DURABILITY OF CARBON FIBRE REINFORCED POLYMERS ON TIMBER BRIDGES

Genevieve Christou

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TIMBER AS A MATERIAL

Strengths Weaknesses

Lightweight Rot, Infestation, Moisture Swelling

Natural Source Fiber damage

Economic Joints

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TIMBER BRIDGES IN AUSTRALIA

Queensland: 17 000 Timber Rail Bridges

New South Wales: 1000 timber beam bridges, 100 timber truss bridges

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CFRPS AND TIMBER

Studied since 1960s

Applying CFRP to timber:

Increases Stiffness

Increases overall Ultimate loadCFRP sheet glued to tensile side of timber

(Zhou et al, 2015)

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DURABILITY

Timber bridges need to endure environmental exposures that have not been as comprehensively understood for the case of Timber-CFRP composites

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PREVIOUS WORK

Investigations of CFRP retrofitting of aged timbers

Kim et al (2013)

Schober and Rautenstrauch (2006)

Borri et al (2005)

Li et al (2009)

Nowak et al (2013)

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PREVIOUS WORK

Effect of Moisture on the Mechanical Properties of CFRP-Wood Composite: An Experimental and Atomistic Investigation (Zhou et al, 2015)

Macroscopic & atomistic investigations

Quantifies mechanical response of CFRP–wood system under different moisture conditions at different length scales (2014)

Evidence that saturated bonds are 30% weaker

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PREVIOUS WORK

Seawater Durability of Glass and Carbon-Polymer Composites (Kootsookos et al, 2004)

Study into the mass-loss of CFRP over time, as they are submerged in water with salinity 2.9% (average salinity of the ocean)

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PREVIOUS WORK

Evaluation of FRP/wood Adhesively Bonded Epoxy Joints on Environmental Exposures (Vanerek et al, 2014)

Study of environmental exposure on bond strength

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AIM

The aim of this project is to create an optimised profile of potential long-term Timber-CFRP composite specimens for timber bridges.

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OBJECTIVES

Specific objectives:

1. To identify the key parameters affecting bond characteristics between Timber-CFRP composites

2. To examine the effect of environmental conditions on the debonding failure mechanism

3. To develop a new theory, based on above findings, for strengthening of timber structure by smart CFRP retrofitting

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BACKGROUND

Economic loss due to timber degradation

Myrtle Creek Bridge in Victoria

108 year old bridge, $650 000 to repair

effects on local economy

Canna & Grey, 2004

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BACKGROUND

Evolution of the smart strengthening material

41% of Australian timber bridges do not meet standards

$3-$7 Million spent on bridges annually

Reinforcement is necessary to combat these issues

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BACKGROUND

World trends towards the external strengthening of CFRP to important bridges

Many cases of CFRP use in rehabilitation of bridges

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RESEARCH PROJECT

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RESEARCH PROJECT

Literature Review

A previous study conducted on 20 papers in the field of Timber-CFRP strengthening

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THEORY DEVELOPMENT

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THEORY DEVELOPMENT

Significance of the project

cost effective infrastructure rehabilitation

Reducing the cost of infrastructure maintenance

Safe Infrastructure for people

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THEORY DEVELOPMENT

New Methodologies and Innovation

smart material as a choice

Adds to field of timber strengthening

Adds to field of material durability

Leads to economic advantages

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THEORY DEVELOPMENT

Approach and Methodology

Critical Issues and Shortcomings in Existing CFRP Strengthening

Extreme and low Temperatures

Moisture

Chemical Solution (Alkali and Salt)

Percentage Mass Loss

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PROPOSED PLAN FOR RESEARCH

Experimental work package addressing all objectives

Durability conditions followed by strength testing

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PROPOSED PLAN FOR RESEARCH

Four point bending (simulating beam conditions)

Two types of specimen

Near Surface Mounted (NSM) Bonding

Externally Bonded Reinforcement (EBR)

