Diego Henrique de Almeida

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.

Restoration of Structural Timber Elements Using Epoxy Resin: Analysis of Mechanical Properties

Brazil cultural heritage is composed by numerous constructions that describe the various historical periods lived by country. Constructions arent in good conservation status, showing systematically some deterioration level of their structural elements, among them those of wood. Restoration process aims to preserve the identity of original cultural heritage. It is essential maintain structural characteristics related to mechanical loads response which are closely dependent on wood properties avoiding possible structural shocks. Wood deterioration can be characterized by fungi decay or termite attack. Depending on level and position of the deteriorated area in structural set, local interventions are enough to maintain structural integrity. Polymeric resins are material options that can be used when removed these deteriorated regions, requiring compatibility with wood to maintain structural elements properties. This paper aims use of a technical for restoring structural timber from historic buildings, based on removal of decayed regions and filling them with epoxy resin. To analyze restoration effectiveness, properties in static bending, according to Brazilian standard, were determined. Samples were produced containing one and three restorations along the specimens (105 cm in length and nominal square cross section of 4.5 cm side), on the same side. Samples of Pinus taeda with gaps generated in the specimens with dimensions of 1.10 cm in depth and 8 cm in length were tested, with restorations placed in central region. For grafting of these gaps bicomponent epoxy resin was employed, prepared by mixing components in 1:1.5 proportions. Resin was injected into splices and its cure occurred in a seven days period, using methodology restoration to simulate a situation in which these structural elements have been used. Samples were requested in static bending to obtaining the product of inertia, analyzing the amendment under the aspect of tractioned and as well under compressed edge. It is observed the viability of restoration using filling epoxy resin in timber samples, considering the mechanical performance and practicality of the methodology for local keeping.

Influence of Proportion Polyol/Pre-Polymer Castor-Oil Resin Components in Static Bending Properties of Particleboards Produced with Pinus sp.

The aim of this research is to evaluate the influence of castor-oil based polyurethane resin formulation (particularly proportion pre-polymer/polyol) in static bending properties of particleboards produced with Pinus sp. wood specie. Results related to modulus of rupture (MOR) and modulus of elasticity were determined. Four proportions polyol/pre-polymer were evaluated: 0.75:1; 1:1; 1:1.25; 1:1.5. Results showed improvement in MOR and MOE with increase of pre-polymer component. Proportion 1:1.25 (poliol: pre-polymer) was considered the most interesting once employs the least amount of the petroleum-derived component.

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.

Influence of growth ring orientation of some wood species to obtain toughness

Wood toughness is a mechanical property of interest in structural design where the load impact must be considered, finding a strong application in bridges, however, not an integral part of the mechanical properties commonly investigated in the characterization of this material. This study aimed to investigate with the aid of variance analysis, the influence of growth ring orientation to obtain toughness for Angelim Saia (Parkia pendula), Eucalyptus grandis, Pinus elliottii and Corymbia citriodora wood species, considering three different positions, so that the orientation causes tensile strength in fibers near the pitch, near the bark, and in the radial direction. The results of the statistical analysis revealed that there was no significance in the orientation of the growth rings to obtain the toughness of the wood species investigated, where the highest values were for Corymbia citriodora and the least values were for Pinus elliottii.

Modulus of Elasticity of Schizolobium amazonicum Wood Evaluated by Transversal Vibration Technique

Schizolobium amazonicum is being much used in Brazil for several purposes because, besides being a native Brazilian wood specie, has important features such as low density and small incidence of natural defects. At this point, researches with the purpose of obtaining further knowledge of their properties are being conducted to better targeting their use. The aim of this research is to evaluate the modulus of elasticity of structural size pieces of Schizolobium amazonicum wood using the technique of transverse vibration. Tests were carried out using 30 pieces (standard moisture content 12%) with sizes of 3 cm x 15 cm x 2.5 m. The average value of elastic modulus determined for lumber of Schizolobium amazonicum was interesting to its low specific gravity.

Hardness of the Schizolobium amazonicum Wood

Brazil has an infinity of native species that provide wood with good properties for use in civil engineering, industries and other segments. Schizolobium amazonicum Wood is a species that is much used in Brazil to manufacture of wood based-products. Researches regarding the properties are being performed in order to rationalize their use. The aim of this research is to determine the hardness of the Schizolobium amazonicum Wood in directions parallel and normal to the grains. The tests occurred in accordance with the Brazilian Code ABNT NBR 7190: 1997. The average values determined were interesting hardness upon the low specific gravity presented by Schizolobium amazonicum Wood.

