Featured Technical Papers
Seismic Testing of Full Scale Fluid Viscous Dampers
Reduction of Shock Response Spectra Using Various Types of Shock Isolation Mountings
History, Design, and Applications of Fluid Dampers in Structural Engineering
U.S. Design of Structures with Damping Systems
Damper Retrofit of the London Millennium Footbridge -- A Case Study in Biodynamic Design
Modular Tuned Mass Damper Units for the Spring Mountain Road Pedestrian Bridges
Structural Control using Hybrid Spring-Damper Isolator with Integral Gapping Function.
Structural Performance Enhancement with Integral Spring -Damper Elements- Four Case Studies
Using Modern Technology for the Prevention of Earthquake Damage in Buildings and Bridges
A Study in the Long-Term Performance of Specialized Low Friction Hermetically Sealed Fluid Viscous Dampers under Nearly Continuous Operation on a Pedestrian Bridge
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- Design of Structures with Dampers per ASCE 7-16 and Performance for Large Earthquakes
An impediment to the use of seismic protection devices has been the difficulty for practicing engineers to design buildings with isolation system or damping devices. ASCE/SEI task committees charged with development of new generation of codes for seismic design and retrofit of buildings have updated the relevant code sections with one goal being to encourage the use of such devices.
- Seismic retrofit and FEMA P-58 risk assessment of mid-rise soft-story concrete towers: Kit Miyamoto, Ph.D., S.E., Amir SJ Gilani, Ph.D., S.E. and Lon Determan, S.E.
The two frame office towers, constructed in the 1970s per the 1967 edition of the UBC, use perimeter reinforced concrete moment frames to resist seismic loading. The buildings are rectangular in plan and have certain characteristics that adversely affect their seismic performance, in particular the presence of a soft-story response at the first floor (approximately 50% taller than typical floors), and limited ductility typical of buildings of that era. Risk analysis showed that for the towers the PML exceeded 20%. Nonlinear response history analysis (NLRHA) of the towers was conducted and showed that in the existing configuration, the story drift ratios (SDRs) at the first floor exceeded 2%, shear hinging of the first floor beams was expected and that the SDRs would need to be reduced to approximately 1.4% for the first floor to limit the extent of nonlinear response. Seismic retrofit included addition of 300-kip viscous dampers in both directions to the first floor of the building.
- Sustainability in Soft Weak Open Front Buildings: F.H. Schott, D.A. Lee, J. Karns and M.D. Symans
Soft weak open front (SWOF) buildings often perform poorly in earthquakes. Two examples are buildings with a street facing garage, or commercial facilities with extensive open display windows. The poor performance of SWOF structures can consist of complete loss of use or even total collapse. This paper presents an approach to protecting such structures via the addition of an energy dissipation system (viscous dampers) such that peak inter-story drifts are limited to about 1% under relatively severe seismic events, thus keeping the deformations within the elastic range. With this addition of damping, earthquake survivability of this class of structures increases significantly. A series of seismic analyses are presented herein to demonstrate the potential performance of the damping system. In addition, a variety of damper installation configurations that provide enhanced energy dissipation are discussed.
- Wind Effects on Long Span Cable Stayed Bridges: Assessment and Validation – N. Jones, E. Ozkan
The well known collapse of Tacoma Narrows Bridge in 1940 clearly identified the importance of aeroelastic effects on long span bridge performance. Extensive research has been carried out since then to better understand the effects of wind on long span bridges, producing various analytical response prediction techniques. An example of the application of such techniques is presented. However, due to challenges related with full scale measurements, these prediction techniques have commonly been validated using only wind tunnel experiments. Recent research has revolved around the conduct of long term full scale measurements on a cable stayed bridge to compare actual bridge performance with those of analytical predictions. In order to ensure the reliability of predicted response, the input parameters, such as wind conditions at the site and modal properties of the bridge are also calibrated using corresponding measured quantities. This paper summarizes some of the preliminary results and outlines their implications.
- Validation of the 2000 NEHRP Provisions' Equivalent Lateral Force and Modal Analysis Procedures for Buildings with Damping Systems – O. Ramirez, M. Constantinou, A.Whittaker, C. Kircher, M. Johnson, C. Chrysostomouf
Equivalent lateral force and modal analysis procedures for yielding buildings with damping systems were developed, validated, and incorporated in the 2000 NEHRP Provisions. Key to the implementation of the procedures was the validation process that demonstrated the accuracy of the proposed procedures. The procedures for implementing yielding, viscoelastic, linear viscous, and nonlinear viscous dampers were tested using the results of nonlinear response history analysis on sample three- and six story frames and were found to be robust.
- Torsional Control of Two Adjacent Office Buildings using Viscous Dampers – W. Gates, G. Hart, H. Mabramzadeh, S. Huang, D. Lee, L. Jacobson
Two adjacent wings of a three story office building in Southern California were found by analysis to be excessively responsive in torsion under an earthquake on the near-by Newport-Inglewood fault, some five miles from the site. The generous 4.5" seismic separation between the two office building segments was found to be inadequate to prevent heavy pounding even in a moderate event, having a high probability of occurrence at this location. A variety of structural retrofit schemes were evaluated to mitigate the excessive torsional responses of the two building segments. These included converting the perimeter gravity frames to moment resisting frames, adding diagonal bracing to the perimeter frames, tying the two structures together at each floor level, and using viscous dampers as attachments between the buildings. The best solution from a cost, schedule, construction disruption, and earthquake performance standpoint, turned out to be joining the two building segments with horizontally oriented viscous dampers at a single floor level. This paper describes the analysis and retrofit solution that was used, and discusses the advantages and disadvantages of the retrofit options studied.
- Use of Motion Amplification Devices and Fluid Dampers to Reduce the Wind Induced Response of Tall Buildings – R. McNamara
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.
