Published: Građevinar 74 (2022) 8
Paper type: Scientific research paper
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Steel frame collapse assessment method based on dynamic increase factor
Abstract
To study the laws of evolution of dynamic increase factors (DIFs), relationship between the DIFs and progressive collapse resisting capacity of a structure with web cleat joints under the column removal scenario, a refined finite element model is established based on an existing quasi-static test. The laws of evolution of DIFs are studied for different loading type, beam height, and joint rotation stiffness. It was observed that the displacement-based dynamic increase factor (DIFu) increases with an increase in the load level in elastic and elastic-plastic stages, and it decreases with an increase in the load level in the plastic stage. With an increase in structural damage, DIFu reaches the maximum value when the frequency ratio is equal to 1 and decreases with a further increase in frequency and damping ratios. The load-based dynamic increase factor (DIFp) is negatively corelated to the “arch compression effect” of the beam. Finally, a method based on DIFu is proposed for judging the collapse of structures with web cleat joints. In addition, an improvement is provided for the design the web cleat joint. The improvement is proved to be reasonable and effective with the help of collapse evaluation method proposed in this study.
Keywordsprogressive collapse, dynamic increased factor, collapse evaluation method, joint improvement, energy balance method
