Fillet Weld Design for Rectangular HSS Connections

In recent years the use of closed sections/tubes as structural members has increased significantly. Designers all around the world approve of the advantages that round as well as rectangular hollow structural sections (HSS) can offer, such as uniform strength and stiffness independent of the loading direction, high torsional and buckling strength and the aesthetic appearance. Splicing structural members is a common practice in construction to allow for long spanning trusses, changes in cross sections and transportation to site, to name but a few. The results of an experimental investigation of four bolted flange-plate connections between rectangular hollow structural sections, with bolts on all four sides, have been presented. A brief overview of different design methods for bolted flange-plate connections for square and rectangular hollow structural sections under tension load has also been given. A comparison of the load predictions of the various methods for the specimens in the experimental program supports the use of the design procedure that can be found in the AISC HSS Connections Manual (AISC, 1997).

Cold Formed Steel (CFS) is one of the materials that recently used in building structures. There are many advantages of CFS compared with other materials, such as lightweight, high tensile strength, and fast construction. Hollow Structural Sections (HSS) is the most commonly used as beam and column CFS sections. The purposes of this study are determining the behavior and capacity of CFS beam column joint under lateral load with manual calculation, numerical analysis and experimental. The test specimens used 1 mm thick, 4x4cm HSS for column and 2x4cm HSS for beam. Beam and column connected by two single angle plates placed above and below the beam sides. Both parallel and staggered fastener configurations used in this experiment. Four 4 mm diameter bolts used in this connection. Monotonic static loading applied on beam for modelling the lateral load. The experimental results show the behavior and the capacity of the beam column joint with parallel fastener configurations. The numerical results show that the staggered fastener configuration has better performance compared with the parallel fastener configuration. The CFS beam column joint are adequate to resist the lateral load and feasible to be apply as structural components in building structures.

In late 2005, the American Institute of Steel Construction issued its most recent Specification for Structural Steel Buildings (ANSI/AISC 360-05). This specification includes updated design provisions in both allowable strength design (ASD) and load and resistance factor design methods (LRFD), and incorporates the design provisions for hollow structural sections and single angles. Amongst the major changes are a complete revamping of the methodologies for assessing stability of framed structures, new provisions for composite columns and updated material requirements. This paper will describe the changes and highlight those of practical significance.

Rectangular hollow structural sections (HSS) are commonly used as bracing in concentrically braced frames (CBFs) designed and detailed for seismic design requirements. As the primary yielding component in CBFs, braces are expected to sustain large inelastic axial deformation during earthquake loading. It is well known that their deformation capacity depends on the width-to-thickness ratio (local slenderness). Until 2013, HSS sections were produced to meet ASTM standard A500/A500M; after 2013, the ASTM 1085 specification was implemented, and since that time, HSS sections have also been produced to meet ASTM A1085/A1085M standards. Where the ASTM A500/A500M specification requires minimum yield and tensile stress values as well as a minimum elongation and tolerances on the wall thickness, the ASTM A1085/A1085M specification also requires a minimum Charpy V-notch (CVN) toughness, a maximum yield stress of the steel, and tighter tolerances on the wall thickness and radius of curvature of the corner. These requirements offer a more reliable brace for CBFs in seismic regions. Yet there has been limited research investigating the cyclic axial response of these members. A research study was undertaken to investigate the response of ASTM A1085/A1085M tubes using the response of ASTM A500C tubes as their reference. Forty-one brace specimens were tested under cyclic inelastic axial deformation. Comparison of the data shows that most of the ASTM A500/A500 M Grade C and ASTM A1085/1085M braces meet the respective requirements of their respective ASTM standard and that the differences between the performance of ASTM A500/A500M and ASTM A1085/1085M braces are not dramatic. In addition, the study investigated the impact of width-to-thickness ratio, global slenderness, and displacement history on the response of the braces. The data show that the current AISC 341-22 high-ductility slenderness limit for special concentrically braced frame (SCBF) braces is slightly conservative. However, the data suggest that the moderate ductility slenderness limit used for ordinary concentrically braced frame (OCBF) braces is significantly more conservative than required for consistent seismic safety. Further research is required to determine appropriate limits; this paper provides some initial recommendations based on this dataset.

