Abstract: The paper presents a laboratory, theoretical and numerical study of four-point bending on forty-five ply glued
and solid structural beams joined at wedge joints (quality class of structural lumber KS, KG) in the technical scale
(82 × 162 × 3650 mm), on unreinforced beams, and beams reinforced with prestressed steel, basalt and glass
rods, in a free-support scheme. The aim of the study was to determine the load-bending, load-stress relationships
in glued and solid beams and to determine the effectiveness of the reinforcement used, together with the
strength, load-bearing capacity and stiffness in both steel and 10 mm diameter composite pre-stressed beams. In
the case of laminated beams reinforced with prestressed steel, the stiffness increased by 13.15 %, the load
carrying capacity increased by 34.41 % and ductility increased by 13.16 %. For structural solid beams assembled
at wedge joints reinforced with pre-stressed steel bars, stiffness increased by 8.11 %, load carrying capacity
increased by 19.55 % and ductility increased by 13.86 %. For the glued laminated beams reinforced with pre-
stressed basalt bar – the load capacity increased by 31.12 %, stiffness increased by 9.91 % and ductility
increased by 9.87 %; while for the pre-stressed glass bar - load capacity increased by 29.04 %, stiffness increased
by 9.70 % and ductility increased by 17.11 %. For the adopted design model of flexural beams strengthened with
prestressed rods, the effectiveness of reinforcement with respect to stiffness was slightly higher than that ob-
tained in laboratory tests. The numerical analysis is applicable to the design of various reinforcement schemes
with particular reference to the configuration of wood quality classes.
B I B L I O G R A F I A[1] Anshari B, Guan Z, Komatsu K, Kitamori A, Jung K. Explore novel ways to
strengthen glulam beams by using compressed Japanese cedar. In: Proceedings of
the world conference on timber engineering (WCTE 2010), Riva del Garda,
Trentino, Italy, p. 8.
[2] Biliszczuk J, Bie ́n J, Maliszkiewicz P. Mosty z drewna klejonego. Warszawa:
Wydawnictwo Komunikacji i Łączno ́sci
2001.
[3] Yang H, Ju D, Liu W. Prestressed glulam beams reinforced with CFRP bars. Constr
Build Mater 2016
109:73–83.
[4] Krystofiak T, Proszyk S, Lis B. Kleje do produkcji wielkowymiarowych element ́ow
konstrukcyjnych z drewna dla budownictwa. 2007, Instytut Technologii Drewna w
Poznaniu.
[5] Rajczyk M, Stachecki B. Przegląd rozwiąza ́n konstrukcyjnych wzmacniania belek z
drewna klejonego zbrojeniem w postaci pręt ́ow. Zeszyty Naukowe Politechniki
Częstochowskiej, Budownictwo Z 2011
17(167):186–95.
[6] Martus M. Calculation tool for estimation of the material properties of glulam
beams with known layout. Thesis submitted for examination for the degree of
Master of Science in Technology. 2020.
[7] Thelandersson S, Larsen H. Timber Engineering. John Wiley & Sons
2003.
[8] De Luca V, Marano C. Prestressed glulam timbers reinforced with steel bars. Constr
Build Mater 2012
30:206–17.
[9] Maule A. Vantaggi della coazione del legno. Thesis. Venezia (Italy): University
IUAV
1999.
[10] Plevris N, Triantafillou TC. FRP reinforced wood as structural material. J Mater Civ
Eng, ASCE 1992
4(3):300–17.
[11] Brol J, Wdowiak A. The use of glass and aramid fibres for the strengthening of
timber structures. Ann Wars Univ Life Sci For Wood Technol 2017
100:128–38.
[12] Brol J, Nowak T, Wdowiak A. Numerical analysis and modelling of timber elements
strengthened with FRP materials. Ann Wars Univ Life Sci For Wood Technol 2018
104:274–82.
[13] Wdowiak A. Assessment of technical condition of wooden structures. In
Proceedings of the 11th european conference of young researchers and scientist,
Zilina, Slovakia, 22–24 June 2015
Volume 7, p. 326–332.
[14] Wdowiak A. Analysis of bent timber beam reinforcement with the application of
composite materials. Struct Environ 2016
8:10–6.
[15] Wdowiak A. Structural and strength properties of bent wooden beams reinforced
with fibre composites. Ph.D. Thesis, Kielce University of Technology, Kielce,
Poland, 12 April 2019.
