estimation method on deterioration of marine concrete ... · deterioration process on marine...

Estimation Method on Deterioration of Marine Concrete Structures Due to Chloride Attack

Koji TAKEWAKAAssociate Professor

Dept. of Ocean Civil Engineering Kagoshima University

Contents• Outline of deterioration process of marine

concrete structure

• Examination of durability for marine concrete structure in durability design

• Simulation model of corrosion of reinforcement in concrete

• Evaluation of structural performance of concrete structure deteriorated due to corrosion of reinforcement

Outlineof

Deterioration Process

Outlineof

Deterioration Process

Deterioration process on marine concrete structures

Concrete (pH-12.5)

Passive film Passive filmdestruction

Chloride ions H2O

O2

Rust (volumetric expansion)

Crack

DelaminationRebar

Chloride-induced deterioration process

ⅡPropagation

period

Ⅳ

Chloride-induced deterioration process

period

ⅢAcceleration

Deterioration

period

IV

Deg

radat

ion o

fst

ruct

ura

lper

form

ance Life of

Structure

Incubationperiod

Ⅰ


Det

erio

ration


Definition of stages in the deterioration process and primary factors characterizing each stage

StageNo. Definition of period

Primary factorscharacterizing the

deterioration

IPeriod of chloride penetration until the chlorideconcentration around rebars up to the thresholdvalue

･ Chloride diffusion rate･ Cover thickness

II Period of the corrosion progress on rebar untilconcrete cracks due to the corrosion appear

･ Rebar corrosion rate･ Resistivity against cracking of concrete

III Period of the corrosion progress on rebar afterappearance of concrete cracks

IV Period of degradation of structural performanceinduced by rebar corrosion and concrete cracks

･ Rebar corrosion rate･ Width of cracks due to rebar corrosion


Marine environment

Chloride penetration into concrete

Passive film on reinforcement is lost

Reduction of Cross-section of reinforcement

Corrosion of reinforcement starts

Degradation of structural performance of the structure

Introduce of corrosion cracking and spalling of

concrete

Water Oxygen


Penetration of chloride into concrete

Penetration of Cl- via pores to the interior of concrete

Cement hydrate binds some of Cl- chemically Fredel’s salt (C3A･CaCl2･nH2O)

Only the free chloride diffuses into concrete

When critical concentration of free Cl- accumulates on reinforcement surface, corrosion starts on it

In sea water, Splash zone, Marine atmospheric Zone

Example of chloride penetration profile into concrete

Chloride distribution profiles in concrete bridge beams in coastal zone after 17 years of service

14

12

10

8

6

4

2

0

16

0

2

4

6

8

10

12

14

16

Cl-

in c

oncr

ete

(kg/

m3 )

0 1 53 7 99 7 5 3 1 0Depth from concrete surface (cm)

Beam No. G1Beam No. G2Beam No. G3

Mountain side

Coastal side

Microstructure of Cement paste

Gel pores Capillary pores

Water In hydrationUnhydrated

cement

Original particle

boundary

Hydrate

Unhydratedcement

Inner productsC-S-H grains

Schematic representation of porosity classification in concrete

10-210-410-610-810-10

Por

osity

dis

tribu

tion

Radius of pore (m)

Gel pores

Capillary pores

Entrained air

Construction pores

Interlayer pores Micro pores Macro pores1A ~ 50nm 10nm ~ 50µm 50µm ~°

Binding of chloride ions into cement hydrate

Free Cl -

Physicallyabsorbed Cl-

Chemicallybound Cl-

Cement hydrate

Cement hydrate

Chemical binding equation

OHCaClOAlCaOOHCaClOHOAlCaO

2232

22232

103463

⋅⋅⋅→++⋅⋅

Fredell’s salt


Penetration of chloride into concrete Diffusion equation　

(Modified Fick’s second low)

CKzC

yC

xCD

tC

⋅−

∂∂

+∂∂

+∂∂

=∂∂

2

2

2

2

2

2

Cl-

conc

entra

tion(

C)

