Behaviour Of Circular Hollow Sections Research Articles

Analytical and Numerical Study of Glass Fiber-Reinforced Polymer (GFRP) strengthened Steel Tube under Axial Compression

This article presents the results of an analytical and numerical study of the behaviour of circular hollow section (CHS) steel tubes strengthened by Glass fiber-reinforced polymer (GFRP). Glass, aramid, carbon etc. fiber composites are considered for strengthening applications. In this work, glass fiber is used and it is the most popular reinforcing fiber and it is more economical to produce and widely available fiber. Performance of steel tubes is enhanced by providing strength them with glass fiber reinforced polymer (GFRP) for investigating the effect of GFRP thickness, Specimen length, winding angle. FEA Analysis is performed on the steel specimen and model is simulated in ANSYS 16 software.

Behaviour of stub columns with initial crack defects under axial compression

An experimental investigation was conducted to evaluate the axial compressive behaviour of circular hollow section (CHS) stub columns with initial crack defects. A total of 96 specimens – 12 stub columns with one crack, 48 stub columns with two cracks, and 36 stub columns with three cracks – were tested under axial compression loading. The failure modes, load-carrying capacities, overall deflections, and strain intensities of all the specimens were examined. The design parameters were the tube thickness, long crack length, short crack length, crack spacing, and crack number. Additionally, a finite-element analysis was performed using the verified models in combination with the experimental data to evaluate the effects of the main influential factors. The initial cracks formed in the circular thin-walled stub columns accelerated the local buckling and changed both the bearing capacity and deformation capacity. The ultimate loads of the stub columns increased with the tube thickness, decreased slightly with an increase in the long crack length, and decreased with an increase in the crack spacing. The effects of the short crack length and crack number on the bearing capacity were complex and were coupled with the tube thickness. An adjustment coefficient was introduced into the predictive formula to estimate the ultimate bearing capacity. Through this, the ultimate bearing capacity can be accurately predicted.

Fatigue tests and design of CFRP-strengthened CHS gap K-joints

This paper presents an experimental study on the fatigue behaviour of circular hollow section (CHS) gap K-joints strengthened by carbon fibre-reinforced polymer (CFRP) sheets (CFRP-CHS K-joint). Eight CFRP-CHS K-joints and three reference un-strengthened CHS gap K-joints were tested under cyclic axial loading. Fatigue failure modes of the CFRP-strengthened and un-strengthened joints were determined and compared. Fatigue lives in three fatigue failure criteria were recorded: crack-initiation fatigue N2, through-thickness fatigue N3, and end-of-test fatigue N4. The comparisons indicate that CFRP-CHS K-joints have a longer fatigue life than un-strengthened joints in the same nominal stress range, regardless of fatigue failure criteria (N2, N3, or N4). The increase in N3 was approximately 138%, on average. No significant difference in fatigue data in terms of hot spot stress range was found between the CFRP-strengthened and un-strengthened joints. Based on the experimental fatigue data, a modified Sr,hs-N curve based on the CIDECT recommended curve was proposed for CFRP-CHS K-joints.

Testing and analysis of additively manufactured stainless steel CHS in compression

Additive manufacturing, also referred to as 3D printing, has the potential to revolutionise the construction industry, offering opportunities for enhanced design freedom and reduced material use. There is currently, however, very limited data concerning the performance of additively manufactured metallic structural elements. To address this, an experimental and numerical investigation into the cross-sectional behaviour of circular hollow sections (CHS), produced by powder bed fusion (PBF) from Grade 316L stainless steel powder, is presented. The experimental programme comprised tensile coupon tests, initial geometric imperfection measurements and five axially loaded stub column tests on specimens with a range of diameter-to-thickness (D/t) ratios. Similar cross-sectional behaviour to that of conventionally produced stainless steel CHS was observed, with the more slender cross-sections displaying increased susceptible to local buckling. In parallel with the experimental study, numerical simulations were carried out initially to replicate the experimental results and then to conduct parametric studies to extend the cross-sectional capacity data over a wider range of D/t ratios. The generated experimental and numerical results, together with other available test data on stainless steel CHS from the literature, were used to evaluate the applicability of existing design approaches for conventionally formed sections to those produced by additive manufacturing.

Behaviour and design of circular hollow section steel columns strengthened by infilling concrete under preload

The objective of this work is to develop design guidance for existing hollow steel columns that are retrofitted by infilling concrete into the tubes. The primary challenge is the unknown effect of the existing preload on the steel columns prior to the concrete infill. Composite performance and buckling behaviour of circular hollow section (CHS) steel columns strengthened by infilling concrete under preload was experimentally and numerically investigated in this study. A total of 34 CHS steel columns were tested under pin-ended boundary conditions, and the overall buckling failure modes and corresponding ultimate buckling resistances were recorded. Prior to the member testing, material properties of the steel columns and the infilled concrete were attained. By means of the finite element (FE) software package ABAQUS, elaborate FE models for the CHS columns strengthened by infilling concrete were developed and validated against the obtained test results, which were further verified with other available test data. Using the validated FE models, systematic parametric studies were conducted to examine the influences of the major factors affecting the ultimate capacities of the CHS columns strengthened by infilling concrete, including preload ratios, steel and concrete strengths, steel ratios, initial global imperfections, eccentricity ratios and column slenderness ratios. The obtained test and numerical results were therefore utilised to develop design criteria for predicting the overall buckling resistance of CHS steel columns strengthened by infilling concrete. In view of the difficulty of determining the key parameters in practice and the uncertainty of the strengthening process, a new simplified design coefficient was proposed, taking into account the influence of the preload. It has been demonstrated that accurate and reasonable strength predictions can be provided by the proposed design method.

