Research and application of repairing method for fatigue cracks in steel bridge diaphragm employing CFRP and SMA
To repair cracks at the arc-shape cutouts of the diaphragm in steel bridges,reinforcement methods of bonding CFRP sheets,SMA/CFRP composite patches,and Fe-SMA plates were proposed based on the traditional crack-stop hole method.The fatigue tests were conducted on eight cracked diaphragm specimens with different repair methods.The results show that bonding CFRP sheets,SMA/CFRP composite patches,and Fe-SMA plates can effectively improve the stiffness of the cracked region and introduce precompression by activating SMA,thereby reducing the stress concentration,delaying the crack initiation and propagation,thus significantly improving the fatigue life.The fatigue life of diaphragms repaired by CFRP sheets and SMA/CFRP composite patches are 2.59 and 5.10 times that of the diaphragm repaired solely by crack-stop holes,respectively.Moreover,the diaphragm repaired by Fe-SMA plates exhibits a remarkable enhancement,where the resulting fatigue life is 12.68 times that of the diaphragm repaired using crack-stop holes.Furthermore,the feasibility and effectiveness of Fe-SMA plates covering crack-stop holes method were verified through actual repair applications of cracked diaphragm cutouts in the Sutong Bridge and other kilometer-level steel bridges.
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