and 1.831%.When ultimate strain of steel wire is 4%,the safety factor of steel wire at anchor shoe position is 3.04 and 2.19 respectively.Compared with the friction stress of anchor shoe,the tensile stress of steel wire is smaller,and the final strain of steel wire is reduced by 130×10^(-6) to 390×10^(-6) after considering friction effect,and the increase of normal strain of steel wire section caused by mutual extrusion of steel wire is 140×10^(-6),thus the influence of radial force on the strain of steel wire is relatively small.2 tabs,16 figs,25 refs.