Depth from concrete surface (x)

t1

t2

t3

t1 < t2 < t3 : Age of structure

C: Concentration of Cl-at depth (x,y.z) after t

D: Diffusion coefficient

K: Cl- binding coefficient


Critical chloride content [C

l- ]

pH11.5

6.0][

][≥−

−

OHCl

Non-corrosion

Corrosion

Effect of Chloride concentration and pH on initiation of corrosion


Critical chloride content

In case of ordinary reinforcing bar in concrete

0.05% Cl- related to the weight of Concrete

=0.4% Cl- related to the cement weight

or

1.2 kg/m3 of Cl- per unit concrete volume


Corrosion process on reinforcement

Cl-, 　 H2O, 　　O2Cl-, 　 H2O, 　　O2Cl-,

Cl-

Anode CathodeCathode

Fe2+ + 2(OH)- → Fe(OH)2

2Fe(OH)2 + 2(OH)- → 2Fe(OH)3

I

Corrosion current ∝ Corrosion rate

H2O+1/2O2+e- →2(OH)-

Fe→Fe2++ 2e- e-

Passive film)6020( Α−



Anode CathodeCathode

IcorrRc

Electric resistance of concrete

Rp

Polarization resistance

Icorr

Corrosion current ∝ Corrosion rate ∝ 1/Rp



Corrosion weight loss of reinforcement (W)

pcorr R

kI 1⋅=

Corrosion current: Icorr

Rp: Polarization resistance

k: Constant (25~50mV)

Corrosion Weight loss: W[ ] tI

FnFeW corr ⋅⋅⋅

=

[Fe]: Atomic weight (55.84 g)n: Atomic value (Fe: n=2)F: Faraday’s Constant (96,500 A/sec)


Corrosion crack on concrete

Rust:this volume is two to fourtimes of the steel’s one

Tensile stress distributing around steel bar

Stress distributing on concrete surface

Tensile stress

Compressive stress

tp

φ

Corrosion crack

Corrosion crack

(a) Thin Cover1.5< (2tp+φ)/ φ ≤ 3.0

(b) Thick Cover (2tp+φ)/ φ >3.0


Relationship between corrosion amount and corrosion crack on concrete

0.01

0.02

0.03

00. 1 0. 2 0. 3 0. 40

0.10

0.08

0.06

0.04

0.02

00 0. 1 0. 2 0. 3

Cor

rosi

on lo

ss (g

/cm

2 )

Cor

rosi

on lo

ss (g

/cm

2 )

Corrosion crack width (mm) Corrosion crack width (mm)

c/d=5.27

c/d=2.38c/d=2.13

c/d=1.42

c/d=3.35

c/d=2.63

c/d=2.13

Round Bar Deformed Bar

c/d: Cover thickness/diameter of rebar

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6Crack width (mm)

Cor

rosi

on lo

ss (g

/cm

2)HSC: c/d= 2.66 HSC: c/d= 2.00NSC: c/d= 2.13NSC: c/d= 2.63

High strength concrete have smaller crack width opening than High strength concrete have smaller crack width opening than normal strength concrete for same corrosion lossnormal strength concrete for same corrosion lossConcrete strength also influences on the crack width openingConcrete strength also influences on the crack width opening

Relationship between corrosion amount and corrosion crack on high strength concrete


Conceptual figure of degradation process of performance on structure

Water-proofness

Safety forthird parties

Aesthetics

Load bearingcapacity

Elapsed time

Stage I Stage II Stage III Stage IV

Deg

rada

tion

ofea

ch p

erfo

rman

ce

Example of performance degradation on RC beam due to rebar corrosion

0

20

40

60

80

100

120

0 0.1 0.2 0.3 0.4Corrosion Loss (gm/cm2/cm)

Stre

ngth

ratio

(%)

NSC: Mangat et al.NSC: Almusallam et al. HSC: Takewaka et al

Singly reinforced concreteSingly reinforced concrete

Experiment result for loss in load-bearing capacity


0

20

40

60

80

100

120

0 0.1 0.2 0.3 0.4

Corrosion Loss (gm/cm2/cm)

Stre

ngth

ratio

(%)

NSC: Umoto et al.HSC: Takewaka et al.

