concrete research at the university of wollongong, australiafrp bars/strips cross-section of...

Concrete Research at the University of Wollongong, Australia

Assoc Prof. Muhammad Hadi

1

Tim McCarthy Muhammad Hadi Alex Reminnokov Neaz Sheikh Tao Yu Shishum Zhang Lip Teh (Steel)

2

Faez Alhussainy, Hayder Alaa Hasan, Sime Rogic, M. Neaz Sheikh, Muhammad N.S. Hadi

3

4Details of direct tensile test for Concrete

Muhammad N. S. Hadi Faez Alhussainy M. Neaz Sheikh

7

Steel bars are traditionally used inreinforced concrete members.

In general steel bars are solid in crosssection.

Steel tubes that have the same crosssectional area as solid bars will havehigher second moment of area andstiffness.

Using steel tubes in lieu of solid bars willincrease the stiffness of concretemembers.

8Steel tubes

Steel bars

Self-Compacting Concrete is an innovative concrete that can

flow and consolidate under its only weight.

Placement of SCC by pump tremie

(Goodier, 2003)9(Mott MacDonald Ltd)

Self-Compacting Concrete Mix proportion

• Type of mix EFNARC (2002) method.

Self-compacting concrete mix proportion

Material Quantity/1m3 of concrete

Cement 280 kgMineral admixtures 170 kg

Fine aggregate 950 kgCoarse aggregate 780 kg

Water 182 kgHigh Range Water Reducer 3.375 l/ m3

Water/Powder ratio 0.4

10

Check fresh concrete properties with ASTM Methodsa) Slump flow test

Slump flow test

Calculate the slump flow (SF) according to the flowing equation:

Where :dmax = The maximum diameter of the circular spread of the SCC.

.

dperp = The perpendicular diameter to dmax.

This test was carried out according to ASTM C1611 (2014).

2max perpddSF

11

b) J- Ring test

J-Ring test

Calculate J-Ring flow (RF) according to the following equation:

Where:jmax= The maximum diameter of the circular spread of the SCC.jperp= The perpendicular diameter to jmax .

2max perpjjRF

12

This test was carried out according to ASTM C1621 (2014).

Passing Ability= slump flow – J-Ring flow

(250 mm)

(510 mm)

(170 mm)

(50 mm)

(115 mm)

(220 mm)

(230 mm)

(515 mm)

Detail of column mould Detail of collector plate

c) Column segregation test

• ASTM C-1610 (2014).

• This test evaluates the static stability of a concrete mixture.

• This test consists of filling a 660 mm high cylindrical mould with concrete.

(Based on ASTM C-1610, 2014)13

c) Column segregation test (cont'd)

WhereS % = percent static segregation.CAT = mass of coarse aggregate in the top section of the column.CAB= mass of coarse aggregate in the bottom section of the column.

Column test

Percent static segregation is calculated from equation:

100CACACACA2%S

TB

TB

,0%S

if CAB > CAT

if CAB ≤ CAT

14

b) Tensile testing of steel tube

• ASTM A370, (2014). • A design that used for such plugs is shown in Figure.

Gauge Length

d

d

d

d

d

Testing machine jaws should not extend beyond this limit

dd

2d

Metal plugs for testing tubular specimens

Metal plugs

(Based on ASTM A370, 2014)15

C) Compression testing of steel bars and tubes

(a) Steel bars (b) Steel tubes

Compressive test of samples16

Axial tension load-deformation curves for Specimens N12 and ST26.9

17

N12

ST26.9

Axial tension load-deformation curves for Specimens N16 and ST33.7

18

ST33.7

N16

19

Group 1 Group 2 Group 3 Group 4 Group 5

Experimental Program

20

GroupNo.

