基于现场实测应力谱的钢锚箱构造细节疲劳评价

Fatigue evaluation of connection details on cable anchorage based on field measured stress spectrum

为评价某大跨斜拉桥设计索力最大的钢锚箱在桥面通行车辆作用下的疲劳性能,开展随机车流下锚箱疲劳敏感构造细节的现场应力监测,获得构造细节的应力时程和应力谱,并基于Miner准则计算最大应力幅、等效应力幅及疲劳加载次数。基于中国公路钢结构桥梁设计规范(JTG D64—2015)对锚箱构造细节的疲劳寿命进行分析,并讨论锚箱顶底板端部围焊细节的疲劳性能。研究结果表明:货车通行下,钢锚箱顶底板端部围焊构造细节表现为整体结构应力响应特征,在一辆货车通行下仅产生一个应力幅;在锚箱全部构造细节中,顶底板端部围焊细节应力幅高于其他构造细节,也是锚箱疲劳最不利构造细节;其中底板端部围焊处的应力幅最大,实测最大应力幅达56.7 MPa,等效应力幅和日均加载次数分别为10.1 MPa和4484次,该构造细节处疲劳累计损伤主要由相对较大的10~30 MPa的应力幅贡献。研究认为,桥面车辆通行下锚箱构造细节的应力幅较小,其疲劳性能都满足大桥设计要求。

To evaluate a large span cable-stayed bridge cable force of the largest steel anchor box in the fatigue performance of the bridge under the action of traffic,this paper had carried out fatigue sensitive anchor box structure under random traffic details field stress monitoring,from which the structural details of the stress time history and stress spectrum were obtained.Based on the rule of miner,the maximum stress amplitude,the equivalent stress amplitude and fatigue loading times were calculated.Based on the Specification for Code(JTG D64—2015),the fatigue life of anchor box structure details was analyzed,and the fatigue performance of the details of the girth welding at the end of the lower and upper plate of the anchor box was discussed.The results show that the structural details of the welded end of the lower and upper plate of the steel anchor box show the stress response characteristics of the whole structure under the passage of a truck,and only one stress amplitude is generated under the passage of a truck.Among all the structural details of the anchor box,the stress amplitudes of the lower and upper plate are higher than that of other structural details,which is also the most unfavorable structural detail of the anchor box fatigue.Among them,the stress amplitude at the end of the bottom plate is the largest,the measured maximum stress amplitude is up to 56.7 MPa,the equivalent stress amplitude and the average daily loading times are 10.1 MPa and 4484 times respectively,and the cumulative fatigue damage at the details of the structure is mainly contributed by the stress amplitude of 10~30 MPa.It is concluded that the stress amplitude of the structural details of the anchorage box is small and its fatigue performance meets the design requirements of the bridge.