Buckling of elastically restrained steel columns under longitudinal non-uniform temperature distribution (original) (raw)
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Buckling of an Axially Restrained Steel Column Under Fire Loading
International Journal of Structural Stability and Dynamics, 2011
Analytical procedure, based on the linearized stability analysis, is presented for the determination of the buckling load and the buckling temperature of a straight, geometrically perfect, axially loaded steel column subjected to an increasing temperature simulating¯re conditions. The nonlinear kinematical equations and the nonlinearity of material are considered. The stressÀstrain relation for steel at the elevated temperature and the rules for reduction of material parameters due to increased temperature are taken from European standard EC 3. Theoretical¯ndings are applied in the parametric analysis of a series of Euler's columns subjected to two parametric¯res. It is found how the slenderness of the column, the material nonlinearity, the temperature dependence of material parameters, and the sti®ness of restraints at supports e®ect the critical temperature. While these parameters have major in°uence on the critical temperature, they have no e®ect on the shape of the buckling mode. ¯re is regulated by several building codes such as, for example, Eurocode 3 1 , BS5950 2 , and ISO 834 3 . These standards o®er simpli¯ed methods of analysis for isolated columns, which sometimes do not give su±ciently reliable quantitative predictions of the¯re-bearing capacity of a column, if it is a part of a frame.
On the buckling of axially restrained steel columns in fire
2011
This paper describes the behaviour of restrained steel columns in fire. It follows the introduction of extra load into the column through the axial restraint of the surrounding cooler structure and the consequential buckling. Key to this understanding is the post-failure behaviour and re-stabilisation of the column, which is discussed with reference to a finite element model and an analytical model.
Computationally Efficient Method for Steel Column Buckling in Fire
Buildings
The stability of axially loaded steel columns with compact rectangular hollow sections at elevated temperatures is studied in this paper. The current Eurocode model for checking the buckling resistance of columns in fire was developed on a similar basis to that for ambient conditions. Due to the effect of the complex non-linear behaviour of steel in fire, the standard design model is not always fully appropriate, and certain parameter ranges may give unsafe results. In this work, an analytical method to determine the buckling resistance of steel columns at elevated temperatures is proposed, accounting for variable non-linear stiffness properties which have significant effects on the flexural buckling resistance of steel columns in fire. A finite element model was developed, and an extensive numerical study was performed to explore the effects of different parameters on the behaviours of steel columns at elevated temperatures. The proposed method is validated by comparing the perform...
Alternative approach to buckling of square hollow section steel columns in fire
Journal of Constructional Steel Research, 2014
Stability of axially loaded steel columns with square hollow sections at elevated temperatures is studied herein. At present the Eurocode model for checking buckling capacity of columns in fire has been developed on the similar basis as for ambient conditions. It is shown that due to the effect of complex non-linear behavior the standard design model is not always adequate and in certain situations prediction of buckling capacity of columns according to the common design formulas may even reach results on the unsafe side. The main focus of this work is the performance of an analytical model against advanced numerical methods. For this purpose extensive numerical study was performed using non-linear FE method. Based on the results obtained with advanced calculation models of column behavior at elevated temperatures an analytical model has been proposed and verified. The proposed model accounts for variable non-linear stiffness properties, which have significant effect on the buckling capacity of axially loaded columns in fire. The advantage of the method is the format, which is convenient for incorporation into common design algorithms.
Numerical Analysis of Steel Columns Considering the Walls on Fire Condition
Steel columns are structural elements widely used in multi-storey buildings, industrial, commercial warehouse, among others. However, the reduction of stiffness and strength of steel in response to a temperature raise imposes the need to predict the critical time of exposure of the structure in fire, looking for safety and economic design structures. The presence of walls introduces change in gradient temperature at the steel cross section. In those circumstances, this paper aims to present a numerical study of steel columns with open section of type I, whereas the compartment of the environment in fire. The buckling of the compressed element will be marked by a reduction factor obtained using the relationship between the buckling load in a fire situation, characterized by asymptotic displacement, and buckling load identified at room temperature.