Doubly reinforced concrete Doubly reinforced concrete with shear with shear rebarsrebars

Experiment result for loss in load-bearing capacity

Flexural Failure

Shear Failure


Experiment result for loss in ductility of RC beam

0.0

1.0

2.0

3.0

4.0

5.06.0

0.0 0.1 0.2 0.3 0.4Corrosion Loss (gm/cm )2

Duc

tility

Singly RC beam

Doubly RC beam


Analytical result for loss in fatigue property

Corrosion crack width on concrete surface (mm)

Num

ber o

f cyc

lic lo

adin

g at

fatig

ue fa

ilure

1.E+04

1.E+05

1.E+06

1.E+07

0 0.5 1 1.5 2 2.5

Examination results

Analysis result in case that pitting corrosion depth is equal to (corrosion weight loss + 0.15)

Extra Costs for maintaining durability of structure during the service life

Stage I Stage IIStage III

Stage IV

Det

erio

ratio

n C

ost f

or

mai

ntai

ning

du

rabi

lity

1 5

25

125

“The law of fives”presented by De Sitter

Examination in

Durability Design

Examination Examination inin

Durability DesignDurability Design

Schematic of design for structure

Structural design

Durability design Landscape

design

Integrated design

Performance-based design

What is “ Durability of structure”

Qualitative performance

Resistance against deteriorating actions from surrounding environment

To keep the all of required performances on structure to their levels more than the required ones during the service life

Durability designDesign carried out to ensure that the structure can maintain its required performance (functions) during the

service life under environmental actionsdefined by Asian concrete model code

Evaluation of long-term-performance

Examination of durability

General principle

All required performances for structure, such as serviceability, restorability and safety under actions in normal use, wind action and seismic action, shall be examined respectively in regard of their long-term performances in the service life.

Examination of durabilityExamples of durability-limit-state

Durability-limit-state A: All performances maintain the initial conditions.

Durability-limit-state B: Though some material used in structure deteriorates, negligible decay in any performance of structure occurs.

Durability-limit-state C: Though some structural performance deteriorates, function of structure keep in the required condition and the damages are repairable.

Examination of durabilityDurability Limit state Class A

Class C

Deterioration can occur on both performance of structure and material within allowable range .

corrosion initiationtime

Some deterioration on material, No deterioration of structure performance.

( initial period +propagation period)

Corrosion crackGeneration time

No deterioration of both structure performance and

material.

Class B

Durability-limit-state for marine concrete structures

Examination of durability

Durability-limit-state A:• All performances maintain the initial condition

crd tt ≤td : Design service life of marine concrete structuretcr: Duration until reinforcement starts to corrode

tcr is seemed to be the duration until concentration of Cl-accumulating on reinforcement surface reaches a critical

value for starting corrosion

Examination of durabilityEvaluation method in durability-limit-state A

0.1lim

),( ≤⋅C

C Tdcγ

C(c, Td) : Chloride content at reinforcement position duringservice life of structure

Clim : Critical chloride content γ : Safety factor

This concept was Introduced in 1999 version of JSCE standard specification for design of

concrete structure as the verification method of durability of concrete structure

• In sea water or tidal zone

• In splash zone or atmospheric zone

),( TdcC

⋅−=

dTdc TD

cerfCC2

10),(

xCD

tC

2

2

∂∂

=∂∂

Simplified Fick’s second law

C0 : Chloride content on concrete surfaceD : Chloride diffusion coefficient of concreteTd : Design service lifec : Minimum cover thicknessW : Accumulated chloride amount on concrete surface during unit time

Theoretical analysis

⋅−−

⋅=

dd

dTdc TD

cerfD

cDTc

DTWC

21

24exp2

22

),( π

ηπ

η deserfs

∫ −=0

22)(here,

C: Concentration of Cl- at depth x after tD: Diffusion coefficient

logD = 4.5(W/C)2

+0.14(W/C) - 8.47

-8

-7

-6

0.3 0.5 0.7 0.9W/C

log（

D）

logD = 19.5(W/C)2

- 13.8(W/C) - 5.74

-9

-8

-7

-6

0.3 0.5 0.7W/C

log（

D）

(a) In case of OPC (b) In case of BFSC

Relationship between chloride diffusion coefficient and W/C of concrete

Durability-limit-state for marine concrete structures

Durability-limit-state B:• Though some material used in structure deteriorate,

negligible decay in any performance of structure occurs

ckcrd ttt +≤td : Design service life of marine concrete structuretcr: Duration until reinforcement start to corrode

tck: Period of corrosion progress on reinforcement from start of corrosion until occurrence of corrosion crack on concrete

ckcrd ttt +=

tcr: Duration until reinforcement start to corrode

tck: Period of corrosion progress on reinforce-ment from start of corrosion until corrosioncrack occurs on concrete

