Circular Hollow Section Members Research Articles

Cyclic modelling of T-joints with CHS chord members and passing-through plates

This paper focuses on modelling the cyclic response of welded T-joints between Circular-Hollow-Section (CHS) chords and passing-through plates. Recent works have highlighted that, in practical applications, this specific joint typology can be regarded either as a standalone connection or as a component representing one of the main sources of deformability and energy dissipation capacity in more complex beam-to-column joints with CHS columns and passing-through I-beams. Currently, research efforts have primarily focused on predicting the strength and stiffness of this type of connection. However, there is a knowledge gap regarding the characterization of the cyclic response of joints with passing-through members, a crucial aspect for modelling steel structures with these connection types in seismic areas.In light of this, the paper aims to characterize the cyclic response of T-joints with CHS members and passing-through plates using a comprehensive approach that incorporates experimental, numerical, and analytical methods. Initially, the results of an experimental study examining the cyclic behaviour of T-joint specimens with passing-through plates are presented. Subsequently, models of the tested joints are implemented in Finite Element software and validated against the experimental outcomes. The validated models are used to conduct a parametric study, considering 44 different configurations to obtain their force-displacement cyclic responses. These responses are mathematically modelled using the hysteretic uniaxial material from the OpenSees library and a Genetic Algorithm based tool previously developed by the authors (MultiCal). Finally, regression analyses are performed to develop formulations for predicting the mathematical parameters of the hysteretic uniaxial material model starting directly from the geometrical and mechanical properties of the connection.This approach enables designers to model the cyclic response in structural analysis with a straightforward approach, without the need for new calibrations or tests, if the modelled joints fall within the proposed range of calibration. From the point of view of the component modelling, the approach presented aligns with the larger research strand devoted to the extension of the component method codified in Eurocode 3 part 1.8 to cyclic loading conditions.

Monte Carlo simulation study on the reliability of concrete-filled HSS beam-column design provisions

Revisions were recently proposed to the way in which concrete-filled hollow structural section (HSS) 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 (L/D) 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.

Wrapped Composite Joints for Circular Hollow Section Structures

AbstractAn innovative bonding joining technology for truss/lattice circular hollow section (CHS) supporting structures is being developed as replacement for welded joints. Wrapped Composite Joint uses bonding instead of welding to transfer the joint forces and bending moments between the chord and brace CHS members through a dedicated fibre reinforced polymer composite wrap. It is aimed to replace all welds in different types of joints such as X, K, KK and splice joints in fatigue and/or corrosion dominated designs of truss/lattice structures such as offshore wind jackets and floaters, fish farms, truss bridges, etc. Composite material is known for good fatigue performance from aerospace industry and wind turbine blades. Number of joint experiments showed superior fatigue performance of the wrapped composite joints compared to welded CHS joints. This new concept allows for huge reduction of thickness of CHS members resulting in significant truss/lattice structure weight reduction and increase of fatigue lifetime. This paper presents state of development and outlook of the wrapped composite joint technology in terms of design, production and joint performance for ultimate limit state, fatigue and influence of the environment. Framework of prediction methods and design principles based on ongoing experimental and numerical research will be presented. The scope includes material, interface, and joint level experiments from small to full scale (100‐600 mm member diameter) and finite element modeling of complex steel‐composite bonded joints. Advantage of using state‐of‐the‐art monitoring techniques such as Digital Image Correlation, Fibre Optics Strain Measurement and 3D scanning is highlighted

Testing, simulation and design of hot-rolled seamless austenitic stainless steel CHS columns

