1 Introduction
2 Experimental Program
2.1 Details of Specimens
2.1.1 Determination of the Axial Compression Ratio
Combined load cases | Maximum value | Minimum value | ||
---|---|---|---|---|
Axial force/kN | Axial compression ratio | Axial force/kN | Axial compression ratio | |
1.35DL + 1.5LL | 24244.08 | 0.20 | 16045.09 | 0.12 |
1.35DL + 1.5 W(+X) | 22306.86 | 0.17 | 13237.49 | 0.10 |
1.35DL + 1.5 W(+Y) | 20561.50 | 0.16 | 13638.27 | 0.10 |
1.35DL + 1.35LL + 1.35S + 1.35 W(+X) | 22760.59 | 0.17 | 15767.53 | 0.12 |
1.35DL + 1.35LL + 1.35S + 1.35 W(+Y) | 24396.77 | 0.20 | 15981.41 | 0.12 |
1.2DL + 0.55LL + 0.7S + 1.0EQ(+X) | 19825.45 | 0.15 | 13119.34 | 0.10 |
1.2DL + 0.55LL + 0.7S + 1.0EQ(+Y) | 19819.36 | 0.15 | 13155.10 | 0.10 |
1.0DL + 1.0LL + 1.0S + 1.0 W(+X) | 16859.70 | 0.13 | 11679.65 | 0.09 |
1.0DL + 1.0LL + 1.0S + 1.0 W(+Y) | 18071.68 | 0.14 | 11838.08 | 0.09 |
2.1.2 Determination of Specimen Section
2.1.3 Determination of the Axial Force
Specimen | Diameter (mm) | Thickness (mm) | Axial Force (kN) | Axial compression ratio |
\( f_{\text{c}}^{\text{s}} \) (MPa) |
f
cuk (MPa) |
f
ck (MPa) | Reinforcement(mm2) |
---|---|---|---|---|---|---|---|---|
Tube1 | 500 | 50 | 180 | 0.09 | 28.88 | 38.1 | 25.5 | 1178 (15C10) |
Tube2 | 500 | 100 | 360 | 0.09 | 31.92 | 42.0 | 28.1 | 1257 (16C10) |
Tube3 | 500 | 50 | 434 | 0.20 | 27.36 | 36.0 | 24.1 | 1728 (22C10) |
Tube4 | 500 | 70 | 422 | 0.15 | 34.96 | 46.4 | 31.0 | 1571 (20C10) |
2.2 Test Setup and Instrumentation Layout
2.3 Loading System
2.3.1 Axial Compression Load
Vertical axial force 180 kN | ||||
---|---|---|---|---|
Target displacement (mm) | Displacement increment (mm) | Cycle number | Loading rate (mm/s) | |
1 | 3 | 1 | 1 | 0.2 |
2 | 7 | 2 | 2 | 0.5 |
3 | 13 | 3 | 2 | 0.5 |
4 | 22 | 3 | 3 | 0.5 |
5 | 37 | 3 | 3 | 1.0 |
6 | 79 | 6 | 3 | 1.0 |
Vertical axial force 360 kN | ||||
---|---|---|---|---|
Target displacement (mm) | Displacement increment (mm) | Cycle number | Loading rate (mm/s) | |
1 | 3 | 1 | 1 | 0.2 |
2 | 9 | 1 | 2 | 0.4 |
3 | 15 | 3 | 3 | 0.5 |
4 | 39 | 6 | 3 | 0.5 |
5 | 63 | 6 | 3 | 0.8 |
6 | 69 | 9 | 3 | 1.0 |
Vertical axial force 434 kN | ||||
---|---|---|---|---|
Target displacement (mm) | Displacement increment (mm) | Cycle number | Loading rate (mm/s) | |
1 | 3 | 1 | 1 | 0.2 |
2 | 10 | 3 | 2 | 0.5 |
3 | 34 | 6 | 3 | 1.0 |
Vertical axial force 420 kN | ||||
---|---|---|---|---|
Target displacement (mm) | Displacement increment (mm) | Cycle number | Loading rate (mm/s) | |
1 | 3 | 1 | 1 | 0.2 |
2 | 12 | 3 | 2 | 0.5 |
3 | 30 | 6 | 3 | 1.0 |
4 | 48 | 9 | 3 | 1.0 |
5 | 75 | 12 | 3 | 1.0 |
