带大U肋的轻型组合桥面板基本力学性能

为综合解决正交异性钢桥面板疲劳开裂和铺装层易损的难题，提出了由正交异性钢桥面板与薄层超高韧性混凝土STC组合而成的轻型组合桥面板结构。由于STC层显著提高了桥面板的刚度，因此可对结构进行优化。在带U肋轻型组合桥面板的基础上，提出了带大U肋的轻型组合桥面板方案。将此方案拟应用于某大桥，与原结构相比，用钢量基本不变，而面板-U肋-隔板三者间焊缝总长度减少36%，不仅降低了施工难度，也减少了焊接缺陷，进一步解决了钢桥面板疲劳开裂的问题。采用4种不同的结构体系，建立了钢箱梁节段有限元模型，基于热点应力法，对体系的6个典型疲劳细节进行疲劳验算。结果表明：在大U肋轻型组合桥面板中，6个疲劳细节的应力水平与传统U肋轻型组合桥面板接近，降幅效果基本一致；同时，通过计算说明了大U肋轻型组合桥面板具有良好的横向受力性能，其栓钉也具有足够的抗疲劳性能。为探究此轻型组合桥面板STC层的纵向弯拉性能，开展了负弯矩条带足尺试验，确定大U肋轻型组合桥面板的STC顶层名义开裂应力为24.1 MPa，远超STC层计算最大拉应力10.92 MPa。以上分析初步表明：带大U肋的轻型组合桥面板有较好的疲劳和静力性能。

Fundamental Mechanical Performance of Lightweight Composite Bridge Deck with Large U-ribs

A lightweight composite bridge deck (LCD) consisting of an orthotropic steel deck stiffened with super toughness concrete (STC) was proposed in order to solve the problems of fatigue crack, and damage in paving in orthotropic steel deck. In this study, we have considered optimizing the system because the stiffness of bridge deck is significantly improved. The proposed LCD would have large U-ribs replacing the traditional U-ribs. Compared to the LCD with traditional U-ribs, the one with large U-ribs has many advantages:the cost of steel is slightly changed, while the weld length is reduced by 36%, indicating relatively easy welding and a decrease in the amount of weld defect, and further solving the problem of fatigue cracking. Considering a bridge with steel box girder as an example, local finite element models with four different systems were established to investigate the six fatigue details using hot spot stress method. Our results indicate that the stress amplitudes of six fatigue details between LCD with large U-ribs and the one with traditional U-ribs are nearly the same, and the decreasing ranges of stress amplitude are very close. Meanwhile, the results of the finite element analysis suggest that the STC layer in LCD with large U-ribs has a good transverse mechanistic performance, and the studs show a good fatigue property. Finally, in order to investigate the longitudinal flexural tensile performance of the STC layer, a negative bending full-scale test was conducted. The crack stress in the top layer of STC was found to be 24.1 MPa, which is much higher than the calculated tensile stress of 10.92 MPa. The study, thus, implies that LCDs with large U-ribs have good fatigue and static behavior.