BUCKLING, POST-BUCKLING AND ULTIMATE STRENGTH OF COLD-FORMED STEEL LIPPED CHANNEL MEMBERS UNDER FIRE CONDITION

摘要

Steel framed walls are widely applied in industrial building construction and must provide adequate structural integrity/safety under fire conditions, i.e., the framing strength under high temperatures must be enough to ensure fire confinement. Then, the aim of this study is to analyze the structural behavior, under high temperatures (caused by fire), of compressed cold-formed steel lipped channel members incorporated in steel stud (framed) wall systems. The members analyzed are subjected to combinations of (ⅰ) concentric or eccentric compression and (ⅱ) uniform or non-uniform cross-section high temperature distributions. The temperature values adopted correspond to a simplified model based on fire calculations previously carried out inside the wall systems, i.e., between the plaster panels. Moreover, the structural behavior of these plaster panelsis also included in the analyses - namely, their contribution to the restraint of the stud members is taken into account The buckling and post-buckling behavior of the cold-formed steel lipped channel members is determined by means of non-linear shell finite element models, calibrated against experimental and/or numerical results reported in the literature. The lipped channel member collapse is computed for a loading strategy involving the application of (ⅰ) an initial axial compression, which remains constant, followed by (ⅱ) a progressive temperature increase (i.e., one obtains failure temperatures). Finally, a direct calculation procedure aimed predicting ultimate strengths/temperatures is also proposed and validated, through the comparison of the corresponding estimates with 'exact' numerical values.