3 Experimental Results And Specimen Behavior
3.1 Failure Mode
3.2 Lateral Load versus Displacement Relationship
Specimen | Crack point | Yielding point | Ultimate point | Ductility coefficient | |||
---|---|---|---|---|---|---|---|
Displacement (mm) | Load (kN) | Displacement (mm) | Load (kN) | Displacement (mm) | Load (kN) | ||
Tube1 | 4.0 | 17.0 | 23.3 | 44.2 | 115.0 | 59.1 | 4.94 |
Tube2 | 6.0 | 33.6 | 16.0 | 51.0 | 114.0 | 67.4 | 7.13 |
Tube3 | 8.0 | 31.8 | 27.5 | 62.5 | 64.0 | 79.8 | 2.33 |
Tube4 | 10.0 | 38.4 | 22.8 | 56.2 | 99.0 | 74.4 | 4.34 |
3.3 Calculation of Normal Section Strength
Specimen | Tube 1 | Tube 2 | Tube 3 | Tube 4 |
---|---|---|---|---|
Calculation method (kN m) | 141 | 170 | 212 | 206 |
Test result (kN m) | 181.4 | 206.9 | 245.0 | 228.4 |
D-value (%) | 22 | 17.5 | 13.5 | 9.8 |
4 Numerical Simulation
4.1 Finite Element Model
4.2 Constitutive Laws of Steel and Concrete
4.3 Model Validation
5 Parametric Studies
5.1 Influence of Axial Compression Ratio
5.1.1 Hysteretic Loops and Skeleton Curves
5.1.2 Energy Dissipation Capacity
Axial compression ratio | Yielding stage | Limit stage | ||||||
---|---|---|---|---|---|---|---|---|
S
(ABC + CDA) (kN mm) |
S
(OBE + ODF) (kN mm) |
E
|
h
e
|
S
(ABC + CDA) (kN mm) |
S
(OBE + ODF) (kN mm) |
E
|
h
e
| |
n = 0.14 | 198.3115 | 715.3398 | 0.2772 | 0.0441 | 1517.5058 | 2506.6128 | 0.6054 | 0.0964 |
n = 0.20 | 170.1344 | 648.1608 | 0.2625 | 0.0418 | 1446.9708 | 2442.3400 | 0.5925 | 0.0943 |
n = 0.25 | 181.8989 | 847.2856 | 0.2147 | 0.0342 | 1486.9411 | 2975.6870 | 0.4997 | 0.0795 |
n = 0.30 | 189.2101 | 898.9050 | 0.2105 | 0.0335 | 1682.7438 | 3382.3282 | 0.4975 | 0.0792 |
n = 0.35 | 211.7772 | 1040.3058 | 0.2036 | 0.0324 | 1784.3739 | 3604.5775 | 0.4950 | 0.0788 |
n = 0.40 | 215.8960 | 1086.6254 | 0.1987 | 0.0316 | 844.4114 | 2628.8536 | 0.3212 | 0.0511 |
5.1.3 Stiffness
5.2 Influence of Longitudinal Reinforcement
5.2.1 Hysteretic Loops and Skeleton Curves
5.2.2 Energy Dissipation Capacity
Longitudinal reinforcement ratio (%) | Yielding stage | Limit stage | ||||||
---|---|---|---|---|---|---|---|---|
S
(ABC + CDA) (kN mm) |
S
(OBE + ODF) (kN mm) |
E
|
h
e
|
S
(ABC + CDA) (kN mm) |
S
(OBE + ODF) (kN mm) |
E
|
h
e
| |
ρ = 1.00 | 181.8989 | 847.2856 | 0.2147 | 0.0342 | 1486.9411 | 2975.6128 | 0.4997 | 0.0795 |
ρ = 1.25 | 274.8453 | 1158.6722 | 0.2372 | 0.0378 | 2603.9790 | 4096.8782 | 0.6356 | 0.1012 |
ρ = 1.56 | 414.7068 | 1661.2259 | 0.2496 | 0.0397 | 4747.6610 | 5823.3371 | 0.8153 | 0.1298 |
ρ = 1.87 | 538.7275 | 2151.6598 | 0.2504 | 0.0398 | 7278.6079 | 7564.3521 | 0.9622 | 0.1531 |