Hollow Structural Section Research Articles

Hollow Structure

Some present requirements of the mechanical structures are high strength and lightweight. A solution is to adopt the hollow structure design. In mechanical engineering industry are commonly using hollow structural sections, surface – type and even three dimensional hollow parts. The final shape is usually the result of structural optimization in which smallest material quantity fulfil the strength requirements. In this paper the study considers a different distribution of the same mass, more exactly starting with a single whole and “splitting” its surface in smaller and smaller holes each iteration. The intuitive expected result in reducing equivalent stresses considering von Mises criteria was not achieved.

A Quantitative Weld Sizing Criterion and Applications in Load Capacity Evaluation of Hollow Structural Section Joints

Existing weld sizing procedures for hollow structural section (HSS) connections in Codes and Standards are empirical in nature, often resulting in oversized welds. There is a growing interest in quantitative weld sizing for ensuring both structural safety and cost-effective construction of lightweight hollow section structures. In this study, a mesh-insensitive traction stress method is introduced for evaluating strength of fillet-welded HSS joints. The results are then generalized into a closed-form expression with a clearly defined mechanics basis. This expression relates weld throat shear stress to fillet weld size and remote load, with its dimensional geometric parameters being determined through a detailed parametric finite element analysis (FEA) of circular hollow section (CHS) and rectangular hollow section (RHS) connections with various dimensions. The effectiveness of the closed-form expression is demonstrated by comparing the predicted failure loads with those measured from a large number of HSS test data available from literature. Furthermore, the proposed quantitative weld sizing criterion can lead to as much as 20% weld size reduction from those determined using existing empirical-based weld sizing criteria, which can be very beneficial for welding-induced distortion control in construction of lightweight thin-walled structures.

Axial compression behaviours of tubular sectioned C-shape continuous-supported steel walls in MSB

The ultimate strength behaviour of C-shaped continuous-supported walls employing hot-rolled structural hollow section (SHS) columns in modular steel buildings (MSB) was evaluated using two full-scale axial compression tests. The columns' width-to-length (D/B), width-to-thickness (D/t), and material strength were considered experimental parameters. A three-dimensional (3D) finite element (FE) model was validated against test results, accounting for geometry and material nonlinearities while projecting ultimate strength and failure behaviour. The size, spacing, number of columns, stiffener thickness and sidewall effects were evaluated in a parametric analysis. The columns compressive resistance was predicted using prediction equations from EC3:1-1, AISC360, and GB50017. The results revealed that the column nominal strength was reduced to achieve compression yielding due to columns stiffness differences, mutual constraints, and elastic buckling. If the buckling length is considered or omitted, the EC3:1-1 slenderness limit for Class 3 steel members becomes less conservative. Reducing column size and spacing or increasing stiffener size and number improves column and wall compressive behaviour; however, the sidewalls improved the corner columns constraint while weakening the front wall. GB50017 predictions were the safest; whereas, EC3:1-1 made the most unsafe predictions when buckling was not taken into account.

Soft Elastomeric Capacitor for Angular Rotation Sensing in Steel Components.

The authors have previously proposed corrugated soft elastomeric capacitors (cSEC) to create ultra compliant scalable strain gauges. The cSEC technology has been successfully demonstrated in engineering and biomechanical applications for in-plane strain measurements. This study extends work on the cSEC to evaluate its performance at measuring angular rotation when installed folded at the junction of two plates. The objective is to characterize the sensor’s electromechanical behavior anticipating applications to the monitoring of welded connections in steel components. To do so, an electromechanical model that maps the cSEC signal to bending strain induced by angular rotation is derived and adjusted using a validated finite element model. Given the difficulty in mapping strain measurements to rotation, an algorithm termed angular rotation index (ARI) is formulated to link measurements to angular rotation directly. Experimental work is conducted on a hollow structural section (HSS) steel specimen equipped with cSECs subjected to compression to generate angular rotations at the corners within the cross-section. Results confirm that the cSEC is capable of tracking angular rotation-induced bending strain linearly, however with accuracy levels significantly lower than found over flat configurations. Nevertheless, measurements were mapped to angular rotations using the ARI, and it was found that the ARI mapped linearly to the angle of rotation, with an accuracy of 0.416.

