试验研究了国产Q550D高强度结构钢、焊缝的基本力学性能以及横向对接焊缝和非承载横向角焊缝连接件的疲劳性能。介绍了试件的加工方法、焊接工艺、疲劳试验及其数据处理方法，将疲劳试验结果与国内外钢结构设计规范以及他人的研究结果进行了分析对比。研究表明：Q550D高强钢母材及其焊缝具有优良的延伸率和低温冲击韧性，余高磨平的钢板对接焊缝和横向角焊缝连接件的疲劳强度都分别显著地高于国内外钢结构设计规范关于普通强度钢材相应焊接节点的疲劳强度，200万次疲劳强度分别提高了72%~125%和27%~68%。钢板对接焊缝的余高磨平可改善因焊缝的几何形状和缺陷引起的应力集中程度，比原状焊缝具有好的疲劳性能。无论余高磨平或未磨平的钢板对接焊缝，还是横向角焊缝连接件，它们都具有随高强钢屈服强度的增加而疲劳强度提高的趋势。分别提出了Q550高强钢钢余高磨平的钢板对接焊缝和横向角焊缝连接件的S-N曲线，可供抗疲劳设计参考。“,”The basic mechanical property of domestic Q550D high-strength structural steel and its weld, as well as the fatigue behavior of transverse butt weld and non-load carrying transverse fillet-weld attachment were investigated experimentally. The fabrication and welding procedure of test specimens, as well as the methods of fatigue tests and data processing were described. The fatigue test results were analyzed and compared with the domestic and international design standards of steel structures and other research results. It is concluded that both the Q550D steel and its weld had fine elongation and low-temperature impact toughness. The fatigue strength of the Q550D steel butt weldment ground flush to plate surface and transverse fillet-weld attachment was much higher than that of relevant welded joints of normal-strength steel given in the design standards of steel structures, increased by 72%~125% and 27%~68% respectively. Grinding butt weld surface could improve stress concentration due to weld geometry and defects, so as to have better fatigue behavior than the butt weldment as a welded condition. The butt weldment regardless grinding weld surface or not, and the transverse fillet-weld attachment showed a growing trend in fatigue strength as their yield strength increased. Both the S-N curves for the Q550 high-strength steel butt weldment with grinding surface and the transverse fillet-weld attachment were proposed for the application of pertinent fatigue design.