The elevated temperature and opening size effect on the flexural behavior of RC slabs strengthened with CFRP sheets

Existing reinforced concrete (RC) structures are subjected to continuous deterioration and changes in their use, along with being exposed to various environmental conditions. Generally, RC structures could be subjected to high temperatures where their material is exposed to significant deterioration that affects their structural performance, and the need for strengthening is increased. Four strengthening configurations are introduced in this study to substitute for the resulting loss in the slab's mechanical characteristics due to the high temperatures and opening creation within the slab surfaces. A total of twenty-five RC slabs were simulated with (1100x500x120) mm3 dimensions. Square openings were created within the RC slabs with three values (100, 150, and 200) mm corresponding to opening ratios of (2.0, 4.5, and 8.0)%, respectively, subjected to four temperature values (23, 200, 400, and 600) oC. One specimen was left without heat damage or strengthening, twelve were heat-damaged at different temperatures, and the remaining twelve were strengthened using carbon fiber-reinforced polymers (CFRP). Slabs were simulated using the nonlinear finite element analysis (NLFEA) with four four-point loading procedures. Results showed that openings have a negative effect on the behavior of the RC slabs, with a significant enhancement recorded by the CFRP strengthening method.