Stainless steel circular hollow section (CHS) members are favoured by architects and structural engineers because of their aesthetics, superior torsional resistance and corrosion resistance. Hot-rolling is one of the typical production processes for producing CHS members. Nevertheless, few research has been carried out concerning the hot-rolled stainless steel CHS members. This paper reports experimental and numerical investigations into hot-rolled seamless stainless steel CHS columns. Flexural buckling tests on eight columns were firstly carried out in the experimental investigation. This was followed by numerical modelling investigation, where the FE models were developed and validated against the test results. The validated FE models were then used to conduct a series of parametric studies to obtain more data covering a wide range of member slenderness and cross-section sizes. Based on test and FE results, three existing design approaches in the Eurocode, Chinese specification and American specification were assessed and discussed. The assessment results show that the three design approaches all provide relatively accurate strength prediction on the whole, but the design approaches in the 1993-1-4 + A2 and ANSI/AISC 370-21both give overestimated strength predictions while design approach in the CECS 410 gives a relatively conservative strength prediction when the column slenderness is small. In view of this, new column design curve has been proposed, with its advantage over the existing design approaches confirmed by quantitative and graphical comparisons.

Strength predictions of circular hollow section T-joints of steel grade 1100 MPa

This paper presents experimental and numerical investigations of cold-formed high strength steel (CFHSS) circular hollow section (CHS) T-joints. The CFHSS CHS members have nominal 0.2% proof stress of 1100 MPa. The geometric parameters of the T-joints were designed by varying the ratios of β, 2γ and τ. A total of twelve T-joint tests were conducted by applying axial compressive load through the braces without preloading in chords. Non-linear finite element (FE) model was then developed for the CFHSS CHS T-joints. After successful validation, parametric studies were performed by using the verified FE model. The chord plastification failure of the T-joints was mainly found in both test and numerical studies. The relationship between the joint strengths and the variation of geometric ratios were investigated. The test and numerical strengths of the T-joints were used to assess the strength predictions by design equations provided in CIDECT, EN-1993-1-8 and the literature. It was found that these predictions generally provided unconservative predictions. A new equation that considers the effects of geometric ratios on the strengths was proposed based on both the test and numerical results. By adopting the newly proposed equation, the predictions are improved and provide the least scattered results when compared with other predictions.

Mechanical properties of cold-formed steel semi-oval hollow sections after exposure to ISO-834 fire

Due to modern architectural requirements, the applications of novel tubular sections are getting more and more popular. The semi-oval hollow section (SOHS) is one of the novels and recently developed tubular sections, and the post-fire mechanical properties of cold-formed steel semi-oval hollow section (CFSSOHS) members are not yet known. Thus, this paper presents a test programme to investigate the mechanical properties of CFSSOHS members after ISO-834 standard fire (ISO-834, 1999, [1]) exposures in a gas furnace. The CFSSOHS members were made of Q345 steel grade and obtained by cold-forming of hot-extruded seamless circular hollow section members. In total, 4 identical sets (i.e., set-1, 2, 3 and 4) of CFSSOHS members were prepared, and then heated up to different fire exposure temperatures of 300 °C, 550 °C, 750 °C, and 900 °C respectively, followed by their natural cooling inside the gas furnace. Once cooled down to ambient temperature, a total of 51 post-fire longitudinal tensile coupon specimens were fabricated. From each fire exposed CFSSOHS member, coupon specimens were extracted from the flat, curved, and corner portions of the sections. Using the static post-fire stress–strain curves, residual mechanical properties and corresponding residual factors were determined. Empirical equations were proposed to predict the post-fire residual mechanical properties of CFSSOHS members. In addition, using a scanning electron microscope, microstructures of a typical CFSSOHS member for all 4 fire exposure temperatures were compared with those without fire exposed specimens.

Chord plastification in high strength steel circular hollow section X-joints: Testing, modelling and strength predictions

