无背索斜拉桥竖弯刚度评估模型与方法研究

Evaluation model and method for vertical bending stiffness of a cable-stayed bridge without backstays

基于斜拉桥中拉索对桥面梁起弹性支撑作用的受力特点,针对无背索斜塔斜拉桥提出一个新的双梁离散弹簧动力学模型。该模型将斜拉索简化为无质量弹簧,将桥塔和桥面梁视为考虑轴力影响的欧拉柏努利梁。然后基于传递矩阵法基本原理,推导得到了无背索斜塔斜拉桥成桥状态竖弯刚度评估方法的基本理论。最后以长沙市洪山大桥为算例,计算了其成桥状态时的自振频率和模态,并对普通钢索被替换为CFRP斜拉索后对桥梁整体竖弯刚度的影响进行了研究分析。结果表明,提出的模型能很好地评估无背索斜塔斜拉桥的竖弯刚度。另外,相比于传统钢拉索,CFRP斜拉索能不同程度地增加无背索斜塔斜拉桥的整体竖弯刚度。

Here,a new dynamic model named a double-beam system with discrete springs was proposed for an inclined tower cable-stayed bridge without backstays based on cables’elastic support effect on bridge deck beam in a cable-stayed bridge.In the model,cables were taken as springs without masses,tower and deck were regarded as two Euler-Bernoulli beams considering influence of axial force.Then,based on the basic principle of the transfer matrix method,the fundamental theory for evaluating the vertical bending stiffness of the inclined tower cable-stayed bridge without backstays was derived.Finally,Hongshan bridge of Changsha city was taken as an example,and its natural frequencies and modes were calculated.Meanwhile,influences of ordinary steel cables replaced with CFRP ones on the vertical bending rigidity of the bridge were studied.The results showed that the proposed model can be used to effectively evaluate the vertical bending rigidity of an inclined tower cable-stayed bridge without backstays;CFRP cables can improve the bridge’s overall rigidity to some extent compared with the traditional steel ones.