Tuned Seismic Isolation Design Method for Continuous Rigid Frame Bridge with Elevated Pile Cap Foundation
An elevated pile cap foundation in a continuous rigid-frame bridge has low lateral stiffness,which can effectively extend the natural vibration period of the structure and reduce its seismic response.To better utilize the flexible deformation of elevated pile caps,a tuned isolation design method is proposed based on the principle of mass-tuned isolation.This method simplifies the continuous rigid frame bridge into a two-degree-of-freedom(2-DOF)model and establishes an analytical model for tuned isolation calculations.Taking the random vibration as an external excitation,and orienting to minimize the moment at the pier bottom,the functional formula between the frequency ratio(f)and mass ratio(μ)was developed using the frequency domain solution method.Through enumeration analysis,the optimal f was derived as a function of μ,to determine the optimized stiffness of the piers and pile foundation.The results show that the simplified 2-DOF model for continuous rigid-frame bridge can accurately reflect the natural vibration characteristics.Through structural optimization,the reduction ratios of the bending moment at the top and bottom of the pier were 46.5％and 58.7％,respectively,demonstrating the effectiveness of the tuned isolation method for seismic control of the continuous rigid-frame bridge with high-pile cap.
bridge engineeringtuned seismic isolationsimplified modelcontinuous rigid frame bridgerandom vibrationoptimal frequency ratio
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