钢箱梁竖向加劲肋焊接接头疲劳裂纹碳纤维补强修复试验研究

EXPERIMENTAL RESEARCH ON FATIGUE CRACK'S REPAIRING OF WELD JOINT OF OUT-OF-PLAIN STIFFENER IN STEEL BRIDGE BOX GIRDER BY CFRP REINFORCEMENT METHOD

针对钢箱梁顶板与竖向加劲肋焊接接头疲劳细节,选取了3个已有焊趾疲劳裂纹的局部足尺试件作为研究对象,采用CFRP补强法对其中一组试件焊趾裂纹进行修复,其他两组对比试件则在CFRP补强的基础上分别进行钻孔及裂纹焊合处理。修复结束后,采用疲劳试验机进行100 MPa等应力幅疲劳加载,并在试验结束后对试件进行切割,以获取裂纹扩展断面。对试验数据进行处理分析,分别从疲劳裂纹扩展寿命、扩展断面等角度对修复效果进行评价。结果表明:CFRP补强法可显著提高疲劳裂纹的扩展寿命;在CFRP补强的基础上进行钻孔或裂纹焊合处理可进一步降低疲劳裂纹的扩展速率;CFRP布参与工作后可明显降低试件截面的疲劳应力,但粘贴未施加预应力的CFRP布对于短裂纹则几乎没有修复效果。

With regard to the fatigue details for the weld joint of deck and the vertical stiffener of steel bridge box girder, three specimens with a fatigue crack in the position of weld toe were selected as the objects of the study. CFRP reinforce method was used to repair the toe crack of one specimen, and other two reinforced specimens were drilled and crack welding respectively. The fatigue loading under 100 MPa stress amplitude was conducted by fatigue experiment machine after repairing, and the specimens were cut after loading to acquire crack propagating section. The experimental data were analyzed and the repair effect was preliminary evaluated from the standpoint of the propagation life of the fatigue crack, spreading section and so on. The analysis resuhs showed that the propagating life of fatigue crack could be enhanced obviously by CFRP reinforce method. The logical combination of CFRP reinforcement method, drilling-CFRP reinforcement method and welding-CFRP reinforcement method could reduce the propagation rate of fatigue crack further. CFRP could obviously reduce the fatigue stress of specimen＇ s section, however, CFRP without prestress had little repair effect on short cracks.