中、下承式索支承人行桥动力特性的对比分析

Comparison Case Study of Natural Vibration between Half-Through and Through Cable-Supported Footbridge

为了研究中承式人行索桥的动力特性与弯扭耦合特征,以某下承式人行索桥为蓝本,在相同设计条件下变化桥面高度,构造了中承式人行索桥模型,采用Midas/Civil软件建立有限元模型,通过自振特性分析并定义弯扭耦合系数,从动力特性的角度对中、下承式人行索桥进行对比分析,并对中承式索桥桥面位置和抗风缆参数对其动力性能的影响进行了研究。结果表明,同等设计条件下,两种桥型均存在横向弯扭振型耦合,中承式耦合程度更大。撑杆高度增大会使扭转主振型延后,频率增大,但各阶竖弯频率和一阶横弯主振型频率减小。随抗风缆矢跨比的增大,结构竖弯和扭转频率略有减小,对称横弯频率增大,反对称横弯频率减小。随抗风缆倾角的增大,结构竖弯、扭转和高阶横弯频率增大,但会降低结构横弯基频。抗风缆矢跨比和倾角的增大均使中承式索桥振型的弯扭耦合程度增强。

In order to study the dynamic characteristics and bending-torsional coupling performance of halfthrough cable-supported(HTCS)footbridge,a HTCS footbridge was constructed based on an originally de⁃signed through cable-supported(TCS)footbridge with same design parameters,except that the HTCS foot⁃bridge has main cable through deck.Finite element models of two types of bridges were established using Mi⁃das/Civil software.By calculating the natural vibration characteristics and defining the bending-torsional cou⁃pling coefficient,a comparative analysis of the dynamic behavior characteristics was conducted on these two types of bridges,and the effect of the deck position and the parameters of the anti-wind cable were performed for the HTCSF.The results show that under the same design conditions,the vibration modes of both the HTCS and TCS footbridges exhibit lateral bending-torsion coupling effect,with a greater coupling degree in HTCS footbridge.Increasing the height of the strut will delay the torsional vibration mode and increase the corre⁃sponding torsional frequency,while the vertical bending frequency and the first-order lateral bending frequen⁃cy are decreased.With the increase of sag/span ratio of the anti-wind cable,the vertical bending,torsional,and asymmetric lateral bending frequencies decrease,while the symmetric lateral bending frequency is in⁃creased.With the increase of the inclined angle of the anti-wind cable,the vertical bending,torsional,and higher-order lateral bending frequencies increase,but the fundamental lateral bending frequency is decreased.Increasing both the sag/span ratio and inclined angle of the anti-wind cable will improve the lateral bendingtorsional coupling degree of the vibration mode in HTCS footbridge.