Francisco Carlos Rodrigues

Flambagem lateral com torção em vigas com perfis de alma senoidal

A Finite Element model was developed in order to study the behavior of beams with sinusoidal webs, subjected to Lateral Torsion Buckling, taking into account residual stresses and initial imperfections. The numerical model was validated by comparison with four experimental tests. To start the analysis of the model, a linear buckling analysis is made to find the first eigenvalue and the correspondent buckling mode. The next step is to assign the buckling mode to the geometrical model and the initial imperfection to the maximum mode displacement. Then an incremental plastic analysis is done, taking into account large deflections, until the model is unable to take on any other load increments due to physical or geometrical degeneration. Comparisons between numerical and experimental results are included. Comparisons between the results of eight numerical analyses and the correspondent provisions of a procedure based on the Brazilian code NBR 8800 (1986) are also included. For these eight comparisons 6 models were chosen to reach instability in the inelastic range and 2 in the elastic range. The sinusoidal web was ignored for the calculation of the geometrical properties.

Cross Laminated Timber in the International Context and in Brazil: Most Relevant Aspects

Timber is still being rediscovered as building material of excellence in Brazil, and especially as one of the most environmentally friendly one. In the scenario of the production of sustainable buildings, the construction system that uses wood panels - widely used in Europe, USA and Canada - called Glued Laminated Timber (GLULAM) and Cross Laminated Timber (CLT), occupies a prominent place, especially by the possibility of using wood from planted forests. This work aims to provide an overview of what is being produced in Europe and in Brazil.

ANÁLISE EXPERIMENTAL DO COMPORTAMENTO DE BARRAS COMPOSTAS COMPRIMIDAS FORMADAS POR PERFIS TUBULARES CIRCULARES CONCÊNTRICOS LAMINADOS DE AÇO

Este trabalho apresenta um estudo teorico-experimental do comportamento de barras compostas axialmente comprimidas formadas por perfis tubulares circulares concentricos laminados de aco. O uso dessas barras e uma solucao inovadora para situacoes nas quais exista restricao de projeto quanto ao diâmetro maximo que pode ser adotado, ou que um unico perfil laminado nao atinja a forca resistente de compressao requerida. Este estudo inicia-se com a apresentacao do comportamento das barras comprimidas, abordando os aspectos da estabilidade estrutural, a influencia de imperfeicoes iniciais geometricas e de material, os procedimentos de dimensionamento normativos e o mecanismo de colapso. Foi apresentado o estudo numerico desenvolvido para os perfis tubulares circulares concentricos laminados de aco, tal como seu processo de montagem e seu procedimento de calculo. Na analise experimental, foram realizados ensaios de forca axial de compressao em barras compostas rotuladas nas duas extremidades, constituidas por dois e tres perfis tubulares concentricos, sem ligacao entre os perfis ao longo do comprimento e com ligacoes fixas e deslizantes, de modo a obter as respostas em termos de capacidade resistente e facilidade de montagem. Nessa etapa, foi desenvolvido um metodo para medir as imperfeicoes geometricas dos perfis que compoem o conjunto. A analise numerica foi realizada por meio de simulacoes via Metodo dos Elementos Finitos, utilizando o programa ABAQUS. Nessas simulacoes, para calibracao dos modelos numericos, foram consideradas as imperfeicoes iniciais geometricas e relacoes geometricas obtidas nos modelos experimentais. A formulacao proposta para o dimensionamento dos perfis tubulares circulares concentricos apresentaram valores sempre conservadores. Apos a validacao da calibracao, foi feita uma analise parametrica, variando-se as dimensoes da secao transversal dos tubos que compoem as barras compostas e sentidos das imperfeicoes geometricas iniciais desses tubos, com o intuito de investigar a influencia desses parâmetros no comportamento da barra composta e no valor da forca resistente.

Estimation of friction contribution in the behavior of steel-concrete composite beams with flexible shear connectors

A shear connector, developed to be applied to a composite beam whose steel profile is a thin-walled box profile, displayed much greater flexibility than the conventional welded shear connector, leading to particular issues in the composite beam behaviour. One of these issues is the role played by friction at the interface between the steel profile and the slab which, under particular circumstances, may be relevant for serviceability limit states and also for ultimate limit states. The Brazilian and American Standards do not yet recognize the friction contribution in the behaviour of composite beams, though they recognize this contribution in composite slabs. This paper presents the experimental tests carried out with and without friction contribution on simple supported composite beams with flexible connectors and the numerical models developed to simulate the behaviour of the tested beams. The experimental tests revealed significant increases in strength and stiffness of the composite beam due to friction contribution and the comparisons between numerical and experimental results displayed good correlations.

