O slideshow foi denunciado.
Seu SlideShare está sendo baixado. ×

PS18_P176_V.Greepala.pdf

Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Anúncio
Carregando em…3
×

Confira estes a seguir

1 de 21 Anúncio

PS18_P176_V.Greepala.pdf

Baixar para ler offline

Concrete-filled-tube (CFT) column is developed to become an excellent structural element due to its superior strength and ductility performance contributed by the composite action. However in case of the rectangular section of CFT column, this advantage was less than that of the curricular section due to non-uniform distribution of lateral pressure. This paper aims to develop the performance of the square section of the CFT column using preconfining pressure. The square sections of CFT columns were experimentally investigated for its strength and ductility performance based on its compressive strength and load-deformation characteristics under uni-axial load test. The main parameter investigated was the confining pressure, which various from 0, 2.4, 4.8 and 7.2MPa corresponding to 0%, 11.4%, 22.9% and 34.3% of concrete strength. The steel tubes with external dimensions of 98 mm, 98 mm and 350 mm were used to confine the core concrete having a compressive strength of 20.98 MPa. The confining pressure was applied by preconfining of the steel jacket. During the experiments, load-deformation curves were recorded. Test results showed that increasing of confining pressure of 11.4%-34.3% of concrete strength slightly improved the compressive strength of the square section of CFT column by 3.0-19.3% and the more improvement occurs at the preconfining pressure beyond 22.9%. However, it was found that the use of preconfining steel jacket for the square section of CFT column does not enhancing its ductility as well as energy absorbing capacity unlike the circular section.

Concrete-filled-tube (CFT) column is developed to become an excellent structural element due to its superior strength and ductility performance contributed by the composite action. However in case of the rectangular section of CFT column, this advantage was less than that of the curricular section due to non-uniform distribution of lateral pressure. This paper aims to develop the performance of the square section of the CFT column using preconfining pressure. The square sections of CFT columns were experimentally investigated for its strength and ductility performance based on its compressive strength and load-deformation characteristics under uni-axial load test. The main parameter investigated was the confining pressure, which various from 0, 2.4, 4.8 and 7.2MPa corresponding to 0%, 11.4%, 22.9% and 34.3% of concrete strength. The steel tubes with external dimensions of 98 mm, 98 mm and 350 mm were used to confine the core concrete having a compressive strength of 20.98 MPa. The confining pressure was applied by preconfining of the steel jacket. During the experiments, load-deformation curves were recorded. Test results showed that increasing of confining pressure of 11.4%-34.3% of concrete strength slightly improved the compressive strength of the square section of CFT column by 3.0-19.3% and the more improvement occurs at the preconfining pressure beyond 22.9%. However, it was found that the use of preconfining steel jacket for the square section of CFT column does not enhancing its ductility as well as energy absorbing capacity unlike the circular section.

Anúncio
Anúncio

Mais Conteúdo rRelacionado

Mais recentes (20)

