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    Seismic Design of Reinforced

    Concrete Beam-Column Joints :

    byHitoshi Shiohara, Ph. D, Fellow of ACI

    Professor

    Dept. of Architectural Engineering,

    The University of Tokyo

    1

    Beam-column Joint & Collapse of RC Buildings

    Turkey 2011

    2

    Turkey 2011

    Turkey 2011 Turkey 2011

    Beam-column Joint & Collapse of RC Buildings

    Kobe 1995Kobe 1995

    Turkey 1999

    3

    Turkey 1999

    Beam-column Joint & Collapse of Structures

    EarthquakeEnineerin esearchnstitute

    :

    - , ,

    .

    .

    Close Ups of Joint Failure: 1989 Loma Prieta EarthquakeOct. 17

    EarthquakeEn ineerin esearch nstitute

    :

    - .

    :

    - .

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    Beam-column Joint Failure

    Royal Palm Hotel Damage at masonry in-fill stair enclosure.: 1993 Guam Earthquake Aug. 8

    k

    . .

    Beam-column Joint & Collapse of Buildings

    6

    The Pyne Gould Corp. building collapsed when the magnitude 6.3 earthquake struck Christchurch, New Zealand

    in 2011. It was built in the 1960s, before the adoption of modern seismic standards for concrete buildings

    Background and

    Introduction

    7

    Research and Development : RC Beam-Column joint

    1955 The first seismic tests of RC BC joints (Tsuboi and Tomii, Japan)

    1965 The first proposal of joint shear strength for RC B-C joints (Endo, Japan)

    1967 The first seismic tests of RC BC joints (Hanson et al., USA)

    1971 Proposal of joint shear strength for RC BC joints (Koreishi, Japan)

    1975 Proposal of joint shear strength for RC BC joints (Kamimura, Japan)

    1976 ACI-ASCE352 proposed seismic provisions for BC joints

    1976 Paulay (NZ) proposed BC joint mechanism of Strut action and Truss action

    1981 Tests on RC BC joint (Meiheit, Jirsa et al. USA)

    1982 NZS3101adopted seismic provisions for RC BC joints

    1985 ACI318-85adopted seismic provisions for RC BC joints

    1991AIJ Guidelinesfor Seismic Design of RC Buildings adopted seismic provisions for RC BC

    joints

    8

    History of the development of beam-column joint seismic design :

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    Joint Shear in Beam-column Joints

    Vj= Ts + Cs + Cc Vc = Ts + Ts Vc = ats+ atsVc

    Vc

    Vj

    Ts

    Dc

    T's

    'Cc

    C's

    CcCs

    Vc

    Vj

    Ts

    Dc

    CcCs

    column column

    beam

    interior beam-column joint exterior beam-column joint

    beam

    9

    Vj < Joint shear Capacity :Joint shear

    Design Requirement prevent from joint shear failure

    Joint shear

    Joint shear Joint shear

    BC joint mechanism of Strut action and Truss action

    T

    c

    Vcol

    Vcol

    hc

    hc

    Vb

    Vb

    Cc

    Cs

    Cc

    Cs

    T

    hb

    Paulay (1976 ) Joint shear is resisted by strut action and truss action

    Strut action Truss action

    Model of statics : only equilibrium is considered

    Column-to-Beam Strength Ratio

    M

    1

    M

    3

    M

    4

    M

    2

    M

    1

    M

    2

    M

    3

    Interior

    Column

    Column

    Beam

    Beam

    Exterior

    Column

    Beam

    11

    Column-to-beam strength ratio > 1.0 : Beam-hinge Mechanism

    Column-to-beam strength ratio < 1.0 : Column-hinge Mechanism

    Column-to-beam strength ratio Column-to-beam strength ratio

    Introduction

    Current seismic codes protect RC beam-column (BC) joints by

    requiring that;

    - Joint shear not exceeding joint shear capacity

    - where, the design equation for the joint shear capacity are empirical.

    But this requirement may have overlooked significant deficiency in

    BC joint because;

    - The experimental assessments of joint shear capacity have been over-

    emphasized, thus tests were focused only to joints with excessive reinforcement

    in both beam and column,

    - Test dataset are biased in column-to-beam strength ratio

    - Obvious lack of tests on BC joints particularly with low column-to-beam strength

    ratio (1.0 - 1.5), which is obvious choice of structural engineer to optimize for

    stress by seismic load and week beam mechanism,

    12

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    0

    10

    20

    30

    40

    50

    60

    NumberofSpecimens

    1.0- 2.0- 3.0- 4.0-

    Column-to-Beam Strength Ratio

    Interior

    Failure ModeBeam (or Column) 92

    Beam and Joint 162

    Joint 71

    Exhaustive list of interior B-C joint specimens

    13

    0

    10

    20

    30

    40

    50

    60

    NumberofSpecimens

    1.0- 2.0- 3.0- 4.0-

    Column-to-Beam Strength Ratio

    Failure ModeBeam (or Column) 92

    Beam and Joint 162

    Joint 71

    standard rangein practice

    unrealistic

    speicmens

    14

    Interior

    0

    10

    20

    30

    40

    50

    60

    NumberofSpecimens

    1.0- 2.0- 3.0- 4.0