利用哈密顿变分原理以及结构动静态构型的影响,建立了索梁组合结构的约化运动学控制方程.考虑到边界条件和耦合连接条件,我们研究了体系的面内特征值问题.根据求解得到的面内特征值方程,并通过分段函数的引入,结构的模态函数可以被直接确定.随后,我们研究了参数垂跨比f,刚度比K和质量比m对面内固有频率的影响.研究发现从结构的频率谱图中可以看出频率跳跃现象是存在的,另外,频率穿越现象也是十分明显.随后,考虑到局部模态和整体模态,结合之前确定的特征值方程及分段振型函数,我们研究了索梁组合结构可能的模态形状.最后,我们讨论了索-梁组合结构可能发生的内共振形式,比如面内1:1内共振形式以及1:2内共振形式.研究表明梁的静态构型不仅直接影响到耦合力连接条件,还将影响索-梁组合结构频率的确定.
Using the Hamilton principle and the effects of the dynamic and static configuration of the cable and beam, the equations of motion of the cable-stayed beam can be obtained. Considering the boundary and continuity conditions, the in-plane eigenvalue problem is investigated. By introducing the piecewise function,the mode shapes is obtained. Then, the effects of the sag-to-span ratio f, stiffness ratio K and mass ratio m on the in-plane natural frequencies of the cable-stayed beam are studied. It is shown that the curve veering phenomenon can be observed in the natural frequency spectrum of the system, and the fre- quency crossover phenomenon is obvious. By taking the local mode and global mode into account, the mode shapes of the cable-stayed beam are discussed. Finally, the possible internal resonances such as 1 : 1 and 1 : 2 are further discussed. Our results clearly show that the static configuration of the beam influences not only the force continuity conditions, but also the natural frequency of the cable-stayed beam.