This paper reviews the differences between the alternative types of structural hollow section products (cold‐formed versus hot‐finished) as they affect structural design in Europe, using the relevant product and design standards, with an emphasis on Rectangular Hollow Sections (RHS). Manufacturers of cold‐formed structural hollow sections (CFSHS) are more numerous, so that their products are more widely available. Hot‐finished structural hollow section (HFSHS) products are typically between 24 % and 54 % more expensive in Germany than their cold‐formed counterparts, the lower differences being for large tonnages – a strong inducement in favour of CFSHS. The price difference may also vary within the European Union. The geometric and product properties which are distinctly unique to CFSHS are presented and shown to offer no restrictions in their use when in compliance with the appropriate clauses in the European standards. These are the influence of corner radii, welding in the corner area, material choice to avoid brittle fracture and suitability for welding CFSHS. A comparison of the structural performance of CFSHS and HFSHS shows equally efficient structural designs for both products. The points covered are the design of compression members – unfilled and concrete‐filled, joint resistance – which typically governs selection of member sizes, as well as fatigue design, fire design and the resistance of braced steel frames to severe seismic loading. CFSHS are shown to be adequate under all these situations.

A theoretical analysis has been undertaken for unequal width T-joints, haunch-reinforced, in square hollow structural sections (HSS). The unreinforced joint is merely a special case. The theory was based on a finite difference solution to the elastic chord flange plate equation and predicts the branch-to-chord joint stiffnesses under both bending [Formula: see text] and axial force (C = P/δ). The effects of varying the width ratio λ, overall haunch length-to-width ratio λ1, and chord width-to-thickness ratio bc/tc were studied for different plate edge boundary conditions. The latter parameter has the greatest effect on stiffness, but the other two, including haunch size, are also significant. There is reasonable agreement between the joint rotational stiffness factor J, obtained from earlier tests, and the predictions of theory for different edge boundary conditions. The unequal width, unreinforced connection is generally too weak to be viable in design applications. Haunch stiffeners improve strength and stiffness, and are particularly beneficial for large rather than small λ (i.e., 0.833 vs. 0.333).

A longitudinal branch plate-to-rectangular hollow structural section (HSS) member connection tends to cause excessive distortion of the HSS connecting face. Such a connection therefore results in a relatively low, deformation limit state, design resistance. A "through" branch plate connection that extends through both walls of the rectangular HSS member can be used to increase the design resistance of a standard longitudinal branch plate connection. The results of an experimental test program and a corresponding numerical study, using the finite-element method on longitudinal and corresponding through branch plate-to-HSS connections are presented in this paper. The strength and behavior of longitudinal versus through branch plate-to-HSS connections is henceforth determined and a unified limit states design (LRFD) procedure for these cognate connections is proposed.

Revisions were recently proposed to the way in which concrete-filled hollow structural section members are handled in CSA S16. These revisions were based on previous research, comparisons to experiments, and a first-order reliability method analysis of existing provisions for compression and flexural members. In this paper, this topic is further expanded by using Monte Carlo Simulations (MCS) to determine the inherent reliability of the previous and new design rules for concrete-filled rectangular hollow section (RHS) and circular hollow section (CHS) beam-columns. A representative set of concrete-filled RHS and CHS members with variations in concrete strength, wall slenderness, effective length, and loading eccentricity are analyzed. Using MCS, the reliability index ( β+ ) of each is determined over a range of live-to-dead load ratios. Inherent β+ values are compared to the code-specified target (i.e., β+ = 3.0 per Annex B of CSA S16) and the CSA S16:19 and AISC 360-16 provisions.

This paper describes the experimental work on the tests of nine concrete-filled square and rectangular hollow structural section (HSS) columns subjected to axial load, uniaxial bending or biaxial bending. The experimental results suggest that the overall buckling appears accompanying with local buckling near the mid-height of column. Good agreement was found between the semi-sine wave shape and the experimental deflection shape. It is found that the cross-section remains plane before the specimen reached its load-carrying capacity. Also, the experimental results are compared with the values calculated from the AISC-LRFD, EC4 and CECS design codes, which shows that all codes provide safe bearing capacities. Compared with columns subjected to an axial load or uniaxial bending, the calculated capacities of column subjected to biaxial bending are more conservative. Among these three design codes, the capacities based on the EC4 design code yield results which are the closest to the experimental ones. The results calculated from the AISC-LRFD design code are the most conservative.