Development of Flexural Buckling Rules for the New AISC Stainless Steel Design Specification

AbstractThis paper presents the development of flexural buckling curves for austenitic and duplex stainless steel welded I‐sections and structural hollow sections, which are proposed for implementation in the new AISC stainless steel specification. The proposed buckling curves were developed following the same type of reliability analysis employed to develop the flexural buckling curve included in AISC 360 Specification for Structural Steel Buildings for carbon steel, considering all the experimental data available in the literature and a large number of numerical results. In order to facilitate their implementation, the proposed curves follow a similar form as the AISC‐type of curve included in AISC 360, with the only differences being the addition of a yield plateau and the values of selected coefficients used to adjust the shape of the curves.Three different buckling curves are proposed: one buckling curve for circular hollow section (CHS) columns and I‐section columns buckling about the major axis; one for rectangular hollow section (RHS) columns; and one for I‐section columns buckling about the minor axis. The proposed curves represent a significant improvement with respect to the currently available stainless steel flexural buckling curve included in AISC Design Guide 27, providing an increase in strength predictions of up to 55%.

Peculiarities of resistance definition for welded offset T‐joint between RHS members

AbstractSteel structural hollow sections, including rectangular hollow sections (RHS), are nowadays one of the most efficient load‐bearing elements of the lattice structures. Despite its widespread application, there is still lack of design techniques for joints produced with offsets. The article intends to eliminate gaps in knowledge about the mechanical resistance and design of so‐called offset RHS joints, welded T‐joints composed from rectangular hollow sections with a certain lateral offset of a brace from a centreline of a chord, under brace axial compression. The paper presents results of numerical investigations of structural behaviour of the mentioned joints in comparison with existing analytical methods of connection nominal resistance determination for both standard (co‐axial) and offset welded RHS joints. For validation purposes, the full‐scale laboratory tests were conducted. Numerical models were created using a general FE programme Abaqus and a component‐based FE programme IDEA StatiCa. Particular attention was given to mesh size effect and weld seam modelling. The curve fitting analytical model complying to prEN1993‐1‐8:2020 proposed by Wei and Packer [1] is verified by numerical experiments. The limits of validity of considered analytical model are examined and proved by calculations.

Experimental and numerical study on planar multi-column walls behaviours with boundary supports

The continuous-supported multi-column walls have already been used in modular steel buildings (MSB). Therefore, using two full-scale specimens, the current study evaluated the axial behaviour of planar multi-column walls with structural hollow sections (SHS). Then, a 3D finite element model (FEM) was created and validated to study the individual column and boundary support effects on each column. Prediction equations in EC3, AISC360, and GB50017 were then used to predict the ultimate compressive resistance of columns in walls. Because of the elastic buckling, the current slenderness limit for Class 3 steel cross-sections becomes less conservative. The boundary support effect enhances external columns rigidity and capacity than other columns, leading to instability. FEM provides reasonable estimates of the compressive behaviour of walls and each column. Each column exhibits distinct load distribution, confirming that the assumption of uniform load distribution among columns is unacceptable for multi-column modular walls. The prediction equations showed that GB50017 was safer than the EC3 and AISC, while EC3 was the least secure. Hence, the current study concluded experimental, numerical, and analytical findings to evaluate the axial behaviour of multi-column walls in multi-storey MSBs.

Effect of ageing on the mechanical properties of cold formed S700 rectangular hollow

The aim of this work is to study the effect of ageing (250 °C for 1 h) on the mechanical properties of the cold formed S700 rectangular hollow section. The investigated hot rolled steel strip was produced thermomechanical rolling followed by direct quenching. The dimension of the investigated hollow section was 120 x 120 x 10 mm and the corner radii and the other tolerances compliant with EN 10219. Tensile properties and Charpy-V impact toughness were determined for the base material and flat and corner area of the hollow section. The results showed that the tensile strength in the corner was slightly higher in comparison with the flat side, revealing higher cold deformation rate in the corner. Ageing increased the strength level relatively higher than cold forming without losing any elongation properties. The impact energies were at the high level at −40°C and −60°C in cold formed and aged materials. Even at −80°C, the CV results were 118 J/cm2. It is also notable that no difference in CV values between the flat and the corner samples were observed. Thus, the results showed that the flat side specimens testing provides sufficient information of mechanical properties of the cold formed rectangular hollow sections and no need demanding corner sample testing when the structural hollow section is produced by using the thermomechanical controlled and direct-quenched base material. Furthermore, results showed that cold formed S700 is excellent for offshore steels, as steels are used even colder conditions as before.