- Shock Control of Bridges in China using Taylor Devices’ Fluid Viscous Dampers – C. Yongqi, M. Liangzhel, C. Tiezhu, R. Schneider, C. Winters
Fluid Viscous Devices have been found to be a highly effective protection system for bridges. Introduced to China in 1999, the Taylor Devices damper systems have been successfully installed or will be installed in both large and super large bridges in China for protection from earthquake, wind, vehicle and other vibration. Seventeen different bridge projects include the Sutong Yangtze River Bridge, the longest cable stayed bridge in the world, the Nanjing 3rd Yangtze River Bridge, the fifth longest suspension bridge in the world, and the Xihoumen across Sea Bridge, the second longest suspension bridge in the world. The performance of the bridges and dampers have been reported as "very good" during the May 12, 2008 Wenchuan earthquake. All of the dampers produced have been subjected to rigorous static and dynamic testing, which show the dampers will perform well for the next 50 years and possibly much longer.
- Application of Energy Dissipation Technology for Retrofitting Steel Structures with Vulnerable Pre-Northridge Connections – O. Waqfi, R. Hamburger, R. Kanitkar
Prior to the 1994 Northridge earthquake, modern welded moment resisting steel frame structures were regarded as highly resistant to earthquake induced damage and few engineers regarded earthquake induced collapse of such structures as credible. This paradigm changed following the 1994 Northridge, California and 1995 Kobe, Japan earthquakes, creating a new class of potentially hazardous structures. In response to this new information, the Federal Emergency Management Agency retained a consortium of the Structural Engineers Association of California, the Applied Technology Council and the California Universities for Research in Earthquake Engineering, known as the SAC Joint Venture, to research the cause of the unexpected poor performance of these buildings and develop recommended design criteria. The resulting FEAM-351 publication provides performance based design criteria for the evaluation and upgrade of these structures. This paper presents the application of the FEMA-351 criteria to the design of structural upgrades employing energy dissipation technology to an existing 10-story steel structure. The East Bay Municipal Utility District (EBMUD) administration building is nine stories tall, with three below grade basement levels and a rooftop, mechanical penthouse. It was completed in 1991, employing the standard vulnerable moment connections. Alternative upgrade strategies were investigated, including modification of individual connections and application of energy dissipation criteria. The latter approach, using viscous dampers, was selected.
- Seismic Protection System and its Economic Analysis of the Beijing High Rise Building Pangu Plaza – Y. Chen, T. Cao, L. Ma, C. Iuo
Pangu Plaza, located at Beijing close to 2008 Olympic main stadium, is a 191 meter, 39-story steel high rise building. It was analyzed under earthquake and wind loads with both Fluid Viscous Dampers (FVD) and Buckling Restrained Braces (BRB or UBB) as the seismic protection system. The complete seismic response on the horizontal and vertical directions showed that the Fluid Viscous Dampers are highly effective to reduce the structural response, as well as the secondary system response. A comparative analysis of structural seismic performance and economic effect was considered, by the traditional method of increasing steel columns and beams size; by using BRB’s and by using FVD’s to absorb the seismic energy. Structural response analysis showed that using FVD’s to absorb the seismic energy made the structure satisfy the Chinese seismic design code for the "rare" earthquake and also greatly improved the seismic performance. Economic analysis showed that FVD’s were the most economic approach for both one-time direct investment and long term maintenance.
- Scissor-Jack Damper Energy Dissipation System – A. Sigaher, M. Constantinou
Installation of damping devices has been limited to diagonal or chevron brace configurations until the recent development of the toggle brace. This configuration magnifies the effect of damping devices, thus facilitating their use in stiff framing systems. This paper introduces the scissor jack damper system that was developed as a variant of the toggle-brace damper system, with the added advantage of compactness. The effectiveness of the scissor jack configuration is demonstrated through testing of a large scale steel framed model structure on an earthquake simulator. Experiments showed that despite the small size of the damping device considered, the scissor jack system provided a significant amount of damping and substantially reduced the seismic response of the tested structure. Response history and simplified analyses produce results that are consistent with the experimental results.
- Roof Isolation System to Reduce the Seismic Response of Buildings: A Preliminary Assessment – R. Villaverde
A roof isolation system is proposed as a means to reduce the detrimental effect of earthquakes in buildings. This roof isolation system entails the insertion of flexible laminated rubber bearings between a building's roof and the columns that support it and the addition of viscous dampers connected between the roof and the rest of the building. The properties and dimensions of the rubber bearings and viscous dampers are selected in a way that makes the roof, bearings, and dampers form a highly damped vibration absorber. Presented also is a comparative study with a simple five story steel building under a strong earthquake ground motion that is carried out to assess the effectiveness of the proposed system. In this comparative study, it is found that the roof isolation scheme reduces the floor displacements and interstory drifts of the analyzed building by as much as 83 percent. On the basis of these results and in view of its simplicity, it is concluded that the proposed roof isolation system has the potential to become a practical and effective way to reduce earthquake damage in buildings.
- Optimized Damping Device Configuration Design of a Steel Frame Structure Based on Building Performance Indices – W. Li, M. Tong, Y. Wu, G. Lee
Energy dissipation devices (EDDs) have been accepted as one of the viable strategies for enhancing the seismic performance of building structures. However, current design provisions do not provide guidelines for optimizing the EDD configurations. For many building structures an efficient configuration of EDDs may provide considerable performance improvement. Similarly, an optimized configuration may reduce the number of EDDs required to achieve a target performance objective. In this paper an existing building with added linear viscous dampers is redesigned based on different performance index optimization. The results indicate that the optimal device configurations are highly related to the dynamic properties of the structure and its required performance index. In one instance, where the cost is the major concern and a performance requirement is placed on story drift limitation, the total device damping coefficient can be reduced by 26%.
- A Simple Method for the Design of Optimal Damper Configurations in MDOF Structures – D. Garcia
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.
