Consequently, retrofit of many poor existing structures is a very important issue. for Turkey!

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2 Turkey Placed on one of the most active tectonic plates in the world ~96% of the country is under the threat of earthquakes ~98% of the population are live with that risk. Istanbul 1 st degree of earthquake zone Probability of an earthquake of Magnitude is ~60% for next 30 years 12 millions people live ( ~20% of the country population )

3 Existing Structures in Istanbul Low strength concrete ( 10MPa ) Inadequate transverse reinforcement Plain reinforcing bars Since most of the buildings has those deficiencies listed above, it is practically impossible to demolish and re-build all buildings. Consequently, retrofit of many poor existing structures is a very important issue for Turkey!

4 Purpose of the study Low and medium concrete strength ( ~15 MPa and ~31 MPa ) Inadequate transverse reinforcement CFRP jacketed RC columns ( 3 or 5 piles of CFRP sheets ) were tested under compression. In terms of Strength Deformability Energy dissipation Failure mode

5 Significance of the study Relatively larger size specimens Low and medium unconfined concrete strengths Different cross-section shapes Longitudinal reinforcement Adequate* and inadequate transverse reinforcement Various corner radius for specimens with rectagular cross-section Different wrapping patterns* Pre-damage of some specimens* Special anchorage details* Monotonic and cyclic* loads * not included in this paper

6 Reinforcement Details Ø R Ø12 Ø250 Ø10 R TEST ZONE For buckling LS specimens with inadequate spacing of transverse reinforcement (s ~ 15 Φ l ) NS specimens with various spacing of transverse reinforcement* * not included in this paper

7 Specimen Preparation Totally 70 specimens were produced during the experimental study

8 Specimen Preparation

9 Testing Setup Transducers Strain Gages 2x CDP10 LVDT Switching Box Electronic Data Logger 270 mm 4x CDP50 LVDT 4x PL60 SG 500 mm Computer 4x CDP50 LVDT

10 Testing

11 Testing

12 Test Results Specimen f co (MPa) f cc (MPa) ε cc ε ch κ a ρ f LS-C * LS-C * LS-R LS-R NS-C NS-C NS-R NS-R NS-R NS-R NS-R f f ' cc ' co ε ε cc co * Out of order before reaching peak stress

13 Test Results 5 NS-R NS-R Axial Stress (σ c /f' co ) NS-R NS-R Axial Stress (σ c /f' co ) NS-R NS-R Axial Deformation (microstrain) Axial Deformation (microstrain) Axial Stress (σ c /f' co ) NS-C NS-C NS-C Axial Deformation (microstrain) Axial Stress Axial Strain Relationships for NS Specimens

14 Test Results Axial Stress (σ c /f' co ) NS-R NS-R Axial Stress (σc/f'co) NS-C NS-C Transverse Deformation (microstrain) Transverse Deformation (microstrain) Axial Stress Transverse Deformation Relationships for NS Specimens in 60 mm Gage Length

15 Test Results Axial Stress (σ c /f' co ) LS-R NS-R Axial Stress (σ c /f' co ) LS-C NS-C Axial Deformation (microstrain) Axial Deformation (microstrain) Comparison of LS NS Specimens with Circular and Square Cross-Sections in 500 mm Gage Length

16 Test Results Axial Stress (σ c /f' co ) Gage Length : 60 mm Gage Length : 5 mm Axial Stress (σc/f' co ) Gage Length : 60 mm Gage Length : 3 mm NS-C Transverse Deformation (microstrain) NS-C Axial Deformation (microstrain) Comparison of Internal Reinforcement Strain Gages and Surface Strain Gages

17 Test Results Axial Stress (σc/f' co ) GL=60 mm Circular Cross-Section Comparison of Different Gauge Lenghts for LS-C-1-a GL=500 mm GL=270 mm Axial mm 60 mm 500 mm Deformation (microstrain) Comparison of Different Gage Lengths* * not included in this paper

18 Test Results Axial Stress (σc/f' co ) Square Cross-Section Corner Radius of mm Lateral Unconfined Axial Deformation (microstrain) LS-R a LS-R a LS-R a Comparison of Different Corner Radius* * not included in this paper

19 Comparison of Experimental and Analytical Results Specimen Experimental Analytical f cc (MPa) ε cc f cc (MPa) ε cc f l (FRP) LS-C LS-C LS-R LS-R NS-C NS-C NS-R NS-R NS-R NS-R NS-R (MPa) f l (ITR) (MPa) f ' cc( FRP ) f ' co ' cc( ITR ) f f ' Average S. Deviation co f f ' ' ccexp cc analy ε cc exp ε cc analy f cc f co ε cc εco f = l CFRP CFRP κ f l = f co 1.2 h f l = b f co a ρ f ε h, rup frp 2 E 0.5 (ε h,rup ) is assumed to be 70% of the ultimate strain (ε frp )

20 Conclusions The CFRP jackets provide an increase in the compressive strength and corresponding axial strain of the columns with circular, square and rectangular cross-sections While the strength enhancement was more pronounced for circular crosssections, deformability enhancement was more for rectangular cross-sections The premature buckling of the longitudinal reinforcement was prevented and the contribution of longitudinal reinforcing bars to the axial resistance and ductility was maintained until very large axial strains

21 Conclusions Independent of the jacket thickness, the measured maximum transverse deformations of CFRP jackets for NS and LS specimens were between 0.012~0.015 and 0.013~0.015 The test results showed that CFRP jackets were more effective in the case of low concrete strength in terms of strength and deformability enhancements The empirical equations, proposed by the authors before, predicted the compressive strength and corresponding axial strains of the specimens with a reasonable accuracy

22 Conclusions The measured axial deformations in three different gage lengths were quite close to each other, particularly in 270 and 500 mm gage lengths* Specimens with greater corner radius reached higher strengths while no significant difference between ultimate axial strains were observed* * not included in this paper

23 Acknowledgments Thanks to Financial supports of degussa YKS Construction Chemicals Company Set Italcementi Group Tayfun Pala Bulent Turgut Metin Tiryaki Assistance of Volkan Koc Esen Yilmaz

24 Thank You! Questions?