Interface Shear Strength Prediction of CFRP-Strengthened Sulfate-Damaged Shear Keys Using NLFEA

In this paper, the behavior of shear key joints was investigated under the effect of sulfate damage and strengthening by carbon fiber reinforced polymer (CFRP) strips using the nonlinear finite element analysis (NLFEA) technique. After a well-validation against experimental work data from the literature, a total of 21 three-dimensional (3D) simulated models were utilized to examine the effect of CFRP strengthening (strengthened and un-strengthened), CFRP strip number (0, 1, 2, 3, 4, 5, and 6), and ASR damage level (0 (undamaged), one (73 days), and two (123 days)). The load–slip response, crack opening, failure mode, stiffness, toughness, and strengthening profitability were reported for all simulated specimens. Results showed that reinforcing the shear key region with CFRP sheets effectively decreased the crack's opening width and associated slippage. Increasing the number of plates used increases separation capability by an average of 10, 13, and 11% and lowers the slippage values by an average of 0%, 16%, and 35% for sulfate damage levels of 0, 1, and 2. Besides, increasing the number of CFRP plates used increased the stiffness and toughness values for undamaged shear key joints by 10% and 40%. Furthermore, when the joints are subjected to sulfate damage attack levels 1 and 2, their stiffness will have a linearly increasing correlation, beginning with negative improvements and progressing to positive ones after a specific amount of CFRP plates. In general, increasing the number of CFRP plates or the sulfate damage level lowers the profitability index of the utilized strengthening material. The finding of this study could be used as a design and rehabilitation guideline for shear key joints under sulfate damage attack.