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PROPOSED PLAN FOR RESEARCH

Six Durability Scenarios

S1: Control (Normal Humidity Normal Temperature)

S2: Fresh Water Submersion (cycling temperatures 10-30ºC)

S3: Salt Water Submersion (cycling temperatures 10-30ºC)

S4: UV Light

S5: High Humidity High temperature (cycling)

S6: Low Humidity, Low Temperature (cycling)

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PROPOSED PLAN FOR RESEARCHScenario Durability Condition Temp (ºC) Hum (%) Test

ConditionSpecimen

type

S1 Dry 24 65 DryS1NSM

S1 Dry 24 65 DryS1EBR

S2 Saturated 10-35 65Dry

S2NSM DRY

S2 Saturated 10-35 65Dry

S2EBR DRYS2 Saturated 10-35 65Saturated

S2NSM WETS2 Saturated 10-35 65

SaturatedS2EBR WET

S3 Saturated 10-35 65Dry

S3NSM DRY

S3 Saturated 10-35 65Dry

S3EBR DRYS3 Saturated 10-35 65

SaturatedS3NSM WETS3 Saturated 10-35 65

SaturatedS3EBR WET

S4 Dry 24 65 DryS4NSM

S4 Dry 24 65 DryS4EBR

S5 Dry 45-55 85 DryS5NSM

S5 Dry 45-55 85 DryS5EBR

S6 Dry -5-5 45 DryS6NSM

S6 Dry -5-5 45 DryS6EBR

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PROPOSED PLAN FOR RESEARCH

Specimen Requirements:

Whole Curing process (15 days) to occur in controlled environment to limit variables (T=24 humidity=65%)

At least 5 specimens per classification/type

Require at least 90 specimens

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PROPOSED PLAN FOR RESEARCH

Equipment and facilities required

Strain Gauges

Walk in/Large Environmental Chamber

Large Water tanks, Water heaters

UV lights

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DISCUSSION AND CONCLUSION

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DISCUSSION AND CONCLUSION

Expected Outcome

Scenario 1 (Control)

Beams are expected to be strengthened effectively by their respective techniques

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DISCUSSION AND CONCLUSION

Expected Outcome

Scenario 2 & Scenario 3 (Fresh Water, Salt Water)

It is expected that the wet-state results will be significantly weaker than the dry state results for these scenarios

In the case of Scenario 3, the CFRP should begin to lose mass, weakening the hybrid

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Expected Outcome

Scenario 4 (UV Radiation)

previous studies suggest that UV radiation could have an effect on the bond

DISCUSSION AND CONCLUSION

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Expected Outcome

Scenario 5 (High Temperature, High Humidity)

The moisture in the air may infiltrate the bond

As temperature approaches Tg the bond will become more ductile.

DISCUSSION AND CONCLUSION

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Expected Outcome

Scenario 6 (Low Temperature, Low Humidity)

Bonds can become brittle in cold conditions, cracking may occur

DISCUSSION AND CONCLUSION

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Expected Impact

Safe and Secure Infrastructure

Having a durable method for CFRP reinforcement to timber bridges will make it easier to ensure that all bridges are safe

DISCUSSION AND CONCLUSION

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Expected Impact

National Benefit

encouraging growing industries

DISCUSSION AND CONCLUSION

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Due to time constraints the experimental package can not be conducted

DISCUSSION AND CONCLUSION

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REFERENCES

A. Kootsookos, A. P. M. (2004). Seawater durability of glass- and carbon-polymer composites. Composites Science and Technology, 64(10–11), 1503–1511. doi:10.1016/j.compscitech.2003.10.019

Aravinthan, T & Manalo, A. Field Applications and Case Studies of FRP in Civil Infrastructure: The Australian Experience. Retrieved from https://eprints.usq.edu.au/21556/3/Aravinthan_Manalo_CICE2012_AV.pdf

Australian Local Government Association (2013). Bridges to a Stronger Future. Retrieved from http://alga.asn.au/site/misc/alga/downloads/transport/ALGA_BridgesToAStrongerFuture2013.pdf

