O emprego de parafusos auto-atarraxantes em ligações metálicas, nos últimos anos, têm aumentado de forma significativa, principalmente como dispositivo de ligação entre componentes leves da construção metálica, como por exemplo, nas ligações entre telhas metálicas e terças. Tais ligações apresentam modos de falha diferentes dos observados para as ligações parafusadas convencionais, em função do tipo de parafuso e das reduzidas espessuras dos elementos conectados, definidos como \"pull-out\" e \"pull-over\". No Brasil, a carência de estudos específicos nesse tema foi uma das razões da omissão da recente norma brasileira de dimensionamento de estruturas de aço constituídas por perfis formados a frio - NBR 14762:2001, quanto a procedimentos específicos para o projeto de ligações com parafusos auto-atarraxantes. Nesse trabalho foi desenvolvido um estudo abrangente sobre as ligações metálicas com parafusos auto-atarraxantes, com ênfase na ligação telha-terça, onde são apresentados os procedimentos e as recomendações das principais normas estrangeiras, bem como os ensaios padronizados para caracterização dos parafusos e avaliação do comportamento estrutural e resistência de ligações. São apresentados também os resultados de uma investigação experimental, com base no ensaio padrão do AISI (1996) (American Iron and Steel Institute), em 27 corpos-de-prova com variação no diâmetro do parafuso e espessura dos componentes da ligação (terça e telha), com o objetivo principal de avaliar as expressões das AISI (2001b e 1996) para dimensionamento. Como conclusão, são relatadas as dificuldades associadas ao ensaio padrão, que apesar de sua concepção simples, conduz à elevada variabilidade nos resultados, indicando a necessidade da adoção de ensaios mais representativos e confiáveis. / The use of screws in steel connections has increased significantly in recent years, mainly as connecting devices between light-gage components in steel construction, as, for example, in joints between metal roofing and purlins. These connections exhibit different failure modes from those displayed by conventional bolted connections, due to the type of fastener and the reduced thicknesses of the connected elements, defined as pull-out and pull-over. In Brazil, the lack of specific studies of this theme was one of the reasons for the omission of specific procedures for the design of screw connections from the new edition of the brazilian code for cold-formed steel members - NBR 14762:2001. The work reported here involved a comprehensive study of steel connections using screws, with emphasis on the sheating-purlin connection. A presentation is made of the procedures and recommendations of the main foreign codes, as well as of standardized tests for characterizing screws and evaluating the structural behavior and strength of connections. Also presented are the results of an experimental investigation based on the standard test of the AISI (1996) (American Iron and Steel Institute) applied to 27 test specimens with varying screw diameters and connector component thicknesses (purlin and sheeting), whose main purpose was to evaluate the AISI\'s design equations (2001b e 1996). To conclude, a report is made of the difficulties associated with the standard test, which, despite its simple conception, leads to considerably variable results, indicating the need for the adoption of more representative and reliable tests.

Este trabalho apresenta a proposta de recuperação estrutural de uma edificação histórica no município de Uberaba por meio de perfis formados a frio. Para o dimensionamento e cálculo dos elementos estruturais foi utilizado o projeto de norma brasileira de dimensionamento de estruturas de aço constituídas por perfis formados a frio. São apresentados os critérios e procedimentos para a recuperação de estruturas em geral e especificamente para as edificações antigas ou históricas. É feita uma análise da viabilidade técnica, da utilização de perfis formados a frio na recuperação estrutural de obras históricas. / This work presents the proposal of structural recovery of a historical construction in Uberaba city, by means of cold-formed sections. It was used the steel structures increasing brazilian norm project, composed of cold-formed sections. It is presented the criteria and procedures for the general structural recovery to the old or historical constructions. It is also made an analysis of technical viability of cold-formed sections utilization in structural recovery of historical works.

