Brazilian Code ABNT NBR Research Articles

Numerical and Experimental Analysis of Wood Tensile Strength Perpendicular to the Grain

The Brazilian Code ABNT NBR 7190 (1997) is currently under review process and one of the proposals is the change and add of some test procedures. Several specimen geometric configurations and test conditions have been evaluated by the study committee CE-02:126.10. The aim of this paper was the analysis of the tensile strength perpendicular to the grain through the current Brazilian Code and from an adaptation of ISO 13910 (2005). Pine and Indian Cedar were used and simplified relationships were proposed. Numerical simulations were performed to identify the stress distributions in the specimens. The results obtained by ISO 13910 (2005) did not differ statistically for the two species. Brazilian standard method cedar had a higher strength value than pine. The simplified ratios obtained ranged between 0,017 and 0,123. The numerical simulations of ISO 13910 (2005) specimens showed predominant failure by tension in the lower fiber due to stress concentration.

Assessment of design codes for the in-service behaviour of steel-concrete composite slabs

Abstract Steel-concrete composite slabs, also known as steel decking floor slabs or popularly as steel decks® have recent development and are advancing in Brazilian construction. There are relatively few researches about the long-term effects on composite slabs, and it has been identified that they can be significant in the evolution of deflections, mainly due to the effects of non-uniform shrinkage. However, there are no Brazilian references on the subject and Brazilian Code ABNT NBR 8800:2008 does not indicate any procedure for its evaluation. This paper presents a study on the serviceability limit state of excessive deflection with the application of two simplified approaches: Eurocode 4:2004 (European code) and AS/NZS 2327:2017 (Australian code), also comparing them against experimental results by the authors and literature. Due to the impermeability of the soffit face promoted by the steel decking, the occurrence of non-uniform shrinkage is a relevant aspect. As a consequence, the deflections were underestimated by Eurocode 4. At the same time, the simplified approach of AS/NZS 2327, which explicitly takes into account the non-uniform shrinkage, presented good accuracy when compared to the experimental values. Finally, authors indicate the use of more robust prediction models for the evaluation of deflections in composite floors.

Comparative analysis of normative provisions for seismic design and detailing of reinforced concrete structures

Abstract The main objective of this work is to carry out a comparative analysis between the methods and provisions of the Brazilian code ABNT NBR 15421:2006 and those of the ASCE/SEI 7 and the Eurocode 8, on the seismic design of structures. The similarities and differences between these standards, as far as the application of the Equivalent Lateral Forces method (ELFM) and the Response Spectrum method (RSM) are concerned, will be addressed. The responses will be evaluated for a case study that will be modelled by the SCIA Engineer 17 software. This paper also presents some comments on the detailing of reinforced concrete structures to ensure a good performance under seismic loading, allowing for a more favourable interpretation of the seismic analysis results.

Physical and Mechanical Characterization of Cedrelinga catenaeformis Ducke Wood Specie

Wood, a natural and sustainable resource, has been used by humankind for several purposes especially in construction and some manufacturing sectors. Due to predatory harvest of well-known wood species and in consequence, possible shortage of these essences, it is indispensable to characterize new wood species. This study intended to determine, under the requirements of Brazilian Code ABNT NBR 7190, the mechanical and properties of Cedroarana wood (Cedrelinga catenaeformis Ducke). Besides, with the analysis of variance (ANOVA), testing several regression models, it has hoped to estimate the values of strength and stiffness as a function of apparent density. Thirteen specimens were used for each test, totalizing 195 experimental results. The mechanical properties of Cedrelinga catenaeformis obtained demonstrated compatible performance with regular wood species used in temporary civil construction. According the regression models, only two properties were considered significant with apparent density estimation.

Properties of Eucalyptus umbra Wood for Timber Structures

This study involved the study of physical and mechanical properties of Eucalyptus umbra wood for its use in timber structures. Two physical and fourteen mechanical properties tests were performed according to Brazilian code ABNT NBR 7190:1997. Two moisture contents were considered: above the Fiber Saturation Point (30%) and standardized point 12%. Decreasing the moisture content, this study presented an increase in eight mechanical properties. Oppositely, five mechanical properties presented decreasing of values, and one single variable persisted stable. But statistical perspective supported by the t-test, only three mechanical properties (ft90, fH0 and W) increased significantly. According to results obtained in this study, it is possible to use Eucalyptus umbra wood as raw material for structures.

