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SCIENCE CHINA Technological Sciences, Volume 62 , Issue 3 : 511-520(2019) https://doi.org/10.1007/s11431-017-9365-0

Seismic behavior of thin-walled circular and stiffened square steel tubed-reinforced-concrete columns

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  • ReceivedDec 20, 2017
  • AcceptedSep 27, 2018
  • PublishedDec 21, 2018

Abstract

Steel tubed-reinforced-concrete (TRC) columns have been gradually used in the construction of high-rise buildings recently because of their high axial load-carrying capacities and excellent seismic behavior. Existing studies about their seismic behavior were focused on columns with relatively thick tubes, i.e., diameter-to-thickness/width-to-thickness (D/t) ratios were below 100, while little is known about thin-walled TRC columns, especially for square TRC columns. Considering the infilled concrete of square TRC columns is non-uniformly and non-effectively confined, accordingly, stiffened square TRC columns are usually adopted in practice. Thus, two thin-walled circular TRC columns (D/t=120) and two stiffened square ones with diagonal stiffeners in plastic hinge regions (D/t=106) were tested under a constant axial compression combined with cyclic lateral loading. Both the circular and stiffened square TRC columns had the same cross sectional area, tube thickness, reinforcing bar ratio and column height. Flexural failure occurred for all the four specimens. Test results showed the strengths of the stiffened square TRC columns were a little higher in comparison to their circular counterparts; the ductility and energy dissipation capacities were excellent for both the stiffened and circular TRC columns, indicating very good confinement was gained from the yielded steel tubes of the plastic hinge regions at the peak loads. And shear stresses (35–90 MPa) in the sheared plates showed their moderate contribution of carrying lateral loads. Finally, cross sectional capacity analysis results demonstrated the method for TRC columns is acceptable for the stiffened square TRC columns.


Funded by

the National Natural Science Foundation of China(No.,51878097,&,51438001)

Chongqing Research Program of Basic Research and Frontier Technology(No.,2018CDQYTM0043,&,No.,106112015CDJXY200001)

China scholarship council. The opinions expressed in this paper are solely of the authors

however.


Acknowledgment

This work was supported by the National Natural Science Foundation of China (Grant Nos. 51878097 & 51438001), Chongqing Research Program of Basic Research and Frontier Technology (Grant Nos. 2018CDQYTM0043 & 106112015CDJXY200001) and China Scholarship Council.


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  • Figure 1

    (Color online) Tubed RC columns. (a) Circular shape; (b) square shape; (c) TRC columns in Harbin Poly Technology Building, China.

  • Figure 2

    (Color online) Details of specimens (unit: mm).

  • Figure 3

    (Color online) Test setup and instrumentation layout. (a) Schematic of column test-up; (b) instrumentation layout.

  • Figure 4

    (Color online) Strain gages layout. (a) C-55-1.8-120; (b) S-55-2-106.

  • Figure 5

    Sheared plate of the tube.

  • Figure 6

    (Color online) Failure patterns of the beam-columns. (a) C-55-1.8-120-4; (b) C-55-1.8-120-6; (c) S-55-2-106-4; (d) S-55-2-106-6.

  • Figure 7

    Lateral force versus displacement relationships of all specimens. (a) C-55-1.8-120-4; (b) C-55-1.8-120-6; (c) S-55-2-106-4; (d) S-55-2-106-6.

  • Figure 8

    (Color online) Envelope curves of lateral force versus drift ratio.

  • Figure 9

    (Color online) Geometrical method for determining the yield point.

  • Figure 10

    (Color online) Energy dissipation curves.

  • Figure 11

    Energy dissipation index.

  • Figure 12

    (Color online) Equivalent damping ratio heq of the specimens.

  • Figure 13

    (Color online) Load-strain and load-stress relationships of tubes. (a) C-55-1.8-120-6 load-strain at mid-height; (b) C-55-1.8-120-6 load-stress at mid-height; (c) C-55-1.8-120-6 load-strain at the end; (d) S-55-2-106-6 load-strain at mid-height; (e) S-55-2-106-6 load-stress at mid-height; (f) S-55-2-106-6 load-strain at the end.