This paper presents experimental and numerical investigations on cold-formed high strength steel (CFHSS) circular hollow section (CHS) X-joints. The CFHSS CHS members had nominal 0.2% proof stress up to 1100 MPa. The geometric parameters of the X-joints were designed by varying the ratios of β, 2γ and τ. Seventeen X-joint tests were conducted by applying axial compressive load through the braces without preloading in chords. Non-linear finite element model (FEM) was then developed for the CFHSS CHS X-joints. After successful validation of ultimate strengths, failure modes and load-deformation curves, parametric studies were performed by using the verified FEM. The chord plastification failure of the X-joints was mainly found in both test and numerical studies. The relationship between the joint strengths and the variation of geometric ratios were investigated. The strengths of the X-joints obtained in this study together with the test strengths collected from the literature were used to assess the strength predictions by CIDECT and EN-1993–1-8, as well as those from the literature. It was found that the current predictions generally provided unconservative predictions. A new equation that considers the effects of geometric ratios on the strengths was proposed based on both the test and numerical results. By adopting the newly proposed equation, the predictions are improved and provide the least scattered results when compared with the other predictions.

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 and numerical study of hot-rolled duplex stainless steel CHS columns

Stainless steel circular hollow section (CHS) members have been widely used in building structures because of their comparable strength to structural carbon steels, attractive appearance and excellent corrosion resistance. However, research on stainless steel CHS members has been limited to cold-formed members, whereas hot-rolled CHS columns have received less attention. To this end, the flexural buckling performance of hot-rolled duplex stainless steel CHS columns was investigated by a comprehensive experimental and numerical programme. A total of seven hot-rolled duplex stainless steel CHS columns covering two cross-sectional sizes with varying lengths have been tested under compression. Based on the test results, finite element (FE) models were developed and used in parametric studies to generate data points with a wider range of geometric dimensions. Comparing the test and FE results with current design guidance, it was found that the Chinese standard, CECS 410, and North American design guidance, AISC DG 27, underestimate significantly the flexural buckling resistance of such columns, while the design method in Eurocode 3: Part 1–4 might be unsafe in predicting the resistances for low slenderness values. New column buckling curves based on the Eurocode 3 and AISC DG 27 design formulae with improved accuracy and reduced scatters were also proposed and validated through careful reliability analysis.

Investigation on the behaviour of CFRP strengthened CHS members under monotonic loading through finite element modelling

During the past several years, civil infrastructure has made extensive use of tubular hollow steel members as structural elements. However, the rehabilitation and strengthening of tubular hollow steel members is a major concern due to design errors, environmental effects, reduction in material properties over time caused by corrosion and the need to withstand increased loads. A comprehensive investigation on the strengthening of tubular hollow steel members is therefore required. Although carbon fibre reinforced polymer (CFRP) strengthening technique has shown its effectiveness to improve the structural response of different steel members, studies on the structural response of circular hollow section (CHS) steel members strengthened with CFRP is limited. In the present study, an effective finite element (FE) model is first developed by comparing the FE model simulated results with the authors' experimental results. This is followed by a parametric study on the effect of the bond length of CFRP, number of CFRP layers, ratio of CFRP thickness to CHS wall thickness, diameter to thickness ratio of CHS and steel grade of CHS on the structural behaviour of the strengthened member subjected to monotonic loading. These parameters had noteworthy effects on the behaviour of the CFRP strengthened CHS steel members under monotonic loading. The CFRP strengthened CHS steel members showed an improvement in the moment capacity, secant stiffness, energy dissipation capacity and ductility compared to their bare CHS steel members. It can be concluded that the effectiveness of the CFRP strengthening technique is enhanced with the increase in the ratio of CFRP thickness to CHS wall thickness and/or increasing the diameter to thickness ratio of CHS. In contrast, the effectiveness of the CFRP strengthening technique is decreasing with the increasing of the steel grade.

Compressive resistance of high-strength and normal-strength steel CHS members at elevated temperatures

