Post-fire Response of Partially Restrained Connections: Methodology and Application on Top & Seat Angles

Abstract

The post-fire response of partially restrained steel connections is characterized by the reduction in strength after exposure to a full heating–cooling cycle of a fire event. This reduction in strength constitutes one of the crucial factors in assessing the structural performance of partially restrained steel connections post-fire exposure. This paper proposes a methodology for investigating the post-fire response of bolted top and seat angle connections, which are widely used in steel buildings. To achieve this, finite element (FE) models are developed in ABAQUS. The methodology consists of, first, the development of FE beam-to-column connection designed to survive a fire event. The outcome is to compute the post-fire thermal axial forces while varying different geometric and load parameters that impact the behavior. Second, the computed post-fire thermal axial force, along with the post-fire mechanical properties, are both used in developing FE component connection models, which are then subjected to loading until failure. The results show that after a fire event, the load-bearing capacity of the top and seat angle connection decreases with higher fire temperatures. The decrease in connection capacity ranges from 30 to 87% of its initial strength after exposure to post-fire temperatures ranging from 200°C to 500°C, respectively. This methodology, conducted through 3D non-linear FE analysis, represents a significant step in assessing the remaining capacity of steel connections post-fire and offers preliminary data to support the development of design guidelines, offering engineers guidance on assessing the need for replacement or repair of structural members after a fire event. Further experimental work is recommended to investigate different connection configurations, in order to gain a better understanding of the percentage reduction in capacity for this type of connection.