Development of Composite Yielding Dampers

点击翻译按钮获取中文摘要

Passive control of structures is still evolving technologically, with increasing understanding of system behavior, response prediction methodologies, design guidance, and field experiences. Valuable information regarding behavior, design, and implementation of passive control systems is being developed in Japan due to their significant research investment in innovative passive control measures for protection of structures against both seismic and wind forces. One type of innovative passive controlsystem that has been developed recently in Japan is a type of yielding brace damper. The yielding brace contains a single steel plate with large ductility capacity and relatively low yield strength that is encased in a grout filled tube, but is not bonded to the grout. The key concept of the device is that yielding occurs in the encased steel plate equally for both tensile and compressive loading cycles and the system exhibits stable hysteretic energy dissipation capability. A new type of yielding device is proposed which builds on the economic advantages of the yielding brace, but allows tailoring the yielding element materials to achieve specific performance requirements and employs noncohesive media to confine the yielding elements. These two innovations combined provide controlled post-yield slope of the damper that maintains self-centering capability of a structure even during an extreme earthquake when the buildingframe may significantly yield and soften; provide a generally applicable confining technique that does not infringe on existing patents; eliminate high-precision design, detailing, and fabrication of devices at the debonding interface; lower damper cost; ease of repair/replacement of yielding elements after a damaging earthquake; enable inspection; and provide additional friction damping which may be beneficial for wind response mitigation. This new device is defined as a composite yielding damper (CY-damper).The combined attributes of CY-dampers may provide significant technical and economicadvantages over existing devices. A research program, integrating both experimental and analytical components, is proposed to investigate the application of CY-dampers for building structures. The primary objectives of the proposed research project are to: (1) develop prototype CY-dampers, (2) characterize the structural performance of individual CY-dampers and optimize damper properties, (3) determine the behavior ofbuilding frames with CY-dampers under varying magnitude earthquakes, (4) develop analytical models to describe the behavior of CY-dampers and CY-damped systems, and (5) provide guidance for the application of CY-dampers directed toward performance based design. These objectives will be achieved by working in collaboration with a team of Japanese researchers who are the primary developers of this system in Japan. Professional relationships and research collaboration are on-going between the researchers and significant resource and information exchange will take place throughout all phases of the proposed research program. Small and large-scale CY-damper tests under reversed cyclic loading are proposed. Parameters to be studied include: (1) application of different materials including combinations of high and low strength steels or other high-performance materials, (2) investigation of different confining materials and plate slenderness parameters, and (3) long term durability under high-cycle low-amplitude fatigue. A prototype multistory multibay steel frame building will be used to facilitate development of realistic test specimens and permit comparison between different damper designs. In concert with experimental tasks, analytical models will be produced which are compatible with available analysis programs and correlate experimentally observed response. Simplified and practical analysis methods including equivalent linearization techniques will be developed to predict response and develop practical design guidance.