Behavior of semi-prefabricated steel-tube double-layer concrete columns under eccentric compression

Figures & data

Figure 1. Schematic diagram of semi-prefabricated steel tube double-layer concrete (SPSTDC) column.

Figure 2. Section diagram of SPSTDC column.

Figure 3. Schematic diagram of plane section assumption.

Figure 4. Strain diagram of each limit state.

Table 1. Core features of each limit state.

Failure mode	Core features	Symbol of corresponding neutral axis height
Compression failure	The edge of the concrete compression zone is crushed, while the lower flange of the steel tube just reaches yield under tension	xp
Total yield failure	The edge of the concrete compression zone is crushed, while the upper flange of the steel tube just reaches yield under compression	xt
Tension failure	The neutral axis is located at the upper flange, and the compressive stress of the upper flange of the steel tube is zero, while the edge of concrete compression zone is crushed	xn

Figure 5. Strain state of normal section based on plane section assumption.

Figure 6. Stress and strain state of the normal section for the limit state of the compression failure mode.

Figure 7. Stress and strain state of the normal section for the limit state of the total yield failure mode.

Figure 8. Stress and strain state of the normal section for the limit state of the tensile failure mode.

Figure 9. Details of the specimens.

Table 2. Detailed information of all specimens.

Specimen No.	Size of precast concrete layer			Size of post-cast concrete layer		Size of steel tube		Load eccentricity e0 (mm)
	h1×b1 (mm×mm)	t1=t’1 (mm)	as (mm)	h2×b2 (mm×mm)	t2=t’2 (mm)	h3×b3 (mm×mm)	t3 (mm)
SPSTDC-80-130	240×240	45	27	150×150	35	80×80	5	130
SPSTDC-100-150	240×240	45	27	150×150	35	100×100	5	150

Table 3. Mixture designs of concrete (unit: kg/m^3.).

Concrete type	Cement	Mineral powder	Fly ash	Manufactured sand	Aggregate	Superplasticizer	Water	Expansion agent
Precast concrete	230	70	80	889	925	1.8	170	0
Post-cast concrete	280	60	70	882	918	1.8	170	40

Table 4. Main mechanical parameters of concrete.

Concrete type	Compressive strength average value (MPa)	Elastic modulus Ec (MPa)
Precast concrete	39.03	30000
Post-cast concrete	46.98	32500

Table 5. Main mechanical parameters of steel.

Steel type	Tensile strength (MPa)		Elastic modulus (MPa)
	Yield strength	Ultimate tensile strength
Rebar	413	611	209237
Steel tube	253	405	201000

Table 6. Comparison of N_c and N_t values for specimens.

Specimen No.	Eccentricity e0 (mm)	η	Eccentricity e = ηe0 (mm)	Calculated value of Nc (kN)	Test value of Nt (kN)	Nc/Nt
SPSTDC-80-130	130	1.03	134	427	443	0.96
SPSTDC-100-150	150	1.03	155	393	410	0.96

Table 7. Comparison of N_c and N_t values for specimens.

Specimen No.	Calculated value by proposed method Nc (kN)	Calculated value by YB 9082 (2006) NY (kN)	Test value Nt (kN)	Nc/Nt	NY/Nt
SPSTDC-80-130	427	363	443	0.96	0.82
SPSTDC-100-150	393	353	410	0.96	0.86

Table 8. Parameters in concrete damage plasticity (CDP) model.

Expansion angle (◦)	Eccentricity	Compressive strength ratio	Invariant stress ratio	Cohesion coefficient
36	0.1	1.14	0.6667	0.005

Figure 10. Establishment of ABAQUS model.

Figure 11. Mesh convergence analysis.

Figure 12. Comparison between equivalent plastic strain (PEEQ) cloud maps and the actual failure states of specimens.

Figure 13. Load–lateral deflection curve comparison.

Table 9. Comparison of test and simulated bearing capacity values.

Specimen	Eccentricity e0 (mm)	Test bearing capacity Nt (kN)	Simulated bearing capacity Ns (kN)	Nt/Ns
SPSTDC-80-130	130	443	446	0.99
SPSTDC-100-150	150	410	417	0.98

Figure 14. N_s–M_s curve.

Figure 15. N-M correlation curve comparison with CFST column.

Figure 16. Bearing capacity–eccentricity curve.

Figure 17. Bearing capacity–precast concrete strength curve.

Figure 18. Bearing capacity–post-cast concrete strength curve.

Figure 19. Bearing capacity–α_a curve.

Figure 20. Bearing capacity–steel tube strength curve.

Figure 21. Impact of the eccentricity on the horizontal lateral deflection of the mid-height section.

Figure 22. Horizontal lateral deflection–section height curves during loading.

Figure 23. Lateral displacement–load curve corresponding to different α_a values.

Figure 24. Division of lateral deflection–load curve.

Figure 25. Lateral stiffness.