Behaviour of cold-formed steel built-up battened columns composed of four lipped angles: Tests and numerical validation

2019 ◽  
Vol 23 (1) ◽  
pp. 51-64 ◽  
Author(s):  
M Anbarasu
Keyword(s):  
Cross Section ◽  
Finite Element Models ◽  
Test Results ◽  
Design Standards ◽  
Geometric Imperfections ◽  
The North ◽  
Compression Behaviour ◽  
Cold Formed Steel ◽  
Initial Geometric Imperfections ◽  
Box Columns

This article mainly investigates the behaviour and strength of built-up battened box column composed of lipped angles under axial compression. Ten specimens were fabricated and tested under pinned with warping-restrained end condition including two different cross-section dimensions of columns with five different geometric lengths. Three material tensile coupon tests were conducted to obtain the material properties of the steel used for fabricating the test specimens. The overall initial geometric imperfections were measured. The plate slenderness, member slenderness, chord slenderness and slenderness of batten plates may affect the compression behaviour of cold-formed steel built-up battened box columns and were accordingly investigated. It was found that the chord slenderness significantly affects the compressive strength of the built-up columns. Test results, including the compression resistances, the load versus displacement responses and the deformed shapes were presented. The test strengths were compared with the design strengths predicted using the North American Specifications (AISI-S100:2016), EuroCode (EN1993-1-3:2006) and design equations proposed by EI Aghoury et al. The design strengths predictions by these two design standards were unconservative, with EI Aghoury et al.’s standard performing better. Finite-element models were developed and verified against the test results.

Elastic buckling of imperfect circular toroidal shells under external pressure

1998 ◽  
Vol 212 (3) ◽  
pp. 197-209 ◽  
Author(s):  
G D Galletly
Keyword(s):  
External Pressure ◽  
Mode Shapes ◽  
Buckling Mode ◽  
Geometric Imperfections ◽  
Buckling Modes ◽  
The North ◽  
Buckling Resistance ◽  
Maximum Decrease ◽  
Initial Geometric Imperfections ◽  
Toroidal Shells

When perfect, externally pressurized complete circular toroidal shells buckle, the minimum buckling pressure pcr usually occurs in the axisymmetric n = 0 mode, with pcr for n = 2 being only slightly larger. In the present paper, the effects of axisymmetric initial geometric imperfections on reducing pcr for the perfect shell are investigated. Various types of imperfection are studied, i.e. localized flat spots, smooth dimples, sinusoids and buckling mode shapes. The principal geometry investigated was R/b = 10, b/t = 100, although other geometries were also considered. The maximum decrease in buckling resistance, Δ pcr, was found to be about 16 per cent at δ 0/t = 1 and it occurred with smooth dimples at the north (φ = 180°) and south (φ=0°) poles. This value of Δ pcr is not large. Circular toroidal shells thus do not appear to be very sensitive to axisymmetric initial geometric imperfections. The reductions in the buckling pressure of the above shell, arising because of initial imperfections having the shape of the n = 0 and the n = 2 buckling modes, were 12 and 9 per cent respectively for wo/t = 1. These decreases in the buckling resistance are smaller than that for the ‘two smooth dimple’ case mentioned above.

Comparison of Numerical Results With Experiments on the Ultimate Strength of Long Stiffened Panels

2011 ◽  
Author(s):  
Mingcai Xu ◽  
C. Guedes Soares
Keyword(s):  
Numerical Analysis ◽  
Test Results ◽  
Buckling Mode ◽  
Geometric Imperfections ◽  
Geometric Nonlinearities ◽  
Stiffened Panels ◽  
Initial Imperfections ◽  
Linear Buckling ◽  
Initial Geometric Imperfections ◽  
Collapse Behavior

The behavior of long stiffened panels are simulated numerically and compared with test results of axial compression until collapse, to investigate the influence of the stiffener’s geometry. The material and geometric nonlinearities are considered in the simulation. The initial geometric imperfections, which affect the collapse behavior of stiffened panels, are also analyzed. The initial imperfections are assumed to have the shape of the linear buckling mode. Four types of stiffeners are made of mild or high tensile steel for bar stiffeners and mild steel for ‘L’ and ‘U’ stiffeners. To produce adequate boundary conditions at the loaded edges, three bays stiffened panels were used in the tests and in the numerical analysis.

