基于结构应力法的斜拉桥锚箱疲劳寿命评估与试验研究

Fatigue Life Assessment and Test Study of Anchor Box in Cable-stayed Bridges Based on Structure Stress Method

焊接钢结构的抗疲劳设计采用规范推荐的S-N曲线结合试验修正的方法,但由于疲劳细节和荷载的复杂性,很难找到相对应的S-N曲线且试验的成本较高。结构应力法可以从理论上对结构的疲劳寿命进行预测,近年来受到广泛关注。为了评估大连市滨海大道西延伸线工程斜拉桥锚箱结构的疲劳性能,开展了足尺模型试验,并基于结构应力法评估了锚箱的疲劳寿命。通过建立全桥有限元模型分析了各斜拉索的索力,并考虑平均应力的影响确定试验加载的最大峰值和最小峰值。在完成规范要求的疲劳循环后,为进一步探究锚箱超长期服役的疲劳性能,增大加载幅值经过276万次的疲劳加载,锚箱结构的力学性能和刚度均未出现明显变化。基于结构应力法预测锚箱的疲劳寿命为9.17×10^6次。综合结构应力法评估结果和疲劳试验研究表明锚箱的疲劳性能可靠,能够满足工程要求。

The design of the welded steel structure adopts the method of the fatigue test and S-N curve recommended by the specifications. However,due to the complexity of fatigue details and load,it is difficult to find the corresponding S-N curve and the expenditureof the experiment is high.Structure stress method can predict the fatigue life of structures in theory,which has received much attention in recent years.Aiming at the anchor-box anchorage structure in the cable-pylon anchorage zones of Dalian coastal avenue westward extension line Cable-stayed Bridge,adopting the structural stress method,the full-scale model fatigue test and fatigue assessment of anchor box are carried out. Through the finite element analysis of the whole bridge model,the cable forces are determined. Considering the influence of mean stress,the maximum and minimum peak of fatigue loads are calculated. After completing fatigue times that specifications stipulate,in order to study the fatigue performance of anchor box in extra-long term service,the fatigue load amplitude is increased. After 2.76 million times of fatigue cycles,the mechanical property and stiffness of the bolt-box structure have not changed. Adopting the structure stress method,the predicted fatigue life of anchor box is 9.17×10 ^6times. Fatigue assessment and test study indicate that the fatigue performance of anchor box is reliable,and anchor box can meet the requirement of the engineering.