An experimental and analytical investigation was conducted to evaluate the behavior of inflection points as brace points in multi-span purlin roof systems. Seven tests were conducted using "C" and "Z" purlins attached to standing seam and through fastened panels. These tests were subjected to uniform gravity loading by means of a vacuum chamber. The experimental results were compared with analytical predictions based on the 1996 AISI Specifications with and without the inflection point considered a brace point. Finite element modeling of through fastened "C" and "Z" purlin tests were conducted and compared to experimental through fastened results. Conclusions were drawn on the status of the inflection point and on the design of multi-span purlin roof systems with current AISI Specifications. / Master of Science

Presently, the industry accepted method for the determination of the governing buckling strength for cold-formed purlins supporting a standing seam metal roof system is the 1996 AISI Specification for the Design of Cold-Formed Steel Structural Members, which contains provisions for local and lateral buckling. Previous research has determined that the AISI provisions for local buckling strength predictions of cold-formed purlins are highly unconservative and that the AISI provisions for lateral buckling strength predictions of cold-formed purlins are overly conservative. Therefore, a more accurate "hand" method is needed to predict the buckling strengths of cold-formed purlins supporting standing seam roof systems. The primary objective of this study is to investigate the accuracy of the Hancock Method, which predicts distortional buckling strengths, as compared to the 1996 AISI Specification provisions for local and lateral buckling. This study used the experimental results of 62 third point laterally braced tests and 12 laterally unbraced tests. All tests were simple span, cold-formed Z-section supported standing seam roof systems. The local, lateral, and distortional buckling strengths were predicted for each test using the aforementioned methods. These results were compared to the experimentally obtained data and then to each other to determine the most accurate strength prediction method. Based on the results of this study, the Hancock Method for the prediction of distortional buckling strength was the most accurate method for third point braced purlins supporting standing seam roof systems. In addition, a resistance factor was developed to account for the variation between the experimental and the Hancock Method's predicted strengths. / Master of Science

The design of metal building roof and wall systems under uplift and suction wind loading is complicated because the laterally unbraced purlin and girt's free flange is compressed, and the cross-section rotates due to the shear flow. The objective of this thesis is to introduce a Direct Strength Method (DSM) prediction approach for simple span purlins and girts with one flange through-fastened under uplift or suction loading. This prediction method is also applicable for the case when rigid board insulation is placed between the metal panel and through-fastened flange. The prediction method is validated with a database of 62 simple span tests. To evaluate the prediction for the case when rigid board is used, 50 full-scale tests with rigid board insulation are conducted by the author of this thesis. In the experimental study panel failure, connection failure and member (purlin and girt) failure are observed, and they all limit the system's capacity. Another important contribution of this thesis is that it builds the foundation for future study of a general, mechanics-based limit state design approach for metal building roof and wall systems that can accommodate uplift and gravity loads, simple and continuous spans, and through-fastened and standing seam roofs. / Ph. D.

The current specification provisions for the prediction of lateral restraint forces in Z-purlin supported roof systems under gravity loads are in Section D3.1 of the 1996 AISI Cold-Formed Specification. The design equations contained in these provisions are empirical and based on statistical analysis. They were developed using elastic stiffness models of flat roofs and were verified by experimental testing. The provisions need refinement, because the treatment of roof slope and system effects is incorrect. Also, the current design provisions are based upon an assumed panel stiffness value, ignoring the significant difference in required restraint force that occurs when panel stiffness is varied. Therefore, a new restraint force design procedure, having a stronger reliance on engineering principles, is proposed. This new treatment of the static forces in Z-purlin roofs led to a more accurate method of addressing roof slope. Elastic stiffness models, with varying roof slope, panel stiffness, and cross-sectional properties, were used to develop the proposed procedure. The basis of the procedure is to determine the lateral restraint force required for a single purlin system and then extend this result to systems with multiple restrained purlin lines. Roof slope is incorporated into the calculation of the single purlin restraint force, which includes eccentric gravity loads and forces induced by Z-purlin asymmetry. The procedure includes a system effect factor to account for the observed nonlinear increase in restraint force with the number of restrained purlins. An adjustment factor varies the predicted restraint force depending on the shear stiffness of the roof panel. The proposed procedure applies to five bracing configurations: support, third-point, midspan, quarter point, and third-point plus support restraints. / Master of Science

