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列举几种关于拉索索力测量的常用方法,指出频率法测量索力仍是实际工程最为经济、实用的方法,并对国内已有频率法计算索力实用公式做出评价与分析。基于轴向受拉梁振动方程,建立了适用于任意约束条件下的匀质竖直拉索索力实用计算公式模型,并将实用公式中的比例变量表示成为拉弯比的函数;采用有限单元法对拉索在相同拉弯比,不同拉索性质(索力、索长和抗弯刚度)情况下的比例变量进行大量的数值计算,验证了比例变量对拉弯比具有唯一性,同时说明了以拉弯比做为比例变量唯一自变量的正确性;仍然采用数值计算的方法将比例变量分段拟合成为拉弯比的反比例函数,最终给出频率法测量索力实用公式;根据已建立的实用公式,分析了约束条件和抗弯刚度对计算索力的影响,随着拉弯比的增大,约束条件和抗弯刚度对计算索力的影响逐渐减弱、直至可以忽略。与国内已有实用公式对比计算结果和实际工程应用情况均表明:该文建立的根据基频计算索力的实用公式能够对拉弯比大于1的拉索索力做出正确的计算,其计算精度满足实际工程要求。
The common methods of cable force measurement are listed. It is pointed out that the frequency method is the most economical and practical method to measure the cable force, and the practical formula of cable force calculation by the existing frequency method is evaluated and analyzed. Based on the vibration equation of the axially tensioned beam, a practical model for calculating the cable force of a homogeneous vertical cable under arbitrary constraint conditions is established, and the proportional variable in the practical formula is expressed as a function of the bending ratio. The finite element method A large number of numerical calculations were carried out on the proportional variables of the cable under the same bending ratio, different cable properties (cable force, cable length and flexural rigidity), and verified that the proportional variable is unique to the bending ratio, The bending-bending ratio is taken as the correctness of the only independent variable of the proportional variable; the numerical variable calculation method is still used to segment the proportional variable into the inverse proportion function of the bending ratio; finally, the practical formula for measuring the cable force by the frequency method is given; The influence of the restraint condition and bending stiffness on the calculation of the cable force is analyzed. With the increase of the bending ratio, the influence of the restraining condition and the bending stiffness on the calculation of the cable force is gradually weakened until it can be neglected. Compared with the existing domestic practical formulas and practical engineering applications, it is shown that the practical formula for calculating the cable force based on the fundamental frequency established in this paper can correctly calculate the cable tension with a bending ratio greater than 1, and the calculation accuracy Meet the actual project requirements.