Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire

Cold-formed steel (CFS) is a popular material with various advantages. Its easy production and assembly allow engineers to speed up the construction process. However, CFS is susceptible to buckling because of its natural thinness, especially when dealing with high temperatures. The unprotected CFS b...

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Main Author:	Muftah, Fadhluhartini
Format:	Thesis
Language:	English
Published:	2022
Subjects:	TA Engineering (General) Civil engineering (General)
Online Access:	http://eprints.utm.my/id/eprint/101432/1/FadhluhartiniMuftahPSKA2022.pdf
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id	my-utm-ep.101432
record_format	uketd_dc
spelling	my-utm-ep.1014322023-06-14T10:19:58Z Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire 2022 Muftah, Fadhluhartini TA Engineering (General). Civil engineering (General) Cold-formed steel (CFS) is a popular material with various advantages. Its easy production and assembly allow engineers to speed up the construction process. However, CFS is susceptible to buckling because of its natural thinness, especially when dealing with high temperatures. The unprotected CFS behaviour under fire is expected to have little strength compared to the hot-rolled steel. At present, CFS column subjected to standard fire has been done by few researchers. The study included the difference in shape and size of the column, differences in thickness, steel grade, column length, and restraint or unrestraint in thermal elongation. However, the larger size is more reliable to be used as the column but has never been tested in fire. The test for unrestrained thermal elongation columns is also unavailable. As such, the purpose of this study was to evaluate the structural behaviour of CFS columns under ambient and fire conditions. Based on these behaviours, the experimental findings were compared with the prediction from BS EN 1993-1-2: 2005 to evaluate the suitability of the code for CFS column fire design. In achieving the objectives, an investigation into fire resistance subjected to the ISO 834 fire standard was conducted on the 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-sections, known as channel, back-to-back (BTB), and box-up (BU) sections, were studied. First, the column was preloaded at 30%, 50%, and 70% of its ultimate strength to simulate the real fire situation. Then, the column was exposed to the ISO 834 fire standard condition. The temperature at the column surface and the time were recorded until the CFS column failed. The temperature increase on the column surface were monitored using thermocouple Type K, and the analyses of these thermocouple readings were used to evaluate the mean temperature of the column. The results showed that the shape had no significant effects on the critical temperature of the CFS columns. The temperature behaviours of a BTB column for all degrees of utilization showed that the web had a lower temperature compared to the flange due to the greater thickness of the web. Meanwhile, the failure temperature of the CFS could reach up to 600⁰C for 30% degree of utilization. The critical temperature and time for the column could be used in proposing a fire safety design rule for the CFS column. The modified design curve for the CFS column was also proposed. It is concluded that the BS EN 1993-1-2: 2005 could be used to evaluate the safe buckling load under fire by including a modification factor due to buckling behaviour for built-up and channel CFS columns. 2022 Thesis http://eprints.utm.my/id/eprint/101432/ http://eprints.utm.my/id/eprint/101432/1/FadhluhartiniMuftahPSKA2022.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:151639 phd doctoral Universiti Teknologi Malaysia Faculty of Engineering - School of Civil Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TA Engineering (General) Civil engineering (General)
spellingShingle	TA Engineering (General) Civil engineering (General) Muftah, Fadhluhartini Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
description	Cold-formed steel (CFS) is a popular material with various advantages. Its easy production and assembly allow engineers to speed up the construction process. However, CFS is susceptible to buckling because of its natural thinness, especially when dealing with high temperatures. The unprotected CFS behaviour under fire is expected to have little strength compared to the hot-rolled steel. At present, CFS column subjected to standard fire has been done by few researchers. The study included the difference in shape and size of the column, differences in thickness, steel grade, column length, and restraint or unrestraint in thermal elongation. However, the larger size is more reliable to be used as the column but has never been tested in fire. The test for unrestrained thermal elongation columns is also unavailable. As such, the purpose of this study was to evaluate the structural behaviour of CFS columns under ambient and fire conditions. Based on these behaviours, the experimental findings were compared with the prediction from BS EN 1993-1-2: 2005 to evaluate the suitability of the code for CFS column fire design. In achieving the objectives, an investigation into fire resistance subjected to the ISO 834 fire standard was conducted on the 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-sections, known as channel, back-to-back (BTB), and box-up (BU) sections, were studied. First, the column was preloaded at 30%, 50%, and 70% of its ultimate strength to simulate the real fire situation. Then, the column was exposed to the ISO 834 fire standard condition. The temperature at the column surface and the time were recorded until the CFS column failed. The temperature increase on the column surface were monitored using thermocouple Type K, and the analyses of these thermocouple readings were used to evaluate the mean temperature of the column. The results showed that the shape had no significant effects on the critical temperature of the CFS columns. The temperature behaviours of a BTB column for all degrees of utilization showed that the web had a lower temperature compared to the flange due to the greater thickness of the web. Meanwhile, the failure temperature of the CFS could reach up to 600⁰C for 30% degree of utilization. The critical temperature and time for the column could be used in proposing a fire safety design rule for the CFS column. The modified design curve for the CFS column was also proposed. It is concluded that the BS EN 1993-1-2: 2005 could be used to evaluate the safe buckling load under fire by including a modification factor due to buckling behaviour for built-up and channel CFS columns.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Muftah, Fadhluhartini
author_facet	Muftah, Fadhluhartini
author_sort	Muftah, Fadhluhartini
title	Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
title_short	Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
title_full	Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
title_fullStr	Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
title_full_unstemmed	Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
title_sort	structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire
granting_institution	Universiti Teknologi Malaysia
granting_department	Faculty of Engineering - School of Civil Engineering
publishDate	2022
url	http://eprints.utm.my/id/eprint/101432/1/FadhluhartiniMuftahPSKA2022.pdf
_version_	1776100698572718080

Structural behaviour of built-up cold-formed steel column under ambient temperature and standard fire

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