Assessing the impact of corrosion on the seismic performance of moderately ductile steel moment frames

Atmospheric corrosion is an electrochemical process that deteriorates metals under harsh environmental conditions. In steel structures, corrosion incurs significant financial costs and negatively impacts structural safety. To assess the effect of corrosion on seismic performance, the structure is first analyzed dynamically, and the damage level is then evaluated based on performance criteria. In this study, the Incremental Dynamic Analysis (IDA) method was employed to investigate steel moment-resisting frames with moderate ductility. Three frame models with 3, 5, and 8 stories were analyzed, considering corrosion effects at 0, 20, and 50 years. The structures were modeled in OpenSEES software, and corrosion thickness was determined based on ISO 9223 and ISO 9224 standards. The performance levels of the steel frames were evaluated using the maximum inter-story drift ratio as defined in the HAZUS-MH MR5 standard. Based on the fragility curve results, the median probability of complete collapse for the three, five, and eight story structures increased by 4.93 %, 1.14 %, and 2.44 %, respectively, after 20 years of corrosion compared to the uncorroded cases. After 50 years, these probabilities increase to 8.21 %, 4.55 %, and 7.32 %, respectively, compared to the corrosion-free condition. Additionally, the percentage change in collapse probability for the 5-story frame compared to the 3-story frame is 21.34 %, 18.21 %, and 18.21 % in the 0th, 20th, and 50th years, respectively, while for the 8-story frame, the corresponding changes are 26.57 %, 24.65 %, and 25.85 %.