Cyclic experiments on isolated steel sheet connections for CFS framed steel sheet sheathed shear walls with new configurations

The main objective of this research is to experimentally characterize the performance of isolated single sheathing-to-framing fastener connections under cyclic load as utilized in emerging classes of cold-formed steel (CFS) framed steel sheet sheathed shear walls used for seismic lateral resistance. New shear wall variations include the use of steel sheet sheathing sandwiched between framing members (i.e., mid-ply) and the use of heavy hollow structural sections (HSS) chord members with the thin steel sheet sheathing attached by power actuated fasteners (PAF) to the HSS. The cyclic nonlinear response of the framing to steel sheet fastener connection is fundamental for simulating the seismic performance of steel sheet sheathed shear walls. Minimal cyclic fastener-level test data under shear exists for these new configurations. A unique lap shear test following AISI S905 was designed to study and characterize the cyclic fastener connection behavior. The specimens were loaded with an asymmetric cyclic loading protocol which intentionally buckles the thin sheet in the compression direction, and progressively increases in the tension direction. Sixty-three tests covering a wide range of framing thickness, sheet thickness, fastener type and size were completed. Each connection configuration is characterized with a multi-linear backbone curve ready for use in numerical shear wall models. The tested fastener configurations exhibit excellent performance as fastener tilting is largely or completely eliminated in these configurations, and connection degradation from buckling of the steel sheet is minimized. It is also shown that AISI S100 connection strength provisions are applicable to the tested connections.

SEISMIC COLUMN SPLICE DEMANDS IN BRACED FRAMES WITH BUCKLING CONTROLLED BRACES

Numerous experimental tests showed that ductile square hollow structural sections (HSS) are susceptible to premature fracture under design-level earthquake ground motions. In addition, recent research has highlighted the vulnerability of column splices to reach their full strength once ductile square HSS braces experience a fracture in braced frames. In this study, the performance of column splices in 5-and 13-story special concentrically braced frames (SCBFs), with X-bracing configuration, located at a distance permitted by the seismic design provisions (i.e., four feet over the concrete floor level), is evaluated under a large number of ground motion excitations. The performance of identical SCBFs with conventional HSS braces and innovative buckling controlled HSS braces is compared. Overall, results from this research indicate that the prevention of brace buckling in SCBFs yields a substantial reduction in the seismically induced bending demands on the column splices, leading to a large margin of safety to remain elastic.

Elastic Buckling Strength of Hollow Structural Section Steel Beam-Columns under Compression and Bending

This paper describes a methodology to evaluate the global buckling strength of Hollow Structural Section (HSS) steel columns. The methodology is based on the energy method by applying a new displacement function, which is able to describe the buckling modes for various loading conditions defined by end moments and axial force. In this paper, a unique trigonometric series is used as the buckling displacement function. With such displacement function, a closed-form strength formula can be obtained based on the principle of least potential energy. A finite element buckling analysis is also performed for comparison to clarify the accuracy of the evaluation formula.

A General Expression for the Welding Tendon Force

Abstract This study presents a novel expression for the tendon force associated with residual stresses produced during welding of large, thin sections. A general engineering equation is presented as the combination of a closed-form expression, based on idealized treatment, and correction factors to account for the effects of temperature-dependent thermal and mechanical material properties. The closed-form expression corresponds to the assumption of constant material properties. A rigorous mathematical treatment is utilized to derive explicit, exact expressions for the temperature-dependent correction factors without the need for empirical correlations. The temperature-dependent behavior of materials is captured accurately using four dimensionless groups. The analysis was validated through numerical simulations with common structural grades of low-carbon steel, stainless steel, aluminum, and titanium. The idealized treatment resulted in predictions with a mean difference of 18%, which was reduced to 7% by incorporating the correction factors. The remaining error is a systematic overestimate, which can be attributed to compliance effects of the finite plate used in the simulations, and is the focus of ongoing research. The utility of applying the novel tendon force equation to problems in fabrication procedure design is demonstrated with an example predicting distortion during manufacturing of hollow structural sections.

