Glued Laminated Timber Beams Reinforced With Sisal Fibres Nilson T. Mascia, Bruno F. Donadon, and Ramon Vilela University of Campinas/FEC, Campinas, Brazil Email: nilson@fec.unicamp.br, donadon.bf@gmail.com, ramonvilela@outlook.com Abstract—The current appeal for sustainable building materials has expanded the use of timber in construction. However, due to timber be a raw material, natural defects are present, what reduce its strength capacity and cause, in particular, brittle failures in the tensile region of timber beams. In order to increase the mechanical properties of these beams, fibre reinforcement can be applied. In this context, natural fibres, such as Sisal fibres, already used in various fields of construction, are an alternative for reinforcement of timber structural elements, by taking into account their adequate mechanical properties and, in special, for low-mechanical resistance wood species, such as Pinu sp, a species used widely in timber construction. This paper deals with an experimental analysis glued laminated timber beams (Glulam) of Pinus sp species, reinforced by Sisal fibres. Bending tests were performed on six beams with the following dimensions, 53 mm-width by 180 mm- height by 3000 mm-length, which were prepared with eight lamellas by 8 mm-thickness. These beams were reinforced with Sisal strips that were glued by Epoxy adhesive on the bottom part of these beams. In addition, comparisons of result with non-reinforced Glulam were carried out. From the analyses of the experimental results, a decrease of 20 to 30% for the normal stresses, 5 to 10% for the shear stresses and 8 to 12 % for the displacements in relation to non- reinforced beams were verified. Index Terms—natural fibres, Sisal fibres, Glulam, reinforcement, bending test I. INTRODUCTION In long duration life, structural systems are subjected to permanent and variable loads, chemical and biological agents´ interaction or design load variations. These actions can affect a structure in such way that it can no longer maintain its initial design resistance, causing the necessity to repair or reinforce it. According to Ref [1], there are two main methods to rehabilitate affected timber elements, which are: (i) the replacement of the damaged sections; (ii) the utilization of reinforcement materials that complement the mechanical resistance of the damaged timber structural elements. The main issue with the first solution is that it is sometimes restricted by various facts, such as environmental impact, lack or incompatibility of the required wood species and high costs. This generates the necessity to seek other effective alternatives, as the Manuscript received September 4, 2018; revised June 25, 2019. second method, turning the use of FRP (Fibre Reinforced Polymers) materials into a very interesting option that deserves to be specifically studied. Addressing to composite materials used in constructions, they can be divided into three major groups: fibrous composites, laminated composites and particulate composites, with a possible combination among these types [2]. The laminated composites formed by the union of lamellas can consist of the same or different materials or also have different geometrical characteristics and dimensions. Focusing on glued laminated timber beams, it is important to consider the natural defects, such as knots, or the orientation of the fibres, that can influence the mechanical characteristics of the lamellas and in the beam as a whole. This affects the timber mechanical properties reducing, for example, the tensile strength and can cause a brittle failure with a lesser load than the one established in structural design [3]. Thus, the use of fibres as a reinforcement of the structural elements intends to avoid the brittle failure and increase the tensile strength as well. As found in technical literature, natural fibres have attracted attention for presenting adequate mechanical characteristics for such application. The use of natural fibres, as Sisal fibres for example, associated with glued laminated timber beams, in particular, those manufactured with wood species from reforestation, is in accordance with the current economic interest and sustainable appeal [4]. The Sisal fibres are commercialized in Brazil in several formats such as: fabric, cords, strips, wire, rolls, etc. Table I presents the tensile strength and the modulus of elasticity for some fibres [5]. TABLE I. MECHANICAL CHARACTERISTICS OF NATURAL FIBRES Fibre Tensile Strength(MPa) Modulus Elasticity (GPa) Coconut 131-175 4-13 Sisal 511-635 9,4-22 Curauá 859-1404 20-36 Juta 393-773 26,5 The failure strength and the modulus of elasticity, besides the lengthening in rupture, depend on the amount 390 International Journal of Structural and Civil Engineering Research Vol. 8, No. 4, November 2019 © 2019 Int. J. Struct. Civ. Eng. Res. doi: 10.18178/ijscer.8.4.390-397