斜拉索车致荷载效应极值计算方法研究

Research on Methods to Calculate Extreme Vehicle Loads Effect on Stay Cables

为计算斜拉索在未来服役期的车致荷载效应极值,基于经典Rice公式理论,提出斜拉索车致荷载效应极值计算方法。该方法首先采用蒙特卡罗随机抽样法生成过桥车流荷载;然后利用影响线加载的方法求解斜拉索的车致荷载效应应力时程,并拟合Rice公式的最优参数;最后对斜拉索的车致荷载效应极值进行计算。采用该方法对杭瑞高速鄱阳湖二桥斜拉索车致荷载效应极值进行分析,结果表明:斜拉索车致应力受车流状态的影响较大,其随车流密度的增大而增大;经典Rice公式对斜拉索车致应力年跨阈率的拟合效果较好,提出的斜拉索车致荷载效应极值计算方法应用方便;斜拉索车致应力极值随重现期和交通量增长率的增加而增大,且密集车流对斜拉索车致应力极值的影响较大;在目前的随机车流荷载作用下,斜拉索失效概率较小,最长的Z18号斜拉索在设计使用年限20年内的应力极值为51.69 MPa,失效概率为4.6×10^(-3)。

Based on the classical Rice formula theory,a method to calculate the extreme vehicle loads effect on stay cables in the future service period is proposed.In this method,the loads of vehicles passing through the bridge is first calculated using the Monte Carlo random sampling method,then the stress history of the vehicle loads effect on the stay cables was obtained using the influence-line loading method,and the optimal parameters of the Rice formula are fitted.At last,the extreme vehicle loads effect is figured out.The method has been employed in the Second Poyang Lake Bridge that carries the Jiujiang section of the Hangzhou-Ruili Expressway.It is concluded that the stresses in stay cables induced by vehicle loads are under substantial impact of the traffic volume,proportionally increasing as the traffic density is rising.The classical Rice formula can well fit the annual threshold crossing rate of the vehicle-induced stresses in the stay cables,and the proposed method is convenient to calculate the extreme vehicle loads effect on stay cables,longer return period and larger traffic volume give rise to bigger vehicle-induced stresses in stay cables,and the impact of dense vehicles is more significant.Under current random vehicle loads,the failure probability of stay cables is narrow.For instance,within the design service life of 20 years,the extreme stress in the longest stay cable(Z18)is 51.69 MPa,and the corresponding failure probability is 4.6×10^(-3).