Figure 1.
Dimensions of beam-column joint specimens for (a) KJ1-1, KJ1-2, (b) KJ2-1, (c) KJ2-2 (unit: mm). The shadow part in the figure represents steel fiber concrete, and the blank part in the figure represents concrete without steel fibers.
Figure 1.
Dimensions of beam-column joint specimens for (a) KJ1-1, KJ1-2, (b) KJ2-1, (c) KJ2-2 (unit: mm). The shadow part in the figure represents steel fiber concrete, and the blank part in the figure represents concrete without steel fibers.
Figure 2.
(a) Schematic illustration of loading system and (b) Joint specimen KJ2-1.
Figure 2.
(a) Schematic illustration of loading system and (b) Joint specimen KJ2-1.
Figure 3.
History of loading.
Figure 3.
History of loading.
Figure 4.
Arrangement of (a,b) displacement transducers on the joint, and (c) strain gauge of steel. T1, T2, T3, B1, B2, and B3 are the displacement values of the upper and lower sides of the plastic hinge area of the beam end. h1 and h2 are the height difference of the displacement transducers on the upper and lower sides of the beam end, which is 270 mm; l1 and l2 are the displacement transducers layout intervals, l1 = l2 = 200 mm.
Figure 4.
Arrangement of (a,b) displacement transducers on the joint, and (c) strain gauge of steel. T1, T2, T3, B1, B2, and B3 are the displacement values of the upper and lower sides of the plastic hinge area of the beam end. h1 and h2 are the height difference of the displacement transducers on the upper and lower sides of the beam end, which is 270 mm; l1 and l2 are the displacement transducers layout intervals, l1 = l2 = 200 mm.
Figure 5.
The front crack pattern of the joint specimen (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 5.
The front crack pattern of the joint specimen (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 6.
Schematic diagram of calculating shear angle γ.
Figure 6.
Schematic diagram of calculating shear angle γ.
Figure 7.
P-γ diagram of beam-column joint (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 7.
P-γ diagram of beam-column joint (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 8.
The shear angle of characteristic points of beam-column joints.
Figure 8.
The shear angle of characteristic points of beam-column joints.
Figure 9.
Average curvature of plastic hinge area of the beam-column joint. The solid line represents ϕ1, while the dashed line represents ϕ2.
Figure 9.
Average curvature of plastic hinge area of the beam-column joint. The solid line represents ϕ1, while the dashed line represents ϕ2.
Figure 10.
Stirrup strain in the core area for the specimen (
a) KJ1-1/Y-16, (
b) KJ1-1/Y-20, (
c) KJ1-2/Y-16, (
d) KJ1-2/Y-20, (
e) KJ2-1/Y-13, (
f) KJ2-1/Y-14, (
g) KJ2-2/Y-16, (
h) KJ2-2/Y-20. The position of the strain gauge is referred to in
Figure 4c.
Figure 10.
Stirrup strain in the core area for the specimen (
a) KJ1-1/Y-16, (
b) KJ1-1/Y-20, (
c) KJ1-2/Y-16, (
d) KJ1-2/Y-20, (
e) KJ2-1/Y-13, (
f) KJ2-1/Y-14, (
g) KJ2-2/Y-16, (
h) KJ2-2/Y-20. The position of the strain gauge is referred to in
Figure 4c.
Figure 11.
Hysteresis curves of beam-column joint specimen (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 11.
Hysteresis curves of beam-column joint specimen (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 12.
Skeleton curves of beam-column joints.
Figure 12.
Skeleton curves of beam-column joints.
Figure 13.
(a) Schematic illustration of calculating equivalent viscous damping coefficient, and (b) Results of equivalent viscous damping coefficient for each join specimen.
Figure 13.
(a) Schematic illustration of calculating equivalent viscous damping coefficient, and (b) Results of equivalent viscous damping coefficient for each join specimen.
Figure 14.
Results of secant stiffness of each specimen.
Figure 14.
Results of secant stiffness of each specimen.
Figure 15.
Comparison of strength degradation curves of each specimen.
Figure 15.
Comparison of strength degradation curves of each specimen.
Figure 16.
Diagram of (a) the beam-column joint model, (b) the concrete model, and (c) the reinforcement network.
Figure 16.
Diagram of (a) the beam-column joint model, (b) the concrete model, and (c) the reinforcement network.
Figure 17.
Comparison of numerical and experimental hysteresis curves for specimens (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 17.
Comparison of numerical and experimental hysteresis curves for specimens (a) KJ1-1, (b) KJ1-2, (c) KJ2-1, and (d) KJ2-2.
Figure 18.
Influence of volume ratio of steel fibers on the (a) skeleton curves, (b) peak load, and (c) compression damage of concrete.
Figure 18.
Influence of volume ratio of steel fibers on the (a) skeleton curves, (b) peak load, and (c) compression damage of concrete.
Figure 19.
Influence of volume ratio of steel fibers on the displacement ductility coefficients.
Figure 19.
Influence of volume ratio of steel fibers on the displacement ductility coefficients.
Figure 20.
Influence of volume ratio of steel fibers on the (a) Stiffness and (b) Strength degradation.
Figure 20.
Influence of volume ratio of steel fibers on the (a) Stiffness and (b) Strength degradation.
Figure 21.
Influence of stirrups ratio on the (a) skeleton curves, (b) peak load.
Figure 21.
Influence of stirrups ratio on the (a) skeleton curves, (b) peak load.
Figure 22.
Influence of stirrups ratio on the (a) Displacement ductility coefficient, (b) Stiffness, and (c) Strength degradation.
Figure 22.