Terças e longarinas metálicas são geralmente projetadas no Brasil desconsiderando a interação com as telhas, ou seja, como barras isoladas, apesar da norma brasileira NBR 14762:2001 apresentar um procedimento de cálculo que leva em consideração tal interação (método do fator R). O comportamento estrutural do sistema terça-telha é complexo e a análise completa deve considerar a não-linearidade geométrica e física, bem como a influência do contato e da conexão terça-telha. Foram analisados modelos numéricos propostos na literatura e desenvolvido um modelo via método dos elementos finitos (MEF) que incorpora as não-linearidades e o contato terça-telha. O modelo foi calibrado com resultados experimentais e posteriormente foi realizada uma análise paramétrica, a qual permitiu gerar expressões que relacionam a força (vento de sucção) com os deslocamentos. Foi também analisada a viabilidade da aplicação do método da resistência direta (MRD) ao dimensionamento de terças restringidas pela telha, empregando o método das faixas finitas (MFF) para a análise de estabilidade elástica, em que a restrição promovida pela telha foi modelada por meio de vínculos elásticos na mesa conectada com a telha. Foram considerados dois casos de distribuição de tensões normais: (i) tensões oriundas somente da flexão e (ii) tensões oriundas da flexão e torção. Em ambos os casos o momento resistente apresentou diferenças relativamente elevadas em relação ao obtido pelo método do fator R, refletindo a necessidade de uma abordagem específica do método para o sistema terça-telha. / The structural behavior of purlin-sheeting system is complex and the complete analysis should consider the physical and geometrical nonlinearity, as well as the influence of the purlin-sheeting contact and connection. The brazilian code NBR 14762:2001 provides a design procedure to consider the interaction between a purlin or girt connected to the sheeting (factor R method). In Brazil purlins and girts are typically designed as isolated beams, without consideration for this purlin-sheeting combination. Numerical models proposed in the literature were analyzed and a finite element model (FEM) was developed considering nonlinearities and the contact between purlin and sheeting. The model was validated through experimental results and then implemented in a parametrical analysis. Expressions were generated using the parametrical results to relate the loading (wind uplift) to the displacements. The direct strength method (DSM) was analyzed to the designed of purlins restrained by sheeting. The finite strip method (FSM) was used for elastic buckling determination. The restraint applied to the sheeting was modeled using an elastic foundation on the flange connected to the sheeting. Two stress distributions were considered: (i) bending stresses and (ii) bending and warping stresses. In both cases the nominal flexural strength presented considerable differences compared to the factor R design method, reflecting the necessity of a specific study to evaluate the viability of the DSM approach for purlin design.

