Hollow Structural Section Columns Research Articles

Seismic Local Buckling Limits for Hollow Structural Section and Built-Up Box Columns

Recently completed research on seismic local buckling limits for steel hollow structural section (HSS) and built-up box columns is featured. These National Center for Research on Earthquake Engineering (NCREE) studies are led by Dr. Chung-Che Chou and Dr. Tung-Yu Wu in the Department of Civil Engineering at National Taiwan University (NTU). Dr. Chou also serves as the NCREE Director. Dr. Chou’s research has focused on seismic testing, analysis, and design for steel and post-tensioned self-centering structures. Some recent work includes studies on hybrid simulation of a full-scale steel moment frame, a post-tensioned self-centering brace, novel prediction models for early earthquake warnings, and earthquake reconnaissance work in eastern Taiwan. Dr. Chou’s numerous accolades include the Awards for Excellent Research and Technology Transfers for his leadership on a research team developing a sandwiched buckling-restrained brace and a self-centering brace. Dr. Wu’s research interests include collapse behavior of cold-formed HSS columns under seismic loading, subwavelength seismic metamaterial structures, crack growth in railway crossings under high wheel-rail impacts, and seismic resilience of steel buildings. In addition to multiple scholarships and fellowships, Dr. Wu’s honors include the Raymond C. Reese Research Prize, awarded by the American Society of Civil Engineers (ASCE) for papers representing notable achievements in research with impact on design. The National Science and Technology Council is supporting this research on seismic local buckling limits for HSS and built-up box columns. Selected highlights from both projects are presented, along with a preview of future research tasks.

Passing-through I-plates-to-SHS moment resisting joints subjected to symmetric bending moments

When using hollow structural section (HSS) members in multi-storey buildings, beam-to-column moment resisting connections’ design raises critical questions to tackle. With conventional welded and bolted joints’ response being generally very flexible, the design resistance becomes governed by a deformation criterion rather than a strength criterion. This underscores the necessity for smart reinforcement techniques. A widespread solution is the diaphragm approach, in which the stiffeners usually protrude over the tubular column. The solution of plates passing through the HSS column is another stiffening option which was studied recently for CHS, yet, SHS columns have not been subject to comparable scrutiny. The objective of this paper is to study experimentally, numerically, and analytically the mechanical behaviour of I-beam-to-SHS column moment resisting joints using passing through I-plates under symmetric bending moments. The testing of two full-scale specimens corroborates previous findings with CHS columns in the elastic regime. However, significant deviations were observed in the post-peak response, revealing new insights into the behaviour of SHS columns. Failure was due to progressive buckling of passing through plates and yielding of tube-wall in transverse compression. A finite element model using solid and contact elements is developed and validated against experimental data. This model underscores how loads are redistributed between the tube wall and passing plates. A simplified version of the FE model is used to perform a thorough parametric numerical analysis on 101 configurations expanding upon the experimental test database by varying geometrical parameters such as passing plate thickness, tube, and beam dimensions. Finally, an analytical model integrating the different components of the joint is proposed to evaluate the initial rotational stiffness and the bending resistance.

Investigation of cyclic behavior of full-scale tree-like hollow structural section columns with infilled concrete

The cyclic behavior of tree-like hollow structural section (HSS) columns with infilled concrete was experimentally and numerically investigated. A full-scale column, with the height of 3.7 m and the treetop plan dimension of 4 m × 3 m, was designed and manufactured according to a practical engineering prototype. The column was composed of a petal-shaped trunk using a concrete-filled steel tubular (CFST) section, four primary branches using a circular CFST section, and twelve secondary branches using a circular HSS. The column with a capacity protected reinforced concrete foundation was tested under combined constant axial compression and cyclic lateral loading through a specifically designed setup. The cracking and spalling of the reinforced concrete foundation were observed initially, followed by yielding of the bottom end of the primary branches when the story drift ratio reached 1.00%. The specimen failed by fracture of the full penetration groove welded splices in the petal-shaped trunk embedded in the foundation when the story drift ratio reached 3.00%. A detailed finite element analysis model for the tree-like column was then established and verified. Parametric studies were conducted to investigate the influence of the axial load level (0.016–0.3), filling range of concrete (including no filling, partial filling, and overall filling), steel yield strength (235–460 MPa), and the height to width ratio of the petal-shaped trunk (0.75–3.14). The results showed that the higher the filling height of concrete was, the greater the lateral load-carrying capacity and stiffness of the specimen were, but the filling height after reaching the secondary branches hardly affected the mechanical properties of the specimen. With the increase of the axial load level, the load-carrying capacity and deformation capacity decreased. Both the filling range and the height to width ratio of the petal-shaped trunk could change the failure mode of the tree-like column. Finally, some design considerations were proposed.

