The impact of the concave distribution of rolling friction coefficient on the seismic isolation performance of a spring-rolling system

• Concave friction distribution is used to form a spring-rolling isolation system.
• A mathematics model is built for the system.
• Friction can dissipate energy, and change the structural natural period.
• Concave friction distribution improves the seismic isolation efficiency.
• A relatively optimum isolation state is still kept even under uncertain earthquakes.

A complex yet realistic nonuniform rolling friction force distribution of a spring-rolling isolation system could lead to great complexity in determining its seismic response. This paper investigates the isolation performance of a spring-rolling isolation system assuming that the rolling friction force gradually and linearly increases with the relative displacement between the isolator and the ground. A series of ground motions with different characteristics were applied to this system. The analysis results show that the considered concavely distributed friction force is capable of dissipating the earthquake energy, and it is also able to modify the structural natural period. These merits combined help to improve the isolating efficacy of the spring-rolling isolation system compared with scenarios with uniform distribution pattern, and more importantly lead to a relatively optimum isolation state, avoiding a sudden amplification of the structural seismic response, regardless of the input motion characteristics.