Terças e longarinas metálicas são geralmente projetadas no Brasil desconsiderando a interação com as telhas, ou seja, como barras isoladas, apesar da norma brasileira NBR 14762:2001 apresentar um procedimento de cálculo que leva em consideração tal interação (método do fator R). O comportamento estrutural do sistema terça-telha é complexo e a análise completa deve considerar a não-linearidade geométrica e física, bem como a influência do contato e da conexão terça-telha. Foram analisados modelos numéricos propostos na literatura e desenvolvido um modelo via método dos elementos finitos (MEF) que incorpora as não-linearidades e o contato terça-telha. O modelo foi calibrado com resultados experimentais e posteriormente foi realizada uma análise paramétrica, a qual permitiu gerar expressões que relacionam a força (vento de sucção) com os deslocamentos. Foi também analisada a viabilidade da aplicação do método da resistência direta (MRD) ao dimensionamento de terças restringidas pela telha, empregando o método das faixas finitas (MFF) para a análise de estabilidade elástica, em que a restrição promovida pela telha foi modelada por meio de vínculos elásticos na mesa conectada com a telha. Foram considerados dois casos de distribuição de tensões normais: (i) tensões oriundas somente da flexão e (ii) tensões oriundas da flexão e torção. Em ambos os casos o momento resistente apresentou diferenças relativamente elevadas em relação ao obtido pelo método do fator R, refletindo a necessidade de uma abordagem específica do método para o sistema terça-telha. / The structural behavior of purlin-sheeting system is complex and the complete analysis should consider the physical and geometrical nonlinearity, as well as the influence of the purlin-sheeting contact and connection. The brazilian code NBR 14762:2001 provides a design procedure to consider the interaction between a purlin or girt connected to the sheeting (factor R method). In Brazil purlins and girts are typically designed as isolated beams, without consideration for this purlin-sheeting combination. Numerical models proposed in the literature were analyzed and a finite element model (FEM) was developed considering nonlinearities and the contact between purlin and sheeting. The model was validated through experimental results and then implemented in a parametrical analysis. Expressions were generated using the parametrical results to relate the loading (wind uplift) to the displacements. The direct strength method (DSM) was analyzed to the designed of purlins restrained by sheeting. The finite strip method (FSM) was used for elastic buckling determination. The restraint applied to the sheeting was modeled using an elastic foundation on the flange connected to the sheeting. Two stress distributions were considered: (i) bending stresses and (ii) bending and warping stresses. In both cases the nominal flexural strength presented considerable differences compared to the factor R design method, reflecting the necessity of a specific study to evaluate the viability of the DSM approach for purlin design.

No description available.

Lapped joints of cold-formed steel (CFS) Z-shaped purlins are extensively used in metal building roof systems. The research that has been carried out so far for these lapped connections is primarily focused on connections with round holes. However, the lapped connections with vertical slotted holes are extensively used in current construction practice to simplify the erection of continuous Z-shaped roof purlins. There is no design guideline or recommendation available for CFS Z-purlin lapped connections with vertical slotted holes. Presented in this paper are the results of an experimental study and analysis of the structural behaviour of lapped CFS Z-shaped purlin connections with vertical slotted holes. 42 flexural tests were performed on lapped CFS Z-shaped purlins with vertical slotted connections with different lap lengths, purlin depths, thicknesses and spans. The flexural strength and deflection of each specimen were measured. The characteristics of moment resistance and flexure stiffness of the lapped purlins were computed. The test results show that the lapped purlins with vertical slotted holes may be more flexible than the lapped purlins with round holes or continuous purlins without lapped joint. Thus, the slotted connections may need greater lap lengths to achieve full stiffness of continuous purlins. The results also indicate that the characteristics of moment resistance and flexural stiffness in the slotted connections are dependent on the ratio of lap length to purlin depth, the ratio of lap length to purlin thickness, the ratio of purlin depth to purlin thickness, and the ratio of lap length to span. Based on the results, design recommendations for evaluating the moment resistance and flexural stiffness of lapped slotted connections were proposed.