Stress Distribution in Tauari Wood Beam

Wood is widely used in many sectors of civil construction as a structural material. Brazilian code ABNT NBR 7190:1997 Design of Timber Structures governs the method of project design as well as the characterization of wood for structural design. In this aspect the code considers wood as an orthoptic material, however is well known that the organic origin provides great anatomical complexity to its. This work aims to study the distribution of normal stresses in a Tauari wood beam subjected to the elastic regime, and to ascertain the current position of the Neutral Line during test. For this purpose, a four-point static bending test and subsequent compression and tension to the grain tests were performed to determine the modulus of elasticity and calculate the normal stresses by recording deformations and applying Hooke's Law. The data were statistically analyzed to define bests adjusts to Stress vs. Strain diagrams, and thus determine the location of the Neutral Line. It was verified that the position of the Neutral Line was a normal distribution variable, being located at 1,07cm above the geometric center of the board. Finally, the comparison between values of normal tension obtained experimentally and through the theoretical method was determined and similarities were verified in these data, being also plausible the theory for the calculation of the normal tensions of the wood beams, when it is in the elastic regime.

Embedment Parallel to the Grain Strength of the Schizolobium amazonicum Herb Wood Specie

Wood is one of the main raw materials used by man in several uses. It can be used in furniture and package industries, and also in components for building construction. For all these purposes, it is necessary to know the physical and mechanical properties of wood specie being used. Brazilian Code ABNT NBR 7190:1997, in its Annex B, presents methods for determining wood mechanical properties, among them the embedment parallel to grain. This property is important because it relates to the design of bolted and nailed joints in timber structures. This research aims to the experimental determination of embedment strength parallel to grain strength for <i>Schizolobium</i> <i>amazonicum</i> Herb, a wood specie recently used for structural purposes. Results showed that embedment strength for <i>Schizolobium</i> <i>amazonicum</i> Herb wood specie is lower when compared with traditional tropical essences, but sufficient for some structural applications.

Adherence between steel bars and lightweight concrete with EPS beads

Abstract This paper describes the adherence behavior of a structural lightweight concrete with EPS beads (SLCEB) in a monotonic loading, based in a bibliographic review and in pull-out tests. The results of these SLCEB tests were compared with those of an ordinary concrete (OC) and with the values based in indications of the Brazilian code ABNT NBR 6118:2014 - Design of concrete structures. The pull-out tests of two batches of SLCEB and one of OC were analyzed, in a total of 60 tests. Mechanical characteristics were determined too, such as: compressive strength and tensile strength in split cylinder test. The calculated results according to the above mentioned standard were very different from those obtained in the tests, indicating that the theoretical values are more conservative than the experimental ones. It was also verified that it is possible to use SLCEB in structures with respect to the adequate adherence of reinforcement in the concrete.

Influence of nails size and layout to obtain the reduction coefficient of moment of inertia for timber beams with composite cross section

A significant portion of rural building’s roof is supported by timber trusses. Increasing distance between the trusses can be achieved by using composite cross sections (T and I) for beams. With this, it is possible to reduce the number of columns and trusses, bringing significant savings in material and the desired cost reduction, mainly using wood from planted forests. The Brazilian Code ABNT NBR 7190:1997 establishes a coefficient (αr) for the reduction of the theoretical moment of inertia (Iteo) of 0.95 and 0.85, for beams with T and I composite profile, respectively. However, no specification is showed about connections responsible for conferring such coefficients. This research aimed to investigate, based on static bending tests, analysis of variance and polynomial regression models (linear, quadratic, cubic), the precision of αr coefficients set by the Brazilian Code for Pinus sp. beams. We considered to evaluate influence of factors such as: nails number (3, 5, 9, 17, 33), nails size (19×27 mm, 19×33 mm), profile types (I, T) and calculation form to obtain the equivalent modulus of elasticity (Edeq) used to determine the cited coefficients. The highest values of αr were derived from beams with 17 and 33 nails, which provided similar results. The analysis also allowed admitting the adequacy, only to the beams with T section, of αr stipulated by the Brazilian Code. For I section, αr overestimates beams performance. Nails size and form of calculating Edeq were not significant in obtaining αr. The quadratic model showed the best results, indicating that the amount of 25 nails can provides the highest values of αr coefficients.