Buckling of Masts of Bamboos Bundles

Bamboos generally have elasticity module in compression of about 9 GPa, which is a relatively low value compared to timber and concrete, 20 GPa, and steel, 200 GPa. However, the compressive strength is high - 40 to 80 MPa – that, combined with axissimetria of the cross section, makes the bamboos structural elements with high strength and flexibility. Considering the low apparent specific weight of the material 8 kN/m3, photosynthetic production and workability, bamboos have no competitor in the market so that loads can be absorbed independently by any of the above materials. But the industrial structural elements may be produced with dimensions and geometries provided in accordance with the load to be transported. This is not the case of bamboo. Thus, the capacity of the bamboo in compression becomes limited by its natural flexural rigidity, EI. Thus, different structural systems with pipe threads to make large columns or masts were investigated, [1,2], all with bamboo Phyllostachys pubescens species. In this paper, a kind of mast composed of a central bamboo 6 m in length and six smaller segments axi-symmetrically distributed around this central bamboo will be presented. This proposed design is organizationally a set of bars shackled by steel bands along the length of the beam. Flexion-compression tests with bamboo species Phyllostachys pubescens, combined with numerical modeling through the MEF were made. The loading capacity was tripled and the lateral deviations are negligible when compared with the axial bamboo tested alone. This mast, while consuming a relatively high number of bamboo units, has the advantages of ease and constructive possibility of structural use of smaller diameter bamboo. All the design and results of experimental and numerical analyzes will be discussed in this paper.

Bamboo Mast for Lightweight Arquitecture

Bamboo is a pipe produced by solar energy. It is a plant of the graminae family which grows up all over tropical and part of subtropical regions of the world in more than 1250 species. High biomass production, high mechanical resistance, low specific weight and easy workability has done of bamboo a promise to future generations in relationship to sustainable construction systems. Bamboos of the Phyllostachys pubescens species are one of the most resistant and straight axis bamboos, used in China as material construction and other applications, as paper and fabrics. They are the most commercial bamboos of China and its forests covers 5,6 millions of hectare in that country. This exotic species is met on small plantations in Rio de Janeiro and São Paulo states of Brazil. Many characteristics turns bamboo a smart structural element: high resistance/weight ratio; natural nodes spaced along the culm which avoids local buckling and graded distribution of the fibers from inner to outer side of the thickness wall. So, the application of bamboos as tensile structures supports is a coherent choice since these modern tents characterize a lightweight architecture. Some structural bamboos can attain even more than 15 meters long with 10 cm mean diameter. To increase the load capacity of this slender bar and make feasible bamboo use as masts for tensile structures, an hybrid mast using bamboo as axis and 4 steel cables along of was designed and tested in the Structural System Laboratory LASE, and Structures Experimental Analysis Laboratory LAEES, respectively. In this paper it will be presented the results of the mechanical tests for 2 different masts with 6 meters long. Both masts have the same design but important differences which will be discussed in the paper.

Design and Mechanical Tests of Bamboo Masts

Bamboos are smart natural tubes and a resistant material. Many species can be selected with 10 cm basal diameter, 12 m high and approximately straight longitudinal axis. A slender element like that has a relatively low load capacity under compression force. This limitation can be by passed through a composition of bamboo and cables. Through coherent design, this composition may produce an aesthetical and light mast with high axial compression resistance. This hybrid structure opens a big application for bamboo tubes, as for example, masts for the modern tents, known as tensile structures in the low weight architecture. Different compositions which use a large number of bamboos can be derived from this one. So, the mast mechanical performance investigation opens the way for another more complex systems understanding. In this paper, the design of a bamboo mast with 6 meters long is developed. A previous numerical investigation through SAP 2000 v14 structural analysis software was used for mast design and project. Cables and accessories; length and connections of the bracings and others constructive details are investigated until the conquest of a well fitted mast. A non destructive compression mechanical test of the mast rotation free at ends was done. Loads, tension in cables and lateral displacements were gauged in real time. Test results and numerical analysis show that masts can support compression forces many times bigger than bamboo itself.

Incêndio real em um apartamento de interesse social: um estudo de caso

This paper describes the behavior of a cold-formed steel (CFS) framed structure in response to a real fire that occurred in a residential apartment. A set of residential buildings is composed by four identical four-story blocks of eight apartments per floor, housed by poor people; each apartment has 44 m2 of total area. The Brazilian Code does not require that this type of building be checked for fire safety. A real fire in a residential apartment was modeled, as well the structural fire resistance; the maximum fire temperature reached during the burning on the structural material was assessed by scanning electron microscopy tests for the further comparative analysis between the theoretical and actual results. A CFD scenario representative of the actual building geometry, materials and fire behavior was modeled by means of the software SMARTFIRE. A steel thermal analysis in fire situation was conducted by means the software SUPERTEMPCALC, and the structural analysis of the steel frame was performed according to the expressions recommended by the Brazilian Standard for design of CFS for room temperature, based on the AISI/USA, but using the strength reduction factors recommended by Eurocode 3 part1.2.