The Repair of Timber Beams with Controlled-Debonding Steel Plates

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In this paper a non-invasive technique for the repair of ancient wooden floors is presented. Steel plates are glued on one side only by epoxy-adhesive into longitudinal grooves in order to allow the free swelling and shrinkage of the wood in the direction transversal to the plate glueing surface, thus reducing the risk of plates’ delamination. A set of high strength steel nails guarantees the transmission of the load from the steel plates to the wooden beam in case of loss of adhesion due to fire or delamination. This technique was used to repair a precious beam in a wooden floor of the 15th century in Palazzo Calini (Brescia, Italy). The presented technique requires particular attention because it might be affected by the delamination of the glued reinforcement due to the stress concentration, which occurs at the end of the repairing element or at the cracks of the repaired beam.The main results of experimental and numerical studies focusing on the delamination phenomenon are also presented and discussed. They have shown that the risk of plate debonding can be markedly reduced by the capability of the sapwood to develop plastic strain. The wooden floor has been monitored for more than eleven years, confirming the effectiveness of the adopted technique. The monitoring has also shownthe importance of limiting the wooden moisture content variation to reduce the floor’s creep deflection.

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Edited by:

Maurizio Piazza and Mariapaola Riggio

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588-595

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G. Metelli et al., "The Repair of Timber Beams with Controlled-Debonding Steel Plates", Advanced Materials Research, Vol. 778, pp. 588-595, 2013

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September 2013

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$38.00

[1] P. Gelfi., E. Giuriani and A. Marini. Stud shear connection design for composite concrete slab and wood beams. Journal of Structural Engineering 128: 12, 1544-1550, (2002).

DOI: https://doi.org/10.1061/(asce)0733-9445(2002)128:12(1544)

[2] M. Piazza, G. Turrini. Una tecnica di recupero dei solai in legno (A technique for the restoration of timber floors). Recuperare, 5 – 7, (1983).

[3] G. Tampone. Il restauro strutturale con lamine metalliche dei solai lignei della sede del Genio Civile di Firenze (The structural rehabilitation of timber floors by means of steel plates in Genio Civile Building - Florence), Atti del 2° Congresso Nazionale Restauro del Legno, 8-11 Novembre, Firenze, 1, 263-281, (1989).

DOI: https://doi.org/10.2307/j.ctt1tqx87n.28

[4] J. Peterson. Wood beams prestressed with bonded tension elements. Journal of Structural Division, ASCE 91: 1, 103-119, (1965).

[5] K. B. Borgin, G. F. Loedolff and G. R. Saunders. Laminated wood beams reinforced with steel strips. Journal of Structural Division, ASCE 94: 71, 596-602, (1968).

[6] U. Meier. Strengthening of structures using carbon fibre/epoxy composites. Construction and Buildings Materials 9: 6, 341-351 (1995).

DOI: https://doi.org/10.1016/0950-0618(95)00071-2

[7] F.W. Kropf and U. Maierhofer. Strengthening, retrofitting and upgrading of timber structures with high-strength fibres. Structural Engineering International 10: 3, 178-181, (2000).

DOI: https://doi.org/10.2749/101686600780481536

[8] T.C. Triantafillou and N. Deskovic. Prestressed FRP sheets as external reinforcement of wood members. Journal of Structural Engineering 118: 5, 1270-1285, (1992).

DOI: https://doi.org/10.1061/(asce)0733-9445(1992)118:5(1270)

[9] A. Borri, M. Corradi, A. Grazini. A method for flexural reinforcement of old wood beams with CFRP materials. Composites 2005; 36: 143–53.

DOI: https://doi.org/10.1016/j.compositesb.2004.04.013

[10] C. Gentile, D. Svecova and S.H. Rizkalla. Timber Beams Strengthened with GFRP Bars: Development and Applications. Journal of Composites for Construction 6: 1, 11-20, (2002).

DOI: https://doi.org/10.1061/(asce)1090-0268(2002)6:1(11)

[11] H. Alhayek and D. Svecova (2012). Flexural Stiffness and Strength of GFRP-Reinforced Timber Beams. Journal of composites for construction, 16: 245-252.

DOI: https://doi.org/10.1061/(asce)cc.1943-5614.0000261

[12] P. Alam, M. P. Ansell and D. Smedley (2009). Mechanical repair of timber beams fractured in flexure using bonded-in reinforcements. Composites: Part B, 40, pp.95-106.

DOI: https://doi.org/10.1016/j.compositesb.2008.11.010

[13] R. N. Swamy, R. Jones and J. W. Bloxham. Structural Behaviour of Reinforced Concrete Beams Strengthened by Epoxy-Bonded Steel Plates. The Structural Engineering 65A: 2, 59-68, (1987).

[14] D. J. Oehlers and J. P. Moran. Premature failure of externally plated reinforced concrete beams. Journal of Structural Engineering 116: 4, 978-995, (1990).

DOI: https://doi.org/10.1061/(asce)0733-9445(1990)116:4(978)

[15] J. G. Teng, J.W. Zhang and S.T. Smith. Interfacial Stress in reinforced concrete beams bonded with a soffit plate: a finite element analysis. Construction and Building Material 16: 1, 1-14, (2002).

DOI: https://doi.org/10.1016/s0950-0618(01)00029-0

[16] M. Malek, H. Saadatmanesh and R. Ehsani. Prediction of failure Load of R/C Beams Strengthened with FRP plate due to stress concentration at the plate end. ACI Structural Journal 95: 1, 142-152, (1998).

DOI: https://doi.org/10.14359/534

[17] E. Cosenza, M. Pecce. Shear and normal stresses interaction in coupled structural system. Journal of Structural Engineering 127: 1, 84-88, (2001).

DOI: https://doi.org/10.1061/(asce)0733-9445(2001)127:1(84)

[18] S.T. Smith, J.G. Teng. FRP-strengthened RC beams. II: assessment of debonding strength models. Engineering Structures 24: 4, 397-417, (2002).

DOI: https://doi.org/10.1016/s0141-0296(01)00106-7

[19] R. Wong and F.J. Vecchio. Towards modeling of reinforced concrete members with externally bonded fiber-reinforced polymer composites, ACI Structural Journal 100 (1), pp.47-55, (2003).

DOI: https://doi.org/10.14359/12438

[20] A. Aprile and E. Spacone. Role of bond in RC beams strengthened with steel and FRP plates. Journal of Structural Engineering 127: 12, 1445-1452, (2001).

DOI: https://doi.org/10.1061/(asce)0733-9445(2001)127:12(1445)

[21] Giuriani E., Gubana A. (1993). A penetration test to evaluate wood decay and its application to the Loggia monument. Materials and Structures, vol. 26, pp.8-14.

DOI: https://doi.org/10.1007/bf02472232

[22] Giuriani E. and Metelli G. (2004). The role of sapwood plasticity in the delamination phenomenon of repaired timber beams. Int. Journal for Restoration, vol. 10, n° 4, pp.317-334.

DOI: https://doi.org/10.1515/rbm-2004-5867

[23] G. Metelli. Coupling problem in the structural repair and strengthening (in Italian). PhD thesis, Supervisor: Prof. E. Giuriani, University of Brescia, Italy (2003).

[24] E. Giuriani and P. Gelfi (1982).