Density as Estimator of Strength in Compression Parallel to the Grain in Wood

Wood is a renewable material, presenting wide use in building construction. For its better employability, it is necessary to perform physical and mechanical characterization of the several species available for application. In this respect, Brazilian Code ABNT NBR 7190:1997 - Timber Structures Design, in its Annex B, prescribes the proper tests and adds some relations between properties and strength classes for coniferous and dicotyledonous. The strength classes are function of characteristics values of strength in compression parallel to grain (fc0). However, density is a more easy-determination property and the cited Code presents the mean value of density for each strength class. Therefore, this research aimed to evaluate the possibility of inferring fc0 based on density obtained on tests of three Brazilian tropical wood species: Canafistula (Cassia ferruginea); Angelim araroba (Vataireopsis araroba) e Castelo (Gossypiospermum sp.). Statistical procedures shown it is possible to conclude that, in some cases, density is not a good estimator of fc0.

Cleavage Parallel to the Grain for Schizolobium amazonicum Wood Specie

Wood is one of the main raw materials utilized by man. It can be applied in furniture and package industries, and also in components for building construction, including structures. For all these purposes, it is necessary to know the physical and mechanical properties of wood specie being used. Brazilian Code ABNT NBR 7190:1997 (Design of Timber Structures), in its Annex B, presents methods for determining wood mechanical properties, among them the cleavage parallel to grain. This property is important because it relates to the design of bolted and nailed joints in timber structures. In this context, the present research aims to the experimental determination of cleavage strength parallel to grain strength for Schizolobium amazonicum (Parica) wood specie recently used for structural purposes, in Brazil. With raising availability, due to the great production in planted areas, Parica can achieve some segments in Brazilian exportation trade. Results showed that cleavage strength for Schizolobium amazonicum is lower when compared with traditional tropical essences, but sufficient for several structural applications.

INFLUÊNCIA DA POSIÇÃO DOS INSTRUMENTOS DE MEDIDA NA DETERMINAÇÃO DO MÓDULO DE ELASTICIDADE DA MADEIRA NA COMPRESSÃO PARALELA ÀS FIBRAS (EC0)

RESUMOO módulo de elasticidade na compressão paralela às fibras (Ec0) é um dos parâmetros de referência para estimar o desempenho da madeira. O Anexo B da Norma Brasileira ABNT NBR 7190:1997 estabelece, nos ensaios para determinação do Ec0, que seja tomada a medida de deformações em pelo menos duas faces opostas dos corpos de prova. O objetivo deste trabalho foi verificar a influência dessas condições de ensaio nos valores de Ec0. Tal propriedade foi determinada a partir das deformações de duas faces opostas dos corpos de prova e, em seguida, a partir das deformações obtidas nas faces complementares. Foram utilizadas espécies de madeira de forma a abranger todas as classes de resistência assumidas pela citada norma. Os resultados indicam significativa variação de Ec0determinado nos ensaios referidos, evidenciando que tal situação deve ser considerada para futura revisão dos métodos de ensaio para determinação de propriedades da madeira para aplicação estrutural.

Medium Density Particleboard with Addition of Impregnated Paper

The aim of this research was to produce three-layer Medium Density Particleboard (MDP), with the addition of impregnated paper, in the inner layer, in proportions of 1; 5 and 20%. In this study, MDP was composed with particles of small size in outer layers, and larger particles in internal layer. After panel manufacturing, physical and mechanical tests based on Brazilian Code ABNT NBR 14.810 were carried out to determine moisture content; density; thickness swelling; water absorption; modulus of rupture (MOR) and modulus of elasticity (MOE) in static bending and internal adhesion. Test results were compared to commercial panels, produced with 100% Eucalyptus, considering the requirements specified by Brazilian Code. Properties presented values close to normative specifications, indicating positively the possibility of production of MDP using addition of waste paper impregnated.

Particleboard Manufactured with Additions of Eucalyptus Bark in Different Percentages in the Internal Layer

This study aimed to produce and determine physical and mechanical properties of three layers particleboards produced with Eucalyptus sp. particles, in outer layers, and Eucalyptus urograndis e Eucalyptus saligna bark, in internal layer. Recommendations of the Brazilian Code ABNT NBR 14810-3:2006 were adopted to fundament physical and mechanical tests. Properties considered were modulus of rupture (MOR) and modulus of elasticity (MOE) in static bending; internal adhesion; thickness swelling; water absorption; moisture content and density of the panels. Four different panel compositions were studied, with 5, 10, 15 and 20% of bark (related to particle mass) the internal layer. Results were compared with the requirements of: Brazilian Code ABNT NBR 14810-2; European Code EN 312 and related literature. The produced panels were adequate to all the values stipulated the cited codes and also superior to similar studies found in the literature, for all compositions of bark in internal layer, except for the moisture content test, in which only the composition of 5 % hull met the normative specifications.

