André Luis Christoforo

Metodologia para o cálculo dos módulos de elasticidade longitudinal e transversal em vigas de madeira de dimensões estruturais

This paper proposed a test method to obtain the shear (G) and longitudinal (E) modulus of elasticity in timber beams with structural dimensions, based on the static three-points bending tests and the Euler Bernoulli and Timoshenko beams theories. The woods tested were the Corymbia citriodora and Pinus elliottii. The results revealed that the longitudinal modulus of elasticity of Pinus elliottii is 18.70 greater than the shear modulus, and 21.16 greater than the shear modulus of Corymbia citriodora, being consistent this results when compared to the proposed by the Brazilian standard ABNT NBR 7190:1997 (Design of Wood Structures), being the longitudinal modulus of elasticity twenty times greater than the shear modulus.

The position effect of structural Eucalyptus round timber on the flexural modulus of elasticity

Round timber has great use in civil construction, performing the function of beams, columns, foundations, poles for power distribution among others, with the advantage of not being processed, such as lumber. The structural design of round timber requires determining the elastic properties, mainly the modulus of elasticity. The Brazilian standards responsible for the stiffness and strength determination of round timber are in effect for over twenty years with no technical review. Round timber, for generally present an axis with non-zero curvature according to the position of the element in the bending test, may exhibit different values of modulus of elasticity. This study aims to analyze the position effect of Eucalyptus grandis round timber on the flexural modulus of elasticity. The three-point bending test was evaluated in two different positions based on the longitudinal rotation of the round timber element. The results revealed that at least two different positions of the round timber element are desired to obtain significant modulus of elasticity.

Oat hulls as addition to high density panels production

Wood panels manufacture show advantages of possibility to use alternative raw materials, as agro-industrial waste. Such products have increasing their importance, representativeness and use around the world, including Brazil, stimulated by the economic and environmental benefits of natural and renewable raw materials.Considering wood-based panels from reconstituted wood, particleboard can be highlighted because it is the most consumed and produced worldwide (Brazilian Association of Wood Panels Industry – ABIPA)

Numerical evaluation of the modulus of longitudinal elasticity in structural round timber elements of the Eucalyptus genus

Currently, the standards that deal with the determination of the properties of rigidity and strength for structural round timber elements do not take in consideration in their calculations and mathematical models the influence of the existing irregularities in the geometry of these elements. This study has as objective to determine the effective value of the modulus of longitudinal elasticity for structural round timber pieces of the Eucalyptus citriodora genus by a technique of optimization allied to the Inverse Analysis Method, to the Finite Element Method and the Least Square Method.

Emprego de ferramentas numéricas na avaliação do módulo de elasticidade em vigas roliças de madeira

Beams are structural elements used in the most of civil constructions. The wood can be found in several applications of engineering due to the moderate mechanical strength and low density. The use of round timber as a beam is very attractive, since it does not need to be processed, such as lumber. The design of structural timber elements requires the determination of its physical and mechanical properties in which are obtained based on the recommendations of engineering standards. In case of round timber, the national standards dealing with the determination of strength and stiffness properties are in term for more than twenty years with no technical review. Overall, both national and international standards consider truncated-cone geometry for cylindrical logs of wood, resulting in simplified equations unable to predict the effect of shape irregularities on the longitudinal modulus of elasticity. This paper aims to evaluate the effect of shape irregularity of round timber of Corymbia citriodora and Pinus caribaea to determine the longitudinal modulus of elasticity. The three-point bending test is used to determine the modulus, considering a simplified analytical model, with constant circular section for the element. The irregularities of the wood are considered in the numerical models based on a beam and three-dimensional finite elements. The results showed statistical equivalence between the modulus of elasticity for both methods of calculation, indicating that the constant circular section is a reasonable assumption for the wooden here evaluated.

Materiais compósitos particulados em matriz epóxi reforçados com serragem, cimento e silicato de magnésio

Este trabalho tem como objetivo investigar propriedades fisicas (densidade volumetrica e absorcao de agua) e mecânicas (modulo de elasticidade e resistencia a compressao) de materiais compositos particulados em matriz epoxi reforcados com serragem de madeira, cimento Portland e silicato de magnesio. Um planejamento experimental inicial foi elaborado envolvendo apenas a resina epoxi e a serragem de madeira. Posteriormente, elegeu-se o tratamento que forneceu os maiores valores para o modulo de elasticidade na compressao. Sobre a condicao escolhida, foram desenvolvidas outras quatro, incorporando-se 10% e 20% em fracoes massicas de particulas de silicato de magnesio e cimento Portland sobre a resina. Os compostos com 30% de serragem de madeira Eucalyptus grandis e faixa granulometrica 50-80 US-Tyler apresentaram os melhores valores para o modulo de elasticidade na compressao, sendo utilizados como condicao de referencia para a inclusao das particulas de cimento e do talco. O emprego do cimento nos compostos conferiu aumentos significativos no modulo de elasticidade a compressao, densidade e reducao na absorcao de agua. O mesmo nao ocorreu com a incorporacao de particulas de silicato de magnesio, a qual foi significativa apenas na absorcao de agua, sendo os maiores valores provenientes dos materiais fabricados com a adicao de 20%.

