Atualmente, os perfis de chapa dobrada têm encontrado intensa aplicação como elementos estruturais nas construções em aço e como consequência, estão sujeitos aos mais diversos tipos de carregamentos. Este trabalho apresenta os aspectos gerais do dimensionamento de perfis de chapa dobrada submetidos à flexão enquanto utilizados como vigas propriamente dito e, também, enquanto utilizados como terças. Analisam-se seções tipo U, tipo U enrijecido e tipo Z enrijecido. Os ensaios em perfis fletidos foram realizados sobre 3 diferentes condições de carregamento, com dois vãos distintos, em um total de sessenta e quatro perfis ensaiados. Para os perfis conectados às telhas de aço, os ensaios foram realizados em uma \"caixa de sucção\" desenvolvida especificamente para este projeto. Os perfis foram conectados às telhas pela mesa por meio de parafusos auto-brocantes, sendo realizados quinze ensaios. Os resultados dos ensaios são comparados com os resultados teóricos, resultados normatizados e resultados de alguns procedimentos aproximados. / Nowadays, the cold-formed steel members have intense application as structural elements in constructions and, in consequence, they are subjected to several types of loads. This work presents the general aspects of the study of cold-formed steel members subjected to flexion used as beams and, also, as purlins. Sections of type U, type C and type Z are analysed. The tests in beams were carried out under three different conditions of loads, with two distinct spans, in total of sixty four tests. For the purlins connected to roof system, the tests were in a \"suction box\", developed especially for this project. The purlins were connected to the roof system by the flange by using self-drilling screws, being carried out fifteen tests. The results of those tests are compared with the theoretical results, design specification provisions and results of some approximated procedures.

O presente trabalho apresenta proposta de análise numérica de perfis de aço formados a frio submetidos à compressão centrada. Trata-se de investigação, realizada por meio de elementos finitos, com vistas à análise da influência de imperfeições geométricas iniciais presentes em perfis U simples e U enrijecido, sob os aspectos de sua forma, magnitude e sentido. A imperfeição geométrica é adotada na forma de modos de falha local, global e distorcional, observando a suscetibilidade a tais modos para a seção de interesse. Cada tipo de imperfeição é avaliado de forma isolada e, em seguida, de forma associada (conjunta). São apresentados aspectos referentes à estratégia de modelagem adotada na construção dos modelos numéricos, bem como aspectos de interesse com relação às análises não-lineares aqui consideradas. Para fins de obtenção da força de colapso, fica examinada a possibilidade de empregar modos de falha isolados para representar as imperfeições geométricas, porém, com a amplitude previamente ajustada. Para os casos de imperfeições associadas, para representar a imperfeição geométrica, se destaca o papel do sentido da imperfeição do tipo global com relação a sua associação às imperfeições dos tipos local e distorcional para perfis U enrijecidos, bem como à imperfeição do tipo local para perfis U simples. / The work presents a numerical analysis on cold-formed steel members compressed between pinned ends. One is about an inquiry carried through in finite elements in which it was studied the influence of initial geometric imperfections, existing in plain channels and lipped channels, under the aspects of its form, magnitude and signal. The geometric imperfection is adopted on the forms of the local, global and distortional buckling modes, observing the susceptibility to such modes for each type of section. Each imperfection is evaluated on the isolated way and after that of associated way. Referring aspects to the strategy of modeling adopted in the construction of the numerical models are presented, as well as aspects of interest with regard to the developed nonlinear analyses. For ends of attainment of the ultimate load, it is examined the possibility to use isolated buckling modes to represent the geometric imperfections, as long as the amplitude it is adjusted. The cases that had applied coupled imperfection to represent the geometric imperfection detach the paper of the signal of the imperfection of the global type with regard to its association to the imperfections of the types local and distortional for lipped channels and, to the one of the local type for plain channels.

