The primary objective of the NEESR-Adapt-Struct team is to address a "significant gap" in existing devices designed to protect structures against seismic damage, by developing and testing new forms of adaptive stiffness and damping systems capable of adjusting their performance in response to the behavior of individual earthquakes. To date, adaptive stiffness systems have received relatively little attention as compared to supplemental damping systems and represent a significant gap in earthquake engineering.

In August 2008, the team received a $1.6-million grant to fund its research from the George E. Brown, Jr. Network for Earthquake Engineering Simulation Research Program of the National Science Foundation (NSF).

Existing systems for protecting structures against seismic damage generally are passive in nature, meaning that they cannot adjust their behavior. For example, typical supplemental damping systems that dissipate seismic energy in order to limit structural damage respond with fixed properties in every earthquake.

The "vision" behind the research funded by the NSF is to develop a "new class" of seismic-protection devices that can modify their performance in terms of damping and stiffness depending on the nature of the specific earthquake to which they are responding.

Known as adaptive stiffness and damping (ASD) devices, the system that the team aims to develop potentially could afford greater seismic protection than passive systems by tailoring their behavior to the optimal levels of damping and stiffness required to protect a structure during a particular earthquake.

Although a variable adaptive passive damper has been developed and successfully installed in Japan, the system cannot adjust its performance in terms of stiffness. An ASD device also would differ from so-called semi-active damping systems that use digital feedback from a computer to adjust fluid viscosity or variable orifice or other factors within the system to alter the damping level provided by the device. Although such systems are useful, structural engineers have questioned the necessity and reliability of feedback and computer control during strong earthquakes.

The goal of the NEESR-Adapt-Struct project is to mimic the behavior of active and semiactively controlled devices by developing self-contained, adaptive, passive stiffness and damping devices with internal hydraulic feedback, but without the associated digital feedback and computer control-An actively controlled device is a system that is capable of monitoring and adjusting its performance based on the response feedback and excitation. To achieve the desired internal hydraulic feedback, the ASD device will employ valves and orifices through which fluid will pass. Changes in hydraulic pressure within the device will modify its damping and stiffness performance.

Physical testing of the ASD device will occur at the Structural Engineering and Earthquake Simulation Laboratory (SEESL) at the University at Buffalo, State University of New York. The laboratory houses three earthquake simulators, or shake tables, as well as other equipment designed to simulate seismic conditions. A prototype version of the ASD device will undergo testing alone and as part of a structure at the University of Buffalo NEES site. Finally, the structure(s) with the ASD device incorporated within it will be tested on a shake table. At the completion of the testing, the research team hopes to have a finished ASD device that performs predictably, along with a computer program intended to help structural engineers determine how to include such a device as part of structures they are designing.

In addition to Rice University and the University at Buffalo, the research team includes investigators from the Rensselaer Polytechnic Institute; the University of California-Los Angeles; California State University, Fresno; and Taylor Devices, Inc., a maker of seismic-protection systems that has its headquarters in North Tonawanda, New York.