On the Choice of Initial Geometric Imperfections in Externally Pressurized Shells

1999 ◽  
Vol 121 (1) ◽  
pp. 71-76 ◽  
Author(s):  
J. Błachut ◽  
O. R. Jaiswal
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Carrying Capacity ◽  
Circular Cross Section ◽  
Load Carrying Capacity ◽  
Geometric Imperfections ◽  
Elliptical Cross ◽  
Buckling Strength ◽  
Load Carrying ◽  
Initial Geometric Imperfections

Localized and global, of eigenmode type, initial geometric imperfections were superimposed on perfect torispherical, ellipsoidal, and toroidal shells of circular and elliptical cross section. Reduction of the load-carrying capacity was then calculated numerically for various geometries and the yield point of material which was assumed to be mild steel. Results show that the buckling strength of torispheres and ellipsoids could be strongly affected by imperfections, but reduction of its magnitude was dependent on the choice of imperfection shape and, more importantly, on the imperfection’s location. Calculations carried out for closed toroids of circular cross section show that these shells are not sensitive to eigenmode-type imperfections, while toroids with elliptical cross sections are sensitive to eigen-imperfections.

Development of Proposed European Design Rules for Buckling of Axially Compressed Cylinders

1998 ◽  
Vol 1 (4) ◽  
pp. 273-286 ◽  
Author(s):  
J. Michael Rotter
Keyword(s):  
Laboratory Test ◽  
Shell Structures ◽  
Test Results ◽  
European Standard ◽  
Design Standards ◽  
Geometric Imperfections ◽  
Design Rules ◽  
Laboratory Test Results ◽  
Wide Range ◽  
The World

Thin axially compressed cylinders are used in a wide range of civil engineering shell structures: towers, chimneys, tanks and silos. Design standards throughout in the world differ considerably in their strength predictions, and all are based on empirical lower bounds to laboratory test results. The chief reason for the scatter in strength assessments is the sensitivity to geometric imperfections, which naturally vary from one laboratory to another and according to the method of fabrication. This paper sets out some of the development behind the new proposed rules for the European standard on Strength and Stability of Shells. These rules cover cylinder buckling under axial compression alone, and the strength of internally pressurised cylinders. The design strengths are related to recent calculated buckling strengths, and an attempt is made to indicate the appropriate relationship between design assumed imperfections and tolerances during construction.

scholarly journals Applicability of thin-walled structures for energy-savings in steel construction

2019 ◽  
Vol 91 ◽  
pp. 02042
Author(s):  
Natalia D. Korsun ◽  
Daria A. Prostakishina
Keyword(s):  
Cross Section ◽  
Energy Savings ◽  
Effective Characteristics ◽  
Geometric Imperfections ◽  
Thin Walled Structures ◽  
Steel Construction ◽  
Full Cross Section ◽  
Initial Geometric Imperfections ◽  
Thin Walled ◽  
The Cross

The paper discusses the use of lightweight thin-walled structures which make it possible to save resources in steel construction. The highlighted challenges that this industry face in the Russian Federation involve insufficient development of the domestic standards. A thin-walled sigma-profile element with 300 mm in a section height has been studied. The element, its design diagram and loading have been chosen taking into account the structural performance of the columns and girders involved in CFS frameworks. The paper presents analysis technique for a thin-walled profile which performs under axial compression and axial bending compression. The structures have been calculated taking into account their main feature - the initial geometric imperfections. The analysis of the changed effective characteristics and stresses in the cross-section has revealed the significant influence of the initial geometric imperfections of the profiles and location of the extra eccentricity against the element’s initial curvatures. The elastic-plastic behaviour of material occurs when the stresses in the full cross-section achieve 0.71 Ryignoring the initial geometric imperfections, and 0.58 Ry– with regard to them. The paper substantiates the need to consider unevenness of the mechanical properties of steel distributed over the cross-section of the profile. Based on the experimental data obtained, conclusions have been drawn on the necessary adaptation of the indirect method for evaluating the strength characteristics of thin-walled samples.

