Effects of structure size on post-earthquake fire resistance of CCBCC joints at non-uniform elevated temperatures

Abstract

The probability of secondary fires caused by earthquakes is very high. Due to the residual stress and deformation caused by earthquakes, the mechanical behavior of cruciform combined beam-CFST column (CCBCC) joints is extremely complex. In view of this, the goal of this study is to investigate the effects of structure size on the post-earthquake fire failure mechanism of CCBCC joints under gradient temperatures. The calculation model in this article was validated using existing experimental results, subsequently 20 computational models were established to conduct parameter analysis, including the width-to-thickness ratio (γ) of the CFST column, the slenderness ratio (λ) of the CFST column, the width-to-thickness ratio (α) of beam flange, the height-to-thickness ratio (β) of beam web and the damage variable (D̃). The results have demonstrated that the post-earthquake fire resistance of CCBCC joints is mostly affected by damage variable. Parameters β, α, λ and γ also have a significant impact on the failure of these joints. An empirical bearing capacity prediction model of CCBCC joints is obtained. The research results can provide reference and data support for the design, maintenance, and reinforcement of CCBCC joints under post-earthquake fire.