混凝土铺装层开裂对正交异性钢桥面疲劳性能劣化作用研究

Effect of concrete overlay cracking on fatigue deterioration of orthotropic steel bridge deck

为合理评估混凝土铺装层开裂对正交异性钢桥面板疲劳性能劣化的影响,开展足尺模型疲劳试验并进行数值仿真分析,得到铺装层开裂后钢桥面板典型易损细节疲劳应力,并提出疲劳应力增大系数量化分析裂缝尺寸对各细节疲劳应力的影响效应。结果表明:混凝土裂缝深度不超过其厚度20%时,正交异性钢桥面典型细节疲劳应力增幅很小;混凝土层正下方的横隔板-U肋-顶板及横隔板-U肋细节疲劳应力对混凝土裂缝长度、深度变化较敏感,混凝土开裂对横隔板弧形开口处及U肋圆弧处的影响较小;纵桥向裂缝对疲劳应力的影响比横桥向裂缝显著,且多裂缝会明显增大疲劳细节处应力水平,会加速桥面结构疲劳性能劣化,因此须设钢筋网阻滞裂缝扩展。

To reasonably assess how the concrete overlay cracking affects the fatigue deterioration of the orthotropic steel bridge deck,the fatigue tests on a full-scale model were conducted.The fatigue stresses of the typical vulnerable details of the steel bridge deck after the overlay cracking were comprehensively simulated using numerical simulation,and the effects of concrete cracking on fatigue deterioration of typical details were quantitatively analyzed by applying the amplification factor of the fatigue stress to assessing the effect of crack size on the fatigue stress of each detail.The results show that,the typical fatigue stress increases of the orthotropic steel bridge deck details are very small when the crack depth of concrete does not exceed 20%of the concrete overlay thickness.The fatigue stresses of the diaphragm-U rib-top plate and the diaphragm-U rib details under the concrete overlayer are sensitive to the changes of crack length and depth,while concrete crack affects slightly the diaphragm cutout and the cambered part of U rib.The impact of the longitudinal crack is more significant than that of the transverse crack,and multiple cracks significantly increase the stress levels at the fatigue details,accelerating the fatigue deterioration of the composite bridge deck.Hence,reinforcement mesh shall be deployed to hinder crack propagation in concrete.