基于现场试验和有限元的纵肋-面板双面焊构造细节应力行为研究

纵肋-面板(rib-to-deck,简称RD)双面焊是正交异性钢桥面板制造新技术。为研究该构造细节的轮载应力特征,在某大跨度钢箱梁斜拉桥上开展了横桥向3个典型轮载工况的控制加载试验,记录了卡车缓慢移动和跑车时毗邻的多个RD构造细节的应力时程,研究了RD构造细节轮载应力行为。通过建立正交异性钢桥面板模型,开展了RD双面焊构造细节的精细化有限元分析。现场试验表明:在横桥向3个典型轮载工况中,跨肋式加载是RD构造细节最不利加载工况,此时纵肋侧和面板侧均产生最大应力幅,且面板侧大于纵肋侧;同时,RD构造细节轮载应力的局部效应显著,横桥向当构造细节距离轮载中心大于1倍纵肋中心距后,其纵肋侧和面板侧的应力幅均很小,因此可忽略卡车左右轮和相邻车道卡车并行的应力叠加效应;在纵桥向,轮载对RD构造细节的加载效应也仅局限其所在前后横隔板之间的桥面;另外,横桥向轮胎覆盖的面板下方RD构造细节,其应力时程能分辨单轴,每个车轴产生一个应力峰;否则其应力时程只能识别轴组,一辆卡车通行产生的疲劳加载次数等于卡车轴组数。有限元分析不仅得到了与现场加载试验非常一致的结果,也表明RD构造细节外侧最大应力幅均大于内侧,因此轮载作用下内侧焊焊趾的疲劳抗力高于外侧焊。故对RD双面焊构造细节,基于现场试验获得的外侧焊构造细节应力响应,能给出RD构造细节疲劳性能的合理评价。

Stress Behavior of Both-side Welded Rib-to-deck Details Based on Field Tests and Finite Element Analysis

The both-side welded rib-to-deck (RD) joint is a newly developed technique in fabricating orthotropic steel bridge decks (OSBDs). Controlled truck-loading tests on a long-span cable-stayed bridge were performed at three typical transverse loading locations to investigate the stress behavior at the details under wheel loads. The stress-time histories of the RD details at different transverse locations were obtained. The RD details were subjected to a truck load moving at a very low velocity or a moderate speed. Next, the stress behaviors at the both-side welded RD details under wheel loads were evaluated. Finally, an OSBD panel model was established to perform refined finite element analysis (FEA) of the both-side welded RD details. The field test indicates that among the three typical transverse loading locations, the riding-rib-wall loading is the most critical. The riding-rib-wall loading generates the maximum stress range at both the deck plate and rib wall sides of the RD details, and the stress range of the deck side is higher than that of the rib wall side. In addition, the local stress effect under wheel loads is significant for the RD details. Specifically, in the transverse direction of the bridge, the stress range of the RD detail is very small when its distance to the wheel center is longer than the upper rib width. Hence, the stress at the RD details generated by one side of the wheel does not interfere with that from another side, and the loading effects at the RD detail generated by the side-by-side movement of trucks can be ignored. In the longitudinal direction of the bridge, the wheel loading effect on the RD details can be discerned only when the wheel loads are on the deck supported by the nearby floor beams. The results show that the RD details can identify the individual axle only when underneath the deck plate covered by the tire width, and each axle can produce a stress cycle. Otherwise, the RD detail can only identify the axle group, and the fatigue loading cycles produced by a passing truck is equal to its total number of axle groups. The FEA results are consistent with the field test results, indicating that the maximum stress ranges at the deck plate and rib wall sides of the RD outer weld are higher than that of the RD inner weld. Hence, for both-side welded RD details, a reasonable fatigue assessment can be achieved based on the stress measurements at the RD outer weld detail using field test methods.