No Brasil, o emprego de estruturas de aço constituídas por perfis formados a frio tem crescido consideravelmente, em virtude da ampla disponibilidade de laminados planos no mercado (chapas finas), bem como pela busca de soluções estruturais mais competitivas. Nesse cenário, pode-se destacar as estruturas mistas de aço e concreto destinadas aos edifícios habitacionais de pequeno porte, em que os tradicionais perfis laminados são substituídos por perfis formados a frio tanto nas vigas como nos pilares. Embora o sistema de vigas mistas possa ser considerado consolidado no campo dos perfis laminados e soldados, o comportamento estrutural no caso de perfis formados a frio necessita de investigação mais aprofundada, de modo a verificar os modos de ruína e a viabilidade do emprego dos modelos teóricos clássicos. Nesse trabalho foi desenvolvido um estudo teórico e experimental sobre as vigas mistas em perfis formados a frio duplo U enrijecido, focalizando a ligação mista (ligação viga-pilar) e consequentemente a resposta estrutural da região de momento fletor negativo. O programa experimental consistiu da análise de dois protótipos cruciformes para determinar a curva momento-rotação, o momento resistente, a rigidez, a capacidade de rotação e identificar modos de falha. Foi possível constatar maior capacidade de rotação da ligação com cantoneiras de assento e de alma quando comparada a uma ligação totalmente soldada. Comparando com o modelo experimental o método dos componentes avaliou de forma razoável a rigidez em serviço, já o método proposto por Leon et. al. superestimou muito esse parâmetro, a capacidade de rotação foi avaliada de forma satisfatória pelos dois métodos. O momento resistente negativo da viga mista obtido experimentalmente apresentou um valor intermediário entre os valores teóricos obtidos por processo plástico e elástico. / In Brazil, the cold-formed steel structures have been widely used justified by the large availability of steel sheets in the market (thin sheets) and the search for more competitive structural solutions. Thus as steel and concrete composite structures are applied in small constructions the traditional hot-rolled one is replaced by cold-formed members in the beams and columns. Even though the composite beams system is known in the hot-rolled and welded shapes field, the structural behavior of the cold-formed steel still needs more accurate investigation to verify the failure modes and the viability of the classic theoretical models. In this work a theoretical and experimental study about cold-formed steel and concrete composite beams was developed, focusing on the beam-to-column connection and the structural behavior on the region of hogging bending. For the experimental program two cruciform models of beam-column connections were analyzed to obtain the moment-rotation curves, the stiffness, and the rotation capacity. It was possible to verify the largest rotation capacity of the connection with the steel seat and web angle when compared with the totally welded connection. In the case of connection the method of the components estimates well the secant stiffness and the rotation capacity presenting a value closer to the ones obtained experimentally, Leon et al. procedures estimated well the initial stiffness and the rotation capacity, but the value of the secant stiffness is much larger than the experimental one. In the case of composite beam the ultimate strength (Mmax) experimentally obtained presented an intermediate value to the ones obtained by the plastic and elastic method.

Cold-Formed Steel (CFS) is a material used in the fabrication of structural and non-structural elements for the construction of commercial and residential buildings. CFS exhibits several advantages over other construction materials such as wood, concrete and hot-rolled steel (structural steel). The outstanding advantages of CFS are its lower overall cost and non-combustibility. The steel industry has promoted CFS in recent decades, causing a notable increase in the usage of CFS in building construction. Yet, structural steel elements are still more highly preferred, due to the complex analysis and design procedures associated with CFS members. In addition, the seismic performance of CFS buildings and their elements is not well known. The primary objective of this study is to develop a method for the seismic assessment of the lateral-load resistant shear wall panel elements of CFS buildings. The Performance-Based Design (PBD) philosophy is adopted as the basis for conducting the seismic assessment of low- and mid-rise CFS buildings, having from one to seven storeys. Seismic standards have been developed to guide the design of buildings such that they do not collapse when subjected to specified design earthquakes. PBD provides the designer with options to choose the performance objectives to be satisfied by a building to achieve a satisfactory design. A performance objective involves the combination of an earthquake (i.e., seismic hazard) and a performance level (i.e., limit state) expected for the structure. The building capacity related to each performance level is compared with the demand imposed by the earthquake. If the earthquake demand is less than the building capacity, the structure is appropriately designed. The seismic performance of a CFS building is obtained using pushover analysis, a nonlinear method of seismic analysis. This study proposes a Simplified Finite Element Analysis (SFEA) method to carry out the nonlinear structural analysis. In this study, lateral drifts associated with four performance levels are employed as acceptance criteria for the PBD assessment of CFS buildings. The lateral drifts are determined from experimental data. In CFS buildings, one of the primary load-resistant elements is Shear Wall Panel (SWP). The SWP is constructed with vertically spaced and aligned C-shape CFS studs. The ends of the studs are screwed to the top and bottom tracks, and structural sheathing is installed on one or both sides of the wall. For the analysis of CFS buildings, Conventional Finite Element Analysis (CFEA) is typically adopted. However, CFEA is time consuming because of the large number of shell and frame elements required to model the SWP sheathing and studs. The SFEA proposed in this study consists of modeling each SWP in the building with an equivalent shell element of the same dimensions; that is, a complete SWP is modeled by a 16-node shell element. Thus, significantly fewer elements are required to model a building for SFEA compared to that required for CFEA, saving both time and resources. A model for the stiffness degradation of a SWP is developed as a function of the lateral strength of the SWP. The model characterizes the nonlinear behaviour of SWP under lateral loading, such that a realistic response of the building is achieved by the pushover analysis. The lateral strength of a SWP must be known before its seismic performance can be assessed. In current practice, the lateral strength of a SWP is primarily determined by experimental tests due to the lack of applicable analytical methods. In this investigation, an analytical method is developed for determining the ultimate lateral strength of SWP, and associated lateral displacement. The method takes into account the various factors that affect the behaviour and the strength of SWP, such as material properties, geometrical dimensions, and construction details. To illustrate the effectiveness and practical application of the proposed methodology for carrying out the PBD assessment of CFS buildings, several examples are presented. The responses predicted by the SFEA are compared with responses determined experimentally for isolated SWP. In addition, two building models are analyzed by SFEA, and the results are compared with those found by SAP2000 (2006). Lastly, the PBD assessment of two buildings is conducted using SFEA and pushover analysis accounting for the nonlinear behaviour of the SWP, to demonstrate the practicality of the proposed technology.

