Concrete-Filled Double-Skin Steel Tubular Columns: Behavior and Design

Front Cover
Concrete-Filled Double-Skin Steel Tubular Columns
Copyright
Contents
About the authors
Acknowledgments
Chapter 1: Introduction
	1.1. General
	1.2. Objectives
	1.3. Book organization
Chapter 2: Development of CFDST columns
	2.1. Introduction
	2.2. Advantages of CFDST columns
	2.3. Erection of CFDST columns
	2.4. Types of CFDST columns
		2.4.1. According to length
		2.4.2. According to straightness
	2.5. Experimental studies
	2.6. Finite element studies
	2.7. Structural behavior
		2.7.1. Confinement effect in CFDST columns
		2.7.2. Effect of initial imperfection and residual stress
		2.7.3. Effect of concrete compaction
		2.7.4. Effect of the hollow ratio
		2.7.5. Effect of the thickness ratio
		2.7.6. Effect of the steel grade of the inner steel tubes
		2.7.7. Effect of long-term sustained loading
		2.7.8. Effect of axial partial compression
		2.7.9. Effect of preloading on steel tubes
		2.7.10. Influence of fibers on the capacity of CFDST short columns
		2.7.11. Improving the interface bonding of CFDST columns
	2.8. Failure modes of CFDST columns
	2.9. The mechanism of the inner tube of CFDST columns
	2.10. Formulas for compressive strength
	2.11. Conclusions
	References
Chapter 3: CFDST short columns formed from carbon steels
	3.1. Introduction
	3.2. Circular-circular CFDST columns
		3.2.1. FE nonlinear analysis
			3.2.1.1. Basic description
			3.2.1.2. Constitutive material models
				Concrete material
					Unconfined concrete with a dilation angle
					Confined concrete
				Structural steel material
			3.2.1.3. Interactions between components
			3.2.1.4. Loading and boundary conditions
			3.2.1.5. FE meshes
		3.2.2. Model verification
			3.2.2.1. Steel material verification
			3.2.2.2. CFDST column verification
		3.2.3. Parametric study
		3.2.4. FE results and discussion
			3.2.4.1. Effects of the hollow ratio
			3.2.4.2. Effects of the thickness of steel tubes
			3.2.4.3. Effects of steel and concrete strengths
	3.3. Circular-square CFDST columns
		3.3.1. Innovation and the scope of this section
		3.3.2. FE modeling
			3.3.2.1. General information
			3.3.2.2. Constitutive material models
			3.3.2.3. Interaction and surfaces
			3.3.2.4. Loading method and boundary conditions
			3.3.2.5. Element mesh
		3.3.3. Verification study
			3.3.3.1. Data collection
			3.3.3.2. Data analysis and discussion
		3.3.4. Parametric study
			3.3.4.1. Effects of the concretes compressive strength
			3.3.4.2. Effects of steel yield strength
			3.3.4.3. Effects of the Do/to ratio
			3.3.4.4. Effects of the Bi/ti ratio
			3.3.4.5. Effects of the hollow ratio
	3.4. Square-square CFDST columns
		3.4.1. FE methodology and validation
			3.4.1.1. Elements and mesh utilized
			3.4.1.2. Step type
			3.4.1.3. Interactions
			3.4.1.4. Boundary conditions
			3.4.1.5. Constitutive models of the sandwiched concrete
				The Zhao model
				The Pagoulatou model
			3.4.1.6. Validation of the FE model
		3.4.2. Parametric studies
			3.4.2.1. Group 1: Effects of the outer tubes thickness
			3.4.2.2. Group 2: Effects of the inner tubes thickness
			3.4.2.3. Group 3: Effects of the hollow section ratio
			3.4.2.4. Group 4: Effects of the concretes compressive strength
			3.4.2.5. Group 5: Effects of steel strength
	3.5. Square-circular CFDST columns
		3.5.1. Existing design approach and test results
		3.5.2. Numerical modeling
			3.5.2.1. General description of the FE model
			3.5.2.2. Material model for the sandwiched concrete
			3.5.2.3. Validation of the FE model
			3.5.2.4. Parametric study and proposed design equation
	3.6. New confining stress-based design for circular-circular CFDST columns
		3.6.1. Background of the available test specimens
		3.6.2. Assessment of the design methods
			3.6.2.1. Design methods
				EC4
				The ACI
				The AISC
				Yan et al.
				Han et al.
