Abstract
Abstract Circular hollow sections are usually used in long-span roof truss systems. One of the typology for connecting elements in such structures involves the flattening of bar ends. This article presents the numerical analysis of a plane truss composed of circular hollow sections, in which diagonal bars have flattened ends. In this sense, a new flattening typology called stiffened flattening is proposed, characterized by a non-flat geometry, with the creation of stiffeners in the lateral edges of the diagonal flattened ends. The diagonal connecting system with the chord members uses connecting plates. The plates are welded to the chords and the diagonals are connected to latter through a single bolt. The numerical analysis using finite elements method was developed in two stages through ANSYS software with the Parametric Design Language (APDL), in which parameters such as geometry, materials, element types, boundary conditions and loads are specified. A non-linear analysis was performed using shell elements on the chords, diagonals, plates and welds, and contact elements between the diagonals with stiffened flattened ends and the connecting plates. Initially, a numerical study of the connecting node and the stiffened flattened end was performed, and the results directed the modeling of the plane truss. The numerical results were calibrated with the experimental truss results in full scale. The numerical result of the plane truss was also compared to a theoretical study, considering the axial load eccentricity applied in the diagonal with stiffened flattened ends. The study was based on the consideration of combined effects of axial force and bending moment provided by the Brazilian standard ABNT NBR 8800:2008. The final results indicate that the numerical model proposed is efficient and has good correlation with the experimental and theoretical results.
Highlights
The industrial market has a wide variety of structural steel sections manufactured with standardized dimensions, where the professional may choose, for instance, the cross‐sectional shape of the structural section that best suits his or her needs.The hollow section presents excellent resistance capacity to the axial loads tension and compression, torsion and combined effects
2.2.2 Numerical analysis results of the plane truss As in the preliminary analyses of the connecting node, the numerical results of the plane truss indicate that the first node in which the yielding stress is observed on the diagonals under compression D2 and D5 and the diagonals under tension D1 and D6 is located in the lateral region of the bar stiffened flattened end, in the transition of the circular cross‐section to the section of the stiffened flattening, as indicated in Figure 10 a
This paper focused on a numerical study of the behavior of a tubular plane truss with an emphasis on a new typology of flattening for the diagonals that comprise the structure, that is, the stiffened flattening
Summary
The industrial market has a wide variety of structural steel sections manufactured with standardized dimensions, where the professional may choose, for instance, the cross‐sectional shape of the structural section that best suits his or her needs. The ruin of the structure was characterized by the collapse of connections, caused by excessive rotations of the nodes formed by the overlapping of flat ends, formation of plastic hinges in the connecting region, and relative sliding between bars In their experimental results, D’Este 1998 and Maiola 1999 observed similar behavior to that presented by Souza 1998. Souza 2003 , Andrade, et al 2005 , Bezerra, et al 2009 , Freitas, et al 2013 and Freitas, et al 2017 analysed the structural behavior of steel space structures using flattened‐ends hollow sections and evaluated the use of structural reinforcements in order to increase the resistant capacity of the structures. In relation to the theoretical values of Brazilian standards ABNT NBR 8800:2008 and ABNT NBR 16239:2013 – Design of steel and composite structures for buildings using hollow sections ABNT, 2013 , a 60% reduction in the resistance capacity of the flattened–end diagonals was observed
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