[16] Wdowiak A, Brol J. Effectiveness of reinforcing bent non-uniform pre-stressed
glulam beams with basalt fibre reinforced polymers rods. Materials 2019
12:3141.
[17] Brol J, Wdowiak-Postulak A. Old timber reinforcement with FRP. Materials 2019
12:4197.
[18] Wdowiak-Postulak A. Natural fibre as reinforcement for vintage wood. Materials
2020
13:4799.
[19] Wdowiak-Postulak A, Brol J. Ductility of the tensile zone in bent wooden beams
strengthened with CFRP materials. Materials 2020
13:5451.
[20] Rudzinski L, Wdowiak A. Strength and structural properties of structural timber.
Struct Environ 2016
8:103–8.
[21] Wdowiak A. Using the visual method to sort polish pine structural sawn timber
with respect to strength. Czas Tech 2016
113:219–24.
[22] Wdowiak A. Defects in structural timber. Struct Environ 2017
9:112–22.
[23] Wdowiak A, Brol J. Methods of strength grading of structural timber—comparative
analysis of visual and machine grading on the example of scots pine timber from
four natural forest regions of Poland. Struct Environ 2019
11:210–24.
[24] Wdowiak A. Examination of structural and geometric characteristics during the
strength sorting of construction timber by visual method. Przeglad Bud 2017
88:
42–6.
[25] Wdowiak A. Structure of construction timber. J Civil Eng Environ Archit 2017
34:
365–80.
[26] Wdowiak-Postulak A. Basalt fibre reinforcement of bent heterogeneous glued
laminated beams. Materials 2021
14:51.
[27] Wdowiak-Postulak A, ́Swit G. Behavior of glulam beams strengthened in bending
with BFRP fabrics. Civil and Environ. Eng. Rep. 2021
31(2):1–14.
[28] Kamionka L, Wdowiak-Postulak A, Hajdenrajch A. Nowoczesne budownictwo
drewniane w technologii CLT na przykładzie budynku Bioklimatycznej Jednostki
Modularnej. Materiały Budowlane 2022
03:49–51. https://doi.org/10.15199/
33.2022.03.07.
[29] Gentile C, Svecova D. Timber beams strengthened with GFRP bars: development
and applications. J Comput Const 2002
6(1):11–20.
[30] Borri A, Corradi M, Speranzini E. Travi in legno rinforzate con barre o con tessuti in
fibre di carbonio, L’Edilizia (4) (2001), p. 48-56.
[31] Habid JD, Tod EK, Stephen M. Effect of FRP reinforcement on low grade eastern
hemlock glulams. University of Maine
1996.
[32] Galloway TL, Fogstad C, Dolan CW, Puckett JA. Initial tests of kevlar prestressed
timber beams. University of Wyoming
1996.
[33] Guan ZW, Rodd PD. Study of glulam beams pre-stressed with pultruded GRP.
Comput Struct, 83 (28–30) (1995), p. 2476-2487.
[34] Mark R. Wood–aluminum beams within and beyond the elastic range. Forest Prod J
1961
11(10):477–84.
[35] Sliker A. Reinforced wood laminated beams. Forest Prod J 1962
12(1):91–6.
[36] Bohannan B. Prestressed wood members. Forest. Prod J 1962
12(12):596–602.
[37] Peterson J. Wood beams prestressed with bonded tension elements. J Struct Eng,
ASCE 1965
91(l):103–19.
[38] Lantos G. The flexural behaviour of steel reinforced laminated timber beams. Wood
Sci 1970
2(3):136–43.
[39] Bulleit WM, Sandberg LB, Woods GJ. Steel-reinforced glued laminated timber.
J Struct Eng, ASCE 1989
115(2):433–44.
[40] Hemandez R, Davalos JF, Sonti SS, Kim Y, Moody RC. Strength and stiffness of
reinforced yellow-poplar glued laminated beams. Res. Pap. FPL-RP-554, Madison
(Wisconsin, USA): Department of Agriculture, Forest Service, Forest Products
Laboratory, 1997.
[41] Haiman M, Zagar M. Strengthening the timber glulam beams with FRP plates, In:
Proceedings of 7th world conference on timber engineering, WCTE 2002, August
12–15, 2002, Malaysia: Perpustakaan Negara
2002. p. 270–6.