Influence of stirrups ratio on the (a) Displacement ductility coefficient, (b) Stiffness, and (c) Strength degradation.
Table 1.
Details of beam-column joint specimens.
Table 1.
Details of beam-column joint specimens.
Specimens Notation | Axial Compression Ratio | Volume Ratio of Steel Fiber (%) | Length of Steel Fiber Mixed into Beam End (mm) | Number of Stirrups in the Joint Core Area | Stirrups Ratio in the Joint Core Area (%) |
---|
KJ1-1 | 0.2 | 0.0 | 250 | 5 | 0.6 |
KJ1-2 | 0.2 | 1.0 | 250 | 5 | 0.6 |
KJ2-1 | 0.2 | 1.0 | 250 | 0 | 0.0 |
KJ2-2 | 0.2 | 1.0 | 250 | 2 | 0.5 |
Table 2.
Mixture proportion of concrete (kg/m3) and tested compressive strength.
Table 2.
Mixture proportion of concrete (kg/m3) and tested compressive strength.
Concrete Notation | Cement (P II 52.5) | Water | Coarse Aggregates | Fine Aggregates | Mineral Powder | Fly Ash | Admixture | Steel Fibers | Compressive Strength (MPa) |
---|
HSC | 406 | 119 | 985 | 723 | 81 | 37 | 8.68 | 0 | 72.1 |
HSFRC | 406 | 119 | 985 | 723 | 81 | 37 | 8.68 | 70 (1.0%) | 84.2 |
Table 3.
Mechanical properties of concrete.
Table 3.
Mechanical properties of concrete.
Concrete Notation | Compressive Strength of Cubes (MPa) | Axial Compressive Strength (MPa) | Splitting Tensile Strength (MPa) | Modulus of Elasticity (MPa) |
---|
HSC | 72.1 | 76.2 | 8.9 | 3.89 × 104 |
HSFRC | 84.2 | 80.9 | 11.5 | 3.80 × 104 |
Table 4.
Mechanical properties of steel reinforcements.
Table 4.
Mechanical properties of steel reinforcements.
Reinforcement | Diameter (mm) | Yield Strength (MPa) | Ultimate Tensile Strength (MPa) | Elongation (%) | Modulus of Elasticity (MPa) |
---|
Stirrups | 8 | 306.9 | 472.7 | 25 | 2.01 × 105 |
Main rebar | 20 | 422.7 | 585.1 | 30 | 2.09 × 105 |
Table 5.
Details of crack parameters.
Table 5.
Details of crack parameters.
Specimens Notation | Maximum Crack Width at the First Loading Level under Displacement Loading Control (mm) | Maximum Crack Width at Failure (mm) |
---|
Core Area | Beam-End | Core Area | Beam-End |
---|
KJ1-1 | 0.5 | 1.3 | 1.2 | 1.5 |
KJ1-2 | 0.1 | 1.0 | 0.2 | Exposed steel |
KJ2-1 | Non-visible | 1.0 | 8.0 | 15.0 |
KJ2-2 | Non-visible | 0.5 | 0.5 | 30.0 |
Table 6.
Summary of experimental results.
Table 6.
Summary of experimental results.
Specimens Notation | Pcr (kN) | Py (kN) | Pmax (kN) | Pu (kN) | Δy (mm) | Δu (mm) | μ |
---|
KJ1-1 | Forward | 20.00 | 41.68 | 43.74 | 37.18 | 16.07 | 41.00 | 2.55 |
Reverse | −20.00 | −42.30 | −52.20 | −44.37 | 11.31 | 30.79 | 2.72 |
KJ1-2 | Forward | 30.00 | 52.65 | 53.70 | 50.17 | 19.31 | 68.76 | 3.56 |
Reverse | −30.00 | −52.01 | −58.48 | −57.91 | 18.93 | 67.88 | 3.59 |
KJ2-1 | Forward | 30.00 | 50.54 | 51.64 | 48.01 | 17.58 | 59.26 | 3.37 |
Reverse | −30.00 | −43.75 | −50.59 | −43.00 | 20.12 | 62.49 | 3.11 |
KJ2-2 | Forward | 30.00 | 53.59 | 56.55 | 53.45 | 22.36 | 65.48 | 3.31 |
Reverse | −30.00 | −46.83 | −51.18 | −50.19 | 21.81 | 64.57 | 3.29 |
Table 7.
Comparison of numerical and experimental results.
Table 7.
Comparison of numerical and experimental results.
Specimens Notation | Pmax-test (kN) | μtest | Pmax-numer (kN) | μnumer | Pmax-test/Pmax-numer | μmax-test/μmax-numer |
---|
KJ1-1 | Forward | 43.74 | 2.55 | 44.04 | 2.17 | 0.99 | 1.18 |
Reverse | −52.20 | 2.72 | −50.32 | 2.64 | 1.04 | 1.03 |
KJ1-2 | Forward | 53.70 | 3.56 | 53.45 | 3.73 | 1.00 | 0.96 |
Reverse | −58.48 | 3.59 | −55.13 | 3.69 | 1.06 | 0.97 |
KJ2-1 | Forward | 51.64 | 3.37 | 50.37 | 3.53 | 1.02 | 0.95 |
Reverse | −50.59 | 3.11 | −53.21 | 3.37 | 0.95 | 0.92 |
KJ2-2 | Forward | 56.55 | 3.31 | 53.48 | 3.63 | 1.06 | 0.91 |
Reverse | −51.18 | 3.29 | −52.53 | 3.59 | 0.97 | 0.92 |
| | | | | Mean | 1.01 | 0.98 |
| | | | | R2 | 0.99 | 0.93 |