PSI - Issue 64

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

864

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mm residual drift). The repair was applied at this point without removing the axial load on the column. Then, same loading history was then applied upon residual displacement to the repaired specimen as like in the R-27-1-1 specimen. At 1.5% drift ratio, a vertical crack at the interface between repair mortar and concrete was observed on the compression side of the pulling direction. At this stage, in contrary with the responses observed for R-27-1-0 and R 27-1-1 specimens, there was no sign of initiation of crushing. At 2.0% drift ratio, similar interface cracks occurred for the pushing direction, and resisting base moment started to decrease in the pulling direction. This lateral strength loss can be attributed to the detachment of the repair mortar. Besides, the initiation of cover crushing was observed at the corner regions of the column on both sides above the repaired zone. At 3.0% drift ratio, cover concrete above the repaired zone spalled, and the mortar apparently separated from the concrete surface. At 4.0% drift ratio, buckling of longitudinal rebars was detected. The experiment was ended at this stage due to 30% drop of the base moment in the pulling direction. The base moment – drift ratio relationship and observed damages can be seen in Figure 7. The interface cracks can be attributed to difference in axial response of mortar and concrete due to repair without removing the axial load. The axial compression strain on the repair mortar was almost zero after the repair works completed before the test, while there was a residual axial strain (0.0005) on the concrete. Thus, the stress state difference of these materials eased the detachment since they reached different deformations during the lateral loading. 3.4. Test results for R-27-1-3 specimen The first stage test of R-27-1-3 specimen was stopped at 3.0% drift ratio when the cover concrete spalling was observed. The response of the first stage was similar to the reference specimen. At the residual condition after the last pull cycle of this drift ratio, there was an 1.3% (20 mm) drift at the pulling direction. After the repair stage, the test was continued from this residual drift as schematically shown in Figure 2(b). The specimen response particularly in the pulling direction was considerably worse than the other repaired specimens in terms of damage propagation, load capacity and ductility. Local crushing of repair mortar was observed at 1.5% and 2.0% drift ratios in the pulling and pushing directions, respectively. After the completion of the first 2.0% target drift ratio cycle, the column could not sustain the lateral load capacity in the pulling direction. At 2.5% pulling direction drift ratio, spalling of repair material, exposure and buckling of the rebars on the compressed side of the column was observed. At 3.0% drift ratio, the lateral strength reduction had reached to 30% along the pulling direction. Thus, the test was stopped at this stage. Together with the views of observed damages, base moment-drift ratio relationship of the R-27-1-3 specimen is given in Figure 8.

Fig 5. Base moment-drift ratio relationship of R-27-1-0 column