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.

Further study on improvement on strain concentration in through-diaphragm connection

Hollow structural section (HSS) columns have been increasingly popular due to their structural and architectural merits. However, practical difficulty lies in developing proper connections. The through-diaphragm connections are considered as suitable connection type that is widely adopted in Asian countries. However, the stress concentration occurs at the location connecting through-diaphragm and steel beam. Furthermore, the actual load path from the beam flange is not uniformly transferred to the HSS column as conventionally assumed. In this paper, tensile tests were further conducted on three additional specimens with beam flange plate to evaluate the load versus displacement response. The load-displacement curves, yield and ultimate capacity, ductility ratio were obtained. Furthermore, the strain development at different loading levels was discussed comprehensively. It is shown that the studied connection configuration significantly reduces the stress concentration. Meanwhile, simplified trilinear load-displacement analytical model for specimen under tensile load was presented. Good agreement was found between the theoretical and experimental results.

Cyclic Behavior of SCBFs with Through-Gusset Plate Connections and Concrete-Filled Tube Columns

ABSTRACT In Hollow Structural Section (HSS) column-beam-brace connections, offset between gusset plate and HSS column webs leads to large distortion and out-of-plane deformation in HSS column face. To alleviate such undesirable effect, this paper proposes a new connection which consists of concrete infill and gusset plate passing through HSS column, called Through-Gusset Plate (TGP).The results indicated that the proposed connection increases the lateral stiffness, lateral strength, and energy dissipation capacity of frame specimens by up to 74, 67, and 73%, respectively. Moreover, due to using this novel connection, the normal force component capacity of connection is enhanced by approximately 3.2 times.

Cyclic Performance of End-Plate Biaxial Moment Connection with HSS Columns

This paper presents a numerical study on the seismic performance of end-plate moment connection between I-beam to HSS (hollow structural section) column stiffened by outer diaphragms (EP-HSS). In previous experimental research, this moment connection showed a satisfactory performance according to requirements established in Seismic provisions. However, one type of joint was studied and bidirectional and axial loads were not considered. In this since, several configurations representative of 2D interior joints and 3D interior and exterior joints in a steel building were modeled and subjected to unidirectional or bidirectional cyclic displacements according to protocol in seismic provisions. Firstly, a similar joint configuration was calibrated from experimental data, obtaining an acceptable adjustment. The assessment of seismic performance was based on hysteretic curves, failure mechanisms, stiffness, dissipated energy, and equivalent damping. The results obtained showed a ductile failure modes for 2D and 3D joint configurations with EP-HSS moment connection. The axial load has no significant effect on the moment connection. However, it affects the column strength due to the increase of the stresses in the column wall. Compared with 2D joints, 3D joints reached higher deformations even when a similar number of beams is used. The external diaphragms to the column panel zone provided rigidity in the joints and no degradation of slope for each loop in load/reload segment for elastic loop; therefore, curves without pinching were observed. All inelastic deformation is concentrated mainly in the beams. A moment resistance above 80% of the capacity of the beam at a drift of 4% is achieved in all joints. From the results reached, the use of EP-HSS moment connection with hollow structural section columns is a reliable alternative in seismic zones when steel moment frames are employed.