- Experimental Study of RC Building Structures with Supplemental Viscous Dampers and Lightly Reinforced Walls – H. Tsai, Shiang-Jung Wang et al
This paper describes an experimental evaluation of viscous dampers used to reduce seismic motion in reinforced concrete moment-resisting building structures. Common practice in Taiwan is to use lightly reinforced concrete exterior walls and interior partition walls, which not considered for their contribution of stiffness and strength in the design process. As these additional walls greatly reduce relative story displacement and velocity, it has been suspected that the effectiveness of supplemental dampers would be very limited. However, the test results show that a new displacement multiplying mechanism, the toggle brace damper system, is effective even with a small relative story drift in the seismic response control of the structure. Dampers produce significant force and displacement reduction in the moment-frame structures that were investigated.
- Energy Dissipation Systems for Seismic Applications: Current Practice and Recent Developments - M.D. Symans, A.M. ASCE; F.A. Charney, F. ASCE; A.S. Whittaker, M.ASCE
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.
- Coupled Truss Walls with Damped Link Elements – A. Rahimian
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.
- Rehabilitation of a 1985 Steel Moment Frame Building – G. Haskell
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.
- U.S. Code Development of Structures with Damping Systems – R. Hanson, K. Miyamoto
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.
- Seismic Performance of Light-Framed Wood Structures with Toggle Braced Fluid Dampers – J. Shindel, M. Symans
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.
- Fluid Dampers for Seismic Protection of Woodframe Structures – M. Symans, W. Cofer, Y. Du, K. Fridley
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.
- Base Isolation and Supplemental Damping Systems for Seismic Protection of Wood Structures: Literature Review – M. Symans, W. Cofer, K. Fridley
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.
- Shock Design of the MK 49 Ship’s Inertial Navigation System (SINS) – J.R. Brazell, D.K. Bruce, G.T. Mayer
The Sperry Marine MK 49 Ship's Inertial Navigation System (SINS) is now in production for marine surface and subsurface applications. This system has been selected as the standard NATO SINS equipment and is the only marine inertial navigator which utilizes ring laser gyros. In order to serve the NATO community, the system must withstand a variety of shock stimuli (STANAG 4141, STANAG 4142, BR3021, etc.). Sperry Marine has shock hardened the system enclosures and developed a shock isolation system for the Inertial Measurement Unit (IMU) using tension compression liquid spring/dampers in a hexapod configuration. This isolator assembly provides the shock attenuation and precision angular alignment return ability that is needed to meet the above specifications. This paper addresses the design process to shock harden the IMU and presents experimental results.
- Mitigation of Military High Shock Transients for Shipboard Gyrocompass with Fiber Optic Gyros (FOG) – J. Lahham, S. J. Ryan, D. J. Wigent, M. W. Mosher, A. Klembczyk
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).
- Hold onto Your Seat – M. Burnett
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.
- Full-Scale Shake Table Tests of 5-Story Steel Building with Various Dampers – K. Kasai, H. Ito, Y. Ooki, T. Hikino, K. Kajiwara, S. Motoyui, H. Ozaki, M. Ishii
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.
- Applicability of Seismic Protective Systems to High Tech Industrial Structures – J.S. Hwang, Y.N. Huang, Y.H. Hung, J.C. Huang
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.
- A Living or Smart Building: The Guangzhou Tower – G. Hart, A. Jain, C.G. Ekwueme
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.
- Fluid Viscous Dampers: An Effective Way to Suppress Pedestrian-Induced Motions in Footbridges – P. Duflot, D. Taylor
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.
- Experience and Practical Considerations in the Design of Viscous Dampers – P. Duflot, D. Taylor
This paper describes how viscous dampers work, and how they significantly reduce seismic excitation in structures.
- Energy Management Utilizing the Hydraulic Shock Absorber – D. Taylor
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.
- 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 – M. Mosher, A. Klembczyk
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.
- Structural Control using Hybrid Spring-Damper Isolation with Integral Gapping Function – D. Taylor, J. Metzger
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.
- Introduction to Shock and Vibration Isolation and Damping Systems – A. Klembczyk
This paper presents an introduction to shock and vibration isolation of complex structures and mechanisms. It provides an outline of various ways to provide isolation, shock absorbing and damping within a wide array of dynamic systems and structures. This paper presents key definitions that are widely used within the shock and vibration community. Additionally, useful formulae are presented that provide the user with an approach to typical problems. Finally, a comparison of different types of shock isolators, shock absorbers and dampers compares their advantages and disadvantages for use in the commercial, military, and aerospace sectors.
- Taylor Devices Hermetic Dampers Description, Applications and Design – D. Taylor
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.
- Modular Tuned Mass Damper Units for the Spring Mountain Road Pedestrian Bridge – D. Taylor, J. Metzger, D. Horne
Modern pedestrian bridges tend to be long and slender, usually causing relatively low frequency primary modes of vibration. This type of structure can be excited to resonance by synchronized crowd footfall. Added damping is often required to prevent excessive structural motions and loadings. This paper describes the Modular Tuned Mass Dampers used to provide the required added damping for the three Spring Mountain footbridges in Las Vegas.
- Seismic Protection with Fluid Viscous Dampers for the Torre Mayor, A 57-Story Office Tower in Mexico City, Mexico – D. Taylor, I. Katz
The new 57 story Torre Mayor Building is the now the dominant structure in the Mexico City skyline. It is also the first tall building to utilize large Fluid Viscous Dampers as a primary means of seismic energy dissipation. A total of 98 dampers are used, including 24 large dampers, each rated at 570 tonnes of output force, located in the long walls of the building. The short walls utilize 74 smaller dampers, each rated at 280 tonnes of output force. The damping technology successfully implemented for Torre Mayor is now being used on five other tall buildings, including three in the USA, and two in Japan.
