分离式承台摇摆抗震及其有限元模拟

Finite element modeling methods of aseismic rocking separated pile-cap foundation

为了提供一种桥梁抗震的可选方案,根据摇摆抗震的基本思想,阐述了自复位分离式承台的构想,将传统桥梁桩基础的承台一分为二,使承台上部能够在地震作用下摇摆,从而在基础部位隔断地震传播途径,达到减隔震的目的。分析了该抗震方法的抗震原理,阐释了该抗震方法可能采用的各种构造工艺与施工方式。传统的摇摆抗震数值模拟技术将摇摆接触面区域视为刚体,不考虑接触面的弹性变形,与实际情况不符,故采用了将摇摆区域(文中为承台)采用三维实体有限元模拟的精细化建模方法,并与传统的建模方法进行对比。分析表明:在现有的桥梁抗震设计技术与施工技术支持下,分离式承台具有工程应用的可能性,在有限元模拟中,将摇摆区域视为刚体的做法会放大结构的位移响应,是一种偏保守的做法。

To propose an alternative seismic strategy,a self-centering separated pile-cap that could rock under seismic load in order to cut off the path at the bottom of the foundation of common bridges that energy would transfer was introduced. The principle of this aseismic system is analyzed and multiple tectonic possibilities with feasible construction methods are illustrated. The traditional simulation method for rocking structure treated the rocking contact surface,i.e.,the rocking foundation as rigid body,ignoring the elastic deformation,which was not quite the case. To optimize this issue,an elaborate finite element model with the rocking area（ which is the cap in this paper） simulated by 3-dimensional solid elements is proposed and then compared with traditional modeling method.The analysis in this paper shows that under current bridge seismic design technique and construction technology,aseismic rocking separated pile-cap foundation has its possibility in engineering application. Therefore,seeing the rocking area as rigid in FEM methods would conservatively amplify the displacement response of the structure.