[42] Triantafillou TC, Deskovic N. Innovative prestressing with FRP sheets: mechanics
of short-term behavior. J Eng Mech, ASCE 1991
117(7):1652–72.
[43] Triantafillou TC, Deskovic N. Prestressed FRP sheets as external reinforcement of
wood members. J Struct Eng, ASCE 1992
118(5):1270–84.
[44] Brunner M, Schnuriger M. Towards a future with ductile timber beams. In:
Proceedings of 7th world conference on timber engineering, WCTE 2002, August
12–15, 2002, Malaysia: Perpustakaan Negara
2002. p. 270–6.
[45] Kim YJ, Harries KA. Modeling of timber beams strengthened with various CFRP
composites. Eng Struct 2010
32:3225–34.
[46] Issa CA, Kmeid Z. Advanced wood engineering: glulam beams. Constr Build Mater
2005
19:99–106.
[47] Jasienko J. Experimental investigation into the force distribution in glued steel
bars and wooden joints. Arch Civ Eng 2002
1.
[48] Jasienko J. On modeling of behaviour of glued steel bar and wood joints. Arch Civ
Eng 2002
2.
[49] Nowak TP, Jankowski LJ, Jasienko J. Application of photoelastic coating technique
in tests of solid wooden beams reinforced with CFRP strips. Arch Civ Mech Eng
2010
2.
[50] Fiore V, Di Bella G, Valenzaa A. Glass–basalt/epoxy hybrid composites for marine
applications. Mater Des 2011
32(4):2091–9.
[51] Wei B, Cao H, Song S. Environmental resistance and mechanical performance of
basalt and glass fibres. Mater Sci Eng A – Struct 2010
527:4708–15.
[52] Wei B, Cao H, Song S. Tensile behavior contrast of basalt and glass fibres after
chemical treatment. Mater Des 2010
31:4244–50.
[53] Berozashvili M. Continuous reinforcing fibres are being offered for construction,
civil engineering and other composites applications. Adv Mater Com News,
Compos Worldwide 2001
6:5–6.
[54] Cerny M, Glogar P, Sucharda Z, Chlup Z, Kotek J. Partially pyrolyzed composites
with basalt fibres – mechanical properties at laboratory and elevated temperaturę.
Compos Part A - Appl S 2009
40:1650–9.
[55] Softwood structural sawn timber sorted using strength methods
PN-D-94021:
2013-10
Polish Committee for Standardization: Warsaw, Poland, 2013. Softwood
Structural Sawn Timber Sorted Using Strength Methods
PN-D-94021:2013-10
Polish Committee for Standardization: Warsaw, Poland, 2013.
[56] Timber structures—glued laminated timber and structural glued solid
timber—requirements
PN-EN 14080:2013-07
Polish Committee for
Standardization: Warsaw, Poland
2013.
[57] ASTM D7205/D7205M – 06 (2011) standard test method for tensile properties of
fiber reinforced polymer matrix composite bars.
[58] ISO 10406–1:2015 Fibre-reinforced polimer (FRP) reinforcement of concrete – Test
methods – Part 1: FRP bars and grid.
[59] ACI 440.3R: 2004 guide test methods for fiber-reinforced polymers (FRPs) for
reinforcing or strengthening concrete structures.
[60] CNR-DT 203:2006 guide for the design and construction of concrete reinforced
with FRP. Bars.
[61] GOST 31938:2012 fiber-reinforced polymer bar for concrete reinforcement –
general specifications.
[62] Timber structures—structural timber and glued laminated timber—determination
of some physical and mechanical properties
PN-EN 408+A1:2012
Polish
Committee for Standardization: Warsaw, Poland, 2012.
[63] Jasie ́nko J. Połączenia klejowe i in ̇zynierskie w naprawie, konserwacji i
wzmacnianiu zabytkowych konstrukcji drewnianych. Wrocław: Dolno ́sląskie
Wydawnictwo Edukacyjne
2003.
[64] Masłowski P, Spi ̇zewska D. Wzmacnianie konstrukcji drewnianych. Warszawa:
Arkady
2000.
[65] Neuhaus H. Budownictwo drewniane, Polskie Wydawnictwo Techniczne 2004.
[66] Abaqus/CAE ver. 6-12.2, User manual, dassault systemes simulia Corp., 2012.
[67] Structural Timber—Strength Classes
PN-EN 338:2016-06
Polish Committee for
Standardization: Warsaw, Poland, 2016. 
DOI