A. F. F. Gomes, Fernando Menezes de Almeida Filho, J. C. Molina, F. Mascarenhas, F. Lahr, A. Christoforo
{"title":"平行纹路压缩弹性模量均值对木桁架设计的影响","authors":"A. F. F. Gomes, Fernando Menezes de Almeida Filho, J. C. Molina, F. Mascarenhas, F. Lahr, A. Christoforo","doi":"10.4025/actascitechnol.v45i1.58733","DOIUrl":null,"url":null,"abstract":"The Brazilian standard ABNT NBR 7190 (Associação Brasileira de Normas Técnicas [ABNT], 1997) recommends adopting the mean value of the modulus of elasticity to compression in the direction parallel to the grain (Ec0,m) in the calculation of displacements. The values of wood stiffness vary considerably, and they can generate displacements above the limit (L 200-1, where L is the span) established by the referred standard, which contributes to the appearance of pathologies in the structure. To evaluate the influence of the adoption of Ec0,m in the calculation of displacements, mechanical properties of wood species were obtained experimentally. With the aid of numerical models and experimental values, ten types of trusses were analyzed (Porch, Inclined Chord, Top Inclined Chord, Parallel Chord, Bowstring, Fink, Howe, K Truss, Pratt, Scissor), three spans (5, 10, and 20 m) and two species (Hymenolobium petraum Ducke e Hymenolobium sp). Initially, adopting Ec0,m for all members and performing a linear analysis, the maximum loads for the displacement L 200-1 were determined. Subsequently, experimental stiffness values were randomly assigned to each bar, and the maximum displacements were determined through nonlinear geometric analyses. Based on 1260 numerical simulations, deflections of approximately 17% (span of 5 m), 30% (span of 10 m), and 34% (span of 20 m) were observed to be higher than the result considering Ec0,m. This problem can be overcome by using non-destructive methods in the pre-classification of the structure bars, positioning the elements rationally in the regions of the highest demand.","PeriodicalId":7140,"journal":{"name":"Acta Scientiarum-technology","volume":"20 1","pages":""},"PeriodicalIF":0.6000,"publicationDate":"2022-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Influence of mean value of the modulus of elasticity in compression parallel to the grain on the design of timber trusses\",\"authors\":\"A. F. F. Gomes, Fernando Menezes de Almeida Filho, J. C. Molina, F. Mascarenhas, F. Lahr, A. 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引用次数: 0
摘要
巴西标准ABNT NBR 7190 (associa o Brasileira de Normas t cnicas [ABNT], 1997)建议在计算位移时采用平行于颗粒方向的压缩弹性模量的平均值(Ec0,m)。木材刚度的值变化很大,它们可以产生超过参考标准规定的极限(l200 -1,其中L是跨度)的位移,这有助于结构出现病态。为了评价采用Ec0、m对位移计算的影响,对不同树种木材的力学性能进行了实验研究。利用数值模型和实验值,对10种桁架类型(Porch、Inclined Chord、Top Inclined Chord、Parallel Chord、Bowstring、Fink、Howe、K Truss、Pratt、Scissor)、3种跨度(5、10和20 m)和2种(Hymenolobium petraum Ducke和Hymenolobium sp .)进行了分析。首先,对所有构件采用Ec0,m并进行线性分析,确定了位移l200 -1的最大载荷。随后,随机分配每个杆的试验刚度值,并通过非线性几何分析确定最大位移。基于1260次数值模拟,观测到挠度约为17%(跨度为5 m), 30%(跨度为10 m)和34%(跨度为20 m)高于考虑Ec0,m的结果。采用非破坏性的方法对结构杆进行预分类,将构件合理定位在需求最高的区域,可以克服这一问题。
Influence of mean value of the modulus of elasticity in compression parallel to the grain on the design of timber trusses
The Brazilian standard ABNT NBR 7190 (Associação Brasileira de Normas Técnicas [ABNT], 1997) recommends adopting the mean value of the modulus of elasticity to compression in the direction parallel to the grain (Ec0,m) in the calculation of displacements. The values of wood stiffness vary considerably, and they can generate displacements above the limit (L 200-1, where L is the span) established by the referred standard, which contributes to the appearance of pathologies in the structure. To evaluate the influence of the adoption of Ec0,m in the calculation of displacements, mechanical properties of wood species were obtained experimentally. With the aid of numerical models and experimental values, ten types of trusses were analyzed (Porch, Inclined Chord, Top Inclined Chord, Parallel Chord, Bowstring, Fink, Howe, K Truss, Pratt, Scissor), three spans (5, 10, and 20 m) and two species (Hymenolobium petraum Ducke e Hymenolobium sp). Initially, adopting Ec0,m for all members and performing a linear analysis, the maximum loads for the displacement L 200-1 were determined. Subsequently, experimental stiffness values were randomly assigned to each bar, and the maximum displacements were determined through nonlinear geometric analyses. Based on 1260 numerical simulations, deflections of approximately 17% (span of 5 m), 30% (span of 10 m), and 34% (span of 20 m) were observed to be higher than the result considering Ec0,m. This problem can be overcome by using non-destructive methods in the pre-classification of the structure bars, positioning the elements rationally in the regions of the highest demand.
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