Impact of corrosion deterioration on the seismic performance of steel frame structures

Abstract

Steel structures designed before the introduction of modern seismic design codes may be characterised by high seismic vulnerability due to their reduced ductility capacity. Additionally, these structures may be affected by significant corrosion deterioration, as one of the major atmospheric degradation phenomena when built in corrosive environments. Corrosion deterioration leads to a thickness reduction of sections, reduced bearing capacity, stiffness degradation and loss of energy dissipation capacity. Thus, old-corroded steel structures located in seismically active regions could experience a reduction of their seismic performance, significantly increasing the failure probability under earthquake events. The present study investigates the effect of atmospheric corrosion deterioration on steel frames and uses a nonseismically designed three-storey moment-resisting frame for case-study purposes. Atmospheric corrosion models based on the recommendation of ISO 9224:2012 have been adopted considering a 50-years ageing time and modelled as uniform corrosion on steel members. A probabilistic seismic performance assessment of the pristine and ageing steel frames is performed through Incremental Dynamic Analyses (IDAs). IDAs are performed for a set of 43 ground motion records accounting for the influence of the earthquake input’s uncertainty (i.e., the record-to-record variability). The corrosion effects on the seismic performance are evaluated by monitoring both global and local engineering demand parameters (EDPs), allowing the development of seismic fragility functions at components- and system-level