Cold-Formed Steel (CFS) is a material used in the fabrication of structural and non-structural elements for the construction of commercial and residential buildings. CFS exhibits several advantages over other construction materials such as wood, concrete and hot-rolled steel (structural steel). The outstanding advantages of CFS are its lower overall cost and non-combustibility. The steel industry has promoted CFS in recent decades, causing a notable increase in the usage of CFS in building construction. Yet, structural steel elements are still more highly preferred, due to the complex analysis and design procedures associated with CFS members. In addition, the seismic performance of CFS buildings and their elements is not well known. The primary objective of this study is to develop a method for the seismic assessment of the lateral-load resistant shear wall panel elements of CFS buildings. The Performance-Based Design (PBD) philosophy is adopted as the basis for conducting the seismic assessment of low- and mid-rise CFS buildings, having from one to seven storeys. Seismic standards have been developed to guide the design of buildings such that they do not collapse when subjected to specified design earthquakes. PBD provides the designer with options to choose the performance objectives to be satisfied by a building to achieve a satisfactory design. A performance objective involves the combination of an earthquake (i.e., seismic hazard) and a performance level (i.e., limit state) expected for the structure. The building capacity related to each performance level is compared with the demand imposed by the earthquake. If the earthquake demand is less than the building capacity, the structure is appropriately designed. The seismic performance of a CFS building is obtained using pushover analysis, a nonlinear method of seismic analysis. This study proposes a Simplified Finite Element Analysis (SFEA) method to carry out the nonlinear structural analysis. In this study, lateral drifts associated with four performance levels are employed as acceptance criteria for the PBD assessment of CFS buildings. The lateral drifts are determined from experimental data. In CFS buildings, one of the primary load-resistant elements is Shear Wall Panel (SWP). The SWP is constructed with vertically spaced and aligned C-shape CFS studs. The ends of the studs are screwed to the top and bottom tracks, and structural sheathing is installed on one or both sides of the wall. For the analysis of CFS buildings, Conventional Finite Element Analysis (CFEA) is typically adopted. However, CFEA is time consuming because of the large number of shell and frame elements required to model the SWP sheathing and studs. The SFEA proposed in this study consists of modeling each SWP in the building with an equivalent shell element of the same dimensions; that is, a complete SWP is modeled by a 16-node shell element. Thus, significantly fewer elements are required to model a building for SFEA compared to that required for CFEA, saving both time and resources. A model for the stiffness degradation of a SWP is developed as a function of the lateral strength of the SWP. The model characterizes the nonlinear behaviour of SWP under lateral loading, such that a realistic response of the building is achieved by the pushover analysis. The lateral strength of a SWP must be known before its seismic performance can be assessed. In current practice, the lateral strength of a SWP is primarily determined by experimental tests due to the lack of applicable analytical methods. In this investigation, an analytical method is developed for determining the ultimate lateral strength of SWP, and associated lateral displacement. The method takes into account the various factors that affect the behaviour and the strength of SWP, such as material properties, geometrical dimensions, and construction details. To illustrate the effectiveness and practical application of the proposed methodology for carrying out the PBD assessment of CFS buildings, several examples are presented. The responses predicted by the SFEA are compared with responses determined experimentally for isolated SWP. In addition, two building models are analyzed by SFEA, and the results are compared with those found by SAP2000 (2006). Lastly, the PBD assessment of two buildings is conducted using SFEA and pushover analysis accounting for the nonlinear behaviour of the SWP, to demonstrate the practicality of the proposed technology.