Influência da rigidez de ligações parafusadas em estruturas planas de madeira do tipo treliça

Trusses are structural systems commonly used in projects, being employed mainly in roof structures, present in most rural buildings. The design of trusses, as well as other structural systems, requires the determination of displacements, strains and stresses. However, the project is developed from an ideal model of calculation, considering free rotation between the elements of a connection. This paper presents a computer program for the analysis of bidimensional wooden trusses with connections formed with two screws per node. The formulation is based on the flexibility method, taking into account the influence of the effect of semi-rigid connections formed by two screws. An example of a structure is presented and analyzed by the program developed here, highlighting the importance of behavior analysis on semi-rigid connections.

Numerical Analyses of Timber Columns Reinforced by Particulate Composite Material

Beams are structural elements commonly used in structure for construction designs. Usually wood is applied as structural elements and its use is very important because it is a material of renewable source, low density and satisfactory mechanical performance. When the wood surface is not properly treated, the structure can be destroyed not only by environmental conditions but also the attack of insects, compromising the structural design. This research presents the use of a particulate composite material of epoxy resin reinforced with white Portland cement in order to be applied as repair in timber columns. The mechanical performance of this material is essentially numerical, based on the Finite Element Method. The wood used in the simulation was the Eucalyptus grandis. The elastic properties were obtained from the specialist literature in the field of timber structures. The results of numerical simulations in terms of tension and buckling loads, the inclusion of the composite in the damaged regions (for all dimensions of the defects studied) provided buckling load results significantly higher than the buckling load values for the conditions without composite, and near to the values of the buckling loads without defect, highlighting the good performance of the particulate composite material in the repair of timber columns. INTRODUCTION Columns and beams are fundamental elements in the majority of structures. In a building, we highlight the use of wood for being a renewable source material, presenting excellent relationship between strength and density, according to [1] this gets to be four times higher when compared to steel. The wood, which until the early twentieth century represented one of the main structural materials in construction [2]. The buildings constructed with wood require appropriate maintenance and use. According to [3], structural elements of wood are susceptible to variations in their mechanical properties due to natural factors, such as growing conditions Accepted: November 5, 2015 * Address correspondence to this author at the Centre for Innovation and Technology in Composites (CITeC), Department of Civil Engineering (DECiv), Federal University of São Carlos (UFSCar), São Carlos, 13565-905, Brazil; Tel: (+55) 16 33066828; E-mail: christoforoal@yahoo.com.br

15 – High performance fibre-reinforced concrete (FRC) for civil engineering applications

Abstract: Portland cement concrete is a brittle material. The main reason for incorporating fibres into a cement matrix is to improve the cracking deformation characteristics, increasing not only the toughness, impact and tensile strength, but also eliminating temperature and shrinkage cracks. Several different types of fibres have been used to reinforce cement-based materials. This chapter briefly discusses the characteristics of fibre-reinforced concrete (FRC), reporting the effect of the fibres on the physico-chemical and mechanical properties. It also presents some of the recent research and future perspectives of FRC.

Evaluation of strength to shear and delamination in glued laminated wood

The Glued Laminated Wood has a large range of applications. In Brazil, its employment as cross-piece poles for overhead electrical power has attracted the attention of companies in the industry, motivated by the potential use of this material. Among the factors that influence the mechanical performance of Glulam solutions stand out efficiency and affinity of the adhesives to the species of wood used, the type of treatment and moisture content of wood veneer, motivating the development of new research on this topic. This research aimed to investigate, by Design of Experiments (DOE), the influence of wood (pinus, teca, eucalipto), adhesive (Purbond; Cascophen) and treatment (CCA, CCB, CCBS ) in the variable responses shear strength and delamination, consisting in the same combination factors evaluated in ANEEL/EESC-PD220-07 project: Head Crosshead Glulam Series. The results of the statistical analysis showed that the species factor expressed significant effect for both response variables evaluated, did not occur with adhesive and treatment factors. Moisture content was significant in the wood evaluated when analyzed the shear strength, and the teca wood showed the highest shear strength and also relating to the delamination.