Evaluating a Test Parameter in Static Bending for &lt;i&gt;Pinus sp&lt;/i&gt;. Wood

Abstract. The study aimed to analyze the longitudinal modulus of elasticity (Em), based on static bending tests, in different spans and confirm that it’s necessary adopt as 21 the ratio between span and height of the cross section of the specimen to turn no significant the influence of shear stress on vertical deflection. So, simplified equation to determine Em can be employed. Specimens of Pinus elliottii var. elliottii and Pinus elliottii var. elliottii × Pinus cariabeae hondurensis (hybrid), came from Itapeva region, São Paulo State, Brazil, were considered. Bending tests were conducted in Labs of Experimental Campus Itapeva, UNESP, adapting recommendations of Brazilian Code ABNT NBR 7190. Twelve specimens of each species were tested. The trend lines for the plotted graphics showed clearly a nonlinear behavior until the neighborhood of ratio 21 and no expressive variations after this point, confirming that normative recommendations are correct.

Physical and Mechanical Properties of&lt;i&gt; Dipteryx&lt;/i&gt; &lt;i&gt;odorata&lt;/i&gt; (Aublet) Willd

The aim of this work is to determine the main mechanical properties, related to timber structures design, of the Brazilian tropical wood specie: Dipteryxodorata (Aublet) Willd. Tests were conducted according to the guidelines of the Brazilian Code ABNT NBR 7190: 1997 "Design of Timber Structures". Specimens were obtained from a so-called homogeneous clear wood lot, with moisture content around 12% . Mean values ​​of strength and stiffness properties confirmed Dipteryxodorata (Aublet) Willd as a good alternative for structural uses.

Hardness of the &lt;i&gt;Schizolobium amazonicum &lt;/i&gt;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.

Embedment Strength of Pinus sp. Wood to Metal Pins

To know the physical and mechanical properties of wood to be employed as structural elements in is an important factor for its use in a rational way. The connections between members of timber structures are also relevant topic once local stress concentrations can occur and safety must be seriously taken in account. Brazilian Code ABNT NBR 7190: 1997 "Design of Timber Structures" provides guidelines for connections calculation based on two alternative limit states: wood strength to embedment or bending of the bolt. The purpose of this paper is estimate the strength to embedment of Pinus sp. to bolts in three directions with respect to the grain: parallel, perpendicular and inclined at 45o. Specimens obeying requirements of Brazilian Code related to bolts diameter (10mm) were prepared and tested. The embedment strength in parallel direction to the fiber was the highest and the failure modes were more frequent crushing and cleavage.

Evaluating vibrations on a small-scale model of a timber footbridge

In Brazil, the study of pedestrian-induced vibration on footbridges has been undertaken since theearly 1990s, for concrete and steel footbridges. However, there are no recorded studies of this kind fortimber footbridges. Brazilian code ABNT NBR 7190 (1997) gives design requirements only for staticloads in the case of timber footbridges, without considering the serviceability limit state from pedestrianinducedvibrations. The aim of this work is to perform a theoretical dynamic, numerical and experimentalanalysis on simply-supported timber footbridges, by using a small-scale model developed from a 24 mspan and 2 m width timber footbridge, with two main timber beams. Span and width were scaled down(1:4) to 6 m e 0.5 m, respectively. Among the conclusions reached herein, it is emphasized that theEuler-Bernoulli beam theory is suitable for calculating the vertical and lateral first natural frequenciesin simply-supported timber footbridges; however, special attention should be given to the evaluation oflateral bending stiffness, as it leads to conservative values.

Bases do dimensionamento de pilares mistos de aço e concreto segundo o projeto de revisão da NBR 8800

Apresentam-se os procedimentos para dimensionamento de pilares mistos de aço e concreto do projeto de revisão da norma brasileira ABNT NBR 8800:1986, quando da atuação conjunta de força axial de compressão e momentos fletores. São, também, apresentadas as bases teóricas dos procedimentos, que têm como referências principais a norma européia EN 1994-1-1:2004 e a americana ANSI/AISC 360-05. Mostra-se, ainda, que os resultados fornecidos pelos procedimentos do projeto de revisão têm boa concordância com resultados mais precisos obtidos por uma análise pelo método dos elementos finitos.