SpecimenLabels

Diameter (mm)

Height(mm)

Longitudinal Reinforcement Transverse Reinforcement Loading ModesNo.

of Bars or Tubes

External Diameterof Bars or

Tubes (mm)

Thickness of Tubes,

(mm) %

Diameter of Bars (mm)

Pitch (mm)

%

1

N16H50C 240 800 6 16 (N16) ‐‐‐‐‐ 2.67 R10 50 3.3 Concentric

N16H50E25 240 800 6 16 (N16) ‐‐‐‐‐ 2.67 R10 50 3.3 e = 25 mmN16H50E50 240 800 6 16 (N16) ‐‐‐‐‐ 2.67 R10 50 3.3 e = 50 mmN16H50F 240 800 6 16 (N16) ‐‐‐‐‐ 2.67 R10 50 3.3 Flexural

2

ST33.7H50C 240 800 6 33.7 2 2.64 R10 50 3.3 Concentric

ST33.7H50E25 240 800 6 33.7 2 2.64 R10 50 3.3 e = 25 mm

ST33.7H50E50 240 800 6 33.7 2 2.64 R10 50 3.3 e = 50 mm

ST33.7H50F 240 800 6 33.7 2 2.64 R10 50 3.3 Flexural

3

ST33.7H75C 240 800 6 33.7 2 2.64 R10 75 2.2 Concentric

ST33.7H75E25 240 800 6 33.7 2 2.64 R10 75 2.2 e = 25 mm

ST33.7H75E50 240 800 6 33.7 2 2.64 R10 75 2.2 e = 50 mm

ST33.7H75F 240 800 6 33.7 2 2.64 R10 75 2.2 Flexural

4

ST26.9H50C 240 800 6 26.9 2.6 2.63 R10 50 3.3 Concentric

ST26.9H50E25 240 800 6 26.9 2.6 2.63 R10 50 3.3 e = 25 mm

ST26.9H50E50 240 800 6 26.9 2.6 2.63 R10 50 3.3 e = 50 mm

ST26.9H50F 240 800 6 26.9 2.6 2.63 R10 50 3.3 Flexural

5

ST26.9H75C 240 800 6 26.9 2.6 2.63 R10 75 2.2 Concentric

ST26.9H75E25 240 800 6 26.9 2.6 2.63 R10 75 2.2 e = 25 mm

ST26.9H75E50 240 800 6 26.9 2.6 2.63 R10 75 2.2 e = 50 mm

ST26.9H75F 240 800 6 26.9 2.6 2.63 R10 75 2.2 Flexural

Details of Tested Specimens

21

Construction of formwork

Fabricated reinforcing cages

22

Strain Gauges

3D View 3D View 3D ViewSide Elevation View Side Elevation View Side Elevation View

Front Elevation ViewFront Elevation ViewFront Elevation View

Plan View Plan View Plan View

Positions of PFL‐10 Gauges for longitudinal reinforcement

Positions of FCA‐10 Biaxial Gauges for longitudinal

reinforcement

Positions of FLA‐5 Gauges for transvers reinforcement

Photo of Strain Gauge Gluing

23

After casting of specimensBefore casting of specimens

24 Typical set up of a column Specimen

Loading heads

Four point loading method

25

Columns groups N16H50 ST33.7H50 ST26.9H50 ST33.7H75 ST26.9H75

Maximum load (kN) 2734 2729 2598 2633 2443

26

Failure Modes

Tao [email protected]

FRP = Fiber-Reinforced Polymer

0

10

20

30

40

50

60

70

0 0.01 0.02 0.03

axial strain

axia

l stre

ss (M

Pa)

unconfined concrete

Steel confined concrete

FRP confined concrete

1. Corrosion-resistant skin 2. Stay-in-place formwork for

casting concrete3. Confining device for

improved strength and ductility

FRP tube

Hybrid FRP-concrete-steel double-skin tubular structural columns (DSTCs)

Excellent ductility & seismic resistance Excellent durability Ease for construction

FRP tube

Concrete

Steel tube

No. Specimen ID.Thickness of FRP wrap

(ply)

Steel tube diameter (d/mm)

Steel tube thickness (t/mm)

Void ratio D/t

1 DSTC-A2-I, II 2 plies 139.7 3.5 (A) 0.68 39.9

2 DSTC-A3-I, II, III 3 plies 139.7 3.5 (A) 0.68 39.9

3 DSTC-A4-I, II 4 plies 139.7 3.5 (A) 0.68 39.9

4 DSTC-B3-I, II, III 3 plies 139.7 5.4 (B) 0.69 25.9

5 CFDSTC-A3-I, II 3 plies 139.7 3.5 (A) N/A 39.9

6 CFDSTC-B3-I, II 3 plies 139.7 5.4 (B) N/A 25.9

7 FCSC-2-I, II 2 plies - - - -



10 CESC-A-I N/A 139.7 3.5 0.68 39.9

11 CESC-B-I N/A 139.7 5.4 0.69 25.9

12 FCESC-H2-I, II 2 plies Dimensions of the H-section steel column

13 FCESC-H3-I, II 3 plies b h tf tw14 FCESC-H4-I, II 4 plies 100 152.6 6.8 6.131

Columns with a PET FRP Tube

0 10 20 30 40 50 60 70 80 900

500

1000

1500

2000

2500

3000

3500

Axi

al L

oad

(kN

)