- Seismic Rehabilitation of a Historic Concrete Structure with Fluid Visco-Elastic Dampers – K. Miyamoto, L. M. Determan, A. Gilani, R. Hansen
This paper presents the nonlinear seismic analysis, development, and implementation of an innovative seismic retrofit strategy for a six story nonductile reinforced concrete 145,000 square foot historic building. Dynamic and nonlinear static analytical results verified that the building had a weak soft story with inadequate post yield capacity and large torsional response. Hotel Stockton, in Stockton, CA, is also torsionally irregular. The analysis indicated that the existing building was not seismically adequate to withstand anticipated lateral forces generated by earthquake excitations at the site. A "collapse prevention" performance upgrade for a 475-year return event was developed. Nonlinear fluid viscous dampers were placed at the first story level to reduce the seismic demand and obtain a more uniform response. Viscoelastic fluid viscous dampers were strategically placed at one side of the building to reduce the torsional irregularity of the building. This cost effective retrofit significantly improved the seismic performance of the building.
- Analysis, Optimization and Development of a Specialized Passive Shock Isolation System for High Speed Planing Boat Seats – M. Mosher, A. Klembczyk
The Mk V Special Operations Craft (SOC) is used to carry Special Operations Forces (SOF) into and out of combat operations. During operation, particularly during extended training missions, the passengers and crew have reported numerous cases of musculoskeletal injuries from operation in high sea states. This paper describes the analysis, development and operational testing of a highly specialized, non-linear, passive shock isolated seat for this craft. Initial sea trial testing of the isolation system resulted in positive operator feedback that correlated well with earlier field measurements and also validated the analytical predictions.
- History, Design and Applications of Fluid Dampers in Structural Engineering – D. Taylor
This paper is a shortened version of Paper 56, BUILDINGS: DESIGN FOR DAMPING – D. TAYLOR. It shows four examples of recent structures which use dampers.
- U. S. Design of Structures with Damping Systems – K. Miyamoto, R. Hanson
This paper presents an earthquake design procedure and a case study of the Vacaville Police Headquarters. The design goal for this essential facility was to provide immediate occupancy after a 475-year return seismic event. The project also required construction cost within typical code conforming buildings. A combination of Special Moment Resisting Frames (SMRF) and Fluid Viscous Dampers (FVDs) was used as the lateral force resistance system. This system, as described by Gimmel, Lindorfer, and Miyamoto, (2002) results in cost efficiency and superior seismic performance. The 2000 NEHRP (FEMA, 2000) guideline was used to design the project, since it is considered to be a state-of-art procedure for seismic damping devices. This project was the first structure in the United States to use this advanced procedure.
- Damper Retrofit of the London Millennium Footbridge-A Case Study in Biodynamic Design – D. Taylor
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.
- Viscous Damper Development and Future Trends – D. Lee, D. Taylor
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.
- Retrofit of a Metropolitan Midrise to Improve Torsional Response using Non-Linear Fluid Viscous Dampers – M. Gemmill, K. Lindorfer, K. Miyamoto
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.
- Virtual Base Isolation by Building Softening with Drift Control Provided by Fluid Viscous Dampers – M. Gemmill, K. Lindorfer, K. Miyamoto
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.
- Structural Control of a Building using a Tuned Mass with Integral Hermetically Sealed, Frictionless Hydraulic Dampers – B. Breukelman, A. Klembczyk
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.
- A Numerical Investigation of Combined Shock and Vibration Isolation through the Semi- Active Control of Magnetorheological Fluid Damper in Parallel with an Air Spring – M. Mosher, T. Tanner
Combining shock and vibration isolation into a single isolation mount is investigated numerically through the use of the Bouc-Wen model of a magnetorheological fluid damper in parallel with an air spring. The stability and dissipative capabilities of the Bouc-Wen model are proven mathematically. The response characteristic of this hybrid isolator to shock and vibration inputs is explored. The advantages of combining shock and vibration isolation into a single package is discussed. It is possible, using this technique, for a single device to perform equally well as a shock and a vibration isolator.
- Fluid Lock-up Devices – A Robust means to Control Multiple Mass Structural Systems Subjected to Seismic or Wind Inputs – D. Taylor
Fluid Lock-up Devices have recently become popular for passive control of large structures subjected to earthquake or wind storm effects. The Lock-up Device, a variation of the Fluid Viscous Damper, allows unrestricted motion at low translational speeds. When a transient event occurs the Lock-up Device activates and forms a rigid connection. After the transient event the Lock-up Device reverts to low force output, permitting structural sections to thermally expand or contract without added stress. The operation of the device is completely passive. It enables multi-mass structures to be dynamically braced without resorting to the cost and complexity of an active actuator system.
- Test Report for 50 Tonne Force Viscous Damping Devices (Taylor Devices Part Number 67DP-16394-01 – Test Report 00/2/15)
This test report describes the dynamic testing under sinusoidal excitation of a large viscous damper.
- Viscous-Damper with Motion Amplification Device for High Rise Building Applications – R. McNamara, C.D. Huang, V. Wan
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.
- Structural Control of Dynamic Blast Loading using Fluid Viscous Dampers – K. Miyamoto, D. Taylor
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.
- Buildings: Design for Damping – D. Taylor
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.
- Experimental Study of Bridge Elastomeric and other Isolation and Energy Dissipation Systems with Emphasis on Uplift Prevention and High Velocity Near-Source Seismic Excitation – M. Constantinou, A. Kasalanati
A series of shake table tests on an isolated bridge model included low and high damping elastomeric isolation systems, and low damping elastomeric systems with added linear and nonlinear viscous dampers. Each of these configurations could withstand much stronger seismic excitations than the non-isolated configurations. A set of low intensity tests was conducted to form a basis for comparison with the non-isolated configurations and also to test the effectiveness of these systems under low intensity excitation. The results of these tests are presented, followed by a discussion of the effects of scragging, the benefits of seismic isolation, and the significance of damping, the importance of added damping in near source seismic excitation and on the benefits and drawbacks of using nonlinear viscous damping.
- Taylor Fluid Viscous Dampers Protect Against Earthquake Damage – Here’s how it Works
This article from Bridge Builder magazine shows how Taylor Devices dampers reduce seismic response of bridges.
