Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

Table 1

Specimen details.

Specimen	D2(D1) × t × L (mm)	L/D1	L/D2	D2/t	fcu1 (MPa)	fcu2 (MPa)	fsl (MPa)	fs2 (MPa)	Nu (kN)	Nu,theo (kN)
Ref	154 × 0 × 1850	12.0	—	—	32.83	—	365	—	656	677	1.03
t3-C50-5.7	219 × 3.25 × 1240	8.1	5.7	67.4	32.83	52.58	365	352	2980	2622	0.88
t3-C50-7.1	219 × 3.25 × 1550	10.1	7.1	67.4	32.83	52.58	365	352	2810	2574	0.92
t3-C50-8.4	219 × 3.25 × 1850	12.0	8.4	67.4	32.83	52.58	365	352	2751	2525	0.92
t3-C50-9.8	219 × 3.25 × 2140	13.9	9.8	67.4	32.83	52.58	365	352	2703	2474	0.92
t2-C50-8.4	219 × 1.80 × 1850	12.0	8.4	121.7	32.83	52.58	365	390	2319	2621	1.13
t4-C50-8.4	219 × 3.90 × 1850	12.0	8.4	56.2	32.83	52.58	365	342	2932	2500	0.85
t3-C40-8.4	219 × 3.25 × 1850	12.0	8.4	67.4	32.83	43.01	365	352	2633	2373	0.90
t3-C60-8.4	219 × 3.25 × 1850	12.0	8.4	67.4	32.83	57.29	365	352	2845	2600	0.91

D₁ and D₂ are the diameters of unstrengthened and strengthened column; t is the measured thickness of outer steel tube; L is the length of column; f_cu1 and f_cu2 are the cubic compressive strengths of original concrete and SCC; f_s1 and f_s2 are the tensile strengths of steel rebar and steel tube; N_u and N_u,theo are the experimental and theoretical load-bearing capacities of specimens.