Citation: Heinemann, P.; Isopescu, D.-N. Experimental Case Studies about Uniplanar SHS Joints with Full-Overlapped Top Connection. Materials 2022, 15, 4089. https:// doi.org/10.3390/ma15124089 Academic Editor: Alessandro Pirondi Received: 6 May 2022 Accepted: 7 June 2022 Published: 9 June 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁl- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Experimental Case Studies about Uniplanar SHS Joints with Full-Overlapped Top Connection Patrick Heinemann * and Dorina-Nicolina Isopescu * Department of Civil and Industrial Engineering, Faculty of Civil Engineering and Building Services, “Gheorghe Asachi” Technical University of Iasi, 1, Prof. Dr. Docent Dimitrie Mangeron Blvd., No. 59A, 700050 Iasi, Romania * Correspondence: patrick.heinemann@tuiasi.ro (P.H.); isopescu@tuiasi.ro (D.-N.I.) Abstract: Squared hollow steel proﬁles are commonly used in the construction of offshore structures or building facades. By welding two or more pipes, typical joints are created that are speciﬁc for different areas of applications. These joints are less resistant than straight pipes due to the geometrical heterogeneity and the complex stress behavior of the welding. Standards deﬁne these joints, but there are restrictions imposed regarding the material or geometry. This paper focused on full-overlapped joints with squared hollow section proﬁles and on-top connection, which are disregarded in current standards. The aim was to ﬁgure out the inﬂuence of the inclination angle on the resistance of the joint. In the analysis, experimental and numerical studies were performed. Four different inclination angles commonly used on construction sites were the focus. It was discovered that there is a total diminishment of 46% in the load bearing capacity between the steepest and the most obtuse angles. The structural behavior is non-linear and is inﬂuenced by the value of the angles. The second aspect is related to the inﬂuence of the steel proﬁle, which is evaluated by a comparison between a squared proﬁle and two circular proﬁles. It was discovered that the joint made with squared proﬁles has a higher bearing capacity than the one made with circular proﬁles, a statement valid for similar thicknesses of the elements. Keywords: hollow sections; numerical simulation; welding line; construction; steel 1. Introduction Squared hollow section (SHS) proﬁles are commonly used in the construction of offshore structures or for facades of buildings. These proﬁles are characterized by high resistance to torsion and less intense buckling effects. In some ﬁelds of application, it is necessary to connect two or more members to obtain a two-dimensional structure. This joint can be designed by welding or cast steel. Thus, different geometries of the node can be used. Depending on the cross section of the pipes, there are variations including intermediate plates or directly connected pipes. This paper is about welded joints without intermediate plates. Due to geometric discontinuity and complexity in stress distribution, tubular joints require more attention [1]. Current standards, such as Eurocode 3, part 1–8 [2], or design guides, such as the CIDECT [3], deﬁne the joints made of hollow section proﬁles in general. The joints deﬁned by design codes are only valid for regular cases and do not include special variations in geometrical features. The regular case consists of hollow section members, which are connected to the side ﬂank of another member. The load is always set to the inclined member, not to the basic member in the case of a Y- or K-joint. The standards do not include variations related to the steel joint, which are analyzed in this paper. The steel joint is deﬁned as a uniplanar SHS joint with a full-overlapped top connection, commonly used for industrial applications. Two pipes (typically named braces or branches) are full-overlap connected to the end of a vertical member (also called a chord). Beside the geometry, the load scenario offsets the standard. The branches are connected at Materials 2022, 15, 4089. https://doi.org/10.3390/ma15124089 https://www.mdpi.com/journal/materials