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Seminar Ecc

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    BEHAVIOR OF CONCRETE

    AND ECC STRUCTURESUNDER SIMULATED

    EARTHQUAKE MOTION

    1

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    OVERVIEW

    INTRODUCTION

    MANUFATURING OF ECC

    ADVANTAGES OF ECC

    BEHAVIOUR OF ECC

    FIELD APPLICATIONS

    CASE STUDY

    CONCLUSIONS2

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    INTRODUCTION

    ECC - Bendable concrete

    - High performance fiber reinforced

    cementitious composite

    - Polymer fibres instead of coarse aggregate

    3

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    MIX DESIGN OF ECC

    5

    Mix design of ECC and regular concrete

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    ADVANTAGES OF ECC

    High tensile ductility

    Ease of processing

    Resistance to micro cracking

    Good strain hardening behaviour

    High energy absorption

    Lesser life cycle cost6

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    BEHAVIOUR OF ECC

    Tensile Behaviour

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    Tensile stress-strain curve and crack width development of ECC

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    Compressive Properties

    Compressive strength : 30-90 MPa

    Compressive strain : 0.45-0.65 %

    Under compressive loading

    - gradual bulging of material

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    Flexural Characteristics

    Flexural strength : 10-15 MPa

    ECC showing large deflection and Fine multiple cracking

    on the tensile side of beam9

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    Structural Behaviour

    Excellent shear capacity

    Damage behaviour under cyclic loading

    (a) R/C and (b) R/ECC without stirrups (Fisher and Li, 2002)

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    Sustaining large imposed deformation

    Due to its high tensile strain hardening capacity Used in link slabs in bridges

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    Structural behaviour contd...

    Uniaxial tension test of ECC strip(Fisher and Li, 2002)

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    Compatible deformation between ECC

    and reinforcement

    No shear lag between ECC and steel

    Bond between ECC and steel is not critical

    12

    Structural behaviour contd...

    Compatible deformation between concrete and steel in (a) R/C and (b) R/ECC

    Fisher and Li, 2002

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    Durability

    Associated with

    Dense concrete matrix

    Low permeabilty

    Reduced transport of corrosives to steel

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    Corrosion Resistance

    Experiment by Electro-chemical method

    Crack width of 0.1mm - Reinforced ECC specimen

    Crack width of 2 mm - R/C specimen

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    (a) ECC (300 hours) and (b) mortar (75 hours)

    after accelerated corrosion test (Sahmaran, 2006)

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    Impact Resistance

    Three point bending drop weight impact test by Yang andLi (2012)

    15

    Damage under three-point-bending drop weight impact test

    (a) R/C beam after the 1stimpact and (b) R/ECC beam after the 10thimpact

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    Load capacity of beams against impact

    R/C - 9 kN

    R/ECC - 20 kN

    16

    Impact resistance contd...

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    Field applications

    For constructing deck slabs

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    The Mihara Bridge in Hokkaido, Japan

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    For repair of spalling of concrete

    18Mitaka Dam in Hiroshima

    Field Applications Cntd...

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    Reinforced ECC as coupling beams in high-rise buildings

    19Nabeaure Tower in Yokohama

    Field Applications Cntd...

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    Description of the Experimental

    Program

    This study focuses on the performance assessment

    of concrete and ECC building structures under

    various loading conditions

    Small scale testing (1/8-scale factor) are utilized to

    investigate

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    Materials used

    Micro concrete instead of exactly duplicating the prototype material,

    stress-strain response is imitated.

    ECC

    Four different ECC mixtures are investigatedI. M45( Commonly used ECC design)

    II. High Fly Ash (HFA) mixture

    III. Poly Propylene Fiber (PPF) mixture

    IV. Silica Fume (SF) mixture

    Reinforcing bars made of steel

    Longitudinal bars threaded bars of effective diameter3.4mm (corresponds to metric #25-29 bar in full scale)

    Transverse bars smooth bars of diameter1.2mm(corresponds to metric #10 bar in full scale)

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    Design and fabrication of specimens

    Two two-story two-bay frames (story height 3.05 m

    and a bay width 6.1 m) are designed according to

    the weak columnstrong beam (WCSB) principle.

    The left exterior column of the first story is selected

    to be the experimental component for the frame

    tests

    The design checks are performed according to ACI

    318 (ACI 2008).