Anúncio

PS18_P176_V.Greepala.pdf

  1. 1. EFFECT OF CONFINING PRESSURE ON COMPRESSIVE STRENGTH AND DUCTILITY OF SQUARE SECTION CONCRETE FILLED TUBE COLUMN Department of Civil and Environmental Engineering, Faculty of Science and Engineering, Kasetsart University Chalermprakait Sakon Nakhon Province Campus, Sakon Nakhon, Thailand Asst.Prof. Dr.Vatwong Greepala
  2. 2. #1 CONTENT INTRODUCTION OBJECTIVE EXPERIMENTAL INVESTIGATION RESULTS AND DISCUSSION CONCLUSIONS
  3. 3. INTRODUCTION Structural Properties Construction Cost Construction Time Fire Protection WHAT IS CFT? WHY USE CFT? Concrete-filled steel tubes (CFT) is a type of structural element where structural concrete is placed inside a structural steel shell.
  4. 4. INTRODUCTION Infill concrete in steel tube delays local buckling of the tube and so increases the stability and strength of the column Steel tube performs as primary longitudinal main reinforcement to concrete core Confinement of steel tube improves concrete compressive strength and ductility Ductility of CFT is significantly enhanced when compared with steel tube and concrete alone Advantages of CFT column
  5. 5. #4 INTRODUCTION Statement of problems The square or rectangular CFT columns present less gain of the advantages than the circular CFT due to some loss of the confinement effect How to improve it? Pre-confining?
  6. 6. #5 OBJECTIVE  The purpose of this study is to investigate the influence of preconfining pressure on the strength and ductility performance of the square sections of CFT columns.
  7. 7. #6 EXPERIMENTAL INVESTIGATION SPECIMEN  The steel tubes with external dimensions of 98x98x2.3 mm (width x depth x thickness) were used to confine the infill concrete with compressive strength of 20.98 MPa (BS1881-116 1983).  The width-to-thickness ratio (B/t) is 42.6.
  8. 8. #7 EXPERIMENTAL INVESTIGATION
  9. 9. #8 Start Specimen Preparation Compressive Strength Testing Determination of Compressive Strength Determination of Ductility Factor (µcu) Conclusion End Max. Compression Forced Axial Stress-Strain Relation Step 1 Step 2 Step 3 Step 4 EXPERIMENTAL INVESTIGATION Concrete compressive strength of 20.98 MPa (BS1881-116 1983)
  10. 10. #9 Specimen Preparation Casting CFT specimen Jacketing Preconfining CFT Specimen
  11. 11. Test Setup Wielding line LVTD Dial Gauge LVTD Dial Gauge Strain Gauge No.1 Strain Gauge No.1 Strain Gauge No.3 Strain Gauge No.4 Axial Load Axial Load Bearing Plate Bearing Plate LVTD Dial Gauge LVTD Dial Gauge 98mm CFT Specimen 98mm Core Concrete 350mm Steel Tube Thickness 6mm Welding Welding A A Strain Gauge No.2 Section A-A Strain Gauge No.1 & No.2 Strain Gauge No.3 & No.4 Strain Gauge No.2
  12. 12. #11 Determination of ductility factor 1 cu cu ε µ ε = ( ) ' max 1 cu cu c e W f ε = × Ductility factor Work index Energy absorption capacity factor (ecu) is defined as the area under the stress-strain curve up to the rupture of the CFT jacket Suggested by Sheikh et al. (1994)
  13. 13. #12 RESULTS AND DISCUSSION
  14. 14. #13 RESULTS AND DISCUSSION
  15. 15. #14 RESULTS AND DISCUSSION The squared section did not provide a large confining effect especially when the width-to- thickness ratio was large (B/t>30. In this study B/t is 42.6 therefore the crushing plane of concrete show less efficiency confinement.
  16. 16. #15 RESULTS AND DISCUSSION
  17. 17. #16 Compressive Strength
  18. 18. Ductility Ductility Factor (µcu) Work Index (Wcu)
  19. 19. l f a σ l σ l f l f l f l σ l σ l σ a σ High Tensile Stress Uniform Tensile Stress RESULTS AND DISCUSSION In preconfining process of most of the hoop stress and hoop strain of the square section occurred at the pre-stressing side unlike the hoop stress and hoop strain in a circular which are constantly distributed along the hoop ring. At the loading state, the ultimate hoop stress and hoop strain at the pre-stressing side may reach the yield limit early results in poor improvement of compressive strength and ductility of the square section.
  20. 20. Conclusion The influence of the preconfining pressure of CFT column on its compressive strength and ductility was experimentally investigated. The following conclusions can be drawn: ▫ 1) The increasing of confining pressure of 11.4%-34.3% of concrete strength slightly improved the compressive strength of the square section of CFT column by 3.0- 19.3% and the more improvement occurs at the preconfining pressure beyond 22.9%. ▫ 2) The use of preconfining steel jacket is not enhancing its ductility and energy absorption.
  21. 21. THANK YOU

×