Prestressed glulam beams reinforced with CFRP bars

Abstract

9This paper describes an experimental test program and theoretical analysis which examines the reinforcing in flexure 10 of glued laminated timber (glulam) beams using bonded-in carbon fiber reinforced polymer (CFRP) bars. A series of 11 four-point bending tests were conducted till failure on unreinforced, passively reinforced and prestressed Douglas fir 12 glulam beams in a simply-supported scheme. The focus of this research was to evaluate the reinforcing efficiency of 13 both passively reinforced and prestressed beams. Test results showed that the flexural capacity of the reinforced, 14 prestressed, prestressed & reinforced (bottom prestressed and top reinforced) beams greatly increased by 64.8%, 15 93.3% and 131%, respectively. While the maximum improvement of the bending stiffness reached 42.0%. Another 16 important finding was that the extreme fiber tensile strain of timber beams at failure could be remarkably increased 17 due to the presence of the tension reinforcement, which indicated it overcomes the effects of local defects and 18 therefore the failure mode was changed from brittle tension failure to ductile compression failure. Based on the 19 experimental results, a theoretical model was proposed to predict the flexural capacity of unreinforced, reinforced 20 and prestressed timber beams, which was validated by the test data. 21 2 in Europe and is widely used nowadays in buildings and bridges [1]. Glulam has an excellent strength-to-weight ratio, 27shape and size flexibility, as well as high strength and dimensional stability. 28However, despite all of these benefits, glulam beams are usually underused due to the naturally defects such as knots 29 and cross grain [2]. Another problem is the relative low stiffness as a result of which the design of glulam beams is 30 often controlled by deflection limits [3]. For these reasons, many attempts have been made to reinforce or strengthen 31 glulam or solid timber beams by using high tensile strength materials. In the earlier decades, the majority of this 32 work focused on the use of metallic reinforcement [4][5][6][7]. More recently fiber reinforced polymers (FRP) was used as 33 structural reinforcement for timber beams, which in the form of sheets, plates and bars [8][9][10][11][12][13][14][15][16][17][18][19]. It showed from these 34 researches that the reinforcement in the tension zone would improve the strength, stiffness and ductility. Furthermore, 35 both short-term and long-term deflections of the reinforced timber beams were decreased [3,20]. 36But the reinforcing materials usually has a notable higher ultimate tensile strain than that of wood, which means it 37was not effectively used while the failure occurs in this kind of timber members with passive reinforcement. Thus its 38 economic efficiency was argued by some researchers [21,22]. Attempt then was made by introducing prestress in 39 reinforcing materials [2,[23][24][25][26][27]. As a result, the flexural strength is further increased due to the full use of both FRP 40 and wood, while bendi...

Mechanical Properties of Laminated Veneer Lumber Beams Strengthened with CFRP Sheets

“…However, the best results of the increase in bending strength and cross-section stiffness are achieved by using reinforcement in both zones [13]. The most often used composite materials are fabric sheets [1,14], laminates [6,22], and rods [8,21] reinforced with:…”

Flexural Property of String Beam of Pre-Stressed Glulam Based on Influence of Regulation and Control

“…At present, scholars at home and abroad have carried out a series of researches on the mechanical properties of glulam beams [Fava, Carvelli and Poggi (2013); Franke, Franke and Harte (2015); Sinha, Way and Mlasko (2014); Issa and Kmeid (2005)] in order to strengthen glulam with new materials [Uzel, Togay, Anil et al (2017); Ribeiro, Abílio, Lima et al (2009); Ferrier, Labossière and Neale (2012); ; Wei, Ji, Duan et al (2017); Anshari, Guan, Kitamori et al (2012); Zhong, Wu, Ren et al (2017); Fang, Sun, Liu et al (2015)]. In order to improve the flexural property of glulam beams, make full use of materials and increase the application scope of glulam beams, scholars at home and abroad put forward the idea of applying pre-stress to ordinary wood beams and glulam beams, and made a series of explorations, mainly including two aspects: application of pre-stress through stretching the pre-stressed tendon and tensioning fibre materials [Guo, Wang and Zuo (2017); Luca and Marano (2012); D'Aveni and D'Agata (2017); McConnell, McPolin and Taylor (2014); Yang, Ju, Liu et al (2016); Guan, Rodd and Pope (2005); Negrão (2016)] . At present, scholars at home and abroad haven't carried out the research on the flexural property of string beams of pre-stressed glulam based on the influence of regulation and control, so this study is of great significance.…”

Studying the influence of the cross section height on the distribution of the internal efforts of wooden glued beams

“…In addition, in order to increase the bearing capacity and to reduce the cross section of the bent elements, reinforcement with steel or composite rods is used. [3,4] When selecting the cross section of reinforcement, to strengthen wooden structures, it is necessary to take into account not only its strength, but also elastic characteristics, since the ratio of normal stresses in reinforcement and wood during their normal joint operation depends on the ratio of their elastic modulus. [5] In addition to this, an important point is the design of structures, taking into account the full use of the physicomechanical and operational properties of wood and reinforcing material.…”