The 2022 edition of the AISC Specification for Structural Steel Buildings allows member and system instability effects to be accounted for by using advanced analysis methods that model these effects directly or through the use of the B1 (P-δ) and B2 (P-Δ) multipliers. For compression members subject to end moments only, the B1 multiplier is expressed as a function of the smaller to larger end moment ratio. This ratio is taken as positive when the member bends in reverse curvature and negative when it bends in single curvature. This code equation for B1 often overestimates the P-δ effect for double curvature bending under a high axial force but underestimates the P-δ effect for single curvature bending under almost all values of axial force. The reason for the overestimation is because the derivation of the B1 equation uses the equivalent moment concept and ignores the actual location where the maximum moment occurs in the member. When this condition is taken into consideration, it is shown herein that the equation is no longer applicable for members bent in reverse curvature under any value of axial force. The reason for the underestimation is because the effect of axial force on the moment ratio is ignored. By incorporating this effect in a new equation for B1, it is shown that this underestimation is drastically reduced. The validity of this proposed B1 multiplier is established by comparison with the corresponding theoretical values.

Numerical Study on Lateral-torsional Buckling of Honeycomb Beam

Tests and numerical study of ultra-high strength steel columns with end restraints

Companies performing international structural design work are confronted with varying requirements imposed by different standards and methodologies. This paper presents a brief comparison of stability analysis procedures for steel structures using the Eurocode 2022 and the American Institute of Steel Construction Specification for Structural Steel Buildings (ANSI/AISC 360‐22) standards. Several structural types will be investigated, ranging from those with clearly defined effective lengths to others with more ambiguous effective lengths requiring stability analysis techniques involving explicit modeling of system imperfections and member (bow) imperfections. Geometric and material nonlinear imperfection analysis (GMNIA) will be used for comparison. Through these case studies, we illustrate the practical implications of each method, highlighting key differences. Ultimately, this study aims to enhance understanding of stability analysis and inform international best practice in structural design, contributing to safer and more efficient engineering solutions.

A large boiler support structure for a coal-fired power plant in Australia was designed by a structural engineer in the United States. Approximately 9,000 tons (8,181 tonnes) of structural steel for this project was supplied from a steel fabricator in China, using shop drawings prepared by an American detailing firm. A registered professional engineer from the designer's Australian offices supervised the work in the United States to ensure compliance with local codes and standards. Member sizes were selected from ASTM shapes, using the provisions of the Australian Standard for steel structures AS4100 (Council of Standards, 1998). However, to expedite steel delivery, it was decided to allow the detailing firm to prepare connection designs using the American Institute for Steel Construction's (AISC), Specification for Structural Steel Buildings—Allowable Stress Design and Plastic Design (ASD) (AISC, 1989). Demonstrating the compatibility of connection designs prepared using these two methods highlighted the unique difference between simple code compliance, and the art of connection design. The intent of this study is not to establish the appropriate limit states for a clip angle connection. There are numerous references that deal with this topic (Birkemoe and Gilmor, 1978; Munse, Bell and Chesson, 1959). The purpose is also not to demonstrate that one country's design approach is either superior to or less conservative than that of another country. What has been shown is that, given a structural design problem as common as a clip angle, two different approaches to engineering, based on training and experience, can interpret relatively similar design specifications, to produce significantly different results.

A statistical survey was made for a broad sample of mill test reports (MTR) of plate grades typically used in building construction including A36, A572, A588, A852, and A514 steels. Tensile properties, impact properties, and chemical compositions were analyzed. The tensile statistics agreed with assumptions made in the development of the AISC Load and Resistance Factor Design Specification for Structural Steel Buildings (LRFD Specification) (AISC, 1999). The yield-tensile ratios varied from 0.61 to 0.94, following the typical trend of increasing yield-tensile ratio with increasing strength level. The mean CVN values at 70ºF were generally over 100 ft-lbs. for all the steels, which is attributable to the fact that the toughness data were generally reported for product with specified minimum values. The minimum CVN values at 70ºF all met or exceeded the 20 ft-lbs. value specified by AISC for plate material over 2 in. thick used for built-up cross sections spliced with complete-joint-penetration groove welds and subjected to tension. The statistical analysis of composition generally indicated good weldability, particularly for A36 and A572 Grade 50.