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.

iv ABSTRACT SEISMIC DESIGN OF COLD FORMED STEEL STRUCTURES IN RESIDENTIAL APPLICATIONS Uygar, Celaletdin M.Sc., Department of Civil Engineering Supervisor: Prof. Dr. &Ccedil / etin Yilmaz May 2005, 82 pages In this study, lateral load bearing capacities of cold formed steel framed wall panels are investigated. For this purpose lateral load bearing alternatives are analyzed numerically by computer models and results are compared with already done experimental studies and approved codes. In residential cold formed steel construction, walls are generally covered with cladding material like oriented strand board (OSB) or plywood on the exterior wall surface and these sheathed light gauge steel walls behave as shear walls with significant capacity. Oriented strand board is used in analytical models since OSB claddings are most commonly used in residential applications. The strength of shear walls depends on different parameters like screw spacing, strength of sheathing, size of fasteners used and aspect ratio. SAP2000 software is used for structural analysis of walls and joint force outputs are collected by Microsoft Excel. The yield strength of shear walls at which first screw connection reaches its shear capacity is calculated and load carrying capacity per meter length is found. The nonlinear analysis is also done by modeling the screw connections between OSB and frame as non-linear link and the nominal shear capacities of walls are calculated for different screw spacing combinations. The results are consistent with the values in shear wall design Guide and International Building Code 2003. The other lateral load bearing method is flat strap X-bracing on wall surfaces. Various parameters like wall frame section thickness, flat strap area, aspect ratio and bracing number are investigated and results are evaluated. The shear walls in which X-bracing and OSB sheathing used together are also analyzed and the results are compared with separate analyses.

O presente trabalho apresenta proposta de análise numérica de perfis de aço formados a frio submetidos à compressão centrada. Trata-se de investigação, realizada por meio de elementos finitos, com vistas à análise da influência de imperfeições geométricas iniciais presentes em perfis U simples e U enrijecido, sob os aspectos de sua forma, magnitude e sentido. A imperfeição geométrica é adotada na forma de modos de falha local, global e distorcional, observando a suscetibilidade a tais modos para a seção de interesse. Cada tipo de imperfeição é avaliado de forma isolada e, em seguida, de forma associada (conjunta). São apresentados aspectos referentes à estratégia de modelagem adotada na construção dos modelos numéricos, bem como aspectos de interesse com relação às análises não-lineares aqui consideradas. Para fins de obtenção da força de colapso, fica examinada a possibilidade de empregar modos de falha isolados para representar as imperfeições geométricas, porém, com a amplitude previamente ajustada. Para os casos de imperfeições associadas, para representar a imperfeição geométrica, se destaca o papel do sentido da imperfeição do tipo global com relação a sua associação às imperfeições dos tipos local e distorcional para perfis U enrijecidos, bem como à imperfeição do tipo local para perfis U simples. / The work presents a numerical analysis on cold-formed steel members compressed between pinned ends. One is about an inquiry carried through in finite elements in which it was studied the influence of initial geometric imperfections, existing in plain channels and lipped channels, under the aspects of its form, magnitude and signal. The geometric imperfection is adopted on the forms of the local, global and distortional buckling modes, observing the susceptibility to such modes for each type of section. Each imperfection is evaluated on the isolated way and after that of associated way. Referring aspects to the strategy of modeling adopted in the construction of the numerical models are presented, as well as aspects of interest with regard to the developed nonlinear analyses. For ends of attainment of the ultimate load, it is examined the possibility to use isolated buckling modes to represent the geometric imperfections, as long as the amplitude it is adjusted. The cases that had applied coupled imperfection to represent the geometric imperfection detach the paper of the signal of the imperfection of the global type with regard to its association to the imperfections of the types local and distortional for lipped channels and, to the one of the local type for plain channels.