The compressive behaviour of hot-finished circular hollow section (CHS) steel members in fire is investigated in this paper through numerical modelling. CHS members with high-strength steel grades of S690 and S460 are taken into consideration in addition to those made up of normal-strength grades S355, S275 and S235. Numerical models of CHS structural steel members able to replicate their response in fire are validated. Using the validated finite element models, extensive parametric studies are carried out for the purpose of exploring a broad range of factors influencing the cross-section and member buckling response of CHS steel members under axial compression at elevated temperatures. The accuracy and safety of the design recommendations provided in the European structural steel fire design standard EN 1993-1-2 for the determination of the axial compression resistances of CHS steel members in fire are assessed. New design methods able to provide accurate and safe estimations of the cross-section axial compression resistances and flexural buckling resistances of CHS steel members at elevated temperatures are proposed. The higher accuracy, reliability and safety of the proposed design methods relative to the existing design provisions in EN 1993-1-2 are illustrated. • Behaviour and design of high-strength and normal-strength steel CHS members under compression in fire are investigated. • FE models able to mimic response of CHS steel columns in fire are developed and validated using results from experiments. • New design rules for cross-section and flexural buckling resistance of CHS steel columns in fire are established. • Proposed design rules lead to more accurate results relative to the current design rules in EN 1993-1-2. • Accuracy, safety and reliability of proposed design rules are verified against extensive numerical data.

Numerical study of fire resistance of stainless steel circular hollow section columns

Stainless steel has countless desirable characteristics for a structural material. Although initially more expensive than conventional carbon steel, stainless steel structures can be competitive due to their smaller need for fire protection material and lower life-cycle cost, thus contributing to a more sustainable construction. The most common stainless steel groups used in structural applications are the austenitic, ferritic and austenitic–ferritic (also known as Duplex grades). This work presents a numerical study on the behaviour of stainless steel circular hollow section members under axial compression at elevated temperatures, with different cross-section slenderness. The numerically obtained ultimate load-bearing capacities are compared with simplified calculation formulae from Eurocode 3 for columns under fire situation. A parametric study, considering different stainless steel grades from the aforementioned groups, cross-sectional classes and slendernesses, is here presented for different elevated temperatures. The numerical analyses were performed with the finite element programme SAFIR, with material and geometric non-linear analysis considering imperfections. Comparisons between the numerical results and the Eurocode 3 rules demonstrated that a specific design approach must be developed for stainless steel columns under fire situation.

Hysteretic performance of CHS steel members under cyclically fluctuating axial loads and lateral displacement

Circular hollow section (CHS) steel members have been widely used in large-span reticulated shells. However, both the axial force and bending moment fluctuate significantly in single-layer reticulated shell members during earthquake events. Therefore, to understand the hysteretic performances of CHS members under a complex loading status, in this study, laboratory tests were performed using eight full-scale CHS samples subjected to combined fluctuating axial force and cyclically increasing lateral drift. Then, the experimental results were compared to those of a numerical analysis. Through full-scale laboratory experiments, ultralow cycle fatigue data for five compressive and three tensile CHS specimens were obtained under different combinations of loading patterns to investigate the different factors influencing the hysteretic behavior of the CHS. These influencing factors include the fluctuating amplitude, frequency, and phase of axial loading cycles relative to unilateral drift. The CHS members under varying compressive axial forces were shown to have a more pronounced global deformation and asymmetric lateral resistance than the members under varying tensile forces. Members under an uncoupled combination of axial load and lateral displacement showed slightly asymmetric lateral force-displacement hysteresis loops. The uncoupled varying axial load and lateral drift slightly influenced the single-cycle energy dissipation capacity of the tensile specimens. However, with a longer fracture life, the total exhausted energy of the tensile specimens increased. In addition, the cyclic void growth model (CVGM) micromechanical fracture prediction theory, which is based on finite element numerical simulations, was also conducted in ABAQUS for comparison to validate the experimental findings. The CVGM theory should not be adopted when the Lode parameters extracted from a “cracked element” are close to 0 in the middle stress triaxiality range with fully developed plasticity.

