EXPERIMENTAL INVESTIGATION ON BOX-UP COLD-FORMED STEEL COLUMNS IN FIRE

Abstract

Cold-formed steel is a popular material with various advantages. Its easy production and
assembly give engineer an option to speed the construction process. However, thinness relates to the major
issue of buckling, especially when dealing with high temperature. The unprotected cold-formed steel
behaviour under fire is expected to have a little strength as compared to hot-rolled steel. Information on such
behaviour is still limited. Fire resistance testing on built-up box CFS column was presented in this paper.
Two fire resistance tests were carried out under compression load. The Standard ISO 834 Fire Resistance
Test under 50% and 70% degree of utilisation measured the temperatures at several points of the steel
column surface by using a surface thermocouple and axial column deformation. For reference purpose, one
same static test at ambient temperature was carried out to assess the load bearing capacity. Results found that
the failure temperature of built-up CFS could reach up to 515 ºC and 443 ºC within 8 minutes and 7 minutes
resistant time for 50 % and 70% degree of utilisation, respectively. Based on deformation analysis, buckling
temperature of the column was 448 ºC and 394 ºC with a critical time of 7 minutes for 50 % and 70% degree
of utilisation, respectively. This concluded that the higher degree of utilisation results in lower critical
temperatures of the columns.