Laser Cut passing-through Open-to-CHS Beam-to- Column Connections

Abstract

Structures built using hollow sections can have approximately 40% lighter weight than the contemporary H-section structures [1] and also requires a lesser volume of fire protection material due to a comparatively smaller surface area [2]. Existing examples with Hollow Sections (HS), especially the Circular Hollow Sections (CHS), demonstrate their excellent properties in resisting high compression , tension as well as bending in all directions, thanks to their inherent shape and geometry [3] along with an aesthetic architectural appearance. They have also proved to be the best shape for elements under wind-, water-or wave-loading scenarios [4]. Additionally, as filling the hollow sections with concrete provides a simple way to achieve a composite behaviour, it also offers an extra advantage towards fire resistance. Therefore, over the past few decades , researches have tried to implement such hollow sections in structures to improve the global resistance by exploiting the significant advantages in offer. However, as structural beams are commonly constructed with open sections, a suitable open-to-CHS column connection is necessary to utilize the structural advantages offered by a CHS column. To that purpose, several different types of open-to-hollow section joints have been developed in the current industry and CIDECT has provided significant understanding [5] regarding their strength, fire protection, wind loading, composite construction , and their static and fatigue behaviour based on successful identification of the force-transfer mechanism. The present Euro-code rules regarding the design and practical implementation of such structural hollow section connections are largely based on the foretold CIDECT research works. However, it is seen that most common types of open-to-hollow section connections used in the current industry are built by connecting the open sections to the hollow section chord surface by direct welding or diaphragm connections (further named "conventional CHS connections" in this study). Both of these connection types require a substantial amount of stiffeners or gusset plates, therefore making the design and construction rather complicated with added expenses. The complex detailing ORIGINAL ARTICLE Abstract Although Circular Hollow Sections (CHS) have always demonstrated their excellent properties in resisting high compression, tension as well as bending in all directions, thanks to their inherent shape and geometry, the existing open-to-CHS connections used in the current industry (conven-tional connections) generally require a substantial amount of stiffeners or gusset plates due to their construction method i.e. direct welding or diaphragm connections. As a result, huge welding quantities are required which further complicates the fabrication procedure. Furthermore, due to a direct connection, the CHS column becomes prone to localized distortions. In order to minimize the aforementioned drawbacks, a "passing-through" approach was proposed and investigated in the EU-RFCS research project LASTEICON where connecting elements (i.e. one or more steel plates or a piece of I-profile) pass through the CHS column through Laser Cut slots made in the column and the primary beams (namely the "main" I-beams) are connected to both ends of the passing through elements (named as "through-members"). The applied shear force, and if relevant the applied moment, is effectively transferred by the "through-member" to the CHS column, whereas, the CHS column contributes significantly in resisting it through its large flexural and shear capacity. The present article summarizes the most interesting results obtained based on the experimentally validated numerical simulations for the different types of LASTEICON connections. Thanks to the superior fabrication quality and versatility offered by the laser cutting technology, different types of connection configurations were developed within the project. This article introduces a few of these possibilities: (1) Two-way steel moment resisting connections, (2) Asymmetric steel connections, (3) Four-way steel connections, and (4) Composite connections.