基于有效缺口应力法的钢桥焊接细节疲劳分析

Fatigue analysis of typical welded joints of steel bridges using effective notch stress approach

为了验证有效缺口应力法对于钢桥焊接构造细节疲劳寿命评估的适用性,简化基于S-N曲线的疲劳寿命评估程序,开展3种典型钢桥焊接构造细节在应力比为0.1的条件下的高周疲劳试验.采用ABAQUS有限元分析局部有效缺口应力,得到不等厚对接焊接接头、十字形非传力角焊缝接头和十字形传力角焊缝接头疲劳试样的有效缺口应力S-N曲线,探讨局部有效缺口应力对焊接接头失效模式的影响.结果表明,焊接位错量会严重影响十字形传力角焊缝接头的失效模式,采用有效缺口应力法可以有效地区分焊根或焊趾失效;名义应力S-N疲劳设计曲线与有效缺口应力FAT225疲劳设计曲线相比,具有更高的安全保证.3种构造细节的有效疲劳试验数据表明,采用有效缺口应力FAT200疲劳设计曲线更合理.

The fatigue life evaluation procedure based on the S-N curves was simplified in order to validate the applicability of the effective notch stress approach to the welded joints of steel bridge.Fatigue tests were performed for the unequal thickness butt-welded joints,non-load-carrying fillet-welded cruciform joints and load-carrying fillet-welded cruciform joints when the stress ratio is 0.1.Then the local effective notch stress at the weld toe or weld root was analyzed by numerical calculation with ABAQUS,and the SN curves in the effective notch stress system of the above-mentioned welded details were obtained.Effects of the values of effective notch stress on the fatigue failure modes of welded joints were investigated.The experimental and analytical results indicate that the size of the welding misalignment will determine the fatigue failure mode of the load-carrying fillet-welded cruciform joint,and the effective notch stress approach can distinguish the crack initiation location at weld toe or root.Nominal stress approach exhibits more conservative than the effective notch stress approach with FAT225 design curves.Experimental data demonstrates that FAT200S-N curve will be more acceptable.