				Hassanein and Kharoob
				Uenaka et al.
			3.6.2.2. Reliability analysis method
			3.6.2.3. Comparisons with test strengths
		3.6.3. Lateral confining pressure
			3.6.3.1. Background
			3.6.3.2. Proposed formula for CFDST sections
		3.6.4. Proposed design model
			3.6.4.1. Comparison with all test specimens of the database
			3.6.4.2. Comparisons with different subgroups
				Columns with permitted slenderness (Do/to)
				3.6.4.2.1. Columns with disallowed slenderness (Do/to)
			3.6.4.3. Comparison with specimens with large void ratios
			3.6.4.4. Comparison with large-sized CFDST specimens
	3.7. Conclusions
	Appendix
	References
	Further reading
Chapter 4: CFDST short columns formed from stainless steel outer tubes
	4.1. Introduction
	4.2. Finite element models
		4.2.1. Finite element type and mesh
		4.2.2. Boundary conditions and load application
		4.2.3. Material model
			4.2.3.1. Lean duplex stainless steel
			4.2.3.2. Concrete
				The concrete core of CFSST columns and sandwiched concrete of both CFDST and CFDT columns
				The concrete core of CFDT columns
	4.3. Comparisons with the experimental results
		4.3.1. Lean duplex stainless steel hollow columns
		4.3.2. Concrete-filled steel tubular (CFST) columns
		4.3.3. Concrete-filled stainless steel tubular (CFSST) columns
		4.3.4. CFDST short columns with both carbon steel tubes
		4.3.5. CFDST short columns with external stainless steel tubes
		4.3.6. CFDT short columns with external stainless steel tubes
	4.4. CFSST columns
		4.4.1. Fundamental behavior
			4.4.1.1. General
			4.4.1.2. Load-strain responses
			4.4.1.3. Effects of the concretes compressive strength
			4.4.1.4. Effects of the D/t ratio
		4.4.2. Comparisons with design strengths
			4.4.2.1. The ACI code
			4.4.2.2. Eurocode 4
			4.4.2.3. Continuous strength method
			4.4.2.4. Liang and Fragomenis design model
			4.4.2.5. Verification of design models
	4.5. CFDST columns
		4.5.1. Fundamental behavior
			4.5.1.1. General
			4.5.1.2. Effects of the concretes compressive strength
			4.5.1.3. Effects of the nominal steel ratio
			4.5.1.4. Effects of the hollow ratio
			4.5.1.5. Effects of the ti/te ratio
			4.5.1.6. Effects of the steel grade of the inner carbon steel tube
		4.5.2. Design of CFDST short columns
			4.5.2.1. The ACI code
			4.5.2.2. Design model by Han et al.
			4.5.2.3. Continuous strength method
			4.5.2.4. The proposed new design model
			4.5.2.5. Verification of design models
	4.6. CFDT columns
		4.6.1. Fundamental behavior
			4.6.1.1. General
			4.6.1.2. Effects of the concretes compressive strength
			4.6.1.3. Effects of the d/D ratio
			4.6.1.4. Effects of the ti/te ratio
			4.6.1.5. Effects of the steel grade of the internal carbon steel tube
			4.6.1.6. Comparison between CFDT and CFSST columns
		4.6.2. Comparisons with design strengths
			4.6.2.1. The ACI code
			4.6.2.2. The proposed new design model
	4.7. Summary and conclusions
	References
Chapter 5: CFDST slender columns formed from stainless steel outer tubes
	5.1. Introduction
		5.1.1. Research on composite slender columns
		5.1.2. Classification of the columns with respect to length
	5.2. Nonlinear finite element analysis
		5.2.1. Stress-strain relationships for stainless steels
		5.2.2. Stress-strain relationships for the confined concrete
	5.3. Validation of the FE model
		5.3.1. CFST columns
		5.3.2. CFSST columns
		5.3.3. CFDST columns
	5.4. CFSST columns
		5.4.1. Parametric study
			5.4.1.1. Failure modes and load-strain curves
			5.4.1.2. Effect of the column slenderness ratio
			5.4.1.3. Effect of the diameter-to-thickness ratio
			5.4.1.4. Effect of the compressive strength of the concrete
		5.4.2. Comparisons with design codes
			5.4.2.1. Eurocode 4
			5.4.2.2. The AISC specification
			5.4.2.3. Comparisons and discussions
			5.4.2.4. The proposed design model based on Eurocode 4
	5.5. CFDST columns
