高桩承台连续刚构桥的调谐隔震设计方法

Tuned Seismic Isolation Design Method for Continuous Rigid Frame Bridge with Elevated Pile Cap Foundation

高桩承台连续刚构桥具有基础抗侧移刚度小的特点,能有效延长结构自振周期,减小地震内力响应。为更好地利用高桩承台的柔性变形,基于质量调谐原理,提出了一种调谐隔震设计方法。该方法将连续刚构桥简化为2自由度体系,建立调谐隔震的力学模型,将随机振动作为外部激励,以墩底弯矩最小为优化目标,采用频域解法建立了墩底弯矩响应与桥墩-桩基的频率比f、主梁-承台质量比μ的函数关系。通过枚举法,得出最优频率比与质量比的函数关系,进而求出优化后的桥墩刚度和桩基刚度。计算结果表明:连续刚构桥的2自由度简化模型可以准确反映其主要动力特性,经调谐隔震优化设计后,墩顶和墩底弯矩的减震率分别可达46.5%和58.7%,验证了调谐隔震方法可有效控制高桩承台连续刚构桥的地震响应。

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 ofμ,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.