Three-Dimensional Finite Element Analysis of Compressive Behavior of Circular Steel Tube-Confined Concrete Stub Columns by New Confinement Relationships

Haghinejada, Akbar; Nematzadeh, Mahdi

doi:10.1590/1679-78252631

Akbar Haghinejada

Department of Civil Engineering, University of Mazandaran, 47416-13534, Babolsar, Iran

Mahdi Nematzadeh ^*m.nematzadeh@umz.ac.ir, Tel. +98 9111146772; fax: +98 1135302903.

Department of Civil Engineering, University of Mazandaran, 47416-13534, Babolsar, Iran

m.nematzadeh@umz.ac.ir, Tel. +98 9111146772; fax: +98 1135302903.

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Figure 1
Finite element mesh of steel tube-confined concrete.

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Figure 2
Equivalent stress-strain curve of steel.

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Figure 3
Equivalent uniaxial stress-strain curves of confined and unconfined concrete.

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Figure 4
f_l / f_y obtained from matching results versus D / t of STCC columns.

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Figure 5
Relationship of K ^' _s and K ^' _c versus D / t and f_c for STCC columns.

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Figure 6
Extended linear Dracker-Prager yield surface.

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Figure 7
Stress condition of confined concrete in circular STC.

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Figure 8
Parameter study of flow stress ratio (axial load-displacement curves of STCC for different values of K).

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Figure 9
Plastic flow and volumetric behavior.

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Figure 10
Parameter study of dilation angle with friction angle of 10 (axial stress-strain curves of STCC for different values of w).

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Figure 11
Relationship between experimental results of compressive strength and analytical results of STCC at the points of steel yielding, initial peak and failure.

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Figure 12
Axial stress-strain curves of STCC specimens.

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Figure 13
Lateral stress-strain curves of STCC specimens.

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Figure 14
A comparison between analytically predicted and experimentally observed failure mode for a typical STCC specimen (N50P650-2.5).

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Figure 15
Relationship of compressive strength of STCC columns _c at the points of steel yielding, initial peak and failure for different values of D / t.

versus f

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Figure 16
Relationship of compressive strength of STCC columns _y at the points of steel yielding, initial peak and failure for different values of fc.

versus f

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Figure 17
Interface shear stress along concrete height at the points of steel yielding, initial peak and failure.

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Figure 18
Confining pressure along concrete height at the points of steel yielding, initial peak and failure.

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Figure 19
Load carrying portion of concrete core and steel tube in STCC columns for different values of f_c.

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Figure 20
Normalized axial stress of composite column versus volumetric strain of concrete core.

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Figure 21
Axial stress distribution on concrete core cross-section at the points of steel yielding.

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Table 1
Mechanical properties of steel tube (Nematzadeh, 2012Nematzadeh, M. (2012). Determining the relationships of active confinement of fresh concrete by prestressing steel tubes. Dissertation for Degree of Doctor of Philosophy, University of Mazandaran [in Persian].).

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Table 2
Properties of STCC specimens (Nematzadeh, 2012Nematzadeh, M. (2012). Determining the relationships of active confinement of fresh concrete by prestressing steel tubes. Dissertation for Degree of Doctor of Philosophy, University of Mazandaran [in Persian].).

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Table 3
Finite element analysis results.

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Table 4
Specimen information for parametric study.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8a)

(8b)

(9)

(10)

(11)

(12)

(14)

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

(A.1)

(A.2)

(A.3)

(A.4)

(A.5)

(A.6)

(A.7)

(B.1)

(B.2)

(B.3)

