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).
83. BOAT SEAT ISOLATORS
This article appeared in Special Operations Technology magazine. It provides a very complete explanation of the Taylor Devices isolated seat for the Navy, complete with many photos. The article also includes the experiences of the seat occupants under high speed ocean travel.
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.
80. A LIVING OR SMART BUILDING: THE GUANGZHOU TOWER
This paper presents the evolution of the structural design of one of the tallest structures in the world. The architectural design was developed by Mehrdad Yazdani at Cannon Design Group. The basic architectural vision of the Guangzhou Tower is three twisting interconnected legs. The architectural plan at each level of the tower rotates and twists. The basic structural vision here is of a Living Structure that can be adapted and improved from a structural engineering perspective as new high-tech products become available, as our understanding of the forces of nature improves using ground and aerial instrumentation and as we improve the accuracy of our structural modeling to estimate structural response to wind and earthquake loading.
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.
78. EXPERIENCE AND PRACTICAL CONSIDERATIONS IN THE DESIGN OF VISCOUS DAMPING
This paper describes how viscous dampers work, and how they significantly reduce seismic excitation in structures.
77. ENERGY MANAGEMENT UTILIZING THE HYDRAULIC SHOCK ABSORBER
The advent of high speed equipment and machinery has brought with it numerous problems associated with slowing and stopping masses of various forms. The hydraulic shock absorber has proven to be one of the most satisfactory means of solving these problems, yet the shock absorber still remains as one of the least understood fluid power components. This paper presents design constraints, design parameters and a description of how to use shock absorbers into a system for the purpose of dissipating kinetic energy. Information is presented in both qualitative and functional equation format to enable the reader to grasp the subjective aspects of shock absorber usage which go beyond normal mathematical constraints.
76. SIMULATION, DEVELOPMENT, AND FIELD MEASUREMENT VALIDATION OF AN ISOLATION SYSTEM FOR A NEW ELECTRONICS CABINET IN THE SPACE SHUTTLE LAUNCH ENVIRONMENT WITHIN THE MOBILE LAUNCH PLATFORM
This paper describes the dynamic analysis of an isolator system for the cabinet-mounted low voltage power switchgear in the Space Shuttle Mobile Launch Platform (MLP). The addition of electronic sensing and control components to this cabinet combined with the harsh vibration environment experienced during a Shuttle launch necessitated a six degree of freedom isolation system to prevent the spurious tripping of breakers. An added benefit of the isolation system is that it provides vibration isolation during the Shuttle’s approximately three mile journey between the Vehicle Assembly Building (VAB) and either of its two launch pads. The isolation system was designed, built, and integrated within the MLP. Broadband dynamic measurements were made during an actual Shuttle launch to verify the effectiveness of the isolation system and to validate the predictions of the analysis. Measurements made during the launch of STS-115 on September 9, 2006, affirmed the effectiveness of the isolators and validated the predicted performance of the isolation system.
75. STRUCTURAL CONTROL USING HYBRID SPRING-DAMPER ISOLATOR WITH INTEGRAL GAPPING FUNCTION
The spring-damper isolators described in this paper were used on the world’s largest cable stayed bridge – the Sutong Bridge over China’s Yangtze River, completed in 2008. The Sutong Bridge is located north of Shanghai in China’s Jiangsu Province at a site where catastrophic earthquakes, typhoons, and ship impact are key design issues. The total length of the bridge is 4.7 miles, with a .67 mile long center span. The tall support towers of this bridge and the long support cables create long period motions along the primary axis of the bridge. The need to accommodate thermal expansion and contraction of the deck axially means that extensive motion can occur in this direction. The configuration of the bridge permits large axial motion of the suspended deck during earthquakes, typhoons, and synchronized truck/car braking loads such as would occur during a mass vehicular accident on the bridge. During dynamic earthquake loading, the long period of the suspended deck provides inherent isolation, albeit essentially undamped. Analysis indicated that added viscous damping would reduce deck motions substantially. During other events like typhoons and vehicle loading, analysis determined that the most cost-effective solution was to incorporate a snubbing type spring element that would only engage (become active) when the damper was approaching its end of travel in either extension or compression. The spring-dampers on this bridge have only damping forces for roughly 85% of the available displacement from the neutral (center of travel) position. Beyond this travel the spring element engage and a combined response of spring plus damper forces results. Essentially, the spring elements are “gapped” through all but approximately the last 15% of the damper stroke in either direction.