Fiber‐based hysteretic model for simulating strength and stiffness deterioration of steel hollow structural section columns under cyclic loading

SummaryAn efficient component model has been developed that captures strength and stiffness deterioration of steel hollow structural section (HSS) columns. The proposed model consists of two fiber‐based segments at a member's ends along with an elastic segment in between. The fibers exhibit nonlinear uniaxial stress–strain behavior, which is explicitly defined by uniaxial monotonic tensile and cyclic round coupon tests. The postbuckling behavior of an HSS column is traced through a proposed uniaxial effective stress–strain constitutive formulation, which includes a softening branch in compression and an energy‐based deterioration rule to trace the influence of cyclic deterioration in the inelastic cyclic straining. These may be inferred by uniaxial stub‐column tests. The component model captures the coupling between the column axial force and flexural demands. Consistent model parameters for a number of steel materials used in the steel construction in North America and Japan are proposed along with the associated model calibration process. The efficiency of the proposed model in predicting the hysteretic behavior of HSS columns is demonstrated by comparisons with physical steel column tests subjected to various loading histories, including representative ones of ratcheting prior to earthquake‐induced collapse. The proposed model is implemented in an open‐source finite element software for nonlinear response history analysis of frame structures. The effectiveness of the proposed model in simulating dynamic instability of steel frame buildings is demonstrated through nonlinear response simulations of a four‐story steel frame building, which was tested at full‐scale through collapse. Limitations as well as suggestions for future work are discussed.

Superior design solutions of section sizes in steel buildings for different lateral frame systems and column shapes

Superior design solutions of section sizes in steel buildings for different lateral frame systems and column shapes

Collapse Behavior of Hollow Structural Section Columns under Combined Axial and Lateral Loading

AbstractHollow structural sections (HSS) are used as columns in frame systems because of their ability to efficiently resist multiaxial loads. While the majority of previous studies of special mome...

Experimental studies on through-plate moment connection for beam to HSS/CFT column

A new moment connection for a steel beam to hollow structural section (HSS) and concrete-filled tube (CFT) columns using the through-plate technique is proposed. In the through-plate connection, all the demands of the beam are initially transferred to a vertical plate by in-plane action and are subsequently transferred to a column. Three full-scale interior planar connections are loaded cyclically under displacement control as per the AISI/AISC341-16 loading protocol. An axial compression force corresponding to 10% of the column axial capacity is applied to the column. The goals of the experimental study are as follows: (1) to evaluate the connection performance under cyclic loading and (2) to evaluate the connection components for extracting key design parameters. Square-shaped HSS sections with electric resistance welding are utilized for the column. To investigate the effect of concrete infill on the connection performance, the HSS column and one of the CFT columns are constructed using the same steel tube. The width-to-thickness ratio (b/t) for the corresponding specimens is 27, and another CFT specimen with a higher ratio of 34.5 is considered. In all the specimens, the plasticity is concentrated in the beam hinges, without any damage to the column or connection components. The proposed connection exhibits extremely high strength, stiffness, and ductility and is categorized as a rigid connection. Additionally, it exhibits stable cyclic behavior and high energy dissipation up to a story drift of at least 6% and satisfies the AISC seismic provisions as a special moment connection.

Seismic behavior of composite beam connected to HSS column with large width-to-thickness ratio

This paper discusses out-of-plane deformations in a HSS (Hollow Structural Section) column connected to a composite beam. Width-to-thickness ratio of HSS column is an important parameter in the flexural deformation capacity of the connection. Beam web connection moment transfer efficiency in HSS column connection is poor and significantly less effective when compared to a connection with W-shape columns. This condition is more severe in the case of composite beam connected to thin walled HSS columns having large width-to-thickness ratio. In this research, the force flow pattern and ultimate flexural capacity of web connection are evaluated by considering main parameters affecting the out-of-plane deformations namely: width-to-thickness ratio of HSS column, height-to-thickness ratio of beam web, yield strength ratios of beam and column, height-to-width ratio of connection, slab strength, stud layout and geometry of weld access hole. Results from the analysis are utilized to illustrate the location of neutral axis and structural condition of web connection in different width-to-thickness ratios and different concrete slab strengths. Also, equations for evaluation of ultimate flexural capacity of web connection are derived; interaction curves of Moment-Axial force acting at the web are drawn. It was found that in the HSS column with large width-to-thickness ratio of 29, axial force subjected to the web connection results in significant reduction of web flexural capacity. Experimental tests showed that plastic rotation capacity of composite beam decreased to almost half of the capacity of bare steel beam. In order to improve seismic behavior, a gap was provided between concrete slab and column face. However, experimental tests revealed that the application of a gap between concrete slab and column face solely did not improve the rotation capacity. The Finite element study showed that despite the existence of a gap, headed studs contribute to the composite action and modification of stud layout is needed. Investigation about the contribution of studs located on the loaded beam and transverse beam has been conducted. Recommendations for seismic application of composite beam connected to HSS column with large width-to-thickness ratio have been presented.

