Characterization of moment resisting I-beam to circular hollow section column connections resorting to passing-through plates

ABSTRACTCircular hollow sections (CHS) represent several advantages, such as uniform behaviour in all directions, possibility to obtain composite behaviour by concrete infill, hence high strength, stability and good fire resistance. Moreover, their aesthetic appeal has a great potential for the decision maker's attention, be that the architect or the building owner. However, they are not widely adopted in practice due to the complexity and high cost of their joint details. EU‐RFCS project LASTEICON (Laser Technology for Innovative Connections in Steel Construction), started on July 2016 [1] proposes simpler joint solutions with reduced fabrication costs, to be adopted between CHS columns and I beams, making use of laser cutting technology (LCT). The primary objective of the LASTEICON project is to overcome the complexity of steel joints between CHS columns and I beams, and let engineers and architects exploit the outstanding structural properties of hollow section profiles. Laser cutting will allow the reduction of the shop fabrication time, obtaining higher precision high quality joint fabrication, and improving workplace safety reducing the amount of manual labor while increasing computer‐programmed automation. This paper presents the preliminary results obtained in the Work‐Package 1 of the LASTEICON project (www.lasteicon.eu), which consisted in a study of tolerance optimization for an efficient fabrication of I‐beam‐to‐CHS column joints.

As thin walled HSS columns are very flexible, they usually exhibit excessive deformation when resisting a bending moment or transverse loads. Adding exterior/interior diaphragms is one way to remedy the problem. Another option that can significantly increase strength and stiffness is to allow passing plates through the hollow column by means of Laser Cutting Technology (LCT). This solution was tested on CHS columns within the RFCS LASTEICON project. The first outcomes were promising. One of LASTTS new RFCS project's overarching concerns is to enlarge the range of application of the passing‐through solution onto SHS columns.The goal of this research paper is to present the behaviour of I‐beam‐to‐SHS column moment resisting joints using passing‐through plates under opposite bending moments. First, a solid‐based finite element model is presented. This model is used to conduct a sensitivity analysis with different SHS column and passing plates geometry. The failure mode is resulting contribution of both weld/tube‐wall tearing in tension, and chord face crushing in compression. Analytical models are developed in an attempt to ascertain the bending resistance and initial rotational stiffness of this new type of connections.

Experimental study on stainless steel blind bolted T-stub to square hollow section connections

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 (conventional 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.

Ehab Ellobody? Department of Structural Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt Ben Young? Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (Received September 13, 2006, August 13, 2007) Abstract. The investigation on the behaviour of cold-formed stainless steel non-slender circular hollow section columns is presented in this paper. The normal strength austenitic stainless steel type 304 and the high strength duplex materials (austenitic-ferritic approximately equivalent to EN 1.4462 and UNS S31803) were considered in this study. The finite element method has been used to carry out the investigation. The columns were compressed between fixed ends at different column lengths. The geometric and material nonlinearities have been included in the finite element analysis. The column strengths and failure modes were predicted. An extensive parametric study was carried out to study the effects of normal and high strength materials on cold-formed stainless steel non-slender circular hollow section columns. The column strengths predicted from the finite element analysis were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. The numerical results showed that the design rules specified in the American, Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel non-slender circular hollow section columns of normal and high strength materials, except for the short columns and some of the high strength stainless steel columns. Therefore, different values of the imperfection factor and limiting slenderness in the European Code design rules were proposed for cold-formed stainless steel non-slender circular hollow section columns.

Experimental study discussion of the seismic behavior on new types of internal/external stiffeners in rigid beam-to-CFST/HSS column connections

Behaviour and strength of hollow flange channel sections under torsion and bending

Numerical investigation and design of aluminum alloy circular hollow section columns

This paper presents the stress distribution, confinement distribution and complete average longitudinal stress-strain curves for concentrically loaded short concrete-filled steel circular, octagonal, square and rectangular hollow section (HS) columns using 3-D finite element (FE) analyses. The curves predicted by FE analyses are in good agreement with those obtained from previous experimental work. The compressive design strengths and the compressive moduli of concrete-filled steel HS columns are also obtained. A unified method is proposed for the design of concentrically loaded short concrete-filled steel HS columns with different cross-section geometries.