  • Figure 14

    Comparison of the test results and the predictions. (a) cf. [22]; (b) cf. [23].

  • Table 1   Parameters, nomenclature, and failure modes of the specimens

    Group

    Specimens

    D (mm)

    λ

    D/t

    αa)

    fco (MPa)

    n0

    Failure mode

    C-55-1.8-120

    C-55-1.8-120-4

    226

    1.8

    120

    3.3%

    39.6

    0.4

    Flexural

    C-55-1.8-120-6

    0.6

    S-55-2-106

    S-55-2-106-4

    200

    2.0

    106

    3.8%

    39.6

    0.4

    S-55-2-106-6

    0.6

    α is the steel ratio of the steel tube.

  • Table 2   Properties of steel tubes and reinforcing bars

    Type

    Thickness (or diameter) t (mm)

    Yield strength fy (MPa)

    Ultimate strength fu (MPa)

    Tube

    1.89

    309.2

    399.0

    Longitudinal reinforcing bars

    16.36

    357.0

    554.5

    Stirrups

    8.02

    316.4

    458.3

  • Table 3   Lateral load-carrying capacities, deformation capacities, and ductility ratios of the specimens

    Specimens

    Py (kN)

    Pu (kN)

    Py/Pu

    Δy (mm)

    Δu (mm)

    Δ0.85 (mm)

    Δuy

    μΔ

    R0.85

    C-55-1.8-120-4

    213.2

    253.6

    0.84

    6.31

    18.04

    47.7

    2.86

    7.56

    6.0%

    C-55-1.8-120-6

    248.8

    285.1

    0.87

    7.12

    21.08

    48.3

    3.06

    6.78

    6.0%

    S-55-2-106-4

    211.8

    265.5

    0.80

    7.68

    25.3

    50.0

    3.29

    6.51

    6.0%

    S-55-2-106-6

    247.1

    310.8

    0.80

    6.98

    29.6

    45.2

    4.24

    6.48

    5.6%

  • Table 4   Test results at the peak load

    Specimens

    Loading direction

    Peak load

    εns (με)

    εs (με)

    σv (MPa)

    σh (MPa)

    τ (MPa)

    σz (MPa)

    C-55-1.8-120-4

    Negative

    --181.0

    862.5

    3692.5

    1.7

    1.2

    36.9

    63.9

    Positive

    253.6

    716.0

    1861.0

    2.4

    --3.9

    53.6

    92.9

    C-55-1.8-120-6

    Negative

    --272.3

    672.0

    6296.5

    --8.0

    --7.4

    71.6

    124.4

    Positive

    285.1

    565.0

    2488.0

    --6.7

    6.7

    62.8

    109.4

    S-55-2-106-4

    Negative

    --270.1

    525.8

    2710.0

    --23.2

    --16.2

    66.2

    117.3

    Positive

    259.6

    230.3

    2267.0

    --4.0

    24.7

    67.3

    119.9

    S-55-2-106-6

    Negative

    --309.3

    1162.0

    3586.0

    --22.7

    55.7

    73.0

    164.8

    Positive

    312.3

    1060.8

    3376.0

    --0.2

    38.9

    87.5

    159.8

  • Table 5   Comparison of the predictions of moment capacity with tests

    Specimen

    Applied axial load (kN)

    Pu (kN)

    Mut (kN m)

    Mup (kN m)

    Mup/Mut

    C-55-1.8-120-4

    635.4

    253.6

    78.5

    87.4

    1.11

    C-55-1.8-120-6

    953.1

    285.1

    91.9

    96.17

    1.05

    S-55-2-106-4

    633.6

    265.5

    87.7

    84.28

    0.96

    S-55-2-106-6

    950.4

    310.8

    107.3

    87.81

    0.82

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