Seminar Ecc
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Transcript of Seminar Ecc
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BEHAVIOR OF CONCRETE
AND ECC STRUCTURESUNDER SIMULATED
EARTHQUAKE MOTION
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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
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MIX DESIGN OF ECC
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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
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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)
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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
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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
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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
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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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