Seismic Fragility Analysis of Corroded Chimney Structures

Abstract

High-rise reinforced concrete chimneys, used to expel waste gases, are commonly used structures in facilities such as chemical and power plants. Chimney structures located in marine areas are prone to corrosion. Regardless of the causing factors, corrosion causes the degradation of the strength of steel bars, creating a detriment to the safety of the chimney structure. A more severe situation is a corroded chimney structure that is subjected to other natural hazards such as strong winds and earthquakes. Very few documented research studies have evaluated the seismic performance of chimney structures under the combined hazards of corrosion and seismic loading. In this study, seismic fragility was used to compute the probability of damage to two corroded chimney structures of differing heights under near-fault ground motions. In the fragility analysis, the uncertainties of materials and ground motions were considered. Based on the numerical simulation results, fragility curves were generated. The results indicated that corrosion had a significant effect on the seismic performance of chimney structures. With an increased corrosion level, the probability of moderate damage, major damage, and collapse increased significantly if the intensity of the ground motion was greater than a threshold value. The threshold value was determined by the corrosion severity. Therefore, it is suggested to inspect the severity of corrosion and adopt measures for reinforcement to minimize the impact of that corrosion on the stability of the chimney, especially in areas susceptible to earthquakes.