Experimental Investigation on Box-Up Cold-Formed Steel Columns in Fire (original) (raw)
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Temperature Rise of Cold-Formed Steel Built-Up Back-To-Back Column Under Standard Fire
Jurnal Teknologi, 2016
Cold-formed steel (CFS) structure is one of the most popular construction materials due to its various advantages. Its most popular use is as a structural framing for residential and light loading buildings. Constructions of lightweight building components such as the CFS have been used to build or renovate existing single-and two-families' private homes [1]. The applications of built-up shapes such as in a composing member truss have attracted many designers of light-steel framing to widen the applications of CFS to larger scale structures. In addition, the CFS built-up has several advantages in its production, handling, and mechanical strength. Therefore, it is suitable to be used for fast constructions of low rise ups to double storey buildings as well as emergency houses. However, the fire resistance of this material is a critical issue as it is susceptible to have a low level of stiffness when exposed to fire compared to other materials like hotrolled steel member. Many researchers had conducted the studies of CFS under high temperature. Most of these researches were mainly focused on the elevated temperature test and the finite element simulation of CFS at elevated temperatures [2, 3, 4, 5, 6, 7, 8]. However, there is still a limited amount of research data on individual tests of CFS exposed directly to the fire. A research conducted by Kankanamge [9] found that in the case of fire, the CFS beam always experienced the local buckling failure mode similar
Metals
An investigation into fire resistance subjected to the ISO fire standard was conducted on a cold-formed steel (CFS) column. The variables involved were the CFS sections with various cross-section types and service loadings known as the degree of utilization. Three types of cross-section, known as channel, back-to-back (BTB), and box-up (BU) sections, were studied. All supports for the column are in constant condition. To simulate the real fire situation, the column was preloaded at 30%, 50%, and 70% of its ultimate strength. After the load was static, the column was exposed to the ISO fire standard. The column was loaded at the centroid of the section. The temperature at the column surface and the time was recorded until the column became unstable. The results show that the shape did not have any significant effects on the critical temperature of the CFS columns. The higher the applied load—or as used in this study, the higher the degree of utilization of the CFS columns—the greater...
Numerical study on structural behaviour of cold-formed steel columns under fire conditions
Research and Applications in Structural Engineering, Mechanics and Computation, 2013
This paper presents the results of numerical studies on the behaviour of cold-formed galvanized steel columns under fire conditions, based on results of experimental tests, previously conducted by the authors. This numerical study was performed by the finite element program ANSYS. First, it is presented the details of the finite element models used in this research and compared the finite element analysis results with those obtained in the experimental tests. Moreover, it is carried out a parametric study in order to investigate the influence of the axial restraining to the thermal elongation of the column, the axial preload ratio on the columns mechanical behaviour.
Cold-formed steel members differ greatly from hot-rolled steel members in shape, as well as strength and deformation properties. The cold work process alters the properties of the steel, resulting in a higher post-forming strength of the cross section by about 20-50% depending on the type of forming and thickness of the section. Among a variety of steel sections available, hollow sections are preferred to be used as columns in residential, commercial and industrial buildings due to their architecturally pleasing shape which are also structurally efficient and economical.
Experimental studies of cold-formed steel hollow section columns at elevated temperatures
School of Civil Engineering Built Environment Science Engineering Faculty, 2014
This paper reports the details of an experimental study of cold-formed steel hollow section columns at ambient and elevated temperatures. In this study the global buckling behaviour of cold-formed Square Hollow Section (SHS) slender columns under axial compression was investigated at various uniform elevated temperatures up to 700℃. The results of these column tests are reported in this paper, which include the buckling/failure modes at elevated temperatures, and ultimate load versus temperature curves. Finite element models of tested columns were also developed and their behaviour and ultimate capacities at ambient and elevated temperatures were studied. Fire design rules given in European and American standards including the Direct Strength Method (DSM) based design rules were used to predict the ultimate capacities of tested columns at elevated temperatures. Elevated temperature mechanical properties and stress-strain models given in European steel design standards and past researches were used with design rules and finite element models to investigate their effects on SHS column capacities. Comparisons of column capacities from tests and finite element analyses with those predicted by current design rules were used to determine the accuracy of currently available column design rules in predicting the capacities of SHS columns at elevated temperatures and the need to use appropriate elevated temperature material stress-strain models. This paper presents the important findings derived from the comparisons of these column capacities.
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.
Parametric Study on the Fire Resistance of Steel Columns with Cold-Formed Lipped Channel Sections
Applications of Structural Fire Engineering, 2016
Steel structural elements with cold-formed thin-walled sections are becoming increasingly common in buildings due to their lightness and ability to support large spans. In these members, local, distortional and global instabilities are important common failure modes. At high temperatures, these instability phenomena are intensified. This paper presents a numerical study on the behaviour of columns with cold-formed C-sections in case of fire when subjected to compression. A parametric study, considering different steel grades, temperatures and different cross-sections with different slendernesses, is presented. Comparisons are also made between the numerical results and analytical design rules, such as the EN1993-1-2, using its Annex E or its French National Annex, where a different constitutive law is recommended for cold-formed profiles. It is possible to conclude that the simple calculation rules are on the safe side but sometimes too conservative.
Buckling of stainless steel columns and beams in fire
Engineering Structures, 2007
Material properties and their response to elevated temperatures form an essential part of structural fire design. At elevated temperatures, stainless steel displays superior material strength and stiffness retention in comparison to structural carbon steel. Although independently important, the relationship between strength and stiffness at elevated temperature also has a significant influence on the buckling response of structural components. This paper examines existing test results and presents the results of a numerical parametric study, using ABAQUS on stainless steel columns in fire. Sensitivity to local and global initial geometric imperfections, enhancement of corner strength due to cold-work and partial protection of the column ends is assessed. Parametric studies to explore the influence of variation in local crosssection slenderness, global member slenderness and load level are described. Test results are compared with the current design rules in Eurocode 3: Part 1.2, the Euro Inox/ SCI Design Manual for Structural Stainless Steel and those proposed by CTICM/ CSM. The results of a total of 23 column buckling fire tests, 6 stub column fire tests and 6 fire tests on beams have been analysed. Overly conservative results and inconsistencies in the treatment of buckling phenomena and the choice of deformation limits are highlighted. A revised buckling curve for stainless steel in fire, consistent strain limits and a new approach to cross-section classification and the treatment of local buckling are proposed. These revisions have led to a more efficient and consistent treatment of buckling of stainless steel columns and beams in fire. Improvements of 6% for column buckling resistance, 28% for stub column (crosssection) resistance and 14% for in-plane bending resistance over the current Eurocode methods are achieved.
Fire resistance of steel columns with restrained thermal elongation
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The behavior of steel columns subjected to fire depends on their interaction with the surrounding building structure. To improve knowledge of the phenomenon a great many fire resistance tests have been carried out on steel columns with restrained thermal elongation. A new experimental system was designed and constructed to carry out the tests.