Table 1:
Mix proportions of the concrete used in this study
| Materials | Amount |
|---|---|
| Cement (kg/m3) | 390 |
| Sand (kg/m3) | 685 |
| Gravel (kg/m3) | 1075 |
| w/c (–) | 0.47 |
| f′ c at 28 days (MPa) | 32 |
Figure 1:
Layout of reinforcement in the tested columns
Table 2:
Details of the examined specimens
| Group no. | Specimen symbol [Ci] | Fire exposure [Ti] [ºC] | Fire duration [Di] [min] | Repair of fire damaged specimen [R] |
|---|---|---|---|---|
| Control | C1 | - | - | - |
| One | C2 T500D60 | 500 | 60 | - |
| C3 T500D60R | 500 | 60 | R | |
| C4 T500D120 | 500 | 120 | - | |
| C5 T500D120R | 500 | 120 | R | |
| Two | C6 T700D60 | 700 | 60 | - |
| C7 T700D60R | 700 | 60 | R | |
| C8 T700D120 | 700 | 120 | - | |
| C9 T700D120R | 700 | 120 | R |
Figure 2:
Casting process phases
Figure 3:
Description of the loading frame
Figure 4:
Specimens subjected to fire exposure under pre-loading curve
Figure 5:
Measured average furnace temperature versus ASTM E119-20 time-temperature curve
Figure 6:
Sequential steps of RC column repair
Figure 7:
Test setup with instrumentation details
Table 3:
Results of laboratory testing on column specimens
| Group no. | Specimen symbol [Ci] | Ultimate load capacity [kN] | Reduction in ultimate load relative to control [%] | Enhancement in ultimate load relative to control [%] | Recovery in ultimate load relative to corresponding fire-damaged specimen [%] | Ultimate axial deformation [mm] | Ultimate mid-height lateral deflection [mm] |
|---|---|---|---|---|---|---|---|
| Control | C1 | 163 | 0 | 0 | - | 9.3 | 13.85 |
| One | C2 T500D60 | 144 | 11.65 | - | - | 8.27 | 14.67 |
| C3 T500D60R | 197 | - | 20.86 | 36.81 | 11.9 | 15.24 | |
| C4 T500D120 | 140 | 14.11 | - | - | 8.67 | 15.14 | |
| C5 T500D120R | 185 | - | 13.5 | 32.14 | 11.05 | 17.2 | |
| Two | C6 T700D60 | 129 | 20.85 | - | - | 10.34 | 16.42 |
| C7 T700D60R | 174 | - | 6.75 | 34.88 | 10.84 | 17.27 | |
| C8 T700D120 | 103 | 36.8 | - | - | 11.42 | 18.21 | |
| C9 T700D120R | 171 | - | 4.91 | 66.02 | 13.83 | 19.41 |
Figure 8:
Percentage of load carrying capacity for the tested column specimens
Figure 9:
Load-deflection curves of group one columns
Figure 10:
Load-deflection curves of group two columns
Figure 11:
Load – axial deformation of group one columns
Figure 12:
Load – axial deformation of group two columns
Figure 13:
Load –deflection of exposed to 500°C and 700°C
Figure 14:
Load – axial deformation of exposed to 500°C and 700°C
Figure 15:
Spread of crack in specimens, a. Column specimens without fire, b. Column specimens with fire exposure
Table 4:
Crack width and observed crack location of the tested columns
| Group no. | Specimen symbol [Ci] | Maximum visible crack width after fire exposure before repair [mm] | Visible crack width at service load during mechanical testing [mm] | Location of crack |
|---|---|---|---|---|
| Control | C1 | - | 0.4 | In the last quarter of the column |
| One | C2 T500D60 | 0.16 | 0.62 | In the middle of the column |
| C3 T500D60R | 0.18 | Not visible due to CFRP wrapping | Not visually observable after rehabilitation | |
| C4 T500D120 | 0.4 | 0.66 | In the last quarter of the column | |
| C5 T500D120R | 0.32 | Not visible due to CFRP wrapping | Not visually observable after rehabilitation | |
| Two | C6 T700D60 | 0.48 | 0.68 | In the first quarter of the column |
| C7 T700D60R | 0.56 | Not visible due to CFRP wrapping | Not visually observable after rehabilitation | |
| C8 T700D120 | 0.74 | 0.8 | In the middle of the column | |
| C9 T700D120R | 0.9 | Not visible due to CFRP wrapping | Not visually observable after rehabilitation |
Figure 16:
Failure modes of columns after testing
Figure 17:
Ductility of specimens
Figure 18:
Stiffness of specimens