桥梁群桩基础抗震简化计算模型的适用性研究

摘要

A variety of simplified seismic computational models mainly applied to group pile foundations were compared and then differences between them were pointed out . On this basis , an improved Layered Winkler spring model was put forward . The impact of lateral friction around piles and subsoil vertical resistance at pile tip was considered using the parameter ηin this model , which is equivalent area ratio of a pile . The results show that :The effect of the coupling stiffness should be considered when flexible constraint effect of pile foun‐dations was simulated by using concentrated spring model;The effect of lateral friction around piles and sub‐soil vertical resistance at pile tip should be considered when pile‐soil interaction of group pile foundations was simulated by adopting Layered Winkler spring model ;ηincreases with the increase of pile length and vertical foundation coefficient at pile tip , but decreases with the increase of pile diameter in the improved Layered Win‐kler spring model . The larger the ηvalue is , the greater the impact is on the seismic response of pier and pile foundation .Only when ηis close to 1.0 ,the Layered Winkler spring model can be used for seismic analysis .%本文对群桩基础常用的抗震简化计算模型进行对比分析，指出各计算模型间的差异。在此基础上，提出改进的分层文克尔弹簧模型，并在该模型中采用桩身的等效面积比η间接考虑桩侧摩阻力和桩底土竖向抗力的影响。分析结果表明：应用集中弹簧模型模拟桩基础的柔性效应时，应考虑耦联刚度的影响；应用分层文克尔弹簧模型模拟群桩基础的桩土相互作用时，应考虑桩侧摩阻力和桩底土抗力的影响；在改进的分层文克尔弹簧模型中，桩身的等效面积比η随桩长及桩底土竖向地基系数的增加而增大，随桩径的增加而减小，且η值越大，对桥墩及桩基础的地震响应影响越大，只有当η接近1.0时，方可采用分层文克尔弹簧模型进行抗震分析。