20

1

2

)]/1([4 CCerfDct

ddcr −⋅= −

th

CN

ck ECWcc

tβ

ααα φ

⋅

⋅

−⋅⋅⋅+

=1)/(

1)1(7.1 85.0

th

CN

ck ECWcc

tβ

ααα φ

⋅

⋅

−⋅⋅⋅+

=1)/(

1)1(7.1 85.0

c : Concrete coverW/C : Water to cement ratioα N : Factor for strength of concrete: = 0.5/(W/C)αφ : Factor for diameter of rebar(φ): = 2/φEh : Factor for environment: = 1.5 (in sea water)

2.5 (tidal zone)3.5 (splash zone, coast line)2.0 ( others)

β t : Factor for average temperature: = 0.7 (under 10°C)　　　　　 1.0 (10 ~ 20°C)

　　　　　1.3 (over 20°C)α C: Factor for type of cement: = 1.0 (OPC)

1.25 (BFSC)

Relationship between minimum cover thickness and maximum W/C required for durability

Design conditionOPC, Design service life: 50 years

Durability-Limit-state A Durability-Limit-state B

0

5

10

15

20

25

0.35 0.45 0.55 0.65 0.75

W/C

Cov

er

thic

kness

　(c

m) Splash zone

0.1km

In sea water

0

20

40

60

80

0.35 0.45 0.55 0.65 0.75W/C

Splash zone

Coast line

0.25km

0.5km

0

20

40

60

80

0.35 0.45 0.55 0.65 0.75W/C

Cove

r t

hic

kness

(cm

) Splash zoneCoast line 0.25 km0.5 km1 km

Relationship between minimum cover thickness and maximum W/C required for durability

Design conditionBlast furnace slag: 50%, Design service life: 50 years

Durability-Limit-state A Durability-Limit-state B

0

5

10

15

20

25

0.35 0.45 0.55 0.65 0.75

W/C

Cove

r th

ickn

ess

(cm

)

Splash zone

0.1km

In sea water

0

20

40

60

80

0.35 0.45 0.55 0.65 0.75

W/C

Cove

r th

ickn

ess

(cm

)

Splash zone

Coast line

20

40

60

80

0.35 0.45 0.55 0.65 0.75

W/C

Splash zone Coast line

0.25 km0.250.5 km0.51 km1

Computer Simulation Model

Computer Simulation Computer Simulation ModelModel

Simulation model for deterioration of concrete structure in marine environment

To evaluate more directly the durability in actual condition by using deterioration simulating model

Simulation model• Concrete model considering scatter of quality• Penetration model of chloride and oxygen• Corrosion model of reinforcement

• Progress of corrosion of reinforcement• Period of corrosion crack generation

Estimation

Simulation model for deterioration of concrete structure in marine environment

Framework of Corrosion Simulation model

Oxygen DiffusionConcrete Quality

Progress of Corrosion

Initiationof Corrosion

CO

R R O S I O N

OM

DE

L

Cracks in ConcreteChloride Diffusion

Outline of the concrete modelcircular-pore

2 dimensional reinforced concrete model

Concrete

Sound part Steel

Pore distributionin concrete

Circular-pore distribution• Randomly located • Considering W/C and RH

Aggregate distributionin concrete

Circular-Aggregate distribution• Randomly located • Considering ITZ

Modified pore distribution

0

0.1

0.2

0.3

0.4

0.5

Pore diameter (cm)

Den

sity

of p

ore

volu

me W/C70%

W/C60%W/C50%W/C40%

10-8 10-6 10-4 10-2 1

Capillary pores

Macro pores

(by Shimomura et al)V’(r) = V’(∞)･B・C･rC-1･exp (-Brc)

V’(r) : Density of pore volumeB,C: Parameters depending on W/C

Modified relative humidity

Water-filled pore

Air-filled pore

Steel

Concrete

Water-filled pore volumeTotal pore volume

Relative humidity =

Model of aggregateInterfacial transition zone ( ITZ )

Coarse Aggregate

Steel

Wet-ITZ

Dry-ITZ

Concrete

The zone with several micrometers thickness lying between aggregates and hardened cement paste matrix, which has higher porosity than the bulk cement paste

Steel

Wet-aggregate

Dry-aggregate

Water- filled pore

Air- filled pore

Specification of a route on which chlorides reach rebar in minimum diffusion time

