Prestressed CFRP Sheets for Strengthening Concrete Slabs in Fatigue

Abstract

Six one-way reinforced concrete slabs were constructed and tested to investigate the effectiveness of using prestressed carbon fibre reinforced polymer (CFRP) sheets to strengthen concrete slabs subjected to fatigue loading. The slabs were 90mm × 1000mm × 3000mm and reinforced with 11.3mm diameter steel reinforcing bars. The slabs were tested in two groups of three slabs. In each group, one slab was unstrengthened and used as a control, the second slab was strengthened with non-prestressed FRP sheets and the third slab was strengthened with prestressed sheets. For the first group, the loading range for the three slabs was based on the loads that induced in the reinforcing steel of the control slab stresses that ranged between 10 and 95 percent of the steel yield strength. For the second group, the loading range chosen for the three slabs induced steel stresses in its control slab that ranged between 30 and 95 percent of the steel yield strength. Therefore, the first group of slabs was subjected to a higher load amplitude but lower mean stress than the second group. The CFRP strengthened slabs of the second group were externally loaded while applying the CFRP sheets, to represent the sustained load that may be associated with field strengthening conditions. The test results confirmed that strengthening reinforced concrete slabs with bonded CFRP sheets, especially prestressed CFRP sheets, increases fatigue life. Common to strengthening with non-prestressed and prestressed CFRP sheets are that compared to the control slabs, strains in the steel reinforcement, plastic creep strains in the concrete, and deflections are all decreased, with greater decreases in all these observed with prestressed CFRP sheets. Crack widths are greatly reduced when the CFRP sheets are prestressed. Since fatigue failure of the internal steel occurred at the location of large cracks that were repetitively opened and closed, reducing the crack widths contributes to achieving longer fatigue life. Finally, the presence of anchors at the ends of the CFRP sheets can delay the ultimate fatigue failure of CFRP strengthened slabs by delaying sheet debonding failures.

Keywords

FRP sheets prestressed strengthening slabs fatigue

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References

Char

M.S.

Saadatmanesh

and Ehsani

M.R.

(1994). “Concrete girders externally prestressed with composite plate”, PCI Journal 39:3, pp. 40–51.

Deuring

(1993). “Verstärken von stahlbeton mit gespannten faserverbundwekstoffen” (Post-strengthening of concrete structures with pretensioned advanced composites), EMPA Research Report No.224, Dübendorf, Switzerland, 279 pp. (In German).

El-Hacha

Wight

R.G.

, and Green

M.F.

(1999). “Strengthening concrete beams with prestressed FRP sheets: Behavior at room and low temperatures”, Proceedings of the 4th International Conference on Fibre Reinforced Polymers for Reinforced Concrete Structures (FRPRCS-4), ACI, Baltimore, Maryland, pp. 737–749.

El-Hacha

Wight

R.G.

, and Green

M.F.

(2000a). “Concrete beams strengthened with prestressed CFRP sheets at low temperature”, Proceedings of the 17th Annual International Bridge Conference, (IBC '00). Pittsburgh, Pennsylvania, pp. 21–31.

El-Hacha

Wight

R.G.

, and Green

M.F.

(2000b). “Retrofitting of severely damaged concrete beams using prestressed CFRP sheets”, Proceedings of the 3rd International Conference on Advanced Composite Materials in Bridges and Structures, (ACMBS III). Ottawa, Ontario, Canada, pp. 529–536.

El-Hacha

Wight

R.G.

, and Green

M.F.

(2001). “Prestressed CFRP sheets for strengthening concrete beams: Experimental and analytical investigation”, Proceedings of the 5th International Conference on Fiber Reinforced Polymers for Reinforced Concrete Structures, (FRPRCS-5). Cambridge, England, pp. 261–270.

Garden

H.N.

Hollaway

L.C.

and Thorne

A.M.

(1998). “The strengthening and deformation behaviour of reinforced concrete beams upgraded using prestressed composite plates”, Materials and Structures, 31:208, pp. 247–258.