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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Cold-formed steel purlin systems are widely used in modem building construction, for supporting the roof and floor structures. The rotational behaviour of beam-to-beam bolted connections, which are used between the sections, significantly affects the performance of purlin systems and is hard to predict. The behaviour models currently available for the connections only offer linear or multilinear predictions with low levels of accuracy. The aim of the research presented in this thesis is to develop and propose a nonlinear, more accurate behaviour model for the sleeved modified Z bolted connections, by means of experimental and numerical analysis. Finite element models are presented for the single-bolt, single-lap connection, sleeved modified Z connections in the simply supported arrangement, and a six-span purlin system. Based on the numerical results that have been validated by the experiments, a nonlinear behaviour model is proposed for the sleeved modified Z connections. In the model, the behaviour of the connections is divided into four stages, based on the dominant mechanism that provides the resistance to the rotation. Different formulas are used in different stages to determine the behaviour of the connection, boundary conditions, and magnitudes of bolt forces. The new model reflects well the true behaviour of the connections, and provides a good understanding of what happens inside the connections. The model reveals the failure pattern of the connections and enables optimization in the design of purl in systems, for improving efficiency in material usage.

The main objective of this research is to extend the “Direct strength method” for determining the web crippling strength of cold-formed steel C and Z sections subjected to End one flange loading and Interior one flange loading conditions. Direct strength method is applied for designing the columns and beams earlier. The existing specifications equation for calculating the web crippling strength of cold-formed steels designed by American Institute of Iron and Steel is very old method and it is based on the extensive experimental investigations conducted at different universities. Calculating the web crippling strength of cold-formed steels using direct strength method is a new technique. In the present research the web crippling strength of cold-formed steels were calculated using Direct Strength Method. The experimental data is collected from the tests that were conducted at different universities. The critical buckling strength of the members were calculated using Abaqus. Microsoft excel is used to generate the equations. The safety and resistance factors for the designed equations were calculated using “Load and resistance factor design” and “Allowable strength design” from North American Cold-Formed Steel Specification, 2012 edition book.

In the cold-formed steel construction, the oriented strand board is a common material for shear wall sheathing. an OSB is made by using wood chips as raw materials that undergo high temperature pressing to create a multi-larger structure material. Due to the OSB having a high strength in shear, it is an important material used in the construction field. the thesis is trying to verify published nominal shear strength in AISI-213-07 in the first part. This objective has two parts: the first part is to verify nominal shear strength (Rn) for wind and other in-plane loads for shear wall. the second part is to verify nominal shear strength (Rn) for seismic and other in-plane loads for shear wall. Secondly, the thesis verifies the design deflection equation for nominal shear strength of CFS shear walls with OSB sheathing. the test specimens were divided into eight groups which trying to verify the design deflection equation that was published in AISI-213-07 standard.

This thesis presents a research project aimed at advancing the treatment of cold-formed steel (CFS) structural reliability in roof trusses. Structural design today relies almost exclusively on component-level design, so structural safety is assured by limiting the probability of failure of individual components. Reliability of the entire system is typically not assessed, so in a worst-case scenario the system reliability may be less than the component reliability, or in a best-case scenario the system reliability may be much greater than the component reliability. A roof truss itself, is a subsystem with several possible failure modes that are being studied in this test program. These trusses are constructed of CFS members that nest with one another at the truss nodes and are connected by drilling fasteners through the mated surfaces, as well as having steel sheathing fastened to the top chords for lateral bracing. Presented in this paper is a series of full-scale static tests on single cold-formed steel roof trusses with a unique experimental setup. The test specimens were carefully monitored to address multiple failure modes: buckling of the top chord, buckling of the truss webs, and any connection failures. This research includes the experimental results, the computed system reliability of the trusses as well as their relationship between the components reliability.

In this project, the main research objective is intend to seek criteria for evaluating the capacity of BAC screw fasteners with mixed configuration of waterproof seal washer, sealer tape and different pre-drill holes to determine shear and tension strength values for the screws used in cold-formed steel connections. The thesis presents the design methods and test program conducted to investigate the behavior and strength of the screw connections in shear and tension test. Test results were compared with AISI design provisions to determine if new design equations will be developed for those screws used in BAC cooling tower applications. LRFD resistance factors and ASD safety factors were investigated to the proposed design equations.

No / This paper presents the structural behaviour of cold-formed steel cassette wall panels subjected to in-plane shear loads. To understand the influence of configuration, lining material and connector arrangement on the overall shear behaviour of typical cassette wall panels, different lining materials, fastener spacing and positions, edge stiffeners and specific boundary conditions were assumed in the numerical simulations. The comparison and analysis presented in this paper demonstrate typical effect factors to the load-bearing capacity of selected wall panel systems. In particular, the effect of wall opening to the structural shear behaviour of wall panels is highlighted.