Three‐dimensional behavior of a spherical self‐centering precast prestressed pile isolator

Abstract

SUMMARYA 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.

Optimized friction pendulum and precast-prestressed pile to base-isolate a Chilean masonry house

“…In the current study, the formulation proposed by Pinochet et al (2006) is utilized after modifying the model to account for the friction between the central prestressed cable and its duct. This change was suggested by Jünemann et al (2009), who used additional experimental data to provide further validation of the analytical model proposed by Pinochet et al (2006).…”

“…It should also be noted that one result of using PPP isolators with spherical rolling surfaces is the generation of an initial lateral resistance that is relatively small (Jünemann et al 2009). Ranges of appropriate values for the parameters of the PPP isolators are determined based on the experimental testing performed by Pinochet et al (2006) and by Jünemann et al (2009). The ranges used in this study are somewhat extended from those used in the testing program.…”

“…The original model is modified to account for friction between the central prestressed cable and its duct. This change was suggested by Jünemann et al (2009) upon performing experimental testing on eight full-scale PPP isolators. The effect of friction between the central cable and its duct is taken into account by utilizing the following equations (Jünemann et al 2009):…”

“…As in the analytical formulation developed by Pinochet et al (2006), x eu and y eu are the current coordinates of the center of the top rolling surface, and x su and y su are the current coordinates of the center point of the rolling plate of the top capital. The coefficient of friction μ is assumed to be 1.8% in this study, as suggested by Jünemann et al (2009). This study uses an elastic-perfectly plastic model for the ductile rebar, as done by Pinochet et al (2006).…”

“…Spherical top and bottom rolling surfaces are selected for the PPP isolators to minimize uplift (Pinochet et al 2006). It should also be noted that one result of using PPP isolators with spherical rolling surfaces is the generation of an initial lateral resistance that is relatively small (Jünemann et al 2009). Ranges of appropriate values for the parameters of the PPP isolators are determined based on the experimental testing performed by Pinochet et al (2006) and by Jünemann et al (2009).…”