Borri, A., Corradi, M., & Grazini, A. (2005). A method for flexural reinforcement of old wood beams with CFRP materials. Composites Part B: Engineering, 36(2), 143-153. Retrieved from http://www.sciencedirect.com/science/article/pii/S1359836804000903. doi:http://dx.doi.org/10.1016/j.compositesb.2004.04.013

Canna, X. Gray, D. (2004). Timber bridges struggle to span modern times. p. 1. Retrieved from http://www.theage.com.au/articles/2004/01/18/1074360630811.html

Department of Transport and Main Roads. (2015). Fiber Composite Projects.

Flexural Reinforcement of Glulam Timber Beams and Joints with Carbon Fiber-Reinforced Polymer Rods. (2005). Journal of Composites for Construction, 9(4), 337-347. Retrieved from http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0268%282005%299%3A4%28337%29. doi:doi:10.1061/(ASCE)1090-0268(2005)9:4(337)

FRP-Reinforced Wood as Structural Material. (1992). Journal of Materials in Civil Engineering, 4(3), 300-317. Retrieved from http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290899-1561%281992%294%3A3%28300%29. doi:doi:10.1061/(ASCE)0899-1561(1992)4:3(300)

Francey, M. F. H. K. L. An investigation into the rehabilitation of timber structures with fibre composite materials. Retrieved from http://eprints.qut.edu.au/1407/1/Humphreys_Francey.pdf

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REFERENCES

Khelifa, M., & Celzard, A. (2014). Numerical analysis of flexural strengthening of timber beams reinforced with CFRP strips. Composite Structures, 111, 393-400. Retrieved from http://www.sciencedirect.com/science/article/pii/S0263822314000245. doi:http://dx.doi.org/10.1016/j.compstruct.2014.01.011

Khelifa, M., Vila Loperena, N., Bleron, L., & Khennane, A. (2014). Analysis of CFRP-strengthened timber beams. Journal of Adhesion Science and Technology, 28(1), 1-14. Retrieved from http://dx.doi.org/10.1080/01694243.2013.815096. doi:10.1080/01694243.2013.815096

Li, Y.-F., Xie, Y.-M., & Tsai, M.-J. (2009). Enhancement of the flexural performance of retrofitted wood beams using CFRP composite sheets. Construction and Building Materials, 23(1), 411-422. Retrieved from http://www.sciencedirect.com/science/article/pii/S0950061807002929. doi:http://dx.doi.org/10.1016/j.conbuildmat.2007.11.005

Nowak, T. P., Jasieńko, J., & Czepiżak, D. (2013). Experimental tests and numerical analysis of historic bent timber elements reinforced with CFRP strips. Construction and Building Materials, 40, 197-206. Retrieved from http://www.sciencedirect.com/science/article/pii/S0950061812007842. doi:http://dx.doi.org/10.1016/j.conbuildmat.2012.09.106

Schober, K. U., & Rautenstrauch, K. (2006). Post-strengthening of timber structures with CFRP's. [journal article]. Materials and Structures, 40(1), 27-35. Retrieved from http://dx.doi.org/10.1617/s11527-006-9128-6. doi:10.1617/s11527-006-9128-6

Vanerek, J., Benesova, A., Rovnanik, P., & Drochytka, R. (2014). Evaluation of FRP/wood adhesively bonded epoxy joints on environmental exposures. Journal of Adhesion Science and Technology, 28(14-15), 1405-1417. Retrieved from http://dx.doi.org/10.1080/01694243.2012.698096. doi:10.1080/01694243.2012.698096

Zhou, A., Tam, L.-h., Yu, Z., & Lau, D. (2015). Effect of moisture on the mechanical properties of CFRP–wood composite: An experimental and atomistic investigation. Composites Part B: Engineering, 71, 63-73. Retrieved from http://www.sciencedirect.com/science/article/pii/S1359836814005071. doi:http://dx.doi.org/10.1016/j.compositesb.2014.10.051

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