基于动力方法的改进杆件轴力识别

Vibration-based improved identification of axial force for bar members

在针对杆系结构中轴力杆或者索缆结构中的短索所提出的识别边界不确定的杆件轴力的解析方法基础上,提出了一种改进的轴力识别方法.首先,采用修正的Timoshenko梁理论,充分考虑转动惯量、剪切变形、剪切变形引起的转动惯量和传感器质量对结构动力特性的影响,建立改进的动力方程;然后通过Matlab软件进行数值模拟,提取某杆件的前五阶频率和模态参数,以此构建特征方程进而识别杆件轴力,从4个方面分析了修正Timoshenko梁理论相对传统Timoshenko梁理论识别精度提高的原因;最后通过实验数据验证了该方法的精确性和适用性.这种改进方法的优点在于无须事先假定边界条件,仅知传感器之间的相对位置即可实施,因而适用范围较广.

Improved axial force identification method for bar members is proposed based on the analytical method which was established for vibration-based identification of axial force of tie-bars and short thick cables with uncertain boundary conditions.Firstly,modified Timoshenko beam theory was considered by taking the influence of the rotational inertia,shear deformation,the rotational inertia caused by shear deformation and sensor mass on structural dynamic characteristics into account to establish an improved dynamic equation.Then,the characteristic equation can be solved to identify axial force.The first five-order natural frequencies and modal parameters of a bar are computed through numerical simulation with Matlab.The improved accuracies of identifying axial force by modified Timoshenko beam theory compared to that of traditional Timoshenko beam theory are discussed from four aspects.Finally,a laboratory experiment is employed to investigate the feasibility and accuracy of the proposed method.One significant advantage of the proposed method is that there is no prerequisite information about the boundary condition required,but only the relative locations of sensors to identify the axial force.Therefore,the method can be widely applied to many beam or truss elements.