PSI - Issue 41

Chaaben Arroussi et al. / Procedia Structural Integrity 41 (2022) 752–758 Author name / StructuralIntegrity Procedia 00 (2019) 000–000

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and 45°). Figure 5 presents the bending moment capacity development with the increase in the bend end angular displacement. The bend behaviour follows a typical steel structure trend where it starts with a linear relation followed by a plateau once the maximum capacity was reached. The figure presents as well a comparison between the various studied cases, showing the effect of the pipe bend ratio R/D on the bending capacity, the stiffness at the linear zone where the material still within the elastic zone. It is noted that pipe bends with high R/D ratio tends to have a very smooth transition at the plateau region while bends with lower R/D ratio develop the more expected behavior of a relatively much more aggressive transition. Figure 5.c presents the effect of bend radius, it shows that the initial structural stiffness of the bend is not affected and almost remains the same while at the transition zone the 3D bend tends to have lower bending capacity due to the highter curvature of the bend. This validates the literature reported data indicating a reduction of a bend moment by using larger radius elbow geometry. Except for the radio radius of R/D = 3 in the position 3 of defect at 45°. They present an increasing of the moment bend by …% and a large angular displacement.

Fig6. Reaction of the moment bending versus the angular displacement on the different elbow radius (a) position 1 with default of 10°, (b) position 2 with default of 20° and(c)position 3 with default of 45°.

3. DISCUSSION AND RECOMMENDATION

The radius of curvature results shows a similar trend as of bend angle. Higher the radius of curvature lower is the critical moment (refer to Figures 5). From the both proposal solutions, the following conclusions were derived. For both location of defect and both type repairing mode, the plastic deformation of large arc thinned elbows was started at lower bending moment and smaller rotation than those of small arc thinned elbows. The plastic deformation of intrados thinned elbows was started at lower bending moment and smaller rotation than those of extrados elbows, in the closing mode bending. The failure of local wall thinned elbow was classified into three modes, buckling, ovalization, and crack. For the open mode, buckling was occurred at the thinned region of which the extrados circumferential angle. And, crack was occurred at the intrados region for the other three cases. Ovalization was occurred for all cases, and it was extended to the some region of straight pipe. For the close mode, buckling was occurred at the intrados for all cases. No crack was occurred for all cases. Ovalization was occurred for all cases, and it was extended to the some region of straight pipe. All test cases had at least three times physical safe margin of twice elastic slope moment compared with maximum allowable moment based on construction code.

4. CONCLUSION AND RECOMMENDATIONS

Different method of reparation of pipe elbow such as method by replacing a pipe elbow were used different pipe elbow with different bend angle and bend radius to repair the cracked elbow at 0°, 10°, 45° , the other method is represented in laying down two kind of patch on the pipe elbow damaged and it comes by reparation by composite