Adding damping with various energy dissipating devices has become an accepted method to reduce wind induced vibrations in tall buildings. An example of a 39-story office tower is presented where large projected accelerations generated by the vortex shedding of an adjacent existing 52-story building are reduced by a passive system composed of viscous dampers and a motion amplification system. A description of the damping system and its analytical complexities are discussed. Non-linear analysis of the tower, using time history forcing functions derived from the wind tunnel is presented. Cost data for the damper system is also presented.
Existing methods for the design of optimal configurations of supplemental dampers are usually not simple enough to be used routinely, and typically lead to different damper sizes at virtually every story. This can be avoided with the Sequential Search Algorithm, which lets the designer control the number of different damper sizes. In this paper, a simplification to the Sequential Search Algorithm is developed. This Simplified Sequential Search Algorithm makes it easy for engineers to deal with damper added structures. It was found that the efficiency of damper configurations given by the proposed Simplified Sequential Search Algorithm is comparable to the efficiency of damper configurations given by more sophisticated procedures. The applicability of the method is limited to those cases where the response of the structure with added dampers remains linear.
In recent years, seismic damping systems have been employed in numerous steel and concrete framed buildings. Such systems dissipate a significant portion of the seismic input energy, thereby relieving the energy dissipation demand on the structural framing system and thus reducing damage. As part of a NEESR project to develop a performance based approach to seismic design of multi-story light framed wood structures, the application of damping systems to such structures has been evaluated via seismic shaking table tests and numerical simulations. This paper focuses on the results from shaking table tests of shear walls employing toggle braced fluid dampers. The results demonstrate that toggle braced fluid dampers provide a significant increase in the seismic resistance of the walls, allowing them to achieve high levels of performance when subjected to strong ground motions.
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.
This paper provides a broad overview and a guide to implementation with specific case studies being provided from four of more than 240 major buildings and bridges equipped with fluid dampers by Taylor Devices, Inc.
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.
This paper describes shaking table tests of a multi-story scale model building structure subjected to seismic excitation and controlled by a semi active fluid damper control system. The semi active dampers were installed in the lateral bracing of the structure and the mechanical properties of the dampers were modified according to control algorithms which utilized the measured response of the structure. A simplified time delay compensation method was developed to account for delays within the control system. The results of shaking table tests are presented and interpreted and analytical predictions are shown to compare reasonably well with the experimental results. These tests included an undamped system, passive damping, and semi-active damping. Both the purely passive damper system and the semi-active system significantly reduced seismic response.
Specification for viscous damping devices, including performance, testing and inspection.
25. TEST METHODOLOGY AND PROCEDURES FOR FLUID VISCOUS DAMPERS USED IN STRUCTURES TO DISSIPATE SEISMIC ENERGY
Taylor Devices, Inc. has manufactured damping devices since 1955. Until 1990 most applications were military, using dampers to attenuate weapons effects. Until recently, information on these applications and the associated damper designs has not been public due to security restrictions. Most of these restrictions have now been relaxed and much of this damping technology is now available to the structural engineering community. Taylor Devices can now provide compact fluid viscous dampers in the 100 kip to 2,000 kip output range that greatly reduces earthquake response of structures. This paper describes how the military has been testing shock mitigation dampers for many years and how this type of testing can apply to the large dampers required for seismic protection of structures.
Conventional approaches to the shock isolation of delicate systems often involve the use of low frequency shock mountings. This type of mounting is not usable on systems where precise alignment must be maintained over a long period of time. This paper describes a new type of isolator which combines excellent attenuation with the ability to precisely maintain system alignment in the pre and post shock environment. This new shock absorber acts as a rigid link under normal conditions. Then, when a shock occurs, it strokes in both tension and compression with damping in both directions. After things calm down the shock returns precisely to its original length. Computer simulation and test results are included.