Ductile Fracture Analysis of Welded Hollow Spherical Joints Subjecting Axial Forces with Micromechanical Fracture Models

Two micromechanical fracture models, void growth model (VGM) and stress modified critical strain (SMCS) model, were adopted to distinguish the failure mechanism of welded hollow spherical (WHS) joints under axial load based on FE analysis. Ductile fracture was successfully predicted for WHS joints under axial tension. The predicted fracture location is at the weld toe between WHS joints and circular hollow section members, which is consistent with corresponding test results. The predicted fracture load is lower than the peak load on the load–displacement curve, which indicates that the failure mechanism of WHS joints under axial tension is fracture due to inadequate strength and the fracture load should be taken as the ultimate load bearing capacity of the joints. A simplified SMCS model was proposed and verified for ductile fracture prediction of WHS joints under axial tension. Micromechanical fracture analysis was also conducted on WHS joints under axial compression. It was obtained by both VGM and SMCS model that no fracture would occur before the load reached its peak value, the reason of which was discussed by tracing the variation of the equivalent plastic stain and stress triaxiality at the potential location of fracture. Therefore, the failure mechanism of WHS joints under axial compression is losing stability with the depression of the sphere cap and the peak load on the load–displacement curve should be taken as the ultimate load bearing capacity of WHS joints.

Experimental Study on the Static Behavior of Reinforced Warren Circular Hollow Section (CHS) Tubular Trusses

For truss structures, the question of whether to weld hidden welds or not has been controversial. In the actual construction process of truss structures, the members are usually spot welded in place on the assembly platform, and then welded as a whole, while the hidden welds of the truss are not welded, especially for small pipe diameter trusses. Furthermore, in this study, under hidden weld unwelded conditions, two kinds of reinforcing method (adding a half outer sleeve on each joint and filling concrete into the chord members) are adopted to achieve the purpose of strengthening the truss. Therefore, this paper presents an experimental study on the static behavior of four types of Warren tubular trusses made of CHS members. These four types are (1) T-HW: The truss with hidden welds welded; (2) T-HN: The truss with hidden welds unwelded; (3) TS-AS: The truss strengthened on the basis of T-HN by adding a half outer sleeve on each joint; (4) TS-FC: The truss strengthened on the basis of T-HN by filling concrete into the top and bottom chord members. The mechanical behavior, failure mode, bearing capacity, and load-displacement of all specimens were investigated. The surface plasticity of the bottom chord member, the weld fracture around tubular joints at the bottom chord member, and the bending deformation of the bottom chord member were observed in the tests. Compared with the T-HW specimen, the load carrying capacity of the T-HN specimen decreased by 18%. On the other hand, the T-HN specimen has better deformability than the T-HW specimen. The reinforcing method of adding a half outer sleeve on each joint and filling concrete into the chord members can effectively improve the load carrying capacity and stiffness of the truss, thus reducing the overall deformation of the truss, but the reinforcing method of filling concrete into the chord members is more efficient.

Experimental Study on FRP-Strengthened Steel Tubular Members under Lateral Impact

The hollow structural members are highly vulnerable structural components subjected to transverse impact loads. These tubular members have been used widely in both onshore and offshore structures where lateral impact force can be expected from moving vehicles/vessels or terrorist attacks. Thus, strengthening of steel hollow tubular members is required to safely carry both service static and imposed dynamic impact loads. This paper presents the results from a series of tests on bare and fibre reinforced polymer (FRP) strengthened circular hollow section (CHS) steel members subjected to transverse impact loading at mid span. A total of fourteen (two bare and twelve strengthened) medium scale specimens were tested to investigate the effect of FRP wrapping on the global and local deformation capacity of strengthened members under drop hammer impact. Both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) sheets were used as strengthening materials. The results indicate that the FRP strengthening of the tubes enhances their impact resistance capacity by reducing lateral displacements up to 29% compared to bare steel CHS specimen. The influence of FRP type, CFRP orientation, CFRP thickness and effective bond length on the structural response and failure behaviour of wrapped members were investigated. The results showed that the application of FRP in the longitudinal direction was effective to control the global deformations whereas the hoop layers were effective in reducing local inward deformations of CHS members.

