Abstract

A 3D analytical formulation of a precast prestressed pile (PPP) seismic isolator with top and bottom spherical rolling kinematic constraints is proposed. The PPP isolator was initially conceived as a low-cost seismic isolation (and foundation) system for housing units of low-income people. Since these structures are usually located at sites with poor soil conditions, the PPP isolator also works as a foundation pile by connecting the superstructure with more competent soil layers. The non-holonomic nature of the rolling constraint is dealt with by a structural formulation. The proposed 3D formulation is validated by numerical results obtained from a previously proposed formulation for the 2D problem, and a contact finite element model in ANSYS (www.ansys.com). Other issues associated with the dynamic response of isolated structures with the PPP are also examined, such as expected response reductions, variation in the axial force of the central prestressed cable, and torsional response amplifications. Finally, guidelines to estimate the actual 3D response using 2D analysis results are investigated. Copyright © 2009 John Wiley & Sons, Ltd.