Rocking Isolation of Tall Pier with Pile Foundations Based on Double-Spring Model

A double-spring model for rocking isolation of tall piers with pile foundations, restoring force curve and the spring stiffness are proposed. Rocking isolation for bridges with tall piers are analyzed by using nonlinear time-history method, and the results are compared with those obtained by using concentrated rotational springs which are more simplified. The results show that the vibration period is not fixed after rocking and uplift of the pier, the anti-overturning moment is very close to the peak moment at the bottom of piers with the effect of rocking isolation is stable, and less affected by input ground motions. Displacement-time curve of the top of the pier and the moment at the pier bottom, obtained by using double-spring model is close to those obtained by using concentrated rotational-springs model, which are more simplified.