Glued laminated timber beams reinforced with sisal fibres

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 verified8439039

On the effect of the number od annual growtn rings, specific gravity and temperature on redwood elastic modulus

Debido al origen natural de la madera, parámetros físicos como la gravedad específica y el número de anillos de crecimiento afectan sus propiedades. En este estudio para evaluar el efecto que estos parámetros físicos tienen sobre las propiedades elásticas de la madera, particularmente en el módulo de elasticidad, ensayos de compresión uniaxial se realizó en especímenes. Estos especímenes consistieron en cubos sólidos de la especie de madera Redwood con lado de 10,16 cm. Tres diferentes condiciones de temperatura, temperatura ambiente (18 ° C), temperatura abajo de cero (-28 ° C) y alta temperatura (65 ° C), fueron utilizados para llevar a cabo las pruebas. La gravedad específica osciló entre 0,29 a 0,45 y el número de anillos de crecimiento varió de 2 a 24 anillos por pulgada. El mínimo contenido de humedad en las muestras fue del 2% y alcanzó un máximo del 16% de acuerdo a las condiciones de temperatura. Los resultados del análisis estadístico indicaron que el efecto que el número de anillos de crecimiento por pulgada tiene en el módulo de elasticidad es más importante que los efectos de la gravedad específica o incluso que el de la temperatura. En consecuencia, se sugiere aquí que el número de anillos de crecimiento por pulgada pueda ser utilizado como predictor del módulo de elasticidad de la madera

ON THE EFFECT OF THE NUMBER OF ANNUAL GROWTH RINGS, SPECIFIC GRAVITY AND TEMPERATURE ON REDWOOD ELASTIC MODULUS

Due to the natural origin of wood, physical parameters such as specific gravity and the number of growth rings per inch affect its properties. In this study, to evaluate the effect that these physical parameters have on the elastic properties of wood, particularly on elastic modulus, a uniaxial compression test was performed on specimens. These specimens consisted of solid cubes of the Redwood species of wood with a width of 10.16 cm. Three different temperature conditions-ambient temperature (18° C), cold temperature (-28° C) and hot temperature (65° C)-were used to carry out the tests. Specific gravity ranged from 0.29 to 0.45, and the number of growth rings per inch varied from 2 to 24 rings per inch. The minimum moisture content in the specimens was 2%, and reached a maximum of 16% according to the temperature conditions. The results from the statistical analysis indicated that the effect that the number of growth rings per inch has on elastic modulus is more significant than the effects of specific gravity or even of temperature. As a consequence, we suggest that the number of growth rings per inch can be used as a predictor for wood elastic modulus.Debido al origen natural de la madera, parámetros físicos como la gravedad específica y el número de anillos de crecimiento afectan sus propiedades. En este estudio para evaluar el efecto que estos parámetros físicos tienen sobre las propiedades elásticas de la madera, particularmente en el módulo de elasticidad, ensayos de compresión uniaxial se realizó en especímenes. Estos especímenes consistieron en cubos sólidos de la especie de madera Redwood con lado de 10,16 cm. Tres diferentes condiciones de temperatura, temperatura ambiente (18 ° C), temperatura abajo de cero (-28 ° C) y alta temperatura (65 ° C), fueron utilizados para llevar a cabo las pruebas. La gravedad específica osciló entre 0,29 a 0,45 y el número de anillos de crecimiento varió de 2 a 24 anillos por pulgada. El mínimo contenido de humedad en las muestras fue del 2% y alcanzó un máximo del 16% de acuerdo a las condiciones de temperatura. Los resultados del análisis estadístico indicaron que el efecto que el número de anillos de crecimiento por pulgada tiene en el módulo de elasticidad es más importante que los efectos de la gravedad específica o incluso que el de la temperatura. En consecuencia, se sugiere aquí que el número de anillos de crecimiento por pulgada pueda ser utilizado como predictor del módulo de elasticidad de la madera

Experimental investigation of glued-laminated timber beams with Vectran-FRP reinforcement

The growing interest in sustainable buildings has inspired the improvement of timber structures in the construction market. As a raw material, wood may present natural defects that can cause changes in its mechanical properties, such as strength reduction, as well as brittle failure under tension, which limit the application of this material in construction. In recent decades, synthetic fibers with high tensile strength are available as construction material, and research to evaluate the efficiency of synthetic fibers and adhesive composites as a reinforcement for glued-laminated timber beams has been carried out. This paper deals with an experimental study applying bending tests to glue-laminated timber beams made of Pinus Elliottii, a low-strength wood class originated from reforestation, and strengthened with fiber reinforced polymers of Vectran fibers and epoxy adhesive. A numerical procedure based on the finite element method is also developed to compare with experimental results. Vectran is a synthetic thermoplastic fiber with high mechanical properties, however, its potential application as reinforcement material in structural pieces is still poorly explored. The results obtained in this work demonstrated that the application of Vectran-FRP reinforcement to glued-laminated timber beams provided both an increase of 19.48 to 34.95% in elastic regime stiffness and of 7 to 40% in ultimate load, when compared with unreinforced similar beams. Numerical analysis adequately confirmed the experimental results on elastic behavior, while in the non-elastic phase it revealed a considerable difference. A reduction in the rupture coefficient of variation regarding the reinforced beams was also verified. In addition, the application of fibers as structural reinforcement changed the timbefs failure mode from brittle in tension to ductile in compression. The results show that Vectran fibers are mechanically efficient as reinforcement, with perspectives of application in construction202CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQBrazilian National Council for Scientific and Technological Development (CNPq)National Council for Scientific and Technological Development (CNPq); University of Campinas (UNICAMP); School of Civil Engineering, Architecture and Urban Desig