Durability of CFRP strengthened steel circular hollow section member exposed to sea water

This paper presents the results from a research program to investigate the durability of CFRP strengthened steel circular hollow section (CHS) members with and without embedded glass fibre reinforced polymer (GFRP) at ambient (24°C±4°C) and 50°C temperatures under accelerated corrosion environment. The beams were tested to failure under four-point bending. It was found that the accelerated corrosion adversely affected the durability of the strengthened beams at both temperatures and the embedded GFRP enhanced the durability. Durability design factor has also been recommended. The proposed theoretical approach predicts ultimate loads reasonably compared to experimental value of ultimate loads.

Buckling and Vibration Analysis of Cold-Formed Steel CHS Members and Frames Using Generalized Beam Theory

This paper reports the results of an investigation on the use of Generalized Beam Theory (GBT) to assess the buckling and vibration behaviors of thin-walled members and frames built from cold-formed steel circular hollow section (CHS) profiles. Initially, the concepts and procedures involved in performing GBT buckling and vibration analyses are presented, paying particular attention to the derivation of the mass tensors that account for the influence of the inertia forces. Then, the formulation, numerical implementation and validation of a GBT-based beam finite element for isolated members are described. Next, the determination of the frame linear stiffness, geometric stiffness and mass matrices, which incorporate the influence of the frame joints, is addressed. Finally, in order to illustrate the application and capabilities of the proposed GBT finite element formulation, numerical results are presented and discussed — they concern the buckling and vibration behaviors of an "L-shaped" frame. For validation purposes, most GBT-based results are compared with values yielded by shell finite element analyses carried out in the code ANSYS.

Probabilistic analysis of a twin deck curved cable-stayed footbridge subjected to multiple inputs and corrosion

In order to investigate the benefits of Circular Hollow Section (CHS) structural members to a complex cable-stayed footbridge, this paper presents a simulation-based probabilistic assessment of this type of structures when erected in an aggressive environment. The footbridge studied is located in Pescara, Italy, next to the Adriatic sea. We validated a Finite Element (FE) model of this bridge, and then, we performed a probabilistic study. Owing to corrosion during the bridge design life, both general and localized corrosion models capable of evaluating the reduced load bearing section were adopted; and appropriate probability distributions were assigned to input model parameters. Afterwards, the probabilistic evaluation of the bridge deck response was conducted using non-linear simulations based on Monte Carlo Sampling, where the convergence was accelerated by using Latin Hypercube Sampling (LHS). Serviceability limit state for stresses was satisfied for the footbridge service life for both wind and pedestrian loads. However, for the limit states referred to maximum deck deflection and rotation, the probabilities of failure crossed limiting values suggested in Eurocodes. As a result, for the twin deck curved cable-stayed footbridge with CHS members, the probabilistic analysis was able to predict the exceeding time of limit states’ thresholds. Thus, both repair and a retrofit plan within its design lifetime could be set.

Experimental study of concrete-filled multiplanar circular hollow section tubular trusses

This paper presents an experimental study on concrete-filled multiplanar tubular trusses made of circular hollow section (CHS) members. A total of four types of concrete-filled multiplanar tubular trusses including Triangular truss (TT), Inverse-Triangular truss (IT), Square truss (ST) and Trapezoid truss (TZ) were tested under static loading. The failure mode, load carrying capacity, overall deflection and strain intensity of all specimens are reported. The effects of top and bottom chord members, straight and diagonal brace members and lateral bracings on the load carrying capacity, flexural rigidity and ductility of all specimens were also investigated. The typical failure modes observed from the tests include the local buckling of straight brace members, the surface plasticity and shear failure of the bottom chord members, the weld fracture around tubular joints at the bottom chord members, and the end support failure of the top chord member. The load carrying capacity, flexural rigidity and ductility of different types of multiplanar tubular trusses made of identical CHS members are quite different due to the remarkable changes of the mechanical behaviour of CHS members. On the other hand, the lateral bracings play different roles under different load levels in enhancing the load carrying capacity of different types of multiplanar tubular trusses. It is demonstrated from the comparison that the Inverse-Triangular truss (IT) has optimum flexural rigidity, ductility and efficiency in practice.