Total Axial shortening (mm)

DSTC-A2-I DSTC-A3-I DSTC-A4-I Concrete Filled DSTC-A3-I

0 10 20 30 40 50 60 70 800

600

1200

1800

2400

3000

3600

4200

Axi

al L

oad

(kN

)

Axial Shortening (mm)

CFDSTC-B3-II FCSC-3-II DSTC-B3-II CESC-B

Near-surface mounted (NSM) fiber-reinforced polymer (FRP) reinforcement: An emerging and promising technique for

structural strengthening

Shishum Zhang

Flexural Strengthening of concrete members

Tension rebar

Stirrup

Adhesive FRP

Tension rebar

Stirrup

2c

1c

ea eagagagagw gw gw gw

ghghghgh

Groove Groove filler

fhbhbbbd

bb bwft

Externally bonded FRP laminates

Near-surface mounted FRP bars/strips

Cross-section of strengthened RC beams

The most important advantage of the NSM FRP method over the EB FRP method is the improved bond effectiveness between FRP and concrete, leading to a higher debonding strain of the FRP.

Bond between NSM FRP and concrete

Adjustablesupports

Rollers

Base plate

Bearing plate

Grip

Support block

Concrete block

lbPositioning frame

l

FRP strip/barEstablishment of the first ever 3-D meso-scale finite element model for bonded joints between a near-surface mounted (NSM) FRP strip and concrete.

Teng, J.G., Zhang, S.S., Dai, J.G. and Chen, J.F. (2013). “Three-dimensional meso-scale finite element modeling of bonded joints between a near-surface mounted FRP strip and concrete.”Computers & Structures, Vol. 117, pp. 105–117. (A* journal according to ERA ranking)

Bond-slip model between FRP and concrete

0

2

4

6

8

10

12

14

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Loca

l bon

d st

ress

(MP

a)

S l ip (mm)

Proposed model (h_g/w_g=2.33)

Proposed model (h_g/w_g=4)

Proposed model (h_g/w_g=5.67)

FE analysis (h_g/w_g=2.33)

FE analysis (h_g/w_g=4)

FE analysis (h_g/w_g=5.67)

Can be :1) used to establish the bond strength model of NSM CFRP strip-to-

concrete bonded joints; and2) incorporated into FE models of RC structures strengthened with CFRP

strips to simulate the debonding failure process.

Formulation of the first accurate bond-slip model for CFRP strips near-surface mounted to concrete.

)22

sin()2( 2B

sBB

sBA

619.0422.04.0 cf fG 613.0138.0

max 15.1 cf

0.138 0.6130.72 cA f

0.284 0.0060.37 cB f

Zhang, S.S., Teng, J.G., Yu, T. (2013). “Bond-slip model for CFRP strips near-surface mounted to concrete.” Engineering Structures, Vol. 56, pp. 945–953. (A* journal according to ERA ranking)

Bond strength model between FRP and concrete

2u f f f failureP G E A C

2u L f f f failureP G E A C

66.1

eL

fff

failure

AEGC

2

2max2

0.0

50.0

100.0

150.0

200.0

250.0

300.0

0.0 50.0 100.0 150.0 200.0 250.0 300.0

Test

bon

d st

reng

th (k

N)

P rediction of the proposed model

5.67

Average=0.924STD=0.109CoV=0.118

Work done before joining UOW:Development of a bond strength model for NSM CFRP strip-to-concrete bonded joints, which is the first model that can accurately account for the effect of bond length on bond strength

FRP element cohesive element

P

Zhang, S.S., Teng, J.G., and Yu, T. (2014). “Bond strength model for CFRP strips near-surface mounted to concrete.” Journal of Composites for Construction, ASCE, in press. (A journal according to ERA ranking)