Made available in DSpace on 2014-06-11T19:25:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-19Bitstream added on 2014-06-13T19:32:22Z : No. of bitstreams: 1 pinto_el_me_ilha.pdf: 1624906 bytes, checksum: 5bc2d5cfa5a9fecd4b7df0008cf99be3 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Fundação de Ensino Pesquisa e Extensão de Ilha Solteira (FEPISA) / O desenvolvimento da presente pesquisa tem a finalidade de estudar um dos efeitos principais de restrição de telhas conectadas nas terças, que é a rigidez ao cisalhamento. O valor da rigidez ao cisalhamento é determinado pela influência da restrição da telha no deslocamento lateral da terça sobre o seu eixo longitudinal, em função do espaçamento dos parafusos de conexão. Para a determinação da rigidez ao cisalhamento foi utilizado um procedimento experimental, semelhante ao modelo numérico, referido como DOUBLE BEAM SHEAR TEST - DBST, que permite avaliar a restrição dada pela telha à terça ao cisalhamento. Para os testes do modelo DBST foi utilizado o Laboratório de Engenharia Civil, onde foram ensaiadas séries desse conjunto para a determinação da rigidez ao cisalhamento. As terças são constituídas de perfil formado a frio. As distâncias entre as terças são compreendidas entre os valores de 1000 a 2300 mm. As telhas são do tipo ondulada com altura de 17 mm e trapezoidal com altura compreendida entre 25 mm e 100 mm. As espessuras das telhas estão entre os valores de 0,43 mm e 0,80 mm. / The development of the present research has the purpose to study one of the main effect of restriction of the sheeting connected in purlin, that it is the rigidity to the shear. The value of the rigidity to the shear is determined by the influence of the restriction of the sheeting in the lateral displacement of purlin on its longitudinal axis, in function of the spacing of the connection screws. For the determination of the rigidity to the shear an experimental procedure was used, similar to the numerical model, related as DOUBLE BEAM SHEAR TEST - DBST, that allows to evaluate the restriction given for the sheeting to purlin to the shear. For the tests of model DBST the Laboratory of Civil Engineering was used, where had been assayed series of this set for the determination of the rigidity to the shear. Purlins are constituted of the cold formed profile. The distances between purlins are understood between the values of 1000 the 2300 mm. The sheeting are of the type wavy with height of 17 mm and trapezoidal with height understood between 25 mm and 100 mm. The thicknesses of the sheeting are between the values of 0,43 mm and 0,80 mm.

Orientador: Renato Bertolino Junior / Banca: José Antonio Matthiesen / Banca: Francisco Carlos Rodrigues / Resumo: O desenvolvimento da presente pesquisa tem a finalidade de estudar um dos efeitos principais de restrição de telhas conectadas nas terças, que é a rigidez ao cisalhamento. O valor da rigidez ao cisalhamento é determinado pela influência da restrição da telha no deslocamento lateral da terça sobre o seu eixo longitudinal, em função do espaçamento dos parafusos de conexão. Para a determinação da rigidez ao cisalhamento foi utilizado um procedimento experimental, semelhante ao modelo numérico, referido como DOUBLE BEAM SHEAR TEST - DBST, que permite avaliar a restrição dada pela telha à terça ao cisalhamento. Para os testes do modelo DBST foi utilizado o Laboratório de Engenharia Civil, onde foram ensaiadas séries desse conjunto para a determinação da rigidez ao cisalhamento. As terças são constituídas de perfil formado a frio. As distâncias entre as terças são compreendidas entre os valores de 1000 a 2300 mm. As telhas são do tipo ondulada com altura de 17 mm e trapezoidal com altura compreendida entre 25 mm e 100 mm. As espessuras das telhas estão entre os valores de 0,43 mm e 0,80 mm. / Abstract: The development of the present research has the purpose to study one of the main effect of restriction of the sheeting connected in purlin, that it is the rigidity to the shear. The value of the rigidity to the shear is determined by the influence of the restriction of the sheeting in the lateral displacement of purlin on its longitudinal axis, in function of the spacing of the connection screws. For the determination of the rigidity to the shear an experimental procedure was used, similar to the numerical model, related as DOUBLE BEAM SHEAR TEST - DBST, that allows to evaluate the restriction given for the sheeting to purlin to the shear. For the tests of model DBST the Laboratory of Civil Engineering was used, where had been assayed series of this set for the determination of the rigidity to the shear. Purlins are constituted of the cold formed profile. The distances between purlins are understood between the values of 1000 the 2300 mm. The sheeting are of the type wavy with height of 17 mm and trapezoidal with height understood between 25 mm and 100 mm. The thicknesses of the sheeting are between the values of 0,43 mm and 0,80 mm. / Mestre