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Technical Papers

Review Our Complete Collection of Industry Technical Papers

We have compiled an extensive list of useful information and industry technical papers for your convenience. Whether you are interested in a case study from a recent projects, want to learn more about the latest trends from a white paper written by one of our engineers, or you’re a numbers junky and looking for technical brief, we have something for everyone.  

White Paper

119. A prescriptive method for the design of new steel moment frame structures with supplemental damping

This paper presents a prescriptive method for the design of new steel moment frame structures with supplemental damping using fluid viscous dampers (FVDs). The prescriptive method uses Modal Response Spectrum Analysis (MRSA) instead of Nonlinear Response History Analysis (NLRHA) as the basis for evaluation. Additionally, the procedure decouples the design of the moment frame from the damper frame, reducing design iterations. This makes the use of FVDs in new buildings easier to evaluate at schematic level design and significantly reduces the effort for full design. The procedure produces a 25% viscous damping ratio at the Design Earthquake (10% probability of exceedance in 50 years) and requires the use of nonlinear dampers with a damping exponent, alpha of 0.4.

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White Paper

118. A review of the state of practice for fluid viscous damper applications in North America and New Zealand

This paper will explore best practices collected through involvement with hundreds of damper projects worldwide. Lessons learned through the entire damper design process, from schematic level decisions through construction implementation, will be explored for both steel and concrete buildings. The purpose of this paper is to broaden readers’ understanding of FVD applications in the North American and New Zealand markets with the aim of reducing barriers and to demonstrate the ease of design and implementation of damped solutions.

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Technical Brief

117. Prescriptive Design of Damped Moment Frames: Simplifying building design with fluid viscous dampers by using an ICC-approved prescriptive method

Taylor Devices’ dampers are featured on the cover photo of the November issue of STRUCTURE magazine, along with an article about the Taylor Damped Moment Frame™. Written by Nathan Canney, Ph.D., P.E., Konrad Eriksen, and Alan Klembczyk, the article covers everything from an introduction to dampers to how the TDMF™ compares to other LFRS in building performance, loss and recovery time at the DE level.

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White Paper

116. Practical Design Procedure for Steel Moment Frames with Fluid Viscous Dampers

This paper outlines a practical design procedure for steel moment frames with fluid viscous dampers. The design procedure is being developed in accordance with International Code Council Evaluation Service (ICC-ES) AC 494, “Acceptance Criteria for Qualification of Building Seismic Performance of Alternative Seismic Force-Resisting Systems.” The new design procedure decouples the design of the moment frames and the damping system to minimize model complexity and design iteration. Notably, the design of the moment frames follows typical moment frame design procedures found in AISC 341 and ASCE/SEI-7 chapter 12, but with reduced strength and drift requirements to account for reduction in the seismic response provided by the damping system.
Through state-of-the-art FEMA P-695 incremental dynamic analysis on a suite of nearly 100 archetype designs, the design procedure is shown to produce steel moment frame designs that meet the seismic collapse safety requirements of FEMA P-695 and ASCE/SEI-7, while also significantly reducing steel tonnage when comparing to traditional steel moment frames.

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Product Info

113. SM Structural Feature on 181 Freemont

From a Space Program Hall of Fame induction to one of the tallest, mixed-use buildings in San Francisco, Taylor Devices continues to provide the most efficient, effective and innovative structural protection products on the planet.

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Case Study

108. Seismic Retrofit of the Tower of Hope – Preservation of a Masterwork of Mid-Century Modernism

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.

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White Paper

105. SUSTAINABILITY IN SOFT WEAK OPEN FRONT BUILDINGS

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.

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White Paper

104. Wind Effects on Long Span Cable Stayed Bridges: Assessment and Validation

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.

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White Paper

103. Validation of the 2000 NEHRP Provisions’ Equivalent Lateral Force and Modal Analysis Procedures for Buildings with Damping Systems

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.

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Case Study

102. TORSIONAL CONTROL OF TWO ADJACENT OFFICE BUILDINGS USING VISCOUS DAMPERS

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.

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Technical Brief

101. SHOCK CONTROL OF BRIDGES IN CHINA USING TAYLOR DEVICES’ FLUID VISCOUS DEVICES

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.

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White Paper

100. SHOCK CONTROL OF BRIDGES IN CHINA USING TAYLOR DEVICES’ FLUID VISCOUS DEVICES

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.

