Antonio Alves Dias

Analysis of the strength and stiffness of timber beams reinforced with carbon fiber and glass fiber

An experimental analysis of pinewood beams (Pinus caribea var hondurensis) reinforced with glass and/or carbon fibers is discussed. The theoretical model employed to calculate the beams bending strength takes into account the timbers ultimate limit states of tensile strength and failure by compression, considering a model of fragile elastic tension and plastic elastic compression. The validity of the theoretical model is confirmed by a comparison of the theoretical and experimental results, while the efficiency of the fiber reinforcement is corroborated by the increased strength and stiffness of the reinforced timber beams.

Avaliação da eficiência térmica de telha reciclada à base de embalagens longa vida

This paper presents a study of the influence of roof tiles made of recycled long-life packaging (brand-name IBAPLAC®) on the thermal comfort of zootechnical facilities. The research was conducted at UNESPs Experimental Campus at Dracena, State of Sao Paulo, Brazil. Four prototypes were built, each with an area of 28 m2. One prototype was covered with roof tiles made of recycled long-life packing material and three reference prototypes were roofed with ceramic tiles, ceramic tiles painted white and fiber/cement tiles (Brasilit®), respectively. Black globe thermometers and dry and wet bulb thermometers were installed inside the prototypes. Temperatures inside the structures were recorded in the Summer of 2006/2007 over a 90-day period. A descriptive statistical analysis was made, based on the mean values of black globe temperature and humidity index, radiant thermal load and temperature-humidity index of the period. The results obtained indicated that the thermal behavior of the recycled tile was similar to that of the ceramic tiles.

Tenacidade da madeira como função da densidade aparente

The knowledge on the behavior of wood in situations of short load contributes to the development of a safer structural design. However, toughness is not part of the mechanical properties commonly investigated in the characterization of this material. Therefore, the present study aimed to evaluate, the possibility to estimate the toughness with the knowledge of the apparent density of 6 Brazilian tropical wooden species (Angico, Eucalyptus, Jatoba, Parica, Pine and Teak), by using linear, quadratic and cubic polynomial regression models. The results highlighted the significance and representation of all adjustments investigated, and the cubic polynomial was the most efficient for estimating the wood toughness.

Vigas mistas de madeira de reflorestamento e bambu laminado colado: análise teórica e experimental

This paper presents and discusses the experimental and theoretical analyses of layer composite beams of wood strengthened with bamboo. For this, the mechanical behavior of five composite beams and two wood beams was studied. The beams stuffing was composed of Pinus elliottii and the reinforcement of bamboo Dendrocalamus giganteus. The bamboo reinforcement was placed on the top and at the bottom of the beams. Different thicknesses of reinforcement were investigated. Curves of load vs. displacement and load vs. strain are presented. An increase of 50% was observed in the stiffness, when the composite beams are compared with the wood one. Finally, a numerical study was carried out applying the finite element method and a good agreement was observed between the theoretical and experimental values.

Influência de diferentes materiais de cobertura no conforto térmico de instalações para frangos de corte no oeste paulista

Este trabalho apresenta um estudo da influencia de diferentes materiais de cobertura no conforto termico de instalacoes destinadas a criacao de frangos de corte. A pesquisa foi desenvolvida no Câmpus Experimental da UNESP de Dracena - SP. Quatro prototipos em escala real foram construidos, com area de 28 m2 cada, cobertos com telha reciclada a base de embalagens longa vida, telha cerâmica, telha cerâmica pintada de branco e telha de fibrocimento. Os dados foram coletados durante o periodo de inverno de 2007, totalizando 90 dias. Com esses dados, foram calculados os indices de conforto termico Carga Termica Radiante (CTR) e a variavel ambiental (Ta). Uma analise estatistica por inferencia e descritiva foi realizada com os valores do indice de conforto termico e da variavel ambiental. Com os resultados obtidos, e possivel afirmar que a telha reciclada apresentou indices de conforto termico semelhantes aqueles encontrados para as telhas cerâmicas. O prototipo coberto com telha de fibrocimento apresentou os maiores indices, e o coberto com telha cerâmica branca, os menores indices de conforto termico. No entanto para o periodo de inverno e para os horarios avaliados, todas as instalacoes apresentaram indices de conforto termico fora da zona de termoneutralidade do frango de corte.

Propriedades mecânicas de peças com dimensões estruturais de Pinus spp: correlação entre resistência à tração e classificação visual

The reduction in the availability the native lumber species and its effects on the economy, associated to the invigoration of the concepts of environmental preservation created the necessity of the development of viable alternatives for rational use of reforestation species. One of the options is the accomplishment of visual grading of the pieces. Research works verified the adaptation of the rules of visual grading of Southern Pine Inspection Bureau (SPIB) of the USA for the Brazilian lumber Pinus, presenting a proposal to normalize the process of visual grading of this lumber. In this classification, the most important aspects are the presence of knots, the inclination of the grain in relation of the axis of the piece and the density of growth rings. Therefore, the current work presents an experimental study consisting of a visual grading and determination of the stress strength of 85 Pinus spp pieces and a theoretical study that presents an equation to establish the average strength strain of structural pieces according to the visual grading. With this work, it was possible to observe the influence of the knots and growth rings in stress strength of the analyzed pieces.