- SEAOC Energy Dissipation Committee Appendix A: Guidelines for Buildings using Passive Energy Dissipation Systems
This set of provisions provides minimum design requirements for the incorporation of passive energy dissipation devices in buildings. Energy dissipation devices (also termed damping devices) reduce global and interstory seismic displacement response of structural systems, but may either increase or decrease seismic stresses and accelerations within structural systems. They provide a controlled increase in structural damping, and may also result in an increase in structural stiffness or change in participating mass. Passive energy dissipation systems do not require active control by electrical, pneumatic or hydraulic systems. Buildings designed in conformance with these provisions must also be designed in accordance with all other applicable provisions of the Uniform Building Code, except as specifically defined in this appendix. Design must consider the combined behavior of all elements of both the Lateral Force Resisting System (LFRS) and the Energy Dissipation System (EDS). Energy dissipation devices must not form part of the gravity load - resisting system.
- Developing and Testing of an Improved Fluid Damper Configuration for Structures having High Rigidity – D. Taylor, M. Constantinou
Structures with high rigidity experience relatively small deflections and interstructural velocities under seismic shock. This means that conventional energy dissipation devices may not be feasible or cost effective. An improved damper configuration has been investigated, utilizing a toggle mechanism to magnify internal structural deflections. This provides a more effective way to add damping to a stiff structure. Experimental results were obtained from a 32,000 lb. test structure utilizing two fluid dampers and two toggle brace elements. Test inputs included around eighty individual earthquake transients, varying both in wave form and intensity. The results demonstrated the ability of the toggle mechanism to magnify displacements significantly. The toggle brace damping system appears to be an excellent solution to the addition of supplemental damping devices to rigid structures of all types. Advantages include relatively low damper cost, a simple bracing element design, and low installation cost.
- Applications of Hermetically Sealed Fluid Dampers for Low Level, Wide Bandwidth Vibration Isolation – A. Klembczyk, M. Moser
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.
- Testing and Modeling of an Improved Damper Configuration for Stiff Structural Systems – M. Constantinou, P. Tsopelas, W. Hammel
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.
- Seismic Testing of a Building Structure with a Semi-Active Fluid Damper Control System – M. Symans, M. Constantinou
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.
- Arrowhead Regional Medical Center – An Advertising Supplement to F. W. Dodge, A Division of the McGraw-Hill Companies, Inc.
This article describes every aspect of the design and construction of the Arrowhead Regional Medical Center, including the use of base isolators and viscous dampers to insure continuous operation even after a major seismic event. The article even includes many of the financial aspects of this huge project.
- Development and Testing of an Electronically Controlled Shock and Vibration Damper having an Electrorheological Fluid Medium – D. Taylor, N. Makris
An electrorheological (ER) fluid has been developed comprised of zeolite particles suspended in silicone oil. Testing of this fluid in a damper of 1,000 lbs. nominal output force rating has demonstrated the ability to control damper output with internal pressures above 500 psi and control power requirements of less than one watt. The damper control valve is a simple ER duct, with no moving parts, requiring only that a voltage potential exists across the duct's cross section to activate the ER material, and thus cause the material to exhibit plastic behavior. All tests were successful, with no degradation of the damper or ER material occurring over large numbers of activation cycles or with time.
- Design of Steel Pyramid using Fluid Viscous Dampers with Moment Frames – K. Miyamoto, R. Scholl
The Eleven story 450,000 ft2 pyramid shaped office building described in this article was one of the first new buildings in the United States to use Seismic Dampers. This National Headquarters for a financial institution is located in West Sacramento, CA. The basic lateral force resisting system of the building consists of steel moment frames. In addition, approximately 15% of critical damping was provided using Fluid Viscous Dampers (FVD) in order to reduce displacement and acceleration. The steel moment frames were designed to remain well below the yield strength, and the story drift ratio was limited to 0.005 to protect the welded moment connections for the Design Basis Earthquake (DBE). Earthquake performance, cost effectiveness, and architectural requirements were the primary concerns in designing this building.
- Electrorheological Damper with Annular Ducts for Seismic Protection Applications – N. Makris, S. Burton, D. Taylor
This paper presents the design, analysis, testing and modeling of an electrorheological (ER) fluid damper developed for vibration and seismic protection of civil structures. The damper consists of a main cylinder and a piston rod that pushes an ER fluid through a stationary annular duct. The basic equations that describe the fluid flow across an annular duct are derived. Experimental results on the damper response with and without the presence of electric field are presented. A combination of a simple phenomenological model and a neural network is proposed as a practical tool to approximate the nonlinear and velocity dependent damper response.
- Fluid Viscous Damping as an Alternative to Base Isolation – G. Haskell, D. Lee
Base isolation of large structures has proven to be an effective way to attenuate seismic excitation. However it can be costly, and can also involve major building modification. It is now possible to attain a comparable degree of earthquake mitigation with fluid viscous dampers located throughout a structure, without having to isolate the building. This paper describes several techniques for doing this, provides analytical back-up and describes several applications of this technology.
- Pre-Qualification Testing of Viscous Dampers for the Golden Gate Bridge Seismic Rehabilitation Project
This report presents the results of the testing of a viscous damping device provided to the Earthquake Engineering Research Center (EERC) of the University of California at Berkeley for pre-qualification testing as part of the seismic rehabilitation of the Golden Gate Bridge. In all, four different viscous dampers from four different manufacturers were tested in the prequalification program. This report presents the test results for the damper denoted Damper C. The test results for the other three dampers, Dampers A, B, and D, are presented in separate reports. Conclusions were that Damper C performed consistently and well throughout the entire testing/pre-qualification program. This report also includes a complete specification for production dampers for this project.
- Fluid Dampers for Applications of Seismic Energy Dissipation and Seismic Isolation – D. Taylor, M. Constantinou
SUNY Buffalo has conducted extensive evaluation of fluid viscous dampers including development of an analytical model of the damper, computational models of structures including dampers and a number of experimental verifications. This paper describes this program, along with a history of viscous dampers and a description of some projects that use them.