Minimum diffusion route

For each section (1cm)

Many diffusion route

Minimum diffusion time

One specific route

Chloride Penetration Model

Circumference

Diffusion route

Wet-ITZsurrounding aggregateInstantly

Dry-ITZsurrounding aggregateCircumference

Water-filled poreInstantlyAir-filled pore

Cl-

Cf : free chloride concentration

K : combined coefficientf

ff KCxC

Dt

C−

∂

∂=

∂

∂2

2

Diffusion of Free chloride described by Modified Fick’s 2nd law

Oxygen Penetration Model

Instantly

Instantly

Diffusion coefficient

(1.0E-6 cm2/s)Diffusion coefficient

(1.0E-6 cm2/s)

Diffusion route

Wet-ITZ Surrounding aggregateDry-ITZ Surrounding aggregateWater-filled poreAir-filled pore

O2

Diffusion of oxygen described by stationary state condition

( Fick’s first low )Distribution of concentration

x

C1

C2

Diffusion

qdxdCDq =

q : Flow rate of substanceC: concentration of substanceD: Diffusion coefficient

Cracked concrete Model

Cracks may exist by externalloading, drying shrinkage etc..

Bilinear route

Crack position

Definition of effective crack length

Treat as sound concrete

Effective crack length

Cra

ck le

ngth

Steel

Relationship between effective crack and diffusion coefficient

infinity

1( = in water)

1/101/100 5 cm

3.75cm

2.5cm1.25cm


0 cm

Diffusioncoefficient

Corrosion model- based on macrocell corrosion theory-

Specification of Anode and Cathode area

Steel section

ACCCCC C C C

Anode

Cl- Concentration at rebar > tolerance

Corrosion reactions start

A A

Estimation of corrosion rateCorrosion model

Cathodic control Anodic controlO2+2H2O+4e- → 4OH- Fe2- → Fe2++2e-

4Fe2-+8OH-+O2+H2O→ 4Fe(OH)3

iAiC

The lower rate between iA and i C is selected as the corrosion rate at anode portion

Oxygen diffusion amount to each

section

Calculate corrosion amount

Change of anode area

SIMULATION RESULTSSIMULATION RESULTS


Corrosion initiation time

W/C (%)

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

40 50 60 70Cor

rosi

on in

itiat

ion

time

(yea

rs)

RH 40%RH 60%

RH 80%

W/C (%)

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

40 50 60 70Cor

rosi

on in

itiat

ion

time

(yea

rs)

RH 40%RH 60%

RH 80%

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

40 50 60 70Cor

rosi

on in

itiat

ion

time

(yea

rs)

RH 40%RH 60%

RH 80%

RH 40%RH 60%

RH 80%



0102030405060708090

5 7.5 10 12.5Cover thickness (cm)

Cor

rosi

on in

itiat

ion

time

(yea

rs) W/C 40 %

W/C 50 %

W/C 60 %

W/C 70 %

RH 80%

0102030405060708090


Cor

rosi

on in

itiat

ion

time

(yea

rs) W/C 40 %

W/C 50 %

W/C 60 %

W/C 70 %

RH 60%

the larger the cover thickness, lifetime increases clearly.Relative humidity is also influential parameter.


Corrosion crack generation time

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40 50 60 70W/C

Cor

rosi

on c

rack

gen

erat

ion

time

(yea

rs)

Max.value Avg.value Min.value

RH 60 %

Maximum

Average

Minimum0



50

100

150

200

250

300


Cor

rosi

on c

rack

gene

ratio

n tim

e (y

ears

) W/C 40 %

W/C 50 %

W/C 60 %

RH 80%

0

W/C 70 %

Initial crack modelSIMULATION RESULTSSIMULATION RESULTS


W/C 40%

0

2

4

6

8

10

0 5 10 15 20

Section number

Cor

rosi

on in

itiat

ion

time

(yea

rs)

0 cm 1.25 cm 2.5 cm3.75 cm 5 cm


5 cm of cover thickness

Initial crack modelSIMULATION RESULTSSIMULATION RESULTS


0

5

10

15

20

25

30

0 1.25 2.5 3.75 5Effective crack length (cm)

Cor

rosi

on c

rack

ge

nera

tion

time

(yea

rs)