Evaluation of glued laminated timber beams of cedrinho (Erisma uncinatum Warm.)

Glued laminated timber (glulam) is assembled layers of bonded pieces of timber. In Brazil, the use of native species timber to produce structural elements of glulam does not occur in satisfactory technological conditions. This is because the properties and performance of native species of wood, under various service conditions, are not entirely known. This study aims at determining and to relate the dynamic modulus of elasticity (E Mvt ) and the static modulus of elasticity (E M ), the modulus of rupture (f M ), the compression parallel strength (σ cp ) and the parallel elastic modulus (E cp ), and evaluating the performance of the native species Cedrinho (Erisma uncinatum Warm.) in the construction of glulam beams. Glulam beams were produced with random and nonrandom distributions of graded pieces of bonded lumber by using adhesives of phenol resorcinol formaldehyde (RFF) and polyurethane (PUR); the intensity of pressures used was 0.8 MPa and 1.2 MPa. The evaluation of these glulam beams was also performed using samples of compression parallel to glue lines and delamination. It was found that the E Mvt obtained by transverse vibration dynamic testing revealed a correlation coefficient with the E M obtained on static bending test (R 2 = 0.86) and significance level of 1% probability (P < 0,01). Thus, it can observed that the E Mvt is a good estimator of E M. It was found that this wood species may be used for glulam, and that the hardwoods species is in strength class C30.

Avaliação do módulo de elasticidade de peças de madeira laminada colada (MLC) obtido por meio do ensaio de vibração transversal

O controle da qualidade e fundamental no processo de fabricacao de pecas de madeira laminada colada (MLC), e uma das formas desse controle pode ser por meio da avaliacao nao destrutiva do modulo de elasticidade. O objetivo deste trabalho foi comparar os valores de modulo de elasticidade das pecas de MLC obtidos por meio do ensaio de vibracao transversal livre e do ensaio de flexao estatica, ambos feitos antes e apos tratamento preservativo (contra a acao de agentes biologicos), realizado pelo processo de Celula Cheia. No total, foram produzidas 54 pecas de MLC de dimensoes nominais de 9 cm x 9 cm x 200 cm, com tres especies de madeira de reflorestamento coladas com dois adesivos de aplicacao estrutural e tratadas com tres preservantes. Foi obtida uma correlacao significativa entre os valores do modulo de elasticidade obtidos pelos dois metodos (r variou entre 0,85 e 0,99). Concluiu-se que o ensaio de vibracao transversal livre pode ser utilizado para avaliacao do modulo de elasticidade de pecas de MLC, sendo uma alternativa ao ensaio de flexao estatica.

COMPARISON BETWEEN TEST METHODS TO DETERMINE WOOD EMBEDMENT STRENGTH PARALLEL TO THE GRAIN

This study compares the test methods according to the ABNT NBR 7190:1997, EN 383:2007, ASTM D5764:2007, EUROCODE 5:2004, NDS:2001 standards in order to provide support to establish a new test method for determining the embedment strength of wood parallel to the grain. Parallel-to-grain tests were carried out for six wood species (Schizolobium amazonicum; Pinus elliottii; Pinus oocarpa; Hymenaea spp.; Lyptus(r): hybrid Eucalyptus grandis and Eucalyptus urophylla, and Goupia glabra) using four diameters (8 mm, 10 mm, 12 mm and 16 mm) for the metal pin fasteners (bolts). The experimental results obtained according to the EN 383:2007 standard were closer to the specific values for the metal-dowel connections design used by ABNT NBR 7190:1997, which are considered equal compression parallel to the grain. The use of maximum embedment force or the force causing displacement of 5 mm between the bolt and the test-piece as criteria for determining embedment strength for EN 383:2007 appears to be more appropriate than the criteria used by the Brazilian and American Standards.

Natural Fiber-Reinforced Polymer for Structural Application

The glued laminated lumber (glulam) beams technique is an efficient process for making sustainable use of wood. Fiber-reinforced polymers (FRPs) associated with glulam provide significant gains in terms of strength and stiffness, as well as modify the rupture mode of these structural elements. Certain natural fibers display sufficient mechanical properties to reinforce the polymer used in the glulam technique. This chapter presents a theoretical analysis considering the behavior of stressed lumber and fibers in glulam beam of Pinus sp. and Eucalyptus sp. with and without natural fiber-reinforced polymer (NFRP), and a numerical analysis evaluating the stresses and displacements in glulam beams using the finite element method. Curaua, bamboo, and jute fibers were used for reinforcement. NFRP introduced in the tensioned section of glulam beams guaranteed a gain of strength and stiffness in function of the thickness percentage of NFRP used. In terms of maximum stresses and vertical displacement, theoretical and numerical analyses provided analogous results.