- Sample Technical Specifications for Viscous Damping Devices and Lock-Up Devices
This sample specification can be used for a variety of viscous dampers. It covers material, performance, testing and inspection.
- Energy Dissipation Devices in Bridges using Hydraulic Dampers – E. Delis, R. Malla, M. Madani, K. Thompson
Specially designed energy dissipation systems are well known for improving seismic performance of structures by absorbing earthquake induced energy. In this paper, the use of linear and nonlinear hydraulic dampers is investigated in a bridge application. A two-span, skewed, cast-in-place prestressed concrete bridge with an outrigger bent is examined. The bridge is located in a highly seismic area of Southern California. It is observed that dampers alleviate the torsional movement and reduce the transverse and longitudinal movements of the superstructure.
- Seismic Evaluation and Retrofitting of U.S. Long-Span Suspension Bridges – ASCE Subcommittee on Seismic Performance of Bridges
This paper is a first attempt to raise issues about the seismic evaluation and retrofitting of longspan suspension bridges in the United States. The issues discussed in this paper deal seismic hazards and risks; performance and design criteria; ground motions; geotechnical engineering, substructure mathematical modeling, and soil structure interaction (SSI); actual conditions of structural components; superstructure mathematical modeling; ambient vibration testing; analysis of superstructure; suspension bridge component vulnerabilities; instrumentation and monitoring; laboratory testing; retrofitting; and the effects of limited funding and time constraints.
- Damping Devices for Earthquake Protection of Residential Structures – R. Langenbach
A set of four viscous dampers plus a unique pile foundation system provides seismic protection for a wood frame house in Oakland, CA. This paper describes both the technical aspects of this design and the costs.
- Testing Procedures for High Output Fluid Viscous Dampers used in Building and Bridge Structures to Dissipate Seismic Energy – D. Taylor, M. Constantinou
This paper describes the use of viscous dampers to protect structures from seismic damage and also describes the development of test procedures for very large viscous dampers.
- Viscous Damping for Base Isolated Structures – S. Hussain, D. Lee, E. Retamal
Seismic Base Isolation can use elastomeric pads, sliding plates or inverted pendulums. Each method can include an energy dissipation means, but only as some kind of hysteretic damping. Hysteretic damping has limitations in terms of energy absorption and may tend to excite higher modes in some cases. It’s possible to avoid these problems with viscous dampers. Viscous damping adds energy dissipation through loads that are 90o out of phase with bending and shear loads so even with damping levels as high as 40% of critical adverse side effects tend to be minimal. This paper presents basic theory of viscous damping and also describes a sample project. Viscous dampers being built for the new San Bernardino Medical Center reduce both deflections and loads by 50% compared with high damping elastomer base isolation bearings by themselves.
- Seismic Rehabilitation of a Historic Non-Ductile Soft Story Concrete Structure using Fluid Viscous Damper – K. Miyamoto, R. Scholl
Hotel Woodland is one of the first structures in North America to be seismically retrofitted using viscous dampers. This four story 1927 vintage Historical Landmark reinforced concrete building is located in Woodland, California. It was essential to improve the earthquake response performance of the building and minimize cost while maintaining the historical appearance of the building. This paper presents the processes and decisions regarding retrofit criteria and design procedure for earthquake demand, building response performance, historical interests, and economic considerations.
- Fear of Trembling – The Economist Brochure
This article describes the effects of both the Kobe earthquake and the Northridge earthquake in detail, including technical and economic details. It also discusses building codes and practices and what is being done around the world to lessen the risk of severe seismic damage.
- Martin Marietta Fluid Viscous Damper Study, Oak Ridge Plant – C. Winters
This non-published report describes the seismic analysis of a building at Oak Ridge, TN. It shows that the addition of viscous dampers to this structure provides adequate seismic protection.
- Application of Fluid Viscous Dampers to Earthquake Resistant Design – M. Constantinou
This article summarizes the extensive viscous dampers investigation performed by NCEER at State University of New York, Buffalo Campus. This included computer modeling of both the dampers and complete isolated systems, along with shake table testing and correlation of results. The article also describes a very large damper projects; dampers + base isolation for a set of five hospital buildings near San Bernardino, CA.
- Technical Report NCEER-94-0020, Study of Seismic Isolation Systems for Computer Floors – V. Lambrou, M. Constantinou
This report describes the development and testing of a computer floor seismic isolation systems which uses existing devices developed for the seismic isolation of buildings and shock isolation of military equipment. A computer floor system with raised floor and a generic slender equipment cabinet was constructed. It was isolated by spherically shaped sliding bearings and was highly damped either by utilizing high friction in the bearings or by installing fluid viscous dampers. The spherically shaped bearings provided the simplest means of achieving long period in the isolation system under low gravity load. The isolation system prevented rocking of the cabinet on top of the isolated floor and substantially reduced its acceleration response in comparison to that of a conventional computer floor. An analytical study was also conducted in order to extend the results to a range of parameters which could not be tested.
- Technical Report NCEER-94-0014, Experimental and Analytical Study of a System Consisting of Sliding Bearings and Fluid Restoring Force/Damping Devices – P. Tsopelas, M. Constantinou
This report describes an experimental study of the behavior of a bridge seismic sliding isolation system consisting of flat sliding bearings and fluid restoring force/damping devices. Earthquake simulator tests were performed on a model bridge structure both with isolators and without. The experimental results demonstrate a marked increase of the capacity of the isolated bridge to withstand earthquake forces. Analytical techniques are used to predict the dynamic response of the system and the obtained results are in very good agreement with the experimental results.
- Technical Report NCEER-92-0032, Experimental and Analytical Investigation of Seismic Response of Structures with Supplemental Fluid Viscous Dampers – M. Constantinou, M. Symans
This 206 page report presents the results of an extensive study on fluid viscous dampers. A series of component tests with various dynamic inputs was performed to determine the mechanical characteristics and frequency dependencies of the dampers. In addition, temperature dependencies were evaluated by varying the ambient temperature of the damper during component testing. Based on these component tests, a mathematical model was developed to describe the macroscopic behavior of the damper. Earthquake simulation tests were then performed on one story and three story steel structures both with and without dampers. The addition of supplemental dampers significantly reduced the response of the structure for both interstory drift and shear forces. The experimental responses correlated well with analytical predictions.