Numerical Behaviour of Steel Columns subject to Localized Fire Loading
Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing, 2009
This paper presents the results of numerical simulations of the behaviour in a real fire of a full-size, loaded, two-dimensional, unprotected steel frame. The objective of this study is to gain confidence in the results obtained from different numerical tools, that will be used on the ROBUSTFIRE project and to ensure that these outcomes are comparable. The benchmark example is based on the paper of Franssen published in 1995 about a natural fire test on a fully loaded, two dimensional, unprotected steel framework carried out in a purpose-built compartment in Cardington . The heated members are modelled by beam elements and the restraint offered by the secondary steelwork is simulated by spring elements. Geometrical and material nonlinearity and temperature dependent material properties are taken into account. The influence of the model definition, axial restraint to beam, thermal expansion and non-uniform temperature is discussed for each numerical tool.
2014
This paper is about a series of experimental fire tests on eight full scale steel columns made of slender I shaped class 4 sections. Six columns were made of welded sections (some prismatic and some tapered members) and two columns were with hot rolled sections. The nominal length of the columns was 2.7 meters with the whole length being heated. The load was applied at ambient temperature after which the temperature was increased under constant load. The load was applied concentrically on some tests and with an eccentricity in other tests. Heating was applied by electrical resistances enclosed in ceramic pads. Numerical simulations were performed using shell elements of the software. The paper presents the results obtained in terms of failure mode and ultimate temperature, in the experimental tests and in the numerical simulations.
Effect of Boundary Conditions on the Creep Buckling of Steel Columns in Fire
2016
This paper presents highlights of a preliminary computational study conducted using Abaqus to investigate the influence of boundary conditions on the creep buckling behavior of steel columns at elevated temperatures due to fire. W12×120 wide flange columns with the unsupported length of 240 inches are used in the simulations. Thermal creep of steel is modeled following equations proposed by Fields and Fields for the creep of ASTM A36 steel. Four different classical support conditions and seven imperfection amplitudes are considered to quantify the effect of boundary conditions on the time-dependent strength of steel columns in fire. Thermal restraints, both axial and rotational, were ignored in the analyses. Representative results from creep buckling tests simulated at 500 °C are presented and discussed. Results from creep buckling simulations presented in this paper indicate that the rotational and translational restraint at the column ends along with the initial crookedness of the...
General Method for the fire design of tapered steel columns: Out‐of‐plane flexural buckling
ce/papers, 2019
The General Method (GM) covers the safety check of structural elements with complex support conditions and/or of non-prismatic members. However, it's not widely validated at normal temperature and is inexistent in fire part of the Standard EN 1993-1-2. With that in mind, this investigation aims at proposing and validating the GM to perform the safety check of unrestrained tapered columns at elevated temperatures. This is done, first, by including, in the original formulation, the reduction of steel material properties with the temperature, and later by improving the EN 1993-1-2 out-of-plane buckling curve. With this novel approach, the GM shows good agreement to numerical results and produces accurate predictions of out-of-plane resistance for tapered columns at elevated temperatures.
A simple approach to the behaviour of steel columns in fire
1994
An analytical approach based on simple 'Perry Robertson' principles has been developed to investigate the behaviour of steel columns in fire conditions. The treatment is intended for approximate prediction of failure temperatures for such members, and is consistent with the rationalisations of column behaviour made in current codes of practice. It also has the conceptual advantage of providing a good qualitative description of the behaviour itself, allowing the parameters which affect columns in fire to be easily separated out and their influences to be studied. The Perry approach is tested against previous analytical and test results. It is then used to predict failure temperatures for a limited range of isolated column examples, and the results are compared with existing test results and with current design assumptions. dxx, dyr d(bow) d(cen) E, E2o