This paper discusses model, design, and application of viscous dampers in one the skyscraper in New York City.
106. A Study in the Long-Term Performance of Specialized Low Friction Hermetically Sealed Fluid Viscous Dampers under Nearly Continuous Operation on a Pedestrian Bridge
This paper will outline the specifics in quantifying the continued damper performance through an intermediate inspection after seven years, followed by a successful comprehensive inspection after eleven years. This included the removal, dynamic testing, and re-installation of three selected dampers.
This hermetically sealed damper was developed during the 1980’s for use space platforms. NASA and the U.S. military had experienced difficulties over the years with all types of oil filled products in space. Conventional sliding surfaces that were sealed acceptably on earth proved unacceptable for spacecraft use. Even the tiniest amount of fluid seepage past conventional seals turns into a dense fog in a vacuum, contaminating optics and electronic systems. Taylor Devices’ solution was to develop a damper that uses a flexural seal – thus sealing by non-sliding methods. The seal itself was a so called metal bellows made by laser welding thin discs of stainless steel into a bellows configuration. This paper describes the design and construction of the Taylor Devices Hermetically Sealed Damper.
The Millennium Footbridge was opened to the public on June 10, 2000 – the first new bridge across the River Thames in historic London in more than a century. Nearly 100,000 people used the new bridge in its first day of operation. On June 12, 2000, the Millennium Bridge was ordered closed, due to hazardous deck motions. Seemingly random pedestrian footfalls were causing resonance of the bridge deck, with lateral accelerations measuring up to 0.25 g. The selected method of retrofit was to add fluid damping to the bridge. This paper describes how this was done, including testing of the bridge with groups of up to 2,000 people.
62. STRUCTURAL CONTROL OF HIGH RISE BUILDING USING A TUNED MASS WITH INTEGRAL HERMETICALLY SEALED, FRICTIONLESS HYDRAULIC DAMPERS
Structural control of large buildings using tuned mass damper systems has gained wide acceptance in recent years. Significant structural performance improvements during wind storms have been realized using both active and passive systems. Disadvantages of employing active systems include high engineering and implementation costs, high maintenance costs, unnecessary system complexities, and the requirement for a continuous and non-interrupted power supply. A design for a passive tuned mass damper system is presented with analytical simulations and component test results. These demonstrate the effectiveness of using a tuned mass in conjunction with a maintenance free, hydraulic damper, having frictionless flexural seals to successfully attenuate the response of a high rise building subject to severe wind inputs.
51. APPLICATIONS OF HERMETICALLY SEALED FLUID DAMPERS FOR LOW LEVEL, WIDE BANDWIDTH VIBRATION ISOLATION
Vibration isolation of sensitive components like high resolution cameras requires extremely low friction in the isolator system. Hydraulic dampers for these systems must be leak-free, which equates to relatively high friction seals. There is always a trade-off between allowable leakage and allowable friction in this type of application. This paper describes the isolation performance of a new hermetically sealed damper with essentially zero friction. It contains both an analytical representation of damper performance and dynamic test results.