Mitigation of Floating Roof Pounding in Storage Tanks Subjected to Seismic Loads

Floating roof tanks, which are utilized in a multitude of industrial facilities for the storage of volatile and flammable products, are particularly susceptible to seismic events. These events can result in substantial structural damage and hazardous material releases due to roof sinking and leading to rim fires. The metallic contact between the floating roof and the tank wall, induced by seismic roof oscillations, has been shown to generate sparks. These sparks, in the presence of flammable vapors, pose a significant risk during seismic events. This study investigates the interaction between the floating roof and the tank walls, with a focus on the role of the sealing system and the pounding dynamics during seismic events. Based on experimental findings of mechanical characterization of a spring in a typical sealing system, with a single-degree-of-freedom system with rigid pounding, the horizontal dynamics of the floating roof under seismic excitation were investigated. Then, a gap and a deformable, dissipative bumper system were designed to control the roof's oscillations and protect the sealing system. Seismic analyses demonstrated that the proposed bumpers significantly reduce the number and contact force of impacts, thereby mitigating the risk of generating sparks during the critical phase of maximum seismic energy. The optimized bumper design was found to be fully compatible with the operational conditions of the case study tank, offering an effective solution to improve the seismic safety of floating roof tanks in seismic-prone areas.Summary: Identifies fire hazards from roof-shell pounding in floating roof tanks, an issue overlooked in regulations. Provides experimental characterization of sealing system stiffness and damping properties. Demonstrates that conventional sealing systems lead to excessive oscillations and high contact forces (similar to 10(4) kN) under seismic excitation, with an SDOF system. Proposes deformable and dissipative bumpers to control displacements. Conducts a parametric analysis to optimize bumper stiffness, damping, and gap size. Confirms, through seismic simulations, that optimized bumpers dissipate energy effectively, minimizing impact velocities and enhancing seismic safety.