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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Estrutura mista madeira-chapa dobrada submetida à flexão simples / Mixing structure timber-cold formed steel plates submitted to the bending

MONTEIRO, Vilma França 28 September 2007 (has links)
Made available in DSpace on 2014-07-29T15:03:30Z (GMT). No. of bitstreams: 1 Dissertacao Vilma Franca Monteiro.pdf: 2260410 bytes, checksum: f8bcbca2598f2aaf7b700c53a7bae20c (MD5) Previous issue date: 2007-09-28 / This work deals with theoretical and experimental study of timber beams and timber/cold formed steel plates composed beams, submitted to the bending. A combination of different materials aims to the exploitation the advantages of each material, of manner to have a viable set, in constructive terms, structural and economic. For the accomplish of the research, three beams wooden with dimensions 40mm x 120mm x 1050mm, six hardened beams wooden in the superior face with metallic profile in the dimensions 50mm x 25mm x 2mm and six beams of wooden stiffeners in faces inferior and superior with the same profile metallic had been assayed. The spacing between the connectors had been of 100mm, 200mm and 300mm. With the objective to supply given necessary the sizing, a theoretical formularization for the determination of the internal moment and for the estimative of the deflection was presented. For this, the mechanical properties of the wood, the steel and the connectors had been determined. With the results of the assays of characterization of the materials, the simple and mixing beams had been assayed to the bending, for reading of the deformations and maximum vertical displacements of the landslide in the extremities inferior and superior. Such values had been gotten by means of electric strain gauges and comparing clocks. They had been determined still: the tensions in the elements of the beams and the curves load versus displacement. It was observed that, in relation to the wooden simple beam, it had average increase at the ultimate load, for the beams with parts hardened in the compressed face, of 20%, and of 49 when placed stiffeners in the faces compressed and tensioned. In the value of the deflections it had average reduction of 15% when used stiffener in the superior face and of 49% in the parts with stiffeners in the faces was used compressed and tension. The biggest reduction in the deflections happened in the parts with lesser spacing between connectors, indicating that the influence of the interaction is bigger in relation to the displacements that in relation to the bending moment. In stress distribution diagram in the transversal sections it was adopted, in all the cases, the triangular form for the wood and for the profile it was adopted a rectangular form. It was obtained results that differ from the experimental values in 17% for the simple beams, in 16% for the parts hardened with profile in superior face and 21% for the parts hardened with profile in the faces upper/lower indicating that the formularization proposal can be applied with safety. In the calculation of the deflections the geometric properties of the mixing section, in elastic regimen, had been gotten with the homogenized section. An equation for the determination ofthe factor of correction of the estimated deflection, for the studied cases is presented. / Este trabalho trata de estudo teórico e experimental de vigas de madeira e vigas mistas, compostas de madeira e chapa dobrada, submetidas à flexão simples. A combinação de materiais diferentes visa ao aproveitamento das vantagens de cada material, de forma a se ter um conjunto viável, em termos construtivos, estruturais e econômicos. Para a efetivação da pesquisa, foram ensaiadas três vigas de madeira com dimensões aproximadas de 40mm x 120mm x 1050mm, seis vigas de madeira enrijecidas na face superior com perfil de chapa dobrada em U, nas dimensões 50mm x 25mm x 2mm e seis vigas de madeira enrijecidas nas faces inferior e superior, com o mesmo perfil metálico. Os espaçamentos entre os conectores foram de 100mm, 200mm e 300mm. Com o objetivo de fornecer dados necessários para o dimensionamento, foi apresentada uma formulação teórica para a determinação do momento interno e para a estimativa das flechas. Para tanto, foram determinadas as propriedades mecânicas da madeira, do aço e dos conectores. De posse dos resultados dos ensaios de caracterização dos materiais, foram ensaiadas à flexão as vigas simples e mistas, para leitura das deformações e deslocamentos verticais máximos e do deslizamento nas extremidades inferior e superior. Tais valores foram obtidos por meio de extensômetros elétricos e relógios comparadores. Determinaram-se ainda as tensões nos elementos das vigas e as curvas força x deslocamento. Observou-se que, em relação à viga simples de madeira, houve aumento médio no valor da força de ruptura, para as peças enrijecidas na parte comprimida, de 20%, e de 49% quando colocados enrijecedores nas faces comprimida e tracionada. No valor das flechas houve redução média de 15% quando se utilizou enrijecedor na face superior e de 49% nas peças com enrijecedores nas faces comprimida e tracionada. A maior redução nas flechas aconteceu nas peças com espaçamento menor entre onectores, indicando que a influência da interação é maior em relação aos deslocamentos do que em relação ao momento fletor. No diagrama de distribuição das tensões nas seções transversais adotou-se, em todos os casos, a forma triangular para a madeira e retangular para o perfil e chegou-se a resultados que diferem dos valores experimentais em 17% para as vigas simples, 16% para as peças enrijecidas com perfil na face superior e 21% para as peças enrijecidas com perfil nas faces superior e inferior indicando que a formulação proposta pode ser aplicada com segurança. No cálculo das flechas, as propriedades geométricas da seção mista, em regime elástico, foram obtidas com a seção homogeneizada. Apresenta-se uma equação para a determinação do fator de correção da flecha estimada, para os casos onde houve enrijecimento.

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