Performance of FRP strengthened full-scale simply-supported circular hollow steel members under monotonic and large-displacement cyclic loading

Steel structures are becoming more common in engineering construction as steel possesses excellent ductility, but steel members are often vulnerable to buckling, especially under seismic or cyclic loading. Hollow structural sections (HSS) often buckle locally under loading due to their thin steel walls and the need for rehabilitation and strengthening is increasing. In the present study, circular hollow section (CHS) steel members have been strengthened with both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). Their structural performance, along with that of their bare counterparts, is investigated subjected to monotonic and quasi-static large-displacement cyclic loading experimentally. The types of FRP reinforcement (CFRP and GFRP) and the loading condition (monotonic and cyclic) are chosen as two main parameters in the test program. Results reveal the significant structural improvements of the strengthened CHS members under monotonic and cyclic loading. The ultimate moment capacities of the beams under monotonic and cyclic loading are enhanced by 51.0% and 35.4% respectively with CRFP strengthening and 43.3% and 31.5% respectively with GFRP strengthening compared to the bare beam. In addition, all the FRP strengthened specimens achieved higher moment capacities, rotational capacities, stiffness, energy dissipation capacities and ductility in comparison to their bare counterparts. Moreover, there is a good agreement found between the experimental and theoretically predicted ultimate moment capacities of the bare and strengthened CHSs with a mean ratio of 1.04 and a COV of 0.05.

Experimental Investigation of Foam-Filled CHS Braces under Cyclic Loading

AbstractThe performance of seismic braced frames can become compromised due to premature local buckling–induced fracture of the hollow structural section (HSS) steel braces. A strategy to delay the...

Concrete-filled hollow structural sections. II: Flexural members, beam-columns, tension, and shear

This article reviews contemporary North American and international approaches to the design of concrete-filled hollow structural section (HSS) members for flexure, axial compression plus uniaxial bending, tension, and shear. Results from tests on concrete-filled HSS members under flexure and combined loading are compared to predicted strengths using current (CSA S16:19 and AISC 360-16) and recommended CSA S16 design equations (with limits of validity). A first-order reliability analysis of design provisions for flexure is performed in accordance with CSA S408-11, and recommendations are made for potential revision of CSA S16. Design examples are provided, and results are compared to the counterpart American code (AISC 360-16). This paper is Part II of a two-part series. Part I covers materials, cross-section classification, and concentrically loaded columns.

Concrete-filled hollow structural sections. I: Materials, cross-section classification, and concentrically loaded columns

This paper reviews contemporary rules in CSA S16:19, AISC 360-16, and EN 1994-1-1 for concrete-filled hollow structural sections (HSS), covering materials, cross-section classification, and concentrically loaded columns. Results from 453 tests on axially compressed concrete-filled HSS members were compared to the predicted strengths using current (CSA S16:19, AISC 360-16, and EN 1994-1-1) and recommended CSA S16 design equations (with limits of validity), and a first-order reliability analysis was performed in accordance with CSA S408-11. The recommendations herein are shown to maintain the current CSA S16:19 Clause 18.2 level of reliability for concrete-filled HSS compression members. Design examples are provided, and the results are compared with the counterpart American code (AISC 360-16). This paper is Part I of a two-part series. Part II covers flexural members, beam-columns, tension, and shear.

Seismic behavior of double-HSS links for eccentrically braced frames

This study experimentally and analytically investigates an innovative double-HSS link (DHL) used as the active link in eccentrically braced frames (EBFs). Hollow structural sections (HSS) are mechanically efficient and are used in resisting compression, torsion, and bending. Their high torsional rigidity generally eliminates lateral-torsional buckling (LTB). As a result, the plastic rotational capacity and strength degradation rate are mainly governed by flange local buckling (FLB) and web local buckling (WLB). The proposed configuration consists of a double-HSS connected to braces or columns through a center gusset plate secured by flare-bevel groove welds. The advantages of the proposed configurations are: (1) They effectively reduce the width-thickness ratios (b/t) of the flanges by using two HSSs with much shorter flanges, which considerably increases the compactness thereby enabling a large rotational capacity. (2) They provide simple and practical connection details between the link and braces or columns. (3) Typically, double-HSS sections have an e/(Mp/Vp) ratio much larger than that of wide-flange sections due to the fact that double-HSS sections have four webs which significantly increase the shear capacity. Consequently, a DHL can yield in flexure even with a length similar to that of a wide-flange shear yielding link. This in turn eliminates the need for web stiffeners. (4) The welding requirement for DHLs is less than that of the conventional shear links since no stiffeners are required. (5) The overstrength factor due to strain hardening produced by flexural yielding links is generally less than that produced by shear yielding links leading to more economical designs for the elastic portion of the frame, and (6) the iteration design process is minimized by balancing the link length and rotational demand because of a single flexural yielding mode. Furthermore, experimental and analytical results indicated that the novel DHLs can sustain larger plastic rotations and meet AISC 341′s acceptance criterion for shear yielding links. In addition, DHLs can be potentially used in D-braced EBFs with links attached to columns because the link-to-column connection of DHL remains essentially elastic. DHLs can also be used as a replaceable link which is attached to the beam and column through bolted end plates.