Atualmente, os perfis de chapa dobrada têm encontrado intensa aplicação como elementos estruturais nas construções em aço e como consequência, estão sujeitos aos mais diversos tipos de carregamentos. Este trabalho apresenta os aspectos gerais do dimensionamento de perfis de chapa dobrada submetidos à flexão enquanto utilizados como vigas propriamente dito e, também, enquanto utilizados como terças. Analisam-se seções tipo U, tipo U enrijecido e tipo Z enrijecido. Os ensaios em perfis fletidos foram realizados sobre 3 diferentes condições de carregamento, com dois vãos distintos, em um total de sessenta e quatro perfis ensaiados. Para os perfis conectados às telhas de aço, os ensaios foram realizados em uma \"caixa de sucção\" desenvolvida especificamente para este projeto. Os perfis foram conectados às telhas pela mesa por meio de parafusos auto-brocantes, sendo realizados quinze ensaios. Os resultados dos ensaios são comparados com os resultados teóricos, resultados normatizados e resultados de alguns procedimentos aproximados. / Nowadays, the cold-formed steel members have intense application as structural elements in constructions and, in consequence, they are subjected to several types of loads. This work presents the general aspects of the study of cold-formed steel members subjected to flexion used as beams and, also, as purlins. Sections of type U, type C and type Z are analysed. The tests in beams were carried out under three different conditions of loads, with two distinct spans, in total of sixty four tests. For the purlins connected to roof system, the tests were in a \"suction box\", developed especially for this project. The purlins were connected to the roof system by the flange by using self-drilling screws, being carried out fifteen tests. The results of those tests are compared with the theoretical results, design specification provisions and results of some approximated procedures.

Terças de aço formadas a frio são muito utilizadas em sistemas de cobertura e fechamento. Para conferir continuidade entre tramos adjacentes e possibilitar um melhor aproveitamento de material, são empregadas ligações parafusadas por transpasse e com luva. O comportamento estrutural dessas ligações é muito dependente da sua configuração geométrica e do nível de carregamento. Com base em uma série de nove experimentos e análises teóricas, o comportamento estrutural dessas ligações foi investigado no tocante aos esforços resistentes e à rigidez. Observou-se que o modo de falha tem sempre uma componente distorcional significativa e uma resistência menor que a prevista pela metodologia atual de projeto. No caso do momento fletor resistente, a distribuição de tensões de flexão oblíqua é a que melhor se aproxima do comportamento real das terças, sendo possível a partir de uma análise de estabilidade elástica considerando tal comportamento, e, baseado no método da resistência direta e na curva de dimensionamento do modo distorcional, obter uma previsão segura do momento fletor resistente. Além disso, a rigidez da ligação, com relação aos deslocamentos verticais é bastante dependente do tipo de ligação, sendo que as terças com ligações por luva são mais deformáveis que terças sem ligações. Por outro lado, terças com ligações por transpasse são menos deformáveis que terças fisicamente contínuas. As parcelas de rigidez da ligação são apresentadas, e a componente de deformação do furo é a mais significativa. Uma expressão para deduzir a rigidez rotacional da ligação é apresentada, juntamente com um modelo de barras para modelagem da ligação. Os resultados teóricos se ajustam muito bem aos experimentais. Conclui-se em linhas gerais, que as ligações por transpasse podem ser consideradas plenamente satisfatórias do ponto de vista de comportamento estrutural, sendo que terças com essas ligações são mais resistentes e rígidas que terças com continuidade física. O mesmo não ocorre nas terças com ligações por luva, porém, dada a limitação no número de ensaios, tais ligações carecem mais estudos. / Cold-formed steel purlins are widely used in roofs and wall systems. The continuity of long runs of cold-formed steel purlins is guaranteed by sleeve and overlap bolted connections, which allows a better load distribution and material savings. The structural behavior of these connections is highly dependent on their geometric configuration and load level. The strength and stiffness of these connections were determined through a series of nine experiments, numerical and analytical analysis. Results have shown that distortional buckling has a major contribution on the stability analysis of the cold-formed steel purlin. To safely determine the flexural strength of the purlin, one must consider unrestrained bending stress distribution and distortional buckling. The connection type influences the rigidity of the purlin thus the vertical displacement. Purlins with overlapped connections are stiffer than physically continuous ones, although purlins with sleeved connections are not. The bearing deformation at the connection region is responsible for a reduction in the system stiffness. To account for the change in stiffness and determine the vertical displacement, an expression for the bearing stiffness and a beam model are proposed. The results of this model show good agreement with experimental data. The general conclusion of this research is: overlapped bolted connections enhance the structural response of the purlins when compared to physically continuous ones. The same does not hold true for purlins with sleeved connections.