Fatigue Life Assessment of Saddle-Supported Silencer Structures Under Repeated Seismic Loading

This paper evaluates the long-term fatigue durability of a saddle-mounted silencer structure operating in a seismic-prone nuclear environment. Unlike traditional seismic qualification approaches that verify stress compliance for peak events, this study focuses on the accumulation of fatigue damage from repeated seismic and operational cycles over the plant’s lifespan. Using finite element analysis (FEA) in ANSYS Workbench, stress histories were extracted from critical regions such as the saddle support and gusset plate. The fatigue life was estimated via a Basquin-modeled S–N curve for SS400 steel, and Miner’s Rule was applied to quantify cumulative fatigue damage. Results identified the gusset plate and saddle weld zones as fatigue-critical, with damage indices (D) of 0.68 and 0.42, respectively. While all components remained structurally intact, early signs of fatigue vulnerability highlight the need for weld optimization and material upgrades. The study offers a fatigue-centered framework that complements code-based seismic checks by addressing degradation over multiple seismic events.