Experimental investigation of concentrically and eccentrically loaded circular hollow concrete columns reinforced with GFRP bars and spirals

Concentrically braced frames are earthquake resistant systems commonly used in buildings. Seismic behavior of this type of structures is affected by their configurations, brace properties, and brace to gusset plate connections. In this paper, the results of three experiments conducted to investigate the cyclic behavior of concentrically braced frames with braces built-up of double channels are reported. Significant damage was observed in beam to column connections. Large out of plane deformation of braces caused some cracks in the connector welds; however they did not result in fracture. Although large drift was applied to the frames, no brace fracture was observed. Furthermore, experiments showed that the majority of compressive strength in post-buckling state and a noticeable portion of tensile strength originated from frame action. By choosing connector spacing as the main parameter and using finite element models, a parametric study was performed to investigate the effect of this parameter on this type of frames with two different details of brace to gusset plate connections. It is observed that reducing the connector spacing increases the inelastic strain demand in braces and decreases it in gusset plates. However, gusset plates, which accommodate 2t linear clearance, are less dependent on connector spacing, compared to those accommodating 6t elliptical clearance. It seems that the limitations of slenderness ratio of individual section, stipulated in current seismic provisions, need further study.

Effects of confinement in square hollow concrete column sections

This study proposes an analytical model for the evaluation of the mechanical behaviour of circular hollow section columns infilled with steel fibre-reinforced concrete when exposed to elevated temperatures in a fire situation. This work includes the discussion of the results from a sensitivity analysis conducted through numerical simulation and the development of an analytical model based on the prEN1994-1-2:2021 European standard for the design of reinforced concrete structures exposed to fire. The sensitivity analysis aims to compare the fire resistance of centrally and eccentrically loaded circular hollow section columns infilled with plain and steel fibre-reinforced concrete. The proposed analytical model for determining the design buckling load of composite steel fibre-reinforced concrete-filled tube columns in a ?re situation is ready to serve as an annexe or supplementary technical document to the EN1994-1-2:202x standard.

This paper presents experimental and numerical investigations on the structural performance of six steel tube-encased concrete (SC) columns confined by bolted thin-walled circular steel tubes. All specimens were circular columns with a 300 mm diameter, incorporating an encased circular steel tube of 200 mm in outer diameter. Reversed cyclic lateral force and constant axial compression were applied to these specimens. Key experimental parameters included axial load ratio, presence of infilled concrete and the rank of the encased steel tube. Test results demonstrated that confinement by thin-walled circular steel tubes ensured sufficient deformation capacity up to 0.06 rad drift for SC columns with FB-rank and higher encased steel tube, even without concrete infilled and under high axial compression. Test results also indicated that infilling concrete into the FC-rank encased steel tube enhanced the deformability up to 0.06 rad drift. Parallel to the experimental work, a simple evaluation method for the ultimate flexural strength of the SC column was proposed, and a numerical analysis was conducted to predict the overall structural behavior of the SC columns. Both calculated strength and numerical prediction showed close agreement with experimental results.

Hollow concrete columns (HCCs) are an effective structural system for piles, electric poles, and bridge piers due to their low self-weight in conjunction with the high strength offered and reduced material use. This study investigated the behavior of concentrically loaded circular HCCs reinforced with glass fiber–reinforced polymer (GFRP) bars and spirals. Eleven hollow circular columns with outer/inner diameters of 305 and 113 mm and two solid specimens as controls were fabricated. All had a height of 1,500 mm. The investigated parameters included transverse GFRP reinforcement ratio in terms of the on-center spiral spacing and spiral diameter, configuration (spiral and hoops), and the influence of hollowness. The theoretical ultimate load-carrying capacity and the confined concrete strength of the tested hollow GFRP-reinforced concrete columns were evaluated and predicted using the available design equations and confinement models in the FRP design codes, standards, and literature. The test results indicate that either decreasing the spacing of the spiral/discrete hoops or increasing the spiral diameter could increase the ultimate carrying capacity as well as improve the confinement efficiency and ductility of HCCs.