EM - Escola de Minas

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Design of sleeve connections with cross-bolted on circular hollow sections under axial tension.
(2022) Amparo, Lucas Roquete; Oliveira, Matheus Miranda de; Sarmanho, Arlene Maria Cunha; Xavier, Ellen Martins; Alves, Vinicius Nicchio
This present paper evaluates the behavior and resistance capacity of cross-bolted sleeve connections with circular hollow sections (CHS) under axial tension. This connection allows harmony in the continuity of the tubes. The cross-bolted sleeve connection with CHS comprises outer tubes connected by an inner tube and cross bolts at 90◦. Therefore, an experimental, numerical, and parametric study was conducted to identify the connection’s possible failure modes. The experimental tests were developed with cross bolts at 90◦, which enable the identification of fracture through the effective net area, bearing failure, and bolt bending. Finite element (FE) numerical models were developed and validated by Ansys software to provide a parametric study. Thus, such a parametric study was carried out using the verified FE models. The failure modes were evaluated considering the effects of geometric properties concerning their type and location; a relative slenderness limit for the design of connections was proposed, directing the occurrence of a failure in the outer tube. Normative prescriptions do not foresee the design of the sleeve. Therefore, new formulation methods for estimating the strength were proposed, allowing the design of these connections.
Behavior and design formulation of steel CHS with sleeve connections.
(2021) Amparo, Lucas Roquete; Oliveira, Matheus Miranda de; Sarmanho, Arlene Maria Cunha; Xavier, Ellen Martins; Alves, Vinicius Nicchio
Structures with tubular profiles gain space in civil construction due to their excellent response under tension, compression, and torsion. They are widely used in structural trusses, especially in large lengths. The profiles have a limited size due to the manufacturing and transport process. Therefore, there is a need to use some mechanism to perform the joint of profiles and obtain the desired length. This work aims to develop a new type of bar splice in circular hollow section (CHS) connection called sleeve connection, composed of two tubes connected with another smaller diameter tube with bolts arranged in a line (staggered bolts). This research presents an experimental, numerical, and parametric study of sleeve connection in CHS under centric axial tension. A numerical model was developed using the finite element method (FEM) considering sleeve connection with staggered bolts. From the numerical results, it was possible to analyze the connection behavior and failure modes: yielding gross cross-section, fracture through the effective net area, bolt shear failure, bearing failure of the plate, and bolt bending failure. This way, formulations were proposed to predict the sleeve connections' behavior with staggered bolts as a function of the failure modes.
Numerical analysis of truss systems with stiffened flattened end-bars.
(2018) Mazon, Ana Amélia Oliveira; Sarmanho, Arlene Maria Cunha; Nunes, Gabriel Vieira; Amparo, Lucas Roquete; Neiva, Luiz Henrique de Almeida; Souza, Flávio Teixeira de
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.

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