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This paper describes the behavior of the quintuple friction pendulum isolator, a spherical sliding isolator with six sliding surfaces, five effective pendula, and nine regimes of operation that allow for complex multi-stage adaptive behavior depending on the amplitude of displacement. An analytical model is presented that is capable of tracing the behavior of the isolator in two general configurations of geometric and frictional properties. This analytical model is useful for verifying computational models and in performing simplified calculations for analysis and design. A computational model that can be implemented in the program SAP2000 is also presented and verified by comparison to the analytical model. A model quintuple friction pendulum isolator has been tested and the results have been used to validate the analytical and computational models.

There are currently no applicable hysteresis rules or nonlinear elements available in structural analysis software that can be used to exactly model triple Friction Pendulum bearings for response-history analysis. Series models composed of existing nonlinear elements are proposed since they can be immediately implemented in currently available analysis software. However, the behavior of the triple Friction Pendulum bearing is not exactly that of a series arrangement of single concave Friction Pendulum bearings—though it is similar. This paper describes how to modify the input parameters of the series model in order to precisely retrace the true force-displacement behavior exhibited by this device. Recommendations are made for modeling in SAP2000 and are illustrated through analysis of a simple seismically isolated structure. The results are confirmed by (a) verifying the force-displacement behavior through comparison with experimental data and (b) verifying the analysis through comparison to the results obtained by direct numerical integration of the equations of motion.

Equivalent lateral force and modal analysis procedures for yielding buildings with damping systems were developed, validated, and incorporated in the 2000 NEHRP Provisions. The technical basis for each procedure is described in the paper together with the simplifications adopted for inclusion in the Provisions. Procedures for calculating the effective damping and effective period and higher mode damping ratios for buildings equipped with yielding, viscoelastic, linear viscous, and nonlinear viscous damping devices are presented.

Installation of damping devices has been limited to diagonal or chevron brace configurations until the recent development of the toggle-brace configurations. These configurations magnify the effect of damping devices, thus facilitating their use in stiff framing systems. This paper introduces the scissor-jack-damper system that was developed as a variant of the togglebrace-damper systems, with the added advantage of compactness. The effectiveness of the scissor-jack configuration is demonstrated through testing of a large-scale steel-framed model structure on an earthquake simulator. Experiments showed that despite the small size of the damping device considered, the scissor-jack system provided a significant amount of damping and substantially reduced the seismic response of the tested structure. Response history and simplified analyses produce results that are consistent with the experimental results. [DOI: 10.1193/1.1540999]

The development, experimental testing, and analytical modeling of an intelligent seismic response control system is described in this paper. The control system is in the form of semiactive fluid damping devices which may be installed within the lateral bracing system of buildings or as part of a seismic isolation system for bridges or buildings. The dampers have mechanical properties which can be modified through a closed-loop feedback control system which utilizes the measured earthquake excitation and/or the response of the structural system. Further, the dampers exhibit fail-safe characteristics in that, in the event of failure to operate as semi-active devices, the dampers convert to passive high-damping devices. The dampers were extensively tested to determine the mechanical properties and the dynamic behavior of the devices. Furthermore, mathematical models for describing the damper behavior were developed and utilized for analytically predicting experimental results.

Several different scoring systems have been developed to predict neonatal morbidity and mortality. In this investigation we compared the utility of four severity of illness scoring systems (SISS) as predictors of days on ventilator (DOV), length of hospital stay (LOS), and mortality in very-low-birth weight (VLBW) premature infants who required mechanical ventilation. The SISS assessed were the Score for Neonatal Acute Physiology (SNAP); the Score for Neonatal Acute Physiology—Perinatal Extension (SNAP+PE); Clinical Risk Index for Babies (CRIB), and the Sinkin Score at 12 hours (SS12). Results revealed significant correlations among the SS12, SNAP, SNAP+PE, CRIB, birth weight (BW), DOV, and LOS. However, none of the systems we assessed offered striking advantage over BW in a VLBW ventilated group.

A seismic isolation system for bridges has been tested on a shake table. The system consisted of Teflon disc bridge bearings and displacement control devices. These devices provided restoring force for re-centering the bridge during earthquake excitation, additional energy dissipation capacity and rigidity for service loading. The tests were carried out with a 51-kip model which was subjected to strong recorded earthquake motions with a wide range of frequency content and to simulated motions compatible with CalTrans 0.6g design spectra. In all tests the isolated deck responded with peak acceleration less than the peak table acceleration and peak bearing displacement less than the peak table displacement. Results from an analytical model show very good agreement with experimental results.

This paper reports on a parametric study of the response of bridges supported by an isolation system consisting of sliding Teflon bearings and displacement control devices. The isolated bridges are subjected to simulated earthquake motions which are compatible with CalTrans design spectra. The effects of isolation system properties, deck flexibility, pier flexibility, pier strength, distribution of isolation elements and earthquake type are investigated. Results are presented in a form that is useful in the design of sliding isolation systems for two-span continuous deck bridges. Comparisons with the response of conventionally built bridges demonstrate the significant benefits of seismic isolation. Finally, simplified code-type analysis procedures are presented and evaluated.

An isolation system consisting of sliding Teflon bearings and displacement control devices is described for the seismic protection of bridges. The system utilizes multidirectional Teflon bearings for accommodating thermal movements and for providing the isolation mechanism and displacement control devices which exhibit bilinear behavior with controlled stiffness and characteristic strength. The devices provide rigidity for service loads below their characteristic strength and restoring force and energy dissipation for strong earthquake forces.