System Stabilities and Anti-Fire Redundancy of Steel Frames in Fire

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Collapse of New York World Trade Center buildings suggests the possibilities that, if locally heated and weakened members lose their strengths, so entire frame in fire may lose their overall stability and fall at worst into progressive collapse.The objectives of this research are to clarify the factors controlling the structural overall stabilities of steel frames, especially of domestic steel frames in fire and to study the means improving the redundancies and therefore anti-progressive collapse performances of heated frames in fire. The following results have been found from the research.(1) Mechanical essentials to control the overall collapse of heated frames in fire have been found specifically.(2) The factors to prevent fames in fire from their overall collapse have been identified and formulated theoretically.(3) Based on the above findings the anti-progressive collapse performances of domestic steel frames in fire have been clearly grasped.(4) The characteristics of the progressive collapse and the causes to accelerate the dynamic failure of tall buildings have been clarified by means of a newly developed dynamic three dimensional finite element solutions.(5) The strength and the post strength behaviors of the fundamental structural elements have been clarified both experimentally and analytically in the elevated temperatures. To this end a series of high temperature tests have been conducted on the shearing and bending resistances of bolted connections as well as flexural and local buckling of wide flange columns.