- Questions Concerning Seismic Isolation of Hospitals – D. Taylor
This discussion describes why base isolation is effective for seismic protection of hospitals and how the addition of damping works to maximize its effectiveness.
- University at Buffalo – Taisei Corporation Research Project on Bridge Seismic Isolation Systems – M. Constantinou, S. Fuji, P. Tsopelas, S. Okamoto
This paper describes the first part of a project to produce a class of passive sliding seismic isolation systems for bridges. This includes experimental verification of the systems by large scale shake table testing, analytical techniques for interpretation of the experimental results, and design procedures for sliding bridge isolation systems. A quarter length scale bridge model was tested on a shake table. Restoring force was provided by various means. First, spherically shaped sliding bearings (known as FPS bearings) were used to provide restoring and frictional forces within a compact unit. Next, flat sliding bearings were combined with various devices placed between the deck and the pier to provide restoring force and additional energy dissipation capacity. These devices were in the form of: a) arc-shaped rubber elements between a moving central rod and a cylindrical housing, b) wire rope springs, c) fluid spring-damper devices and d) fluid viscous dampers.
- Testing Procedures for High Output Fluid Viscous Dampers used in Structures to Dissipate Seismic Energy – D. Taylor, M. Constantinou
This paper describes the dynamic testing of a 320 kip viscous damper using both sinusoidal excitation and a drop test machine. Correlation was excellent, showing that drop testing can be used to test very large dampers.
- Test Methodology and Procedures for Fluid Viscous Dampers used in Structures to Dissipate Seismic Energy – D. Taylor, M. Constantinou
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.
- Destruction Caused by the Quasi-Resonance Effects Observed in the Loma Prieta Earthquake On October 17, 1989
This paper describes the widespread destruction caused by the Loma Prieta earthquake in the San Francisco Bay Area. It deals extensively with some of the worst damage, which was the destruction of huge circuit breakers. The article discusses how the repetitive nature of the seismic input excited resonance in many structures.
- Semi-Active Fluid Viscous Dampers for Seismic Response Control – M. Symans, M. Constantinou, D. Taylor, K. Garnjost
The addition of passive damping to a structure greatly increases its earthquake resistance. It is possible to get further increase through an active or semi-active control system for the dampers. Semi-active damping is preferred due to low external power requirements and fail-safe operation. This paper describes the history of the successful use of semi-active fluidic control devices in military applications and how this technology has been adapted to earthquake hazard mitigation. Testing of a semi-active continuously adjustable damping device through fluid orificing is described. Mathematical models of the behavior of the device are also presented.
- Selected Production History High Capacity Taylor Devices Dampers and Energy Dissipators
This description of projects using Taylor Viscous Dampers is dated 1996 and includes only projects up to that time. Since then we have provided dampers for over 300 structures throughout the world. For the latest Project List send us a request. Go to our web site, www.taylordevices.com.
- Seismic Response of Structures with Supplemental Damping – M. Constantinou, M. Symans
This paper presents a review of supplemental damping devices used for the control of the seismic response of structures. The mechanical properties of these devices are discussed and considerations in the design of energy absorbing systems are presented. Conventional structures passively resist earthquakes through a combination of strength, deformability and energy absorption. They have very little damping, so elastic energy absorption is small. Strong earthquakes deform these structures well beyond their elastic limit through localized plastic hinging, which results in increased flexibility and energy dissipation. Most of the earthquake energy is absorbed by the structure through localized damage of the lateral force resisting system. This is somewhat of a paradox in that the effects of earthquakes (i.e. structural damage) are counteracted by allowing structural damage. Structural performance can be greatly improved if a large portion of the input energy can be absorbed, not by the structure itself, but by some type of supplemental device. This paper describes a number of ways to do this, including friction devices, yielding metal systems, elastomeric viscoelastic dampers and fluid viscous dampers.
- Seismic Isolation of Bridges (Unpublished Paper) – M. Constantinou
This unpublished paper by Dr. Michael Constaninou describes the seismic protection of a steel multi-girder highway bridge. Three types of base isolators are included; high damping rubber, lead-rubber and Friction Pendulum. The effect of added viscous damping is also investigated, and is found to greatly enhance the performance of the isolators, even though the dampers required are rather small. This classic paper is hand written by Dr. Constantinou and includes his calculations and his sketches of the bridge, isolation devices and dampers.
- Seismic Damage Control with Passive Energy Devices: A Case Study – R. McNamara
This paper presents a theoretical case study of the effectiveness of supplemental passive damping to reduce structural response to seismic excitation. A six story special moment resistant reinforced concrete frame is studied with and without the aid of supplemental dampers. Response predictions are presented for each case. Fluid dampers proved to be a very cost effective way to significantly reduce the seismic response of the building investigated. Preliminary cost estimates indicate that positive damage control can be economically achieved.
- Seismic Control of Structures with Damped Resonant Appendages – R. Villaverde
This paper shows how Tuned Mass Dampers can provide seismic protection for structures. These dampers consist of a relatively small mass, a spring, and a dashpot attached to a point of maximum vibration and in resonance with the structure to which they are attached. They are widely used to control the response of buildings, bridges, towers, chimneys and other structures to wind forces, machine vibrations and occupant activity. For the most part however, these dampers have been considered ineffective to reduce the seismic response of structures. This paper demonstrates that such devices can be used effectively to control the seismic response of structures. The paper presents a basic mechanism that explains under what conditions such dampers may work effectively under earthquake loads. It also provides recommendations for the selection of the mass, stiffness and damping factors. It includes the results of a series of numerical and experimental tests which verify that properly designed Tuned Mass Dampers effectively and consistently reduce the response of many types of structural systems to various types of earthquake excitations.