W/C 40%W/C 50%W/C 60%W/C 70%

5 cm cover thickness

Example for evaluation of structural performance of deteriorated RC structure

Example for evaluation of Example for evaluation of structural performance of structural performance of deteriorated RC structure deteriorated RC structure

DYNAMIC BEHAVIOR OF REINFORCED DYNAMIC BEHAVIOR OF REINFORCED CONCTERE STRUCTURES DETERIORATED BY CONCTERE STRUCTURES DETERIORATED BY

CORROSION OF REINFORCEMENTCORROSION OF REINFORCEMENT

IntroductionIntroduction

some structures in the severe environmental condition may be in a deteriorated condition due to the corrosion of reinforcement

piers are relatively vulnerable to earthquake because it is suffered with a very large inertial force

IntroductionIntroductionLarge

EarthquakeCorrosion of

Reinforcement

Some pier with corrosion of reinforcement may not have the structural capacities it was designed for

Rehabilitation and Repairing is being

popular

Evaluation of the dynamic behavior of the piers deteriorated by corrosion becomes necessary

IntroductionIntroduction

Objective

Evaluate the dynamic properties such as,stiffnessstiffness, ductilityductility and energy absorptionenergy absorption ofthe piers deteriorated by the corrosion of reinforcement

Behavior of the corroded piers against the cyclic loading which are designed by

Ordinary design, using JSCE code.Seismic design part of JSCE along with the verification of ductility according to JRA’s specification

MethodologyMethodology

Specimen Type

S. No.

Designation Design Principle Axial Load

Corrosion Lossgm/cm2/cm

1 POA-1 0.002 POA-2 0.193 POA-3 0.384 POA-4 0.565 PON-1 0.006 PON-2 0.197 PON-3 0.388 PON-4 0.56

Using JSCE code for ordinary reinforced

concrete design

200 kN

0


Specimen Type (Contd..)

S. No.

Designation Design Principle Axial Load

9 PEA-1 0.0010 PEA-2 0.1911 PEA-3 0.3812 PEA-4 0.5613 PEN-1 0.0014 PEN-2 0.1915 PEN-3 0.3816 PEN-4 0.56

Using seismic resistant part of JSCE code in

conjunction with JRA’s specification

200 kN

0

Corrosion Lossgm/cm2/cm


Specimen Size220 mm

500 mm

1200 mm 320 mm

1000

mm

1200

mm

220 mm

Ducts for post-tensioning

Duct for anchor bolt

Reinforcement Arrangement

4 – D 20φ 9 @200 mm

φ 9 @200 mm6 – D 20

12.7 mm PC Tendons

Ordinary Design

4 – D20φ 9 @80 mm

φ 9 @200 mm6 – D 20

12.7 mm PC Tendons

Seismic Design

Accelerated Corrosion Test

`

Test specimen

3.5% NaCl solution

Longitudinal rebar (anode)

Titanium net (cathode)

Tank

+-

Current supplier

Hydraulic Actuatorwith Force Sensor

Reaction Frame

Anchor Bolt

Test Specimen

Dial Gauge

12.7 mm Tendon


Reaction Frame

Anchor Bolt

Test Specimen

Dial Gauge

12.7 mm Tendon


Reaction Frame

Anchor Bolt

Test Specimen

Dial Gauge

12.7 mm Tendon

Loading Test

Condition

Loading Cycles

Lateral Load History

-150

-100

-50

0

50

100

150

0 4 8 12 16

Cycle Number

Dis

plac

emen

t (m

m) Load Control

Displacement Control


Comparison of Various Corrosion Loss

0.13 gm/cm2 0.45 gm/cm20.04 gm/cm20.0 gm/cm2

10 c

m

Results and DiscussionResults and Discussion

Load Displacement Curve

-80

-60

-40

-20

0

20

40

60

80

-120 -80 -40 0 40 80 120Displacement (mm)

Load (

kN

)

4 5 6 7 8 9 10 11 131214

15

Seismic DesignNo Axial LoadNo Corrosion



-80

-60

-40

-20

0

20

40

60

80

-120 -80 -40 0 40 80 120Displacement (mm)

Load (

kN

)

4 5 6 7 8 9 10 11 1213

14

Seismic DesignNo Axial Load0.17 gm/cm2

Corrosion loss



-80

-60

-40

-20

0

20

40

60

80

-120 -80 -40 0 40 80 120Displacement (mm)