FE modelling of NSM FRP-Strengthened RC beamsTest FE prediction

Work done before joining UOW:Development of an accurate finite element model for predicting end cover separation failures in RC beams strengthened with FRP in flexureZhang, S.S. and Teng, J.G. (2014). “Finite element analysis of end cover separation in RC beams strengthened in flexure with FRP”, Engineering Structures, Vol. 75, pp.550-560. (A* journal according to ERA ranking)

Simplified FE model for debonding failure

Development of an accurate simplified finite element model

Zhang, S.S. and Teng, J.G. (2015). “End cover separation in RC beams strengthened in flexure with bonded FRP reinforcement: simplified finite element approach”, Materials and Structures, 49 (6), 2223-2236

Strength model for debonding failure in strengthened concrete beams

cearDbAEscR fbcl/separation 6.3

16.025.015.16.0008.0952.0

PP

PPR if

if

)08.0100

)(05.15.4( 023.1266.0 c

ccsc

ss

cs

19.04860 ff

AE EA

094.0

85.0

t

clear

Db D

bt

0

1000

2000

3000

4000

5000

6000

7000

0 1000 2000 3000 4000 5000 6000 7000

ε db

from

Sim

plifie

d FE

mod

el (μ

ε)

εdb from proposed model (με)

Average: 1.00STD: 0.070CoV: 0.070

Establishment of an accurate strength model for end cover separation failures in RC beams strengthened with FRP in flexure

Teng J.G., Zhang S.S. and Chen J.F. (2015). “Strength Model for End Cover Separation Failure in RC Beams Strengthened with Near-surface Mounted (NSM) FRP Strips”, submitted to Engineering Structures, under review. (A*journal according to ERA ranking)

Analytical solution to interaction forces between NSM FRP and beam

Analytical and numerical investigations on the prediction of interaction forces in beams strengthened with near-surface mounted FRP bars.

Zhang, S.S. and Yu T. (2015). “Analytical solution for interaction forces in beams strengthened with near-surface mounted round bars”, submitted to Construction and Building materials, under review. (A journal according to ERA ranking)

0)(

)(11)(2

2

2

xVIEIE

dk

xFAEAEIEIE

dk

dxxFd

Tffbb

fbl

lffbbffbb

fbl

l

01

)()(11)(44

qIE

k

dxxdF

IEy

IEykxF

IEIEk

dxxFd

bbv

l

ff

f

bb

bvv

ffbbv

v

0

10

20

30

40

50

60

0 10 20 30 40 50

Tang

entia

l inte

ract

ion

forc

e (N

/ mm

)

Distance from the NSM bar end (mm)

FE modelPresent method

-2

0

2

4

6

8

10

12

0 10 20 30 40 50Nor

mal in

terac

tion f

orce

(N / m

m)

Distance from the NSM bar end (mm)

FE modelPresent method

Novel FRP anchorage system


Adjacent concrete wall

Optical fibers with FBG sensors (to Optical Sensing Interrogator )

GFRP sheets

GFRP anchor


0

1500

3000

4500

6000

7500

9000

0 10 20 30M

icro

stra

in

Load (kN)

FBGStrain guage

Tensile tests

Bond tests


0

500

1000

1500

2000

2500

3000

0 5 10 15 20

Mic

rost

rain

Root moment (kN*m)

FBG-L-3FBG-L-4Strain guage

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 5 10 15 20 25

Mic

rost

rain

Root Moment (kN*m)

FBG-L-1FBG-L-2FBG-R-1FBG-R-2

0

500

1000

1500

2000

2500

3000

0 5 10 15 20

Mic

rost

rain

Root moment (kN*m)

FBG-R-3FBG-R-4Strain guage

0

5

10

15

20

25

30

0 10 20 30 40 50 60

Roo

t mom

ent (

kN*m

)

Free end deflection(mm)

SS-1SS-2

Unstrengthened SS-2: 17.5 kN*m

Unstrengthened SS-1: 15.3 kN*mSlab tests

Other projects

Smart FRP bars

Fiber-optic monitoring of FRP-strengthened RC slabs

Fiber-optic monitoring of underground jacking pipes

Alkaline Resistance of GFRP Bars

concrete research at the university of wollongong, australiafrp bars/strips cross-section of...

Documents