Timber Beam Repair Based on Polymer-Cementitious Blends

Christofóro, André Luis; Panzera, Túlio Hallak; Araújo, Victor Almeida De; Fiorelli, Juliano; Lahr, Francisco Antônio Rocco

doi:10.1590/1809-4430-eng.agric.v37n2p366-375/2017

Cited by 5 publications

(4 citation statements)

References 19 publications

(15 reference statements)

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“…The modulus of elasticity (E m ) (Equation 1) and operating stress (σ m ) in the bending (Equation 2) were determined according to the premises of the Brazilian standard ABNT NBR 7190 (1997). However, the tests were adapted to the non-destructive condition (Christoforo et al, 2017) because the limitation of the maximum displacement in the middle of the span of the bending test ( Figure 1a) respect the L/200 ratio, in which L is the distance between supports, giving physical and geometric linearity. The maximum displacements in the fatigue test were limited to the L/300 ratio, and the linkages of samples at the ends restrict translation and turning movements (support of the 3rd genus).…”

Section: Methodsmentioning

confidence: 99%

INFLUENCE OF FATIGUE ON BENDING OF Pinus caribaea WOOD

et al. 2020

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This research aimed to evaluate the effect of the number of fatigue cycles (NC, 0reference, 450, 4500, 45000, and 90000) for frequencies (Fr) of oscillation equal to 0.5 and 1.0 Hz on the modulus of elasticity (E m) and operating stress (σ m) in the static bending of Pinus caribaea wood. E m and σ m were determined taking into account three specimens (SPEC) manufactured for reference condition and another three for each of the four NC levels and each Fr level, resulting in 27 SPEC. Sixty experimental determinations were obtained, being the approximate total time of sample exposure to fatigue of 350 hours. The same specimens used to determine E m and σ m for the reference condition were also used (via non-destructive tests) to obtain these properties for all fatigue cycles. The frequency and number of cycles significantly influenced both investigated properties. Reductions in E m and σ m values were observed after 45000 cycles. The progressive increase in the number of fatigue cycles caused more marked reductions in mechanical properties when compared to the increase in the frequency of oscillation.

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Section: Methodsmentioning

confidence: 99%

INFLUENCE OF FATIGUE ON BENDING OF Pinus caribaea WOOD

et al. 2020

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“…O módulo de elasticidade (MOE) (Equação 1) foi calculado conforme o disposto na ABNT NBR 7190 [11] e ABNT NBR 9533 [15], porém, o ensaio de flexão estática a três pontos foi adaptado para a condição não destrutiva, admitindo deslocamento máximo igual a L/200 (ABNT NBR 7190 [11]). Tal deslocamento assegura a linearidade física e geométrica do material, sendo comumente empregado na determinação do MOE em ensaios não destrutivos, como nos trabalhos de CHRISTOFORO et al [29], ICIMOTO et al [30], ZANGIÁCOMO et al [31], SEGUNDINHO et al [32], e LAHR et al [33]. No ensaio de carregamento cíclico (fadiga), como o modelo esquemático (Figura 1b) dos apoios impossibilita a livre rotação do corpo de prova na seção dos apoios, uma vez que os parafusos pressionaram as amostras, o limite de deslocamento adotado (garantia de linearidade física e geométrica) foi igual a L/300.…”

Section: Materiais E Métodosunclassified

Avaliação do efeito da fadiga no módulo de elasticidade na flexão de painéis de madeira compensada

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RESUMO Os painéis têm sido cada vez mais utilizados nas construções civis, rurais, entre outras, com destaque para os compensados pelo bom desempenho mecânico. Em muitas aplicações, os painéis podem estar sujeitos à ação de carregamentos cíclicos, e dessa forma, o conhecimento do efeito da fadiga é de fundamental importância. Todavia, as normas ABNT NBR ISO 2426 [12], NBR ISO 1096 [13], NBR 9489 [14] e NBR 9533 [15] que apresentam as classificações e os métodos de ensaios de painéis de madeira, não prescrevem requisitos para considerar o efeito da fadiga nas propriedades do material, o que motiva o desenvolvimento de pesquisas nessa temática. Este trabalho objetivou avaliar o efeito do número de ciclos de fadiga [NC] (0 - referência, 3600, 7200, 22500, 45000, 67500, 90000) para a frequência de oscilação igual a 1,0 Hz nos valores do módulo de elasticidade na flexão (MOE) de painéis comerciais de madeira compensada de eucalipto. Foram fabricados seis corpos de prova para cada número de ciclos, resultando em 36 amostras. Os resultados evidenciaram reduções significativas do MOE a partir de 22500 ciclos, implicando que 0, 3600 e 7200 ciclos forneceram resultados estatisticamente equivalentes. O modelo de regressão logarítmico mostrou ser o de melhor representatividade (R²=64,28%), apresentando-se como alternativa na previsão do decaimento do MOE para ciclos de fadiga superiores aos avaliados nessa pesquisa.

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“…As an orthotropic material, wood shows different mechanical properties in longitudinal, radial, and tangential directions (Lahr et al, 2014, Stolf et al, 2016. It has motivated some researches focused on evaluating the association of wood properties and specific positions of samples under mechanical tests (Icimoto et al, 2015;Christoforo et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Estimation of Tensile Strength Parallel to Grain of Wood Species

Christofóro¹,

Panzera

Lahr

2019

Eng. Agríc.

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According to the ABNT NBR 7190: 1997 standard, tensile strength of wood samples shall be defined as the ratio between the ultimate strength from a stress test and the specimen cross-sectional area (350 mm 2). However, due to the complex wood anatomy and experimental difficulties, the fractured surface in tested samples are not perpendicular to the loading direction; therefore, such fractured surface becomes larger than the sample cross section, overestimating tensile strength by this method. Using an alternative approach, we aimed to determine the approximate fracture surface of wood specimens subjected to tensile test. For this purpose, we used the least square method to estimate tensile strength of four hardwood species, which were equally divided into strength classes. Then, we determined the relationship between the cross-sectional areas of intact and fractured specimens. The results showed that the approximate area of a fractured surface was 2.14 higher than that of an intact sample. As a result, tensile strength estimates were 47% lower than those currently estimated, which is unfavorable for the safety of construction structures.

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Timber Beam Repair Based on Polymer-Cementitious Blends

Cited by 5 publications

References 19 publications

INFLUENCE OF FATIGUE ON BENDING OF Pinus caribaea WOOD

INFLUENCE OF FATIGUE ON BENDING OF Pinus caribaea WOOD

Avaliação do efeito da fadiga no módulo de elasticidade na flexão de painéis de madeira compensada

Estimation of Tensile Strength Parallel to Grain of Wood Species

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