考虑频率测试结果不确定性的拉索索力识别方法

频率法广泛应用于斜拉索和吊杆的索力实测中,但由于仪器误差和噪声的影响,频率测试结果具有一定的不确定性。为研究该不确定性对索力计算结果的影响,基于区间反演分析的思路,提出了一种考虑频率测试结果不确定性的拉索索力识别新方法。首先推导了两端弹簧转动支承拉索自由振动的特征方程,然后将实测多阶频率的上下限作为已知数代入该频率方程,即可识别索力和边界条件的可行解区间域。数值计算结果表明:能有效识别出拉索索力和边界转动刚度,且识别结果的精度随着所采用的频率数量的增加而增加。通过对某实际拱桥吊杆的索力识别,验证了该方法的工程可行性。

Identification of tension in cables with uncertainty frequency measurement using Set Inversion Via Interval Analysis

Frequency method is widely used in tension estimation of stay cables and hangers, however, due to the effect of instrumental errors and noise, the exact frequencies are difficult to be measured and uncertainty is included in the tested results. In order to consider the effect of uncertainty frequencies on the identified cable tension, a methodology is developed for the estimation of cable tension and boundary restraints of stay cables and hangers using set inversion via interval analysis. Firstly, the characteristic equation of free vibration of cables with rotational end restraints is derived, and then the region of feasible solutions of cable tension and end restraints can be solved by substituting the upper and lower boundary of measured frequencies into the characteristic equation. Numerical results show that the cable tension and end rotational stiffness can be identified by the proposed paper, and the accuracy of results increase as the used number of frequencies increase. In the last, the feasibility of engineering application of this method is verified by identifying the cable force of the hanger of an actual arch bridge.