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Case Study

99. APPLICATION OF ENERGY DISSIPATION TECHNOLOGY FOR RETROFITTING STEEL STRUCTURES WITH VULNERABLE PRE-NORTHRIDGE CONNECTIONS

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.

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Case Study

98. SEISMIC PROTECTION SYSTEM AND ITS ECONOMIC ANALYSIS ON THE BEIJING HIGH-RISE BUILDING PANGU PLAZA

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.

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White Paper

97. SCISSOR-JACK-DAMPER ENERGY DISSIPATION SYSTEM

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.

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White Paper

96. ROOF ISOLATION SYSTEM TO REDUCE SEISMIC RESPONSE OF BUILDINGS

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.

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Uncategorized

95. OPTIMIZED DAMPING DEVICE CONFIGURATION DESIGN OF A STEEL FRAME STRUCTURE BASED ON BUILDING PERFORMANCE INDICES

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%.

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Technical Brief

94. A SIMPLE METHOD FOR THE DESIGN OF OPTIMAL DAMPER CONFIGURATIONS IN MDOF STRUCTURES

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.

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White Paper

93. EXPERIMENTAL STUDY OF RC BUILDING STRUCTURES WITH SUPPLEMENTAL VISCOUS DAMPERS AND LIGHTLY REINFORCED WALLS

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.

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White Paper

92. ENERGY DISSIPATION SYSTEMS FOR SEISMIC APPLICATIONS

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.

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White Paper

91. COUPLED TRUSS WALLS WITH DAMPED LINK ELEMENTS

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.

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White Paper

90. REHABILITATION OF A 1985 STEEL MOMENT FRAME BUILDING

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.

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White Paper

89. U.S CODE DEVELOPMENT OF STRUCTURES WITH DAMPING SYSTEMS

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.

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Technical Brief

88. SEISMIC PERFORMANCE OF LIGHT FRAMED WOOD STRUCTURES WITH TOGGLE-BRACED FLUID DAMPERS

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.

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White Paper

87. FLUID DAMPERS FOR SEISMIC PROTECTION OF WOODFRAME STRUCTURES

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.

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White Paper

86. BASE ISOLATION AND SUPPLEMENTAL DAMPING SYSTEMS FOR SEISMIC PROTECTION OF WOOD STRUCTURES

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.

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Case Study

85. SHOCK DESIGN FOR MK-49 ISOLATION

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.

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White Paper

84. MITIGATION OF MILITARY HIGH SHOCK TRANSIENTS FOR SHIPBOARD GYROCOMPASS WITH FIBER OPTIC GYROS (FOG)

The Taylor Devices self-centering hexapod mount provides MIL-S-901D shock protection for the Litton Marine Systems MK27F Attitude and Heading Reference System (AHRS). This new Reference System satisfies stringent military shock and vibration requirements. Unlike Ring Laser Gyro (RLG) which have low fragility levels (Max 50 g), the LN200 Fiber Optic Gyro Assembly can be exposed to levels as high as 90 g. This paper addresses the shock transient mitigation for shock requirements specified by MIL-S-901D. Comparisons between predicted and measured response are provided for a single strut as well as the fully shock isolated platform. Analytical and experimental results are presented to demonstrate the effectiveness of the MK27F Shock Absorber basic design for MIL-S-901D LWSM and predicted response is also presented for the floating platform Heavy Weight Shock Machine (HWSM).

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Uncategorized

83. BOAT SEAT ISOLATORS

This article appeared in Special Operations Technology magazine. It provides a very complete explanation of the Taylor Devices isolated seat for the Navy, complete with many photos. The article also includes the experiences of the seat occupants under high speed ocean travel.

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White Paper

82. FULL-SCALE SHAKE TABLE TESTS OF 5-STORY STEEL BUILDING WITH VISCOUS DAMPING

Realistic simulations of earthquake responses were conducted in March 2009 for a full-scale 5-story building specimens with dampers using the E-Defense, the world’s largest three-dimensional shake table. The building was tested repeatedly, inserting and replacing each of 4 damper types, steel damper, oil damper, viscous damper and viscoelastic damper. This paper discusses the test method and test results as well as details of the 5-story building specimen. Performance improvement by the dampers is addressed for moderately tall buildings that constitute a major portion of the building stock.