Numerical study on force transfer mechanism in through gusset plates of SCBFs with HSS columns & beams

In Special Concentrically Braced Frames (SCBFs), vertical and horizontal components of the brace force must be resisted by column and beam, respectively but normal force component existing at the gusset plate-to-column and beam interfaces, creates out-of-plane action making distortion in column and beam faces adjacent to the gusset plate. It is a main concern in Hollow Structural Section (HSS) columns and beams where their webs and gusset plate are not in the same plane. In this paper, a new gusset plate passing through the HSS columns and beams, named as through gusset plate, is proposed to study the force transfer mechanism in such gusset plates of SCBFs compared to the case with conventional gusset plates. For this purpose, twelve SCBFs with diagonal brace and HSS columns and twelve SCBFs with chevron brace and HSS columns and beams are considered. For each frame, two cases are considered, one with through gusset plates and the other with conventional ones. Based on numerical results, using through gusset plates prevents distortion and out-of-plane deformation at HSS column and beam faces adjacent to the gusset plate helping the entire column and beam cross-sections to resist respectively vertical and horizontal components of the brace force. Moreover, its application increases energy dissipation, lateral stiffness and strength around 28%, 40% and 32%, respectively, improving connection behavior and raising the resistance of the normal force components at the gusset plate-to-HSS column and beam interfaces to approximately 4 and 3.5 times, respectively. Finally, using such through gusset plates leads to better structural performance particularly for HSS columns and beams with larger width-to-thickness ratio elements.

Effects of Radial Imperfection on the Load Capacity of Round Hollow Structural Section Columns

Effects of Radial Imperfection on the Load Capacity of Round Hollow Structural Section Columns

Development of mathematical model for cyclic behaviour of blind bolted HSS column components

This paper presents an experimental and finite element analysis based mathematical modelling of cyclic behaviour of the component of hollow structural section (HSS) columns under bolt tensile loads. This component acts as an important constituent part to the blind bolted connections with HSS columns. Two typical failure modes and their related hysteretic curves are examined experimentally. It is shown that force versus displacement curves under monotonic loading can be regarded as the upper bound of the envelope of the counterpart cyclic response. Moreover, the hysteretic force–displacement curves of test columns with relatively thick tube walls demonstrate significant pinching manner thus less energy dissipative capacity. Based on the calibrated finite element model, the flexibility of tube wall and its influences on the connection response are compared for two failure modes. Parametric analyses are also performed to investigate the influence of geometric parameters on the elastic stiffness and yield strength. The mathematical hysteretic models allowing for the behaviour of the connections in two typical failure modes are proposed that distinguishes the developed model from those reported in the literature. It is demonstrated that the proposed model incorporating degradations of stiffness and/or energy dissipation can achieve a good representation of test hysteretic behaviours.

Low cycle fatigue response of bolted T-stub connections to HSS columns — Experimental study

