PSI - Issue 68

Maha Assad et al. / Procedia Structural Integrity 68 (2025) 252–258 M. Assad et al./ Structural Integrity Procedia 00 (2025) 000–000

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modulus of 289.5 MPa, a tensile strength of 5440 MPa, and an elongation at failure of 1.9%, according to the manufacturer (Structural Technologies, 2016). The CFRP laminates, which comprises of V-Wrap™770 Epoxy and the CFRP sheets, had a thickness of 1.02 mm, an elastic modulus of 73.77 MPa, a tensile strength of 1240 MPa, and an elongation at failure of 1.1% (Structural Technologies, 2016). 3. Results and discussion 3.1. Failure modes Fig. 3 shows the failure modes of the tested beam specimens. The flexure-shear delamination failure of the unanchored beam (UA) can be seen in Fig. 3-a. As expected, cracks were formed near the end of the FRP sheet. Then, the cracks propagated along the level of the steel reinforcement which resulted in the separation of the concrete cover. Beam A14-90 failed by debonding of the CFRP laminates, accompanied by rupture of the anchor at one of the ends, as seen in Fig. 3-b. Specimen A20-90 failed by delamination. However, the delamination was controlled compared to the delamination failure in the unanchored beam. Beams with the inclined anchors exhibited the most unsatisfactory behavior at failure, as shown in Fig. 3-c and 3-e. The failure of these beams involved more extensive cracking and premature failure compared to the beams with vertical anchors. This behaviour could be attributed to several factors, including potential misalignment or inadequate positioning of the inclined anchors during installation, which may have compromised their ability to effectively resist the applied loads. Additionally, the angle of the anchor may have introduced unfavourable stress concentrations or altered the load path, contributing to the earlier onset of cracks and more pronounced delamination. While inclined anchors are intended to provide better shear resistance, improper installation or positioning might reduce their overall effectiveness, leading to the observed unsatisfactory performance. Further investigation into the installation technique and anchor configuration is necessary to confirm these assumptions. 3.2. Load-deflection and load-strain curves The load-deflection curves in Fig. 4-a present the behaviour of the tested beams. It can be seen from the figure that beams anchored with inclined anchors showed closer load-deflection behaviour to the unanchored beam (UA) for both diameters. In fact, specimen UA showed even higher stiffness than specimens A14-45 and A20-45. This indicates that inclined anchors may not provide proper anchorage to the CFRP laminates, potentially due to improper stress distribution or ineffective anchorage at this inclination. Notably, the A20-90 beam, which had 20 mm diameter anchors at 90 degrees, exhibits the highest load capacity. This confirms that larger, vertically placed anchors provide better strengthening effect. The load-strain curves in Fig. 4-c illustrate the strain development in the CFRP laminates under increasing loads. UA beam shows the lowest strain utilization, confirming that it experienced failure before significant utilization of the CFRP strength. Among the strengthened beams, the A14-90 specimen exhibited the highest strain levels. This indicates that the vertical anchors allowed better utilization of the CFRP laminates, delaying the onset of failure.