(B.4)

f_y (MPa)	f_su (MPa)	ε_y	ε_p	ε_su
339	480	0.0016	0.0139	0.114

Specimen ID	Steel tube wall thickness (mm)	Outer diameter-to-wall thickness ratio	Specimen length (mm)	Concrete compressive strength (MPa)	Yield and ultimate strength of steel (MPa)
N25P350-2.5	2.5	24.2	140.0	28.2	339,480
N25P950-1.5	1.5	39	139.6	31.7	339,480
N25P650-1.5	1.5	39	138.9	28.3	339,480
N35P650-1.5	1.5	39	138.5	42.4	339,480
N15P650-1.5	1.5	39	139.5	20.5	339,480
N25P950-2.5	2.5	24.2	138.4	30	339,480
N50P650-2.5	2.5	24.2	140.9	50.5	339,480
N15P550-2.5	2.5	24.2	140.6	16.7	339,480
N35P550-2.5	2.5	24.2	141.2	37.1	339,480
N25P650-2.0	2	29.75	140.3	26.7	339,480
N25P500-2.5	2.5	24.2	141.8	26.7	339,480
N25P2000-1.0	1	57.5	139.2	25.8	339,480
N45P650-1.5	1.5	39	140.3	45.43	339,480
N47P650-1.5	1.5	39	140.7	46.9	339,480

Specimen ID	Strength corresponding to steel yielding (MPa)		EXP/FEA	Initial peak strength (MPa)		EXP/FEA	Failure strength (MPa)		EXP/FEA	Longitudinal to hoop stress ratio of steel tube
	EXP	FEA		EXP	FEA		EXP	FEA		Yielding point	Strain hardening point
N25P350-2.5	98.6	85.4	1.15	111.6	104.3	1.07	219.4	189.9	1.15	2.27	1.46
N25P950-1.5	64.8	61.3	1.06	74.8	79.6	0.94	123.8	128.6	0.96	1.95	1.21
N25P650-1.5	62.7	58.9	1.06	75.0	76.1	0.99	138.3	134.2	1.03	1.94	1.21
N35P650-1.5	76.2	69.3	1.10	83.3	90.41	0.92	122.6	122.6	1.00	2.02	1.22
N15P650-1.5	50.7	54.2	0.94	63.7	67.9	0.94	123.1	121.5	1.01	2.01	1.33
N25P950-2.5	83.2	86.3	0.96	99.3	106.6	0.93	227.7	218.4	10.4	2.29	1.43
N50P650-2.5	116.4	99.3	1.17	132.7	127.7	10.4	221.2	215.8	10.2	2.16	1.36
N15P550-2.5	75.9	77.9	0.97	90.3	91.2	0.99	212.8	179.9	1.18	2.12	1.35
N35P550-2.5	95.3	90.8	1.05	113.0	113.7	0.99	229.0	219.8	1.04	2.23	1.49
N25P650-2.0	85.9	84.6	1.02	99.9	103.7	0.96	224.8	217.3	1.03	2.33	1.44
N25P500-2.5	77.6	71.7	1.08	83.6	89.8	0.93	175.6	165.8	1.06	2.17	1.38
N25P2000-1.0	82.9	71.7	1.16	99.7	93.3	1.07	138.6	143.9	0.96	2.02	1.22
N45P650-1.5	49.2	44.5	1.11	58.1	55.8	1.04	83.7	87.4	0.96	1.89	1.18
N47P650-1.5	89.1	72.3	1.23	101.1	94.8	1.07	141.5	144.7	0.98	1.99	1.20

f_c (MPa)	t (mm)	D/t	f_y (MPa)	D_c (mm)	L_c (mm)	L_s (mm)
20, 30, 40, 50, 60	1, 1.2, 1.5, 2.0, 3.0	57.5, 48.3, 39.0, 29.8, 20.5	300 (bilinear, 339 (bilinear), 339 (trilinear), 400 (bilinear)	55.5	140	150

[1] m.nematzadeh@umz.ac.ir, Tel. +98 9111146772; fax: +98 1135302903.

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Three-Dimensional Finite Element Analysis of Compressive Behavior of Circular Steel Tube-Confined Concrete Stub Columns by New Confinement Relationships

Abstract