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White Paper

81. APPLICABILITY OF SEISMIC PROTECTIVE SYSTEMS TO HIGH-TECH INDUSTRIAL STRUCTURES

This paper summarizes a feasibility study for implementing seismic protective systems into high tech industrial structures in which costly vibration sensitive facilities are housed. Micro-vibration control of an IC fab is essential for optimum yield of reliable chip products. This paper describes the micro vibration analysis and measurement of a test structure before and after the incorporation of Seismic Protective systems. Based on the study, it is found that the incorporation of viscous dampers both enhances seismic safety and also minimizes the micro vibration of the structure. Viscous damper seismic isolation is the most promising method to achieve the “fully operational” seismic performance level of an IC fab.

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Case Study

80. A LIVING OR SMART BUILDING: THE GUANGZHOU TOWER

This paper presents the evolution of the structural design of one of the tallest structures in the world. The architectural design was developed by Mehrdad Yazdani at Cannon Design Group. The basic architectural vision of the Guangzhou Tower is three twisting interconnected legs. The architectural plan at each level of the tower rotates and twists. The basic structural vision here is of a Living Structure that can be adapted and improved from a structural engineering perspective as new high-tech products become available, as our understanding of the forces of nature improves using ground and aerial instrumentation and as we improve the accuracy of our structural modeling to estimate structural response to wind and earthquake loading.

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White Paper

79. FLUID VISCOUS DAMPERS: AN EFFECTIVE WAY TO SUPPRESS PEDESTRIAN-INDUCED MOTIONS IN FOOTBRIDGES

Fluid viscous dampers have found commercial applications on buildings and bridges subject to seismic and/or wind storm inputs. They are now being used as well on footbridges to suppress undesirable pedestrian induced vibrations. This paper provides a brief overview of fluid damping technology with specific case studies for pedestrian bridges now equipped with fluid viscous dampers. These viscous dampers are used to suppress the feedback between the pedestrians and the bridge and/or wind induced vibrations. On-site tests show that fluid viscous dampers provide significant gains in performance at relatively low cost.

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White Paper

77. ENERGY MANAGEMENT UTILIZING THE HYDRAULIC SHOCK ABSORBER

The advent of high speed equipment and machinery has brought with it numerous problems associated with slowing and stopping masses of various forms. The hydraulic shock absorber has proven to be one of the most satisfactory means of solving these problems, yet the shock absorber still remains as one of the least understood fluid power components. This paper presents design constraints, design parameters and a description of how to use shock absorbers into a system for the purpose of dissipating kinetic energy. Information is presented in both qualitative and functional equation format to enable the reader to grasp the subjective aspects of shock absorber usage which go beyond normal mathematical constraints.

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Technical Brief

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.

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Case Study

75. STRUCTURAL CONTROL USING HYBRID SPRING-DAMPER ISOLATOR WITH INTEGRAL GAPPING FUNCTION

The spring-damper isolators described in this paper were used on the world’s largest cable stayed bridge – the Sutong Bridge over China’s Yangtze River, completed in 2008. The Sutong Bridge is located north of Shanghai in China’s Jiangsu Province at a site where catastrophic earthquakes, typhoons, and ship impact are key design issues. The total length of the bridge is 4.7 miles, with a .67 mile long center span. The tall support towers of this bridge and the long support cables create long period motions along the primary axis of the bridge. The need to accommodate thermal expansion and contraction of the deck axially means that extensive motion can occur in this direction. The configuration of the bridge permits large axial motion of the suspended deck during earthquakes, typhoons, and synchronized truck/car braking loads such as would occur during a mass vehicular accident on the bridge. During dynamic earthquake loading, the long period of the suspended deck provides inherent isolation, albeit essentially undamped. Analysis indicated that added viscous damping would reduce deck motions substantially. During other events like typhoons and vehicle loading, analysis determined that the most cost-effective solution was to incorporate a snubbing type spring element that would only engage (become active) when the damper was approaching its end of travel in either extension or compression. The spring-dampers on this bridge have only damping forces for roughly 85% of the available displacement from the neutral (center of travel) position. Beyond this travel the spring element engage and a combined response of spring plus damper forces results. Essentially, the spring elements are “gapped” through all but approximately the last 15% of the damper stroke in either direction.

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White Paper

74. INTRODUCTION TO SHOCK AND VIBRATION ISOLATION AND DAMPING SYSTEMS

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.

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Product Info

73. TAYLOR DEVICES HERMETIC DAMPERS DESCRIPTION, APPLICATIONS, AND DESIGN

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.

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Case Study