Seismic Fragility Analysis of MRFs with PR Bolted Connections Using IDA Approach

Abstract

Partially restrained (PR) bolted beam-to-column connections are a promising typology of connection in modern steel moment resisting frames (MRFs). Both high-fidelity three-dimensional solid models and mechanics-based idealisations have been extensively explored in order to investigate the behaviour of this attractive solution, applicable both to new construction and to retrofitting of existing structures. Despite this, structural safety has been probabilistically assessed and controlled in a relatively few cases, thus neglecting characterisation, modelling and propagation of uncertainties. As such, this paper moves from a deterministic to a probabilistic framework, proposing fragility models at multiple damage states for low-and medium-rise MRF structures with T-stub and top-and-seat angle connections which may be applied for seismic risk assessment and management. After validation against past experimental data, use was made of component-based modelling to reproduce the seismic response of these PR bolted connection systems within planar MRFs designed for earthquake resistance in accordance with current European rules. A set of 44 records scaled at increasing seismic intensity was considered to perform a series of incremental dynamic analyses (IDAs). Fragility functions for each damage state of interest were then derived and compared. The analysis results show the influence of connection typology and structure height.