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Este trabalho apresenta um estudo sobre as estruturas metálicas espaciais abordando os seguintes aspectos: histórico e desenvolvimento, tipos, vantagens do sistema tridimensional e comportamento estrutural. Atenção especial é dispensada às tipologias de treliças espaciais mais comuns no Brasil, formadas por tubos circulares com variações de inércia nas extremidades. A influência da variação de inércia nas extremidades das barras no comportamento destes elementos isoladamente (resistência à compressão) e comportamento global da estrutura, foi estudada via elementos finitos. Descrevem-se vários sistemas de ligações patenteados utilizados em outros países e os comumente usados no Brasil. Apresentamse resultados experimentais e teóricos de uma treliça espacial com dimensões em planta de 7,5 x 7,5m. Na análise teórica foram considerados a variação de inércia nas barras e os efeitos da não linearidade geométrica. Analisou-se também, com as mesmas considerações anteriores, modelos de treliças espaciais de dimensões maiores que o modelo ensaiado.

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Space trusses built in Brazil use basically two connection systems. In system 1, the node is formed by the superimposition of tubular section bars with stamped ends connected by a single bolt. The system 2 is a node consisting of welded steel plates to which bars with stamped ends or bars with end plates are connected. The authors have been engaged in theoretical and experimental studies to characterize the behaviour of these systems, including modifications to improve structural performance and establishing analytical models consistent with experimental behaviour. The theoretical analyses by finite element method have been performed utilizing the ANSYS and LUSAS software programs, using three distinct approaches: (i) analyses of isolated bars with section variations at the ends, (ii) analyses of the global behaviour of the structure considering the eccentricities on the connection, section variations in the bars and nonlinear behaviour, and (iii) numerical analyses of the local behaviour of the connection and its influence on global response and collapse modes.

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This paper describes a strategy for numerical simulation using the Finite Elements Method to analyze connections in steel space trusses composed of circular section bars with stamped ends. This type of space truss is widely used in Brazil and the bar ends are stamped to compose the connection. This is an inexpensive solution, but poses several structural problems, thus requiring studies to establish criteria and limits for its use. The most important variables of connections and structural behavior, such as eccentricities, section variation at the bar ends, and physical and geometrical nonlinearity were introduced into the numerical model. The interaction between the bars (relative displacement and sliding in the nodal region) was simulated by means of contact elements. The numerical analysis involved modeling of a complete joining of the structure with shell elements, which were inserted at different points of the space truss. The results were satisfactory, enabling us to evaluate how the behavior of the connections affects the strength and collapse mode of the space trusses.

Space trusses composed of tubular steel members with stamped ends connected by a single bolt ( system 1) are commonly used in Brazil. Although this is a simple solution and, therefore, interesting from an economic standpoint, it has presented structural problems, since the reduction of inertia at the member ends and the eccentricities are not foreseen in the design phase. This fact has caused some roofs to collapse partially or even totally, posing serious safety risks for their users. Another system that has been widely employed consists of members with stamped ends bolted to a node device made up of welded plates ( system 2), which eliminates eccentricities at the nodes. In this study, the structural performance of the type of stamping was initially analyzed by axial compression tests on members, followed by tests on space truss prototypes composed of system 1 and system 2. The experimental results were compared to the theoretical values obtained based on the classical models adopted in designs, allowing for the overall evaluation of structural performance of both systems, thus contributing toward the safe use of these structures.

This paper presents the results of experimental analysis of space trusses using steel tubular bars with flattened ends. The connections are formed by overlapped bars connected by single bolt. Such system has been used due to the low cost and assembly facilities. The behavior and collapse modes were determined by experimental analysis on six space trusses with 1.5 m height and spans of 7.5 m × 7.5 m and 7.5 m × 15 m. Structures with steel nodes in the top corner and supports points were also tested. The structural collapse was caused by either connection collapse or yielding in the bar ends. Traditional theoretical analysis models (linear truss model) are not suitable for these structures.