Módulo de elasticidade em vigas de madeira de dimensões estruturais pelo método dos mínimos quadrados

Este trabalho propoe uma metodologia alternativa de calculo fundamentada no Metodo dos Minimos Quadrados para a obtencao do modulo de elasticidade na flexao de vigas de madeira com dimensoes estruturais. As equacoes desenvolvidas requerem o conhecimento de um ou cinco pontos de deslocamentos medidos ao longo do comprimento das pecas. Esse metodo permite maior precisao sobre a variavel resposta e tem como base o ensaio de flexao estatica a tres pontos. A metodologia proposta foi empregada em concordância com as recomendacoes da norma Brasileira NBR 7190:1997, adaptada para pecas de dimensoes estruturais. Os ensaios mecânicos foram realizados em sete pecas de madeira Corymbia citriodora com 540cm de comprimento, 15cm de altura e 5cm de largura. Em testes preliminares determinou-se o valor da forca responsavel por provocar um deslocamento vertical no meio do vao de L/200, sendo L a distância entre os apoios das vigas. A forca obtida foi dividida em sete incrementos iguais (39,60N), fornecendo sete valores de deslocamento distintos. Os resultados de ambas as metodologias mostraram-se convergentes a medida que os deslocamentos se aproximaram da razao L/200, validando o uso desta relacao. Os resultados do intervalo de confianca entre medias indicaram equivalencia estatistica entre os modulos de elasticidade por ambas as formas de calculo e para os sete incrementos de deslocamentos. Em razao da possivel presenca de defeitos e da heterogeneidade da madeira, os resultados obtidos nao devem ser extrapolados para outras madeiras de mesma ou de especies diferentes, justificando o uso da presente metodologia de calculo em cada pesquisa desenvolvida.

Nondestructive Evaluation of Timber Columns of a Capela Bridge in the State of São Paulo, Brazil

After years of exposure in environmental conditions, the wood is subject to decay by chemical, mechanical, physical and biological agents. Consequently its physical and mechanical properties can be reduced, affecting their use. Timber used in bridge sustention columns is subject to intense decay process, mainly in outcrop area (area in contact to the ground), the most critical situation, because of the best combination of humidity e oxygen, factors that provide wood decay organisms. Decay process can be minimized with preventive maintenance, as wood impregnation with preservatives, before installation of the timber. After wood is installed, a periodical maintenance is necessary to conserve and prolong its life time. Thus, the aim of this study is to evaluate degradation occurred in timber columns used in Capela Bridge sustention, built with mixed system of wood and concrete, after 10-years-old of use. Located in Piracicaba - SP, Brazil, the bridge was made with Corymbia citriodora CCA-treated. The columns strength and degradation conditions were evaluated in 2 points with isntrumented driller. Point A was approximately 1,5 m of the ground and point B was in outcrop area. Instrumented driller results showed that all the columns, in both points, presented good strength and had no degradation level.

Technical Feasibility Study for the Use of Alternative Timber in Latticework for Roofing with Spans between 16 and 26 Meters

Wood, a renewable source material, has been part of the progress of mankind, being widely used in construction for centuries. However, with the passage of time, new construction techniques were being applied, new materials have been rising and, in the meantime, wood was being left out, being labelled as a material with huge incidence of pathologies. That due to its empirical use without any technical knowledge regarding its physical and mechanical properties, which still happens nowadays, being used mainly for temporary purposes. In order to show the technical viability of the use of this material as a structural element, the elaboration of projects with the following characteristics was proposed: buildings with truss structures (parallel chord) type Howe (10° inclination - steel tile); 16, 18, 20, 22, 24 and 26 meters span; side openings types of the building – 1:1, 2:1, 6:1 and open; preservative treatment. Thus, it was determined the ratio of the volume of wood (m³) and the built area (m²) for timbers classes C-20 and C-30, following the NBR 7190:1997 guidelines. With the results, it is possible to assure the real possibility of using wood species C-20 and C-30 as structural material.