基于实测车流的钢箱梁横隔板疲劳特性

Fatigue characteristics of steel box girder based on measured vehicle flow

为研究车流荷载作用下钢箱梁横隔板弧形切口处母材的疲劳特性,以佛山平胜大桥为背景工程,基于动态称重系统(WIM)监测数据,得到了该桥9种车型的疲劳荷载谱,运用ABAQUS建立了钢箱梁节段模型,计算了横隔板弧形切口处疲劳应力时程曲线。通过模型试验验证,得到了设计弧形切口的疲劳寿命和裂纹扩展规律。研究结果表明:该悬索桥疲劳车型可简化为V2~V10共9类,不同车道的同一车型轴重差异较大,3^#、4^#车道轴重普遍高于1^#、2^#、5^#车道,最大轴重为3~#车道的V10车型的Z3轴,重达151 kN;重车道(3^#、4^#车道)V2~V10车型的比例明显高于其他车道;轮轴作用下弧形切口处沿纵桥向的应力影响线较短,约3个横隔板间距,动力响应始终为压应力,且仅能识别轴组,不能分辨轴组中的单根轴重,当V10车型后轴组通过时,弧形切口的压应力幅达最大,为-169 MPa;考虑车辆超载时,弧形切口处的最小和最大疲劳应力幅分别为不考虑车辆超载时的1.17倍、1.75倍;模型试件在膜压应力幅作用下弧形切口处母材出现疲劳裂纹,开裂位置与实桥一致,均萌生于横隔板弧形切口处起弧点附近,裂纹长度达53 mm;裂纹扩展前期速率较快,后期逐渐减慢;轮载横向作用位置对弧形切口处应力幅影响很大,轮载作用于弧形切口正上方时,该位置应力幅最大。

To study the fatigue properties of the base material at the arc incision of a steel box girder under traffic load, Foshan Pingsheng Bridge was used for the engineering background, and based on the monitoring data of the weigh-in-motion(WIM) system, the fatigue load spectrum of nine vehicle types of the bridge was obtained. A steel box girder segment model was established using ABAQUS, and the fatigue stress history curve of the arc incision of the transverse diaphragm was calculated. Validated by model tests, the fatigue life and crack propagation law of the design arc incision was obtained. The results show that the fatigue model of the suspension bridge can be simplified to V2 to V10, the axle weights of the same model vary in different lanes, the axle weights of lanes 3~# and 4~# are generally higher than lanes 1~#, 2~#, 5~#, and the Z3 axis of the V10 model in lane 3~# has a maximum axle weight of 151 kN. The proportions of V2 to V10 models in heavy traffic lanes(lanes 3~# and 4~#) are significantly higher than in other lanes. The influence lines along the longitudinal bridge at the arc incision under the axles are shorter, about the spacing of the three diaphragms. The dynamic response is always compressive, and only the axis group can be identified. The weight of a single axle in the axis group cannot be distinguished when the rear axle group of the V10 model passes, and the compressive stress amplitude of the arc incision slit reaches a maximum of-169 MPa. When considering the vehicle overload, the minimum and maximum fatigue stress amplitudes at the arc incision are 1.17 and 1.75 times of that without vehicle overload, respectively. Under the action of the film compressive stress amplitude, the fatigue crack occurred in the base material at the arc incision of the model test piece, and the cracking position is consistent with the real bridge, and cracks both appeared near the arcing point of the arc incision of the diaphragm, and the length of the crack was 53 mm. The rate of crack propagation is faster in the early stage and gradually slowing down in the later stage. The lateral position of the wheel load has a significant influence on the stress amplitude at the arc incision. When the wheel load acts directly above the arc incision, the stress amplitude at this position is the largest. 3 tabs, 14 figs, 33 refs.