Heffernan

P.J.

Wight

R.G.

, and Erki

M.A.

, 2002. “Fatigue behaviour of concrete slabs strengthened with prestressed cfrp sheets”, Proceedings of the 2002 Durability of Fibre Reinforced Polymer (FRP) Composites for Construction, Montreal, Quebec, 29–31 May 02. pp. 465–474.

Huang

Y.L.

Yen

J.H.

and Ong

C.L.

(2000). “Strengthening of reinforced concrete beams using prestressed glass fiber-reinforced plastic”, Proceedings of the 4th International Conference on: Repair, Rehabilitation, and Maintenance of Concrete Structures, and Innovations in Design and Construction (ACI SP-193). Seoul, Korea, pp. 925–936.

10.

Izumo

K.M.

Saeki

Asamizu

and Shimura

(1997). “Strengthening reinforced concrete beams by using prestressed fiber sheets”, Proceedings of the 3rd International Symposium on Non-Metallic (FRP) Reinforcement for Concrete Structures, (FRPRCS-3). Sapporo, Japan, 1, pp. 379–386.

11.

Karbhari

V.M.

Seible

Seim

, and Vasquez

(1999). “Post-strengthening of concrete slabs”, Proceedings of the 4th International Conference on Fibre Reinforced Polymers for Reinforced Concrete Structures (FRPRCS-4), ACI, Baltimore, Maryland, pp.1163–1173.

12.

Meier

(1995). “Strengthening of structures using carbon fibre/epoxy composites”, Construction and Building Materials, 9:6, pp. 341–351.

13.

Quantrill

R.J.

and Hollaway

L.C.

(1998). “The flexural rehabilitation of reinforced concrete beams by the use of prestressed advanced composite plates”, Composites Science and Technology, 58, pp. 1259–1275.

14.

Saadatmanesh

and Ehsani

(1991). “RC beams strengthened with GFRP plates: Part I: Experimental study”, Journal of Structural Engineering (ASCE) 117:11, pp. 3417–3433.

15.

Saeki

Shimura

Izumo

and Horigushi

(1997). “Rehabilitation of reinforced concrete beams using prestressed fiber sheets”, Proceedings of the International Conference on Engineering Materials. Ottawa, Canada, II, paper # 104.

16.

Teng

J.G.

Lam

Chan

and Wang

(2000). “Retrofitting of deficient RC cantilever slabs using GFRP strips”, Journal of Composites for Construction, ASCE, 4:2, pp. 75–84.

17.

Triantafillou

T.C.

Deskovic

and Deuring

(1992). “Strengthening of concrete structures with prestressed fiber reinforced plastic sheets”, ACI Structural Journal, 89:3, pp. 235–244.

18.

Wight

R.G.

and Erki

M.A.

(2001). “CFRP strengthening of severely damaged reinforced concrete slabs”. Proceedings of the 3rd International Conference on Concrete Under Severe Conditions Environment and Loading (CONSEC'01). Vancouver, Canada. pp. 2191–2198.

19.

Wight

R.G.

Green

M.F.

and Erki

M.A.

(1996). “Post-strengthening prestressed concrete beams with prestressed FRP sheets”. Proceedings of the 2nd International Conference on Advanced Composite Materials in Bridges and Structures, (ACMBS II). Montréal, Canada. pp. 449–456.

20.

Wight

R.G.

Green

M.F.

, and Erki

M.A.

, 2001. “Prestressed FRP sheets for post-strengthening reinforced concrete beams”, American Society of Civil Engineers Journal of Composites for Construction. Vol. 5, No. 4, Nov 2001, pp. 214–220.

21.

Matsuzaki

Yokoyama

and Kanda

(1999). “Retrofitting method for reinforced concrete structures with externally prestressed carbon fiber sheets”, Proceedings of the 4th International Symposium on Fiber Reinforced Polymer Reinforcement for Reinforced Concrete Structures, (FRPRCS-4). Dolan

Rizkalla

and Nanni

(eds) Baltimore, Maryland, pp. 751–765.