تیرهای فولادی تقویت شده دندانه دار توسط صفحات CFRP Numerical study on notched steel beams strengthened by CFRP plates

1. Introduction The use of fibre reinforced polymer (FRP) to strengthen concrete structures has been extensively studied in recent decades [8,11,21,53,54,55], while carbon fibre reinforced polymer (CFRP) is favoured for strengthening steel structures due to its higher stiffness [22,26,34,35,38,40,52]. The load capacity and stiffness of steel structures, as well as the fatigue life, can be improved by externally bonded with CFRP [14,27,39,49]. However, prior to the full usage of CFRP, premature debonding failure may occur [3,15,17,28,30,32,33], which limits the wide application of the strengthening technique. To clarify the debonding mechanism, researchers have studied the bond behaviour of the CFRP/steel interface [2,10,13,20,36,42,44,45,50]. The common debonding failure modes are cohesive failure (delamination of CFRP or adhesive) and adhesive failure (debonding between the adhesive layer and steel) [52]. Single lap [50] and double strap [18,19] shear tests were conducted to determine the bond-slip relationship, which is important for understanding of the adhesive debonding failure. While delamination failure was considered to occur mainly due to the shear stress concentration, the normal stress concentration is also an important factor [7,9,37,41]. Therefore, both of the slip and separation result in debonding failure, it is necessary to study the bond behaviour of CFRP and steel beams with consideration of the two effects. The mixed-mode cohesive law was applied to simulate the debonding failure of continuous steel beams strengthened by CFRP plates with consideration of both the shear and normal stress concentrations [6,41]. However, strengthened steel beams usually have defects and have different failure modes compared with the case of sound steel beams [15,16,25,56]. The mechanical performance of notched steel beams strengthened by CFRP plates requires further investigation.