PSI - Issue 42

Maha Assad et al. / Procedia Structural Integrity 42 (2022) 1668–1675 Assad et al./ Structural Integrity Procedia 00 (2019) 000 – 000

1673

6

(a)

(b)

Fig. 4. Temperature profiles for point T9 (a) EBR; (b) NSM

3.3. Structural response Thermo-mechanical analysis was performed for the EB and NSM slabs using ANSYS 19.0 (ANSYS, (2019)). In this FE model, the temperature-dependent mechanical properties of concrete, steel reinforcement, and CFRP were incorporated in the model. Also, the sustained load was applied as a static point load at midspan, as in the experimental setup. Convergence of this FE model was challenging due to high non-linearities, resulting from the material degradation under elevated temperatures, the simulation of the debonding process, and geometric non-linearities. Therefore, incrementation of the load was necessary at convergence hurdle points to allow the model to proceed further in the analysis. It can be seen from Figure 4 that the load-deflection curves of the EB and the NSM RC slabs from the FE analysis reasonably agree with the experimental curves. This also verifies the applicability of the material models obtained from EC 2 and previous literature which are assigned in the FE model. A small kink is observed in Figures 5-a and 5-b at about 3 and 16 minutes, respectively. This marks the time when debonding occurred, identified by exceeding the maximum specified interface shear stress in the FE model.

(a)

(b)

Fig. 5. Load-deflection curve under fire (a) EBR; (b) NSM

4. Conclusions This paper presented a numerical study that investigated the response of CFRP-strengthened RC slabs under fire using two different techniques, externally bonded reinforcement (EBR) and Near-surface mounting (NSM). It is