Buckling of shallow torispherical domes subjected to external pressure — a comparison of experiment, theory, and design codes

1987 ◽  
Vol 22 (3) ◽  
pp. 163-175 ◽  
Author(s):  
G D Galletly ◽  
J Kruzelecki ◽  
D G Moffat ◽  
B Warrington
Keyword(s):  
External Pressure ◽  
Test Results ◽  
Spherical Cap ◽  
Initial Shape ◽  
Geometric Imperfections ◽  
Shell Buckling ◽  
Theoretical Predictions ◽  
Design Values ◽  
Initial Geometric Imperfections ◽  
Thickness Measurements

The test results obtained on 24 externally-pressurised torispherical steel shells are given in this paper. The knuckle radius-to-diameter ratio of the domes varied from 0.06 to 0.18 and the spherical cap radius-to-thickness ratios were between 75 and 335. Initial shape and thickness measurements were carried out on all the torispheres and a summary of this information is given. The BOSOR 5 shell buckling program was employed to predict the buckling/collapse pressures of all the domes; both perfect domes and those with axisymmetric imperfections were considered. The correlation between the theoretical predictions and the experimental results was, in general, very good. The main conclusions of the present investigation are: (i) that some of the experimental buckling pressures were lower than those obtained by multiplying the BS 5500 design values by a safety factor of 1.5, and (ii) that those torispheres with sharp knuckle radii failed by plastic collapse in the knuckle region and the collapse pressures were not very sensitive to initial geometric imperfections. It thus appears that the BS 5500 rules relating to the strength of shallow torispheres subjected to external pressure need to be amended, and that the tolerances on geometric shape for cases which are likely to be imperfection-insensitive should be reconsidered.

Measurement of Lined Pipe Liner Imperfections and the Effect on Wrinkling and Collapse Under Bending

2016 ◽  
Author(s):  
Benjamin Harrison ◽  
Lin Yuan ◽  
Stelios Kyriakides
Keyword(s):  
Detrimental Effect ◽  
Internal Surface ◽  
Trigonometric Fourier Series ◽  
Steel Pipe ◽  
Finite Element Models ◽  
Geometric Imperfections ◽  
Left Behind ◽  
Initial Geometric Imperfections ◽  
Seamless Steel ◽  
Outer Pipe

Carbon steel pipe is often lined with a thin layer of non-corrosive material to protect it against corrosion from sour hydrocarbons. The product is commonly assembled by mechanical expansion of a liner shell bringing it into contact with the inner surface of a seamless steel pipe. During installation and operation lined pipelines can experience bending or compression deformations large enough to cause the liner to buckle and collapse inside an intact outer pipe. It has been demonstrated that such buckling instabilities are very sensitive to small initial geometric imperfections in the liner [1–3]. Liner imperfections in 8- and 12-inch lined pipes have been measured using custom scanning devices and have been characterized by trigonometric Fourier series. Imperfection amplitudes large enough to significantly influence the collapse of the liner have been detected. The main source of the imperfections is the internal surface relief in the seamless outer pipe left behind by piercing, rolling and external finishing of the pipe. Dominant circumferential and axial imperfection waves are used in finite element models to demonstrate the detrimental effect of such imperfections on liner collapse under bending.

Cold-formed steel battened built-up columns: Experimental behaviour and verification of different design rules developed

2021 ◽  
pp. 136943322110480
Author(s):  
A.R. Dar ◽  
S. Vijayanand ◽  
M. Anbarasu ◽  
M. Adil Dar
Keyword(s):  
Failure Modes ◽  
Numerical Models ◽  
Experimental Studies ◽  
Design Standards ◽  
Uniform Compression ◽  
Design Rules ◽  
The North ◽  
Current Design ◽  
Cold Formed Steel ◽  
In The Beginning

Some of the past studies on cold-formed steel (CFS) battened built-up columns have resulted in the development of new design rules for predicting their axial strengths. However, the main drawbacks of such studies are that they are purely numerical and the numerical models developed for such parametric studies were validated using the test results on similar built-up column configurations, but not the exact ones. Therefore, experimental studies on CFS battened columns comprising of lipped channels are needed for verifying the accuracy of the proposed design rules for CFS battened columns. This paper reports an experimental study performed on CFS built-up battened columns under axial compression. Adequately spaced identical lipped channels in the back-to-back arrangement were used as chords and were connected by batten plates laterally with self-driving screws to form the built-up members. The dimensions of chords were fixed as per the geometric limits given out in the North American Specifications (NAS) for the design of CFS structural members. The sectional compactness of the chords and the overall slenderness of the built-up columns were varied by altering the thickness of the channels and height of the built-up columns, respectively. A total of 20 built-up sections were tested under uniform compression to investigate the behavioural changes in the built-up columns due to these variations. The behaviour assessment was made in terms of peak strengths, load–displacement response and failure modes of the test specimens. The current design standards on CFS structures were used to determine the design strengths and were compared against the test strengths for assessing their adequacy. Furthermore, as discussed in the beginning, the test strengths were used to verify the accuracy of the different relevant proposed design rules in the literature.

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