PSI - Issue 64

S. Kolemenoglu et al. / Procedia Structural Integrity 64 (2024) 857–868 Author name / Structural Integrity Procedia 00 (2019) 000–000

863

7

Table 3. Material properties of test specimens

Average Value

Number of Tests

Standard Deviation

Material Property

Unit MPa MPa MPa MPa MPa MPa MPa MPa MPa MPa MPa

Cylindrical concrete 10cmx20cm specimen compression strength

38.8 560 655 0.27 512 636 0.28 44.5 38.5 3.29 51

4 2 2 2 2 2 2 2 2 2 5

3.8 4.9

Yield strength of transverse rebars (Ø8) Rupture strength of transverse rebars (Ø8) Rupture strain of transverse rebars (Ø8) Yield strength of main rebars (Ø14) Rupture strength of main rebars (Ø14) Rupture strain of main rebars (Ø14)

4

0.025

1 2

0.005

Compression strength of repair mortar at the test day for R-27-1-1 Compression strength of repair mortar at the test day for R-27-1-2 Compression strength of repair mortar at the test day for R-27-1-3

3

0.5 0.5

Pull-off strength of repair mortar

0.79

Young Modulus of repair mortar (in compression)

20 GPa 7 MPa

Tensile strength in flexure at 7 days

3.1. Test results for R-27-1-0 specimen During the test, the first bending cracks occurred at 1.0% drift ratio ( e c = 0.0012, e s = 0.002), while the initiation of cover concrete crushing was observed at the 1.5% drift ratio ( e c = 0.002, e s = 0.0022). At 2.0% drift ratio ( e c = 0.004, e s = 0.002), the peak load was reached, and the local crushing of concrete cover was observed. At 2.5% drift ratio, the cover spalling and a diagonal shear crack with 0.3 mm width were observed. Also, the drift ratio at the residual condition (lateral load=0 kN) was 0.9% after the application of 2.5% drift ratio in pulling and pushing directions for three times. During the application of 4.0% drift ratio ( e c = 0.008, e s = 0.01), the longitudinal bar buckling was detected. One step after (5.0% drift ratio), severe buckling was observed. Since the base moment dropped more than 20%, the test was concluded. The maximum bending crack width was recorded as 2.5 mm at the base section of the column, which indicated penetration of longitudinal bar strains into the footing. Until the application of 2.5% drift ratio, where cover spalling was observed, all cracks were closed at the residual state except for the base crack. The base moment versus drift ratio curve and observed damages are shown in Figure 5. 3.2. Test results for R-27-1-1 specimen The R-27-1-1 specimen was firstly exposed to an identical loading history as the reference specimen (R-27-1-0) until the 1.5% drift ratio. The response of the first stage was similar to reference specimen. At 1.5% drift ratio, the initiation of crushing was observed, which is the damage level I in this study. After completing the application of three cycles at 1.5% drift ratio, the test was stopped at residual condition. There was a 3.18 mm of residual displacement corresponding to 0.21% drift ratio in the pulling direction. The repair was applied at this point without removing the axial load. Then, the second stage loading history was applied as presented in Figure 2b. The base moment versus drift ratio relationship and observed damages are shown in Figure 6. The repaired specimen exhibited a similar damage propagation to the pre-repair test until the 1.5% drift ratio. At 2.5% drift ratio, local crushing was observed on the repair mortar. At 3.0% drift ratio, repair mortar spalling and cover concrete spalling above the repair zone were detected. At this stage, the resisting base moment started to decrease. At 5.0% drift ratio, buckling of longitudinal bars took place, and resisting base moment was decreased by 27% and %21 in the pulling and pushing directions, respectively. At that stage the test was concluded. 3.3. Test results for R-27-1-2 specimen The R-27-1-2 specimen was firstly tested with the same loading history of the reference specimen (R-27-1-0) until the 2.0% drift ratio, where local cover concrete crushing was observed at the corners of the column bottom region. The response of the first stage was similar to the reference specimen. After completing the 2.0% drift ratio cycles, the test was stopped at residual condition in the pulling direction, which corresponded to 0.59% residual drift ratio (8.63