Experimental study on brace to HSS column connection using through-gusset plate

In Hollow Structural Section (HSS) column, webs are available at both ends of column flanges. Thus, there is an offset between webs and a gusset plate connected to the middle of this column flange. However, in H-shaped column, both the column web and the gusset plate are connected to the middle of the column flange. On the other hand, unlike H-shaped column, HSS column flange does not possess an appropriate support and this problem can induce distortion, out-of-plane deformation, and fracture in HSS column flange. To resolve this problem, this study proposes a new gusset plate connection passed through HSS column and called through-gusset plate. Also, force transfer mechanism and design procedure are presented for through-gusset plate. To evaluate the cyclic response of the proposed connection, an experimental study was conducted on two full-scale one-bay, two-story Special Concentrically Braced Frames (SCBFs). This study considered beam-to-column connection as moment transfer via a through-plate to mobilize the reservation capacity of SCBFs. Square-HSS and circular-HSS cross-sections were used for braces and columns. The experimental results demonstrated that the proposed connection is acceptable since through-gusset plate can eliminate distortion and out-of-plane deformation of HSS column flange at the gusset plate vicinity via providing a new load path. The cyclic response of specimens showed that beam-to-column moment connection by through-plate increased strength, ductility, and energy dissipation capacity for approximately 41%, 79%, and 110%, respectively. In addition, in the phase of reservation capacity, noticeable slip in bolts and sudden fracture in connection plates occurred. Consequently, an acceptable performance was not observed for beam-to-gusset plate connection proposed in AISC.

Self-centering mechanism and seismic response of steel tension-only concentrically braced beam-through frames

Tension-only concentrically braced beam-through frames (TCBBFs) are a newly proposed structural system that has great potential in damage mitigation for seismic design of low-rise steel buildings. In TCBBFs, columns usually have cold-formed hollow structural section (HSS) and are connected to the flanges of H-shaped beams at each floor level as an easy main frame assembly, and tension-only braces are installed to the main frame to provide additional lateral stiffness. The braces also serve as the replaceable fuse elements that contain the self-centering and energy dissipation properties of the system. This paper investigates the self-centering mechanism, structural behavior, and seismic performance of TCBBFs through integrated analytical and experimental studies. Particularly, shaking table tests were conducted to investigate the seismic response of TCBBFs with tension-only braces designed with four different methods. The effects of yielding, prestress level, and design methods of the braces on structural response are evaluated. The experimental results show that TCBBFs are capable of archiving uniform story drift response with self-centering ability upon unloading. Due to the self-centering mechanism of the system, the tension-only braces can be easily replaced and the main frame can be reused after the shaking of major earthquakes.

Evaluation of the slotted-hidden-gap (SHG) connection for square HSS brace members

Hollow structural section (HSS) braces of concentrically braced steel frame structures are often connected using a knife connection, which creates a net area in the brace due to the slot. Tensile rupture of the brace's net section is the controlling failure mode unless reinforcing schemes are utilized. The “Slotted-Hidden-Gap (SHG)” connection, in which a notch is created in the gusset plate to overlap the gross area of the tube to eliminate the net area, represents an attractive alternative to traditional connection reinforcements; however, no design guidelines exist for the SHG connection for square HSS braces. A laboratory testing program and finite element modelling were carried out to determine the minimum overlap length required to develop the yield resistance of a square HSS brace. The test program included monotonic tensile loading tests on short conventional- and SHG- connection specimens, and one reversed cyclic loading test on a 4.86 m long brace specimen with SHG connections. An overlap length of 5% of the weld length was sufficient to develop the yield resistance of the braces with SHG connections. For those specimens, the HSS eventually fractured on their gross area away from the connections, after experiencing extensive yielding along their length. Conversely, braces with the conventional connections suffered localised yielding and fracture at the net section. The long brace with SHG connections attained its yield tensile resistance, including a 15% increase due to strain hardening, while sustaining an axial deformation corresponding to a storey drift of 3.14%.