Analysis of Fiber Reinforced Laminated Timber Beams

Abstract

The necessity to restore the design specifications of a determined structure, combined with cost, weight and environmental impact reduction makes the use of high performance composite systems, involving, either synthetic or natural materials, interesting. By applying a layer of fiber reinforcement bonded with the glued laminated timber beam (Glulam) with an appropriate adhesive, a high performance composite system is obtained, resulting on a significant increase of strength and bending stiffness of the structural element that each isolated material did not have before. This paper carried out an analysis of the feasibility of use synthetic and natural fibers as alternative to structural reinforcement to laminated timber beams, made of the reforestation wood species Pinus caribea and Eucalyptus grandis that represent respectively two resistance classes of monocotyledon and dicotyledonous, exposing, through an analytical model. The numerical results obtained from the analysis of the Glulam beams reinforced with glass, carbon, Vectran® and natural fibers such as sisal fibers, are compared among each other considering cost, weight and gain of resistance and stiffness. It is observed that for small lengths (and therefore, small cross sections), the use of Vectran® fiber is not the best option, since an equivalent resistance gain can be obtained by applying a thicker layer of glass fiber, once it possesses a lower cost and a non-significant impact on the final structure's weight. For all the other considered cases, the choice of the Vectran® fiber is very interesting, since on these situations a thicker layer of glass fiber does not provide much cost reduction and is not enough to achieve the desired strength without increasing the structure's weight significantly. Regarding the sisal fiber, it is a material that is easy to find and with a low cost in Brazil, its utilization is interesting when working with low resistance wood species. Although the gain of resistance provided by this fiber as a reinforcement material is fairly low, the desired result can be obtained by increasing the thickness of the reinforcement layer, which still keeps the cost and weight of the reinforced element much smaller than those resulting from the implementation of a thinner layer of glass fiber.