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Este trabalho aborda construções em madeira sob a ótica de sistemas com estruturas leves; apresenta análise computacional por meio de modelagem pelo método de elementos finitos de diafragmas de piso e vigas I, submetidas a ensaio de flexão a quatro pontos. O objetivo geral é avaliar a resistência e a rigidez de diafragmas horizontais,construídos em Sistemas Leves de Madeira, quando submetidos a ações verticais. As análises foram realizadas por meio do programa computacional SAP2000 e foram avaliadas as influências dos seguintes parâmetros: espaçamento entre vigas que constituem os elementosde ossatura do diafragma horizontal e o espaçamento entre pregos de fixação do contrapiso, composto por chapas de OSB – Oriented Strand Board. Ao final do trabalho, comparam-se os resultados obtidos a partir das análises numérica e teórica, e são apresentadas algumasconclusões.Wood light-frame floor diaphragms, made with OSB panels and I-joists, subjected to vertical loads. This work is focused on lightweight woodframe constructions, and presents a finite element modeling of floor diaphragms and wood I-joists subjected to four-point bending. It presents the results of experimental tests on wood I-joists subjected to vertical loads. The main goal of this research is to evaluate the resistance and rigidity of wood light-frame floor diaphragms, when subjected to monotonic vertical forces acting in the plane of the floor. The analyses were performed using the SAP2000 computer program and tested with diferent constructive arrangements, and the influence of the following variables were examined: distance between wood I-joists, and distance between nails around the perimeter of the OSB boards. Finally, a comparison between analytical and numerical results is performed.

Remediation methods and strength predictions were evaluated for wood I-joists with single, circular holes in the webs, leaving utilities in place. A full-scale bending test using four equally spaced point loads was applied to three depths of joists with varying flange widths and span lengths of 4.88 and 2.44 m. Failure modes for long-span joists without holes were in the flanges in tension, compression, or lateral buckling, but once a hole was introduced, the majority failed in shear. The curved beam approach and manufacturers software were used to predict strength. Seven remediation techniques were investigated initially, and remediation effectiveness was evaluated on the basis of strength, stiffness, and ease of installation/cost. The oriented strand board (OSB) collar remediation worked very well and returned 8 of 12 series of joists to a strength statistically equivalent to the 'no hole' condition. The OSB collar was not quite as effective in returning stiffness to the joists but was easier to install and less expensive than a laminated strand lumber patch. [ABSTRACT FROM AUTHOR]

Remediation methods and strength predictions were evaluated for wood I-joists with single, circular holes in the webs, leaving utilities in place. A full-scale bending test using four equally spaced point loads was applied to three depths of joists with varying flange widths and span lengths of 4.88 and 2.44 m. Failure modes for long-span joists without holes were in the flanges in tension, compression, or lateral buckling, but once a hole was introduced, the majority failed in shear. The curved beam approach and manufacturers software were used to predict strength. Seven remediation techniques were investigated initially, and remediation effectiveness was evaluated on the basis of strength, stiffness, and ease of installation/cost. The oriented strand board (OSB) collar remediation worked very well and returned 8 of 12 series of joists to a strength statistically equivalent to the 'no hole' condition. The OSB collar was not quite as effective in returning stiffness to the joists but was easier to install and less expensive than a laminated strand lumber patch. [ABSTRACT FROM AUTHOR]

Many bamboo species are well regarded for their strength and rapid renewability, although the nonuniformity of bamboo poles has impeded use in developed countries. Described herein are the results of a pilot effort to develop engineered bamboo I-joists for use in common low-rise construction applications. Solid section bamboo materials were used to fabricate I-beams; flanges consisted of single-strand bamboo material and webs consisted of bamboo OSB or three-ply material. Experimental results indicate that flexural strengths were limited to 5.2 ksi (36 MPa) by the failure of the flange finger joints; shear strengths were 2.1 ksi (14 MPa) for the bamboo OSB and 3.3 ksi (22 MPa) for the three-ply web material. The modulus of elasticity averaged 2,000 ksi (14 GPa), while the shear modulus was 250 ksi (1.7 GPa) for the bamboo OSB and 140 ksi (0.94 GPa) for the three-ply material. Design values are developed from the test results following a hybrid approach based on ASTM procedures for wood I-joists and whole bamboo poles. [ABSTRACT FROM AUTHOR]

Two series of tests with different depth wood I-joists were conducted to study the effects of circular and square web openings and the placement of steel angle retrofits at openings. Finite-element analysis of all test configurations was used to improve understanding of how web openings and retrofits affect the stiffness, stress distributions around openings, and ultimate failure mechanisms. Test results show failure loads well above prescribed design loads; however, the presence of web openings affected the type of failure modes. Control joists failed at the tension flange, whereas joists with web openings failed in shear through web openings or by means directly attributable to the presence of an opening. Ultimate capacity and stiffness was generally reduced by the presence of a web opening, with openings located closer to high shear areas producing worse results. Square web openings lowered the ultimate capacity approximately 10% more than circular openings when located at the same location. Steel angle retrofits improved capacity if an adequate retrofit length was used to redistribute stress concentrations. Finite-element models accurately predicted decreases in stiffness due to web openings; however, the models predict an improvement in stiffness due to the presence of steel retrofits that was not ascertained in experimental results. [ABSTRACT FROM AUTHOR]

Tests conducted on oriented strand board (OSB) webbed wood I-joists with web openings revealed that the typical failure mode was that the OSB fractured from tension zones around an opening, with cracks developing diagonally toward the joist flanges. The joist collapsed when the cracks reached the flanges. Finite-element models were developed using ABAQUS to simulate joist behavior. Material nonlinearity, crack propagation, and joist failure were dealt with by a user-defined subroutine. Good correlation was obtained between the test and the analytical results. The finite-element models were then used to investigate the effect of opening size and location on the behavior of joists. The lower bound and the upper bound of the load bearing capacity of joists with openings were found by finite- element modeling and were empirically expressed by polynomials. [ABSTRACT FROM AUTHOR]

Lateral buckling of unbraced beams during construction may be an important cause of fatalities and injuries. Temporary bracing to restrict lateral buckling is a potential preventive approach, but has received little study. Lateral acceleration, lateral displacement, and rotation of wood composite I-joists were measured under different bracing conditions while participants traversed the joists. Five different bracing stiffnesses and two different bracing placements were examined. Lateral displacement and rotation increased near the midspan of the joist, while acceleration remained consistent. Greater lateral displacement and rotation were found with increasing participant weight and lack of construction experience. Construction experience was found to be a significant factor in the amount of joist motion. A safety platform similar to the testing methods discussed may have potential as a training tool to expose workers to partially braced joists. The relationship of lateral displacement and rotation with bracing stiffness was nonlinear. Bracing placement had little effect upon lateral displacement and rotation. Increased bracing stiffness reduced lateral displacement and rotation at a decreasing rate, indicating that bracing stiffness can be optimized to reduce cost. [ABSTRACT FROM AUTHOR]