92. ENERGY DISSIPATION SYSTEMS FOR SEISMIC APPLICATIONS
This paper presents a summary of current practice and recent developments in the application of passive energy dissipation systems for seismic protection of structures. The emphasis is on the application of passive energy dissipation systems within the framing of building structures. Major topics that are presented include basic principles of energy dissipation systems, descriptions of the mechanical behavior and mathematical modeling of selected passive energy dissipation devices, advantages and disadvantages of these devices,
development of guidelines and design philosophy for analysis and design of structures employing energy dissipation devices, and design considerations that are unique to structures with energy dissipation devices. A selection of recent applications of passive energy dissipation systems is also presented.
91. COUPLED TRUSS WALLS WITH DAMPED LINK ELEMENTS
A new structural concept is proposed for the seismic design of tall buildings. This system combines the inherent stiffness and strength of a conventional truss system with the energy absorption characteristic of supplemental damping elements. The damping elements are strategically placed to form the linking elements of a coupled vertical truss system. While the force resistance system of the truss wall is in parallel, the damped link beam is in series with the component of the truss stiffness contributed to the coupled wall action. A series of time history dynamic studies gauged the performance of the proposed concept and found the proposed damped link concept superior in performance compared to the conventional approach.
90. REHABILITATION OF A 1985 STEEL MOMENT FRAME BUILDING
A 1985 steel moment frame was seismically upgraded using passive energy dissipation, without adding stiffness to the system. The design and analysis techniques for sizing the Velocity Braces and their impact on the demand capacity ratios are reviewed in this paper. The original structure was built in the San Francisco Bay Area in compliance with the 1985 Uniform Building Code (UBC). The moment frame contains the classic pre-Northridge nonductile moment connection. Nonlinear time history analysis was used to design a damper system that provides a significant decrease in seismic response.
89. U.S CODE DEVELOPMENT OF STRUCTURES WITH DAMPING SYSTEMS
Damping devices are being increasingly used in both new and existing buildings in both United States and Japan. This increased popularity has created a demand for design guidance and building codes. This paper provides a summary of the code development activities for the 2003 NEHRP by the Building Seismic Safety Council.
87. FLUID DAMPERS FOR SEISMIC PROTECTION OF WOODFRAME STRUCTURES
In the recent past a large number of steel framed buildings have used supplemental energy dissipation systems to provide seismic protection. However, the application of such systems to wood frame structures has been essentially non-existent except for a limited number of experimental laboratory studies. This paper presents a numerical study of the application of fluid dampers for seismic protection of wood framed structures. Such dampers dissipate energy via orificing of a fluid. The seismic response of a wood framed shear wall with and without dampers is evaluated via nonlinear finite element analyses. The results of the analyses demonstrate that the dampers are capable of dissipating a large portion of the seismic input energy while simultaneously relieving the inelastic energy dissipation demand on the shear wall.
86. BASE ISOLATION AND SUPPLEMENTAL DAMPING SYSTEMS FOR SEISMIC PROTECTION OF WOOD STRUCTURES
This paper provides a literature review on the application of base isolation and supplemental damping systems for seismic protection of wood structures. The review reveals that both elastomeric bearings and sliding bearings have been considered for implementation within base isolation systems of wood framed buildings. In addition, friction dampers, viscoelastic dampers, hysteretic dampers, and fluid viscous dampers have been considered for implementation within the framing of wood buildings. Although there are a number of impediments to the widespread implementation of such advanced seismic protection systems, the reviewed literature clearly demonstrates that advanced seismic protection systems offer promise for enabling light framed wood structures to resist major earthquakes with minimal damage.
84. MITIGATION OF MILITARY HIGH SHOCK TRANSIENTS FOR SHIPBOARD GYROCOMPASS WITH FIBER OPTIC GYROS (FOG)
The Taylor Devices self-centering hexapod mount provides MIL-S-901D shock protection for the Litton Marine Systems MK27F Attitude and Heading Reference System (AHRS). This new Reference System satisfies stringent military shock and vibration requirements. Unlike Ring Laser Gyro (RLG) which have low fragility levels (Max 50 g), the LN200 Fiber Optic Gyro Assembly can be exposed to levels as high as 90 g. This paper addresses the shock transient mitigation for shock requirements specified by MIL-S-901D. Comparisons between predicted and measured response are provided for a single strut as well as the fully shock isolated platform. Analytical and experimental results are presented to demonstrate the effectiveness of the MK27F Shock Absorber basic design for MIL-S-901D LWSM and predicted response is also presented for the floating platform Heavy Weight Shock Machine (HWSM).
82. FULL-SCALE SHAKE TABLE TESTS OF 5-STORY STEEL BUILDING WITH VISCOUS DAMPING
Realistic simulations of earthquake responses were conducted in March 2009 for a full-scale 5-story building specimens with dampers using the E-Defense, the world’s largest three-dimensional shake table. The building was tested repeatedly, inserting and replacing each of 4 damper types, steel damper, oil damper, viscous damper and viscoelastic damper. This paper discusses the test method and test results as well as details of the 5-story building specimen. Performance improvement by the dampers is addressed for moderately tall buildings that constitute a major portion of the building stock.
81. APPLICABILITY OF SEISMIC PROTECTIVE SYSTEMS TO HIGH-TECH INDUSTRIAL STRUCTURES
This paper summarizes a feasibility study for implementing seismic protective systems into high tech industrial structures in which costly vibration sensitive facilities are housed. Micro-vibration control of an IC fab is essential for optimum yield of reliable chip products. This paper describes the micro vibration analysis and measurement of a test structure before and after the incorporation of Seismic Protective systems. Based on the study, it is found that the incorporation of viscous dampers both enhances seismic safety and also minimizes the micro vibration of the structure. Viscous damper seismic isolation is the most promising method to achieve the “fully operational” seismic performance level of an IC fab.
79. FLUID VISCOUS DAMPERS: AN EFFECTIVE WAY TO SUPPRESS PEDESTRIAN-INDUCED MOTIONS IN FOOTBRIDGES
Fluid viscous dampers have found commercial applications on buildings and bridges subject to seismic and/or wind storm inputs. They are now being used as well on footbridges to suppress undesirable pedestrian induced vibrations. This paper provides a brief overview of fluid damping technology with specific case studies for pedestrian bridges now equipped with fluid viscous dampers. These viscous dampers are used to suppress the feedback between the pedestrians and the bridge and/or wind induced vibrations. On-site tests show that fluid viscous dampers provide significant gains in performance at relatively low cost.