Flexural stiffness of the composite steel and fibre-reinforced concrete circular hollow section column

The recent development in technology of production and transportation of steel fibre-reinforced concrete enables its utilization in composite steel-concrete structures. This work is a part of a project which focuses on development of mechanical behaviour of circular hollow section (CHS) composite steel and fibre-concrete (SFRC) columns at elevate temperature. Research includes two levels of accuracy/complexity, allowing simplified or advanced approach for design that follows upcoming changes in European standard for composite member design in fire EN1994-1-2 [1].One part is dedicated to determination and description of flexural stiffness of the SFRC CHS columns. To determinate flexural stiffness were prepared series of pure bending tests at elevated and ambient temperature. Presented paper focuses on the results of the tests and determination of flexural stiffness at ambient temperature. Obtained outputs were compared to data of existing studies about concrete-filled tube members with plain concrete and values analytically calculated according to the existing European standard EN1994-1-1 [2].

Behaviour of CHS brace-to-H-shaped chord X-joints under in-plane bending

This paper presents an experimental investigation on the circular hollow section (CHS) brace-to-H-shaped chord X-joints under in-plane bending. A total of six specimens was tested, in which three specimens were reinforced with the internal stiffeners in the H-shaped chord. The load carrying capacities, failure modes, axial load–vertical displacement curves, bending moment–rotation curves, axial load–local deformation curves and strain distribution curves of all specimens were reported. The corresponding finite element analysis was also performed and calibrated against the test results. Therefore, an extensive parametric study was carried out to evaluate the effects of main geometric parameters (β, 2γ and τ) on the behaviour of CHS brace-to-H-shaped chord X-joints. It is shown from the comparison that the load carrying capacities of the joints with small β value (β<0.605) under in-plane bending are effectively enhanced with the increase of the β value, whereas the β has little influence on the in-plane flexural behaviour of the joints with large β value (β≥0.605). Furthermore, the ductility of the joints without the internal stiffeners in the H-shaped chord increases remarkably with the increase of the β value, and the increment of the ductility of the joints without the internal stiffeners is more pronounced than their counterparts with the internal stiffeners. It is shown from the comparison that the current Eurocode is generally unconservative for the design of CHS brace-to-H-shaped chord X-joints with small β value under in-plane bending. The new design equations were proposed in this study which was verified to be more accurate.

Generalised beam theory to analyse the buckling behaviour of circular cylindrical shells and tubes

A formulation of generalised beam theory (GBT) developed to analyse the elastic buckling behaviour of circular hollow section (CHS) members (cylinders and tubes) is presented in this paper. The main concepts involved in the available GBT are adapted to account for the specific aspects related to cross-section geometry. Taking into consideration the kinematic relations used in the theory of thin shells, the variation of the strain energy is evaluated and the terms are physically interpreted, i.e., they are associated with the geometric properties of the CHS. Besides the set of shell-type deformation modes, the formulation also includes axisymmetric and torsion deformation modes. In order to illustrate the application and capabilities of the formulated GBT, the local and global buckling behaviour of CHS members subjected to (i) compression (columns), (ii) bending (beams), (iii) compression and bending (beam-columns) and (iv) torsion (shafts), is analysed. Moreover, the GBT results are compared with estimates obtained by means of shell finite element analyses and are thoroughly discussed.

On the rotation capacity of structural steel circular hollow sections in plastic analysis

In BS5950 (BS5950. Part 1, Structural use of steelwork in building. British Standards Institution, 1990), it is recommended that in order to analyse a structure by plastic methods the section classification of its members must be “plastic”. This condition is necessary so that “large” rotations can be attained without local buckling of the member. For tubular members of circular hollow section the ratio of D/ t must be ≤40 ε 2 for plastic classification. Similar limiting values of D/ t are recommended in EC3 (Eurocode 3. Design of steel structures, Part 1.1. General Rules and Rules for Buildings, British Standards Institution, 1993) as 50 ε 2 and AISC (American Institue of Steel Construction. Load and resistance factor design specification for structural steel buildings. 1986) as, the BS equivalent of, 32 ε 2. The above limitation ensures that the value of the plastic moment of resistance is maintained during sufficiently large rotations and local buckling in the form of longitudinal waves does not occur [Seide P, Weingarten VI. On the buckling of circular cylindrical shells under pure bending. Journal of Applied Mechanics 1961;28(March)]. But it does not take into account the secondary P– δ effect which takes place in the plane of the cross section of the tube. This effect will reduce the plastic section (ovalisation) modulus due to the deformation in the form of flattening of the cross section. The present paper attempts to investigate the behaviour of circular hollow sections beyond the stage of development of the plastic moment of resistance where large rotations will take place in order to achieve load distibution in the structure. It was found that the reduction in the theoretical plastic moment of resistance can be significant, and this was confirmed by experimental evidence.