- San Bernardino County Medical Center - Specification
This specification covers the set of 186 fluid viscous dampers used on the five buildings of the new San Bernardino County Medical Center located in Colton, California. Three major faults are close to this location. The dampers operate in parallel with elastomeric base isolators, and reduce the required isolator stroke from +/- 48 inches to +/- 22 inches. This specification is very detailed and includes testing requirements.
- Rockwell Viscous Dampers - Specifications
This specification covers the set of ten linear fluid viscous dampers along with their mounting brackets and pins for the Rockwell Building located at Jamboree Road and Birch in Newport Beach, California. These dampers provide an output force in either tension of compression that is directly proportional to the relative velocity between the two ends of the dampers. The damper output force varies only with velocity and does not change with damper stroke position or orientation angle. The function of the dampers is to absorb earthquake energy, thereby reducing the amount the building moves when an earthquake occurs.
- Reduction of Shock Response Spectra using Various Types of Shock Isolation Mounts – M. Mosher
This experiment demonstrated how various types of shock absorbers can reduce the overall shock response spectra of a structure subjected to high impact shock. This was accomplished by measuring the acceleration on a weight dropped onto three different shock absorbers from various heights and analyzing the resulting data. A baseline test was performed with a steel hard mount. This was followed by tests with three different soft isolation mounts; a half inch thick neoprene pad, a urethane rubber tube on its side and a hydraulic liquid spring type shock absorber. Results show that both the dominant frequencies and the peak acceleration get lower as the isolation system gets softer. This information can be valuable in the design of isolation systems.
- Precise Positioning Shock Isolators – D. Taylor, D. Lee
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.
- Passive and Active Structural Vibration Control in Civil Engineering – T. Soong, M. Constantinou
This paper describes a large variety of passive energy dissipating devices which can be used within a structural system to absorb seismic energy. These devices can produce significant reductions of inter-story drifts in moment- resisting frames. Furthermore, these devices may under elastic conditions, reduce the design forces.
- Passive and Active Fluid Dampers in Structural Applications – M. Shinozuka, M. Constantinou, R. Ghanem
Analytical and experimental results demonstrate that the performance improvements from active control systems can also be achieved with passive and semi-active fluid dampers. However, passive or semi-active fluid dampers offer the advantages of low cost, no or minimal demand for external power, longevity and reliability.
- Long Term Life Cycle Evaluation of Taylor Devices Products – J. Dragonette
A number of Taylor Devices produced between 1956 and 1965 are kept in storage and are periodically evaluated for corrosion and deterioration. This report describes the present day condition of these dampers and shock absorbers. All are fully functional and corrosion free.
- Investigation of Light Pole Base Integrity – J. Mander, S. Chen, K. Shah, A. Madan
Light poles at Rich Stadium in Buffalo, N.Y., were showing incipient failure of their hold-down bolts, due to wind excitation. This paper describes the measures used to alleviate this problem, including the addition of viscous dampers between the stadium structure and a point around one third up on the light poles. This modification was very successful.
- Golden Gate Bridge Seismic Retrofit Design Specs
This specification, prepared jointly by TY Lin and Imbsen Associates, describes the requirements for the viscous dampers to be used in the retrofit of the Golden Gate Bridge. The specification includes wind excitation as well as seismic, and also describes testing requirements.
- Fluid Viscous Dampers in Applications of Seismic Energy Dissipation and Seismic Isolation – M. Constantinou, M. Symans, P. Tsopelas, D. Taylor
Experimental study of both a moment frame building and a single span bridge, both with and without viscous dampers, are described here. Additions of viscous dampers significantly reduced both drift and shear forces.
- Fluid Viscous Damper for Improving the Earthquake Resistance of Buildings – M. Constantinou, M. Symans, D. Taylor
This paper is a condensed version of Technical Paper
- Experimental Study of Seismic Response of Buildings with Supplemental Fluid Dampers – M. Constantinou, M. Symans
A quarter scale model of a three story steel moment frame building was tested on a shake table using time histories from a large number of earthquakes including Taft, El Centro, etc. Tests were conducted both without dampers and with varying numbers of dampers. Test results correlated well with the analytical predictions. Conclusions; viscous dampers reduced story drifts by 30% to 70%. These reductions are comparable to those achieved by other energy dissipating systems such as viscoelastic, friction and yielding steel dampers. However, the use of fluid dampers also reduced story shear forces by 40% to 70%, while other energy absorbing devices showed no significant reduction.
- Electrorheological Fluid Dampers: Testing, Modeling and Applications in Vibration – N. Makris, D. Hill, D. Taylor
This paper describes an NSF funded project to investigate viscous dampers with controlled variable damping constant, using electrorheological fluid. Experimental results correlate well with analytical predictions.
- Earthquake Protective Systems for Buildings, Bridges and other Structures – Taylor Devices Brochure
This is a one page description of Taylor Devices viscous damping systems for earthquake protection.
- Commentary on Corrosion at Bimetallic Contacts and its Alleviation – BSI Standards
This document shows designers how to avoid corrosion due to the interaction of different metals and alloys at bimetallic contacts. Section one describes the conditions that lead to corrosion at bimetallic contacts and methods to alleviate it. The tables in Section two show the degree of corrosion likely to occur at bimetallic contacts exposed to atmosphere and water.
- Bridge Design Example for 2nd US-Japan Workshop on Protective Systems for Bridges – M. Constantinou, P. Tsopelas
This paper reports on a non-linear analysis of a bridge supported on sliding bearings with elastomeric restoring springs and viscous dampers. Results were verified with shake table tests.
- The Application of Energy Dissipating Damping Devices to an Engineered Structure or Mechanism – D. Taylor
The design of a structure or mechanism subjected to shock and vibration can be greatly improved by the addition of isolation or damping devices. Improvements Include: Reduced Deflection and Stresses, Reduced Weight, Improved Biodynamics, Longer Fatigue Life, Architectural Enhancement and Reduced Cost.