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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。
In order to study the effect of stress ratio on the deformation fatigue behavior of steel decks, fatigue crack initiation and propagation mechanism of typical details of the web gap of steel bridges under different stress-cycles loadings were studied by full-scale fatigue test. Five full-scale specimens were used to carry out fatigue tests. Cracking initiation and propagation behaviors of 40mm and 60mm webs under different cyclic loadings under different stress ratios were studied. The relationship between webs and vertical stiffener weld toe The influence of stress ratio on the fatigue performance of out-of-plane deformation of the structural detail is obtained with the change of detail stress with the cyclic loading. The results show that the out-of-plane deformation fatigue behavior of web and vertical stiffener at the web stiffeners is greatly affected by the stress ratio, and the fatigue crack propagates away from the vertical stiffeners in the web after initiation from the weld toe. Plate gap of 40mm, the stress ratio is less than 0.3, the web and vertical stiffener weld toe detail fatigue strength AASHTO specification Class D and Eurocode specification 71; stress ratio greater than 0.3 and less than 0.5, the details Of the fatigue strength of AASHTO specification Class E ’and Eurocode 45 categories; web gap of 60mm, the stress ratio is less than 0.3, the web and vertical stiffener weld toe detail fatigue strength AASHTO specification C Class 100 and Class 100 of the Eurocode Code; fatigue strength for this detail is reduced to Class A of the AASHTO Code and Class 80 of the Eurocode Specification for stress ratios greater than 0.3 and less than 0.5; fatigue cracks at the weld toes of webs and vertical stiffeners Of the expansion rate under high stress than the cyclic loading lower stress than the cyclic loading faster; details of the fatigue strength with the stress ratio increases significantly reduced with the increase of the web gap to a certain extent.