Bøger af André Luis Christoforo

The wood used in Brazil is in the transition stage from an artisanal model to the industrialized model and its neglected production of essential properties (physical-mechanical properties) for the elaboration of a structural timber design. The use of renowned species on the market results in an excessive consumption of some native species, so the substitution of these species by others with similar properties decreases the large-scale use of the most usual species in the lumber market. The present work studied the possibilities of the use in the civil construction of the wood species Pradosia sp. for structural purposes. The study lot is a wood native to Brazil, from the hardwoods class, and it belongs to the strength class C 60. In addition, the several tests and the cost to the accomplishment of the same ones fomented the search by a correlation between properties of the wood, the specific gravity being an easily obtainable measure related to the other properties by means of four regression models.

The present project aimed to characterize the wood of the species Qualea Albiflora (Mandioqueira), in order to enable its use for structural purposes. The tests to obtain the physical and mechanical characteristics were carried out according to the Brazilian standard ABNT NBR 7190 (1997), allowing the classification of the species as wood suitable for use in heavy constructions. After the characterization, it was verified with the aid of regression models (linear, logarithmic, exponential and geometric), that it is not possible to make use of the apparent density in the estimation of the other physical and mechanical characteristics, obtaining a bad adjustment in all the cases (R² 0.05).

This work aimed to characterize Clarisia racemosa (Oiticica-Amarela) wood specie, with the purpose of making its use feasible for structural purposes. The tests to obtain the physical and mechanical properties were carried out according to the premises established by Brazilian Standard ABNT NBR 7190 (1997), allowing the classification of such species belonging to strength class C60 (hardwood), as well as evaluating the possibility of estimation (linear, exponential, geometric and logarithmic models) of the physical and mechanical properties in function of the apparent density. The obtained values of the mechanical properties evidences the potentiality of the use of this species for structural applications. The results obtained from the regression models implied the possibility of estimating only the mechanical property compressive strength parallel to the grain (fc0) as a function of the apparent density (¿ap, 12%).

This book intends to develop mathematical modeling and illustrates the code program developed to analyze trusses under load considering physical and geometric non-linearities. It is performed the characterization of the structure, its peculiarities and the description of the calculation premises. Physical and geometric non-linearities are described and pointed out the elastoplastic behavior on the structure. The computation aspects and its implementation are discussed and it is presented some examples illustrating code programs.

Wood-based panels have been widely used around the world, replacing solid wood in various segments of the industry, such as furniture, panels, structures and other building components. The large volume of waste generated by agro industry enables the development of alternative and sustainable materials, highlighting the particleboard. This paper presents a study about production and evaluation of particleboard of Eucalyptus grandis and oat hulls, bonded under pressure with two types of resins (polyurethane based on castor oil and urea formaldehyde). Physical-mechanical performance of the panels produced was evaluated based on ABNT NBR 14810:2006, ANSI A208.1: 1999, BS EN 312: 2003 and CS 236-66: 1968. A variance analysis (ANOVA) evaluated the factors influence: Eucalyptus grandis, with mass ratios of 70, 85 and 100%; oat hulls, in proportions of 15, 30 and 100%; adhesives, in proportions of 10, 12 and 14%, and the combination of both, in each of the response variables (physical and mechanical properties) evaluated. Results showed good physical-mechanical properties, in some cases much higher than national and international codes requirements.

The purpose of present study was to create a theoretical model that allowed with security and reliability to obtain, values of strength and stiffness to which the structural element will be submitted throughout its useful life. The effect was studied for strength and stiffness properties, and the modulus of elasticity (EM) and bending strength (fM) were evaluated according to the increasing number of cycles of the fatigue test for the five classes of hardwoods, recommended by NBR 7190 (1997). These results allowed to construct a fatigue curve, relating the two variables as a function of the number of cycles (Nc) - construction of the curves EM x Nc and fM x Nc. The fatigue effect was present and pronounced in all strength classes. A reduction in strength and stiffness properties was observed with increasing loading Nc applied at all frequencies. From the multivariate regression models and the respective determination coefficients, a generic model was obtained for the set involving the five wood species, emphasizing the insertion of the apparent density as an independent variable, which allowed a greater generalization of the use of the adjustments in the estimation of properties.