Load (

kN)

4 5 6 7 8 9 10 1112


Corrosion loss



-80

-60

-40

-20

0

20

40

60

80

-120 -80 -40 0 40 80 120Displacement (mm)

Load (

kN

)3 4

56

7


Corrosion loss


Strength Degradation

0

40

80

0 0.2 0.4 0.6Corrosion loss (gm/cm2)

Str

engt

h

(kN

) PONPOAPENPEA


Strength Degradation ( Contd…)

0

40

80

120


Stre

ngth

Rat

io (%

)

PON POA PEN PEA

Best fit curve from experimental results

result of theoretical calculation of strength reduction due to loss of area of steel only

Pc=(1-0.6745∆w2-0.2969∆w)Pu

R2=0.8323


Ductility Degradation

Displacement (mm)

Loa

d (

kN)

Pu

Py

0.8 Pu

δy δu

µ=δu/δy


Ductility Degradation (Contd…)

02468

10


Duc

tility

PONPOAPENPEA


Ductility Degradation (Contd…)

0

40

80

120


Duc

tility

Rat

io (

%) PON

POAPENPEA

µc=(1-0.6208∆w2-1.0318∆w)µu

R2=0.93

µc=(1-3.2232∆w2-0.2765∆w)µu

R2=0.97

Pier with ordinary design

Pier with seismic design


Stiffness Degradation

-80

-60

-40

-20

0

20

40

60

80

-120 -80 -40 0 40 80 120Displacement (mm)

Load

(kN

) nth cycle

D

F

K = F/D


Stiffness Degradation (Contd)

02468

1012

0 5 10 15 20Corrosion loss (gm/cm2)

Stif

fnes

s (k

N/m

m) PEN-1

PEN-2PEN-3PEN-4

Number of loading cycle


Stiffness Degradation (Contd…)

K = 11.917e-0.6475N

R2 = 0.9839

0

2

4

6

8

0 5 10 15Cycle number

Stif

fnes

s (k

N/m

m)

PON-4bNaeK −=


Stiffness Degradation (Contd….)

05

1015202530


'a' (

kN/m

m)

PONPOAPENPEA


Stiffness Degradation (Contd….)

0

0.2

0.4

0.6

0.8


'b'

PONPOAPENPEA


Energy Absorption Degradation

Displacement (mm)

Loa

d (

kN)

Εn

Ε=ΣΕn


Energy Absorption Degradation

0

20000

40000

60000


Tot

al E

nerg

y A

bsor

ptio

n (k

N-m

m)

PONPOAPENPEA


Energy Absorption Degradation (Contd…)

0

40

80

120


Tot

al E

nerg

y A

bsor

ptio

n R

atio

(%)

PONPOAPENPEA

Ec = (1-2.1114*∆w)Eu

R2 = 0.90

Ec = (1-1.7952*∆w)Eu

R2 = 0.82

Pier with ordinary design

Pier with seismic design


Comparison of Strength and Ductility

0

20

40

60

80

100

0 20 40 60 80 100Strength Reduction (%)

Duc

tility

Red

uctio

n (%

) PONPOAPENPEA


Comparison of Strength and Energy Absorption

-10

10

30

50

70

90

0 20 40 60 80 100Strength Reduction (%)

Ene

rgy

Abs

orpt

ion

Red

uctio

n (%

)

PONPOAPENPEA

ConclusionsConclusions

Seismic performances of reinforced concrete structures are seriously affected by corrosion of reinforcement.

Strength of the pier is slightly reduced with the small increase in corrosion loss and with further increase degradation rate of strength is larger.

ConclusionsConclusionsSmall corrosion amount in reinforcement increases stiffness significantly. However, within few cycles it degrades quickly

With the increase in the corrosion loss of reinforcing bars, reduction rate of ductility and energy absorption of the pier is much higher than that of strength

Final RemarksFinal Remarks

Final remarksProblems awaiting solutions in near future

• To complete modeling performance degradation of structure with reinforcement corrosion process

• To evaluate environmental condition more correctly

• To evaluate construction works, including compaction, curing , etc.

• To establish life cycle cost evaluation method

• To systematize maintenance

• To establish total monitoring system including predictions of both chloride penetration and corrosion of reinforcement

estimation method on deterioration of marine concrete ... · deterioration process on marine...

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