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Fluid Viscous Dampers
Case Study

66. Damper Retrofit of the London Millennium Footbridge

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.
White Paper

65. Viscous Damper Development and Future Trends

Viscous dampers can protect structures against wind excitation, blast and earthquakes. Viscous damper technology originated with military and aerospace applications. Approximately 20 years ago it was found that the same fluid viscous dampers that protect missiles against nuclear attack and guard submarines against near miss underwater explosions could also protect buildings, bridges and other structures from destructive shock and vibration. This paper describes fluid damper technology, analysis considerations, installation methods and development work in progress.
Case Study

64. Virtual Base Isolation by Building Softening with Drift Control Provided by Fluid Viscous Dampers

In many metropolitan areas, mid rise buildings are constructed adjacent to existing buildings, and incorporate concrete shear walls to act as a barrier between the two buildings. The orientation of these shear walls often causes severe torsional response within the building. The addition of a few well placed nonlinear Fluid Viscous Dampers (FVD’s) can significantly decrease the torsional excitation, thereby increasing building performance. This paper describes the retrofit of an 18-story steel frame building that exhibits severe torsional response from the “property line” condition at the lower two stories. FVD’s significantly reduce the displacement and acceleration of the second and third floors of the building, where sensitive telecommunications equipment is being housed. They reduce the demand and drift on the stories above with no additional construction required on these floors. FVD’s offer a very economical and effective means of mitigating undesirable building response due to torsional irregularities. Their use would be effective in the retrofit of many existing buildings with similar “property line” conditions.
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63. Virtual Base Isolation by Building Softening with Drift Control Provided by Fluid Viscous Dampers

The paper describes “virtual isolation” for buildings with one or more soft stories. Using the 1999 SEAOC Blue Book (SEAOC, 1999) recommendations for passive energy dissipation, the building’s Lateral Force Resisting System (LFRS) is designed for strength requirements only, resulting in a relatively flexible LFRS, while Fluid Viscous Dampers (FVD) are incorporated to limit story drifts to acceptable levels. There are many benefits to this “virtual isolation” system. With the elimination of the maximum drift requirements, the moment frames are substantially lighter than a traditionally framed building, thus lowering the structural steel cost of the LFRS. The long period structure also produces significantly reduced forces in the foundation elements. Velocity and displacement are reduced significantly through the use of the FVDs, which protects the sensitive contents of the building. These benefits lead to a reduced response resulting in an enhanced performance level during a major seismic event.
Case Study

58. Viscous Damper with Motion Amplification Device for High Rise Building Applications

Adding damping by the use of various damping devices has become an accepted method to reduce wind induced vibrations in tall buildings. An interesting example of a 39 story office tower is presented where large projected accelerations are the result of vortex shedding of an adjacent existing 52-story building. Viscous dampers and a toggle brace type motion amplification system are used to suppress the anticipated accelerations. A description of the damping system and its analytical simulation are discussed. This paper includes a nonlinear analysis of the tower, with time history forcing functions derived from wind tunnel testing. Cost data for the damper system is also presented.
White Paper

57. Structural Control of Dynamic Blast Loading Using Fluid Viscous Dampers

This paper evaluates the effectiveness of Fluid Viscous Dampers to reduce blast loading responses in steel buildings. The paper addresses the following issues: (1) development of a blast loading time history from a 3,000 pound explosive charge, (2) characteristics and historical applications of fluid Viscous Dampers for blast and weapon effects, and (3) blast effects and performance comparisons of a conventional steel building frame with and without dampers, and a conventional concrete shear wall building. Simulation results indicate that Fluid Viscous Dampers provide a cost effective way to greatly improve the performance of steel building frames under blast loading.
Product Info

56. Buildings: Design for Damping

The end of the Cold War in 1990 heralded a restructuring period for the American military and defense industry. In the civil engineering field, high capacity fluid dampers have transitioned from defense related structures to commercial applications on buildings and bridges subjected to seismic and/or wind storm inputs. Because fluid damping technology was proven thoroughly reliable and robust through decades of Cold War usage, implementation on commercial structures has taken place very quickly. This paper provides a broad overview as well as a guide to implementation; with specific case studies for four of the more than 300 major buildings and bridges equipped with fluid dampers by Taylor Devices, Inc., a defense contractor from the Cold War years.
Product Info

54. Here’s How it Works

This article from Bridge Builder magazine shows how Taylor Devices dampers reduce seismic response of bridges.
Technical Brief

50. Testing and Modeling of an Improved Damper Configuration for Stiff Structural Systems

This report describes a toggle brace damper system that adds significant damping to stiff structures, like reinforced concrete shear wall buildings. It is generally recognized that these stiff structural systems, such as reinforced concrete shear walls and steel braced dual systems, are characterized by small drifts and small relative velocities that make the implementation of seismic energy dissipation devices difficult. This report presents a study on a toggle brace damper system that magnifies the damper displacement and reduces the required damper force to produce the desired damping. The reports presents the concept, describes the theoretical treatment, and includes an experimental study with cyclic and shake table testing of a model structure along with procedures for response history and simplified analysis.

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