Characterization of the low cycle fatigue response of the connection dominated by the hollow structural section (HSS) column in flexural bending and the bolt in tension are necessary to the design of its constitutional semi-rigid joints under earthquake scenarios. This paper presents the results of an experimental programme to evaluate the low cycle fatigue related characteristics of bolted connections to HSS columns. A summary of a total of 69 tension tests of T-stub connections is reported. The geometric parameters were varied as the bolt gauge width, the tube wall slenderness, the bolt size and the tube sidewall depth. Based on the experimental test results, the typical failure mechanisms, the hysteretic load-deformation relation and the response characteristics such as degradations of strength and energy dissipation capacity of the connections are examined. It is shown that the bolt gauge width and the tube wall slenderness have significant influences on the failure mode, the tensile capacity and stiffness which prompt two design parameters; namely, bolt gauge width to tube width ratio (β) and the tube wall thickness-to-half wall width ratio (Ψ0), in quantifying most influential geometric details of the connection. Moreover, the low cyclic fatigue life test results are compared with the codified S–N curves through a transformation of displacement range into effective stress range. It demonstrated a better contrast with test results by further allowing for the geometric parameters of β and Ψ0. Finally, the damage model analysis is employed to study the deterioration progress of the test connections through a comparison with typical damage indices available in the literature. The deficiencies of referred index are identified thereby promoting the proposal of a new model incorporating the stiffness and the energy dissipation in the representation of damage under constant amplitude loading condition. It is shown that the proposed model can give a reasonably well prediction of experimental evidences.

Non-linear finite element investigation on the behavior of CFRP strengthened steel square HSS columns under compression

This paper presents a numerical finite element investigation on the behavior of steel square hollow structural section (HSS) columns strengthened with CFRP. Three dimensional finite element (FE) models of square HSS sections were developed using shell elements considering both material and geometric nonlinearities whereas CFRP strengthening was incorporated with additional layers of shell elements. The developed FE models were used to simulate experimental studies done by past researchers. Good agreement has been found between numerical analysis and past experimental results, which has validated the acceptability of the FE model to carry out further investigation. Study is then focused on some selected non-compact AISC square HSS columns and the effects of number of CFRP layers, slenderness ratio and cross-sectional geometry on the strength gain of those columns has been observed. It is observed that CFRP strengthening is comparatively effective for higher slenderness ratios. For smaller sections strengthening tends to be effective at smaller slenderness ratios as well. For relatively large AISC square HSS columns, with increasing number of CFRP layers (from 1 to 5 layers) the axial strength gain is only approximately by about 1 to 20%. For medium and small square HSS sections, effectiveness of CFRP strengthening increases approximately by about 10 to 90%. The findings of the present study provide us a better understanding of the behavior of HSS sections strengthened with CFRP and shall be useful to engineers in applying CFRP retrofitting techniques to strengthen steel columns.

Shear tab to hollow structural section column connections

This paper presents an experimental study on shear tab to tubular column connections. Specimens were made by welding a single plate to the centerline of a hollow structural section column and were ...

Seismic performance of floor-by-floor assembled steel braced structures with stiffened connections

This paper presents an overview of a full-scale testing on a tension-only concentrically braced beam-through frame (TCBBF). The implementation of TCBBF facilitates the construction of low-rise industrialised residential steel houses by means of floor-by-floor assembling. This type of TCBBF system features cold-formed hollow structural section columns connected to H-section through beams by end plate with bearing-type high-strength bolts. A two-storey, four-span by one-span TCBBF subjected to vertical loads was cyclically loaded horizontally to examine the seismic behaviour. Stable behaviour was observed up to a storey drift angle of 1/10. The cyclic behaviour was characterised by a linear response, a slip range and a significant hardening response. Deteriorating pinched hysteretic behaviour was notable for cyclic loading primarily because of cyclic brace compression buckling and tension yielding. TCBBF incorporates very slender bracing members that are unable to bear much axial load when subjected to comp...

Experimental Examination of the Structural Performance of Restrained HSS Steel Beams and their End Connections in Fire

This paper describes a series of full-scale tests performed in the fire research facilities of Carleton University, Ottawa, Canada. These tests are part of an experimental programme, whose objective is to investigate the structural performance of axially restrained tubular steel beams at elevated temperatures. The primary focus is to determine the effect of the beam end connections on the structural performance of the steel-frame assembly. Four unprotected steel-frame test assemblies, each composed of a hollow structural section (HSS) steel beam restrained between two HSS columns, were subjected to a standard fire while constantly loaded. The main parameters investigated were the end plate thickness and the degree of beam axial restraint. Two different end plate thicknesses were tested, 12.7 mm and 19.0 mm. The experimental results showed a considerable effect of the end plate thickness on the structural behaviour of the connection and the connected beam. Moreover, the fire tests have revealed different connection failure modes, such as excessive end plate deformations, column buckling, and bolts fracture.