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    The frame satisfied all design criteria except for the

    minimum reinforcement ratio requirement of 1% in the

    columns

    A total of 27 specimens are fabricated

    24

    Design and fabrication of specimensCntd...

    Cross-sectional dimensions and reinforcement details of the

    small-scale columns

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    Testing and Simulation Framework

    loading capability provided by the load and

    boundary condition boxes(LBCBs).

    the specimen is in an up side down position duringtesting

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    (a) Overview of the testing framework; (b) test specimen and instrumentation

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    Test types

    Monotonic tests

    monotonically increasing displacements are applied.

    Reversed cyclic tests

    two cycles are applied at drift levels of 0.15, 0.25,

    0.5,0.75, 1, 1.5, 2, and up to 10%, with 1% increments

    Loading history is in accordance with the

    recommendations of FEMA 461

    o with two different boundary conditions : fixed-fixed

    and fixed-pinned27

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    Earthquake excitation

    To better represent the loading and boundary conditions

    under earthquake excitation, in addition to monotonicand reversed cyclic tests, static-time history tests and

    sub structured pseudo dynamic tests (hybrid simulation)

    are conducted.

    The structural frames are modeled using a fiber-based

    finite element analysis software. the displacements and

    forces at the control point are extracted, scaled down,

    and applied to the specimens using the test setup

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    Test types Cntd...

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    Test Matrix

    Different variables considered

    longitudinal and transverse reinforcement ratios

    Two longitudinal reinforcement ratios 0.87 and 1.29%

    The transverse reinforcement ratio is varied from 0.36 to

    0% (nostirrups) Mixture design

    Four ECC mixtures and a concrete mixture

    The level of axial load

    The axial load is kept constant at 7.5% of the columnaxial strength for monotonic and reversed cyclic tests

    Three different axial load levels are considered for thestatic-time history and hybrid tests (5, 7.5, & 10%).

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    Test Matrix Cntd...

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    PRESENTATION AND ANALYSIS OF RESULTS

    31

    Monotonic and Reversed Cyclic Tests

    Summary of Results for Reversed Cyclic Tests

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    32Example of cyclic response and envelope curve

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    33Definitions of yield, maximum, and ultimate points, and ductility

    on a typical envelope curve

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    INITIALSTIFFNESSANDSTIFFNESSDEGRADATION

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    the initial stiffness of ECC specimens is significantlyhigher than that of concrete specimens rangingfrom 20 to 120% depending on the mixture design

    The HFA mixture exhibited the highest initial

    stiffness stiffness increase achieved with ECC for the

    configuration with 1.29% longitudinal reinforcementis significantly higher when compared to the casewith 0.87% reinforcement

    transverse reinforcement ratio has no significanteffect on the initial stiffness or the stiffnessdegradation of ECC specimens.

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    Stiffness degradation of concrete and ECC mixtures

    (1.29%reinforcement ratio)

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    STRENGTHANDSTRENGTHDEGRADATION

    the strength of ECC specimens is significantly

    higher than that of concrete specimens ranging

    from 43 to 67%, depending on the mixture design

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    38Envelope curves for concrete and ECC column specimens,

    6 bars configuration;

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    39comparison of monotonic curves and envelopes from cyclic tests, 4

    bars configuration

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    40Normalized envelope curves for concrete and ECC specimens,6 bars

    configuration

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    envelope curves for ECC specimens with different transverse

    reinforcement ratios

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    ENERGYABSORPTIONCAPACITY

    The energy absorption capacities of ECC mixtures

    up to peak are significantly higher compared to

    concrete ranging from 20 to 220%

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    43Total energy absorption of concrete and ECC specimens

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    difference in energy absorption of ECC mixtures with respect

    to concrete

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    STATICTIMEHISTORYTESTSANDHYBRID

    SIMULATION

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    Summary of Results from Static-Time History (STH) Tests and Hybrid Simulation

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    The initial and final stiffness are

    calculated by fitting a first-order

    polynomial to the force displacement

    response during these small

    amplitude oscillations. The stiffness is

    obtained as the slope of this line

    the secant stiffness during the static-

    time history and hybrid tests iscalculated at peak displacement

    Lateral force resistance versus drift for experimental columns

    (a) case 3; (b) case 4

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