中文摘要：

为研究应力比对钢桥面外变形疲劳性能的影响,通过足尺疲劳试验对不同应力比循环荷载作用下钢桥腹板间隙典型细节的疲劳裂纹萌生和扩展机理进行研究。采用5个足尺试件开展了疲劳试验,研究了40mm和60mm腹板间隙在不同应力比循环荷载作用下的裂纹萌生和扩展行为,分析了腹板间隙处腹板与竖向加劲肋焊趾细节应力随着循环荷载变化的规律,得到了应力比对该构造细节面外变形疲劳性能的影响。研究结果表明：腹板间隙处腹板与竖向加劲肋焊趾处面外变形疲劳性能受应力比影响较大,疲劳裂纹从焊趾处萌生后远离竖向加劲肋在腹板内扩展;腹板间隙为40mm、应力比小于0.3时,腹板与竖向加劲肋焊趾处的细节疲劳强度为AASHTO规范中D类和Eurocode规范中的71类;应力比大于0.3且小于0.5时,该细节的疲劳强度降为AASHTO规范中E′类和Eurocode规范中的45类;腹板间隙为60mm、应力比小于0.3时,腹板与竖向加劲肋焊趾处的细节疲劳强度为AASHTO规范中C类和Eurocode规范中的100类;应力比大于0.3且小于0.5时,该细节的疲劳强度降为AASHTO规范中D类和Eurocode规范中的80类;腹板与竖向加劲肋焊趾处疲劳裂纹的扩展速率在高应力比的循环荷载作用下较低应力比循环荷载作用下更快;细节疲劳强度随应力比的增加而显著降低,随腹板间隙的增大有一定程度的提高。

英文摘要：

Aimed at the effect of stress ratio on out-of-plate distortion-induced fatigue performance of steel bridges,full-scale fatigue tests were carried out to investigate fatigue crack initiation and propagation mechanism of typical details of steel bridge web gaps under cyclic loadings with different stress ratios.Fatigue tests of 5full-scale specimens were carried out to investigate and crack initiation and propagation behaviors of 40 mm and 60 mm web gaps under cyclic loading with different stress ratios and analyze the stress change of weld toe details of web to verticalstiffener details in web gaps with the cyclic loading.The effect of stress ratio on out-of-plane distortion-induced fatigue performance of these structural details was obtained.The results show that the stress ratio has great influence on the out-of-plane distortion-induced fatigue properties of the web to vertical stiffener in web gaps,and fatigue cracks at web to vertical stiffener weld toe initiating from weld toe propagate away from the vertical stiffener in web.As for 40 mm web gap,when stress ratio is less than 0.3,the fatigue strength of web to vertical stiffener weld toe details belongs to the category D of AASHTO Specification and the category 71 of Eurocode.When the stress ratio is between 0.3and 0.5,the fatigue strength of such details belongs to the category E′of AASHTO Specification and the category 45 of Eurocode.As for 60 mm web gap,when the stress ratio is less than 0.3,the fatigue strength of web to vertical stiffener weld toe details belongs to the category C of AASHTO Specification and the category 100 of Eurocode.When the stress ratio is between 0.3and 0.5,the fatigue strength of such details belongs to the category D of AASHTO Specification and the category 80 of Eurocode.Fatigue crack growth rate at web to vertical stiffener weld toes is faster under cyclic loading with high stress ratio than under cyclic loading with low stress ratio.The detail fatigue strength obviously decreases with the increase of the stress ratio,but in