		5.5.1. Numerical study
			5.5.1.1. Input data
			5.5.1.2. Structural behavior
				Effect of the L/r ratio
				Effect of the concrete confinement
				Effect of the hollow ratio
				Effect of the concretes compressive strength
				Effect of the ti/te ratio
		5.5.2. Comparison with design strengths
			5.5.2.1. Original and modified Eurocode 4
			5.5.2.2. The AISC specification
			5.5.2.3. Comparisons and discussions
	5.6. CFDT columns
		5.6.1. Fundamental behavior of the CFDT slender columns
			5.6.1.1. Description of the FE models
			5.6.1.2. Effect of the column slenderness ratio
			5.6.1.3. Typical failure modes
			5.6.1.4. Strain distribution at mid-height sections
			5.6.1.5. Effect of the concretes compressive strength
		5.6.2. Design model
		5.6.3. Verification of design models
	5.7. Conclusions
	References
Chapter 6: Rubberized CFDST short columns
	6.1. Introduction
		6.1.1. Development of rubberized concrete (RuC)
		6.1.2. Methods used to enhance the mechanical properties of RuC
		6.1.3. Double skin tubular (CFDST) columns
	6.2. Square RuCFDST short columns
		6.2.1. Materials and methods
			6.2.1.1. Material properties
				Concrete
				Steel tubes
				Rubber particles
			6.2.1.2. Concrete compression tests
			6.2.1.3. Rubber pretreatment
			6.2.1.4. Concrete mix procedure
		6.2.2. Test program
			6.2.2.1. Specimens
			6.2.2.2. Test procedure
		6.2.3. Material properties
			6.2.3.1. Rubberized concrete (RuC)
			6.2.3.2. Empty square hollow sections
		6.2.4. Test results for rubberized CFDST columns
			6.2.4.1. Fundamental behavior
			6.2.4.2. Deformed shapes of the RuCFDST columns
			6.2.4.3. Concrete and outer steel interface zone
			6.2.4.4. Load-displacement relationships
			6.2.4.5. Energy absorption and ductility
		6.2.5. Strength calculations
			6.2.5.1. Strength predictions of empty hollow sections
			6.2.5.2. Strength predictions of the CFDST columns
				Design model by Zhao and Grzebieta
				Design model by Tao and Han
				Design model by Eurocode 4
				Calculated strengths and discussion
	6.3. Circular RuCFDST short columns
		6.3.1. Materials and methods
		6.3.2. Test program
			6.3.2.1. Specimens
			6.3.2.2. Concrete preparation
			6.3.2.3. Test procedure
				Empty circular steel tube testing
				CFST and CFDST testing
		6.3.3. Test results of empty CHSs
		6.3.4. Test results of CFST and CFDST specimens
			6.3.4.1. Test results of CFST and RuCFST columns
			6.3.4.2. Test results of CFDST and RuCFDST columns
			6.3.4.3. Deformed shapes of normal and rubberized CFST and CFDST columns
			6.3.4.4. Concrete-steel bonding
			6.3.4.5. Exterior steel strain gauge data
			6.3.4.6. Ductility and energy absorption
		6.3.5. Predictions of CFDST and CFST column strength
			6.3.5.1. Design model by Zhao and Grzebieta
			6.3.5.2. Design model by Tao and Han
			6.3.5.3. Design model by Hassanein and Kharoob
			6.3.5.4. Design model by Eurocode 4 (EC4)
			6.3.5.5. Calculated strengths and discussion
	6.4. New confining stress-based design
		6.4.1. Assessment of EC4 design methods
			6.4.1.1. Experimental tests
			6.4.1.2. EC4 design model
				Square cross sections
				Circular cross sections
			6.4.1.3. The AISC design model
				Square cross sections
				Circular cross sections
			6.4.1.4. The AS2327 design model
				Square cross sections
				Circular cross sections
			6.4.1.5. Comparison and discussion
		6.4.2. Lateral confining pressures
			6.4.2.1. ``frp´´ based on the slenderness ratios of the steel tubes
			6.4.2.2. ``frp´´ based on the rubber particle content and slenderness ratios of the steel tubes
		6.4.3. The proposed design model
		6.4.4. Reliability analysis
	6.5. Conclusions
	Appendix I: Progressive axial loading of specimen SHS-O2I2-30
	References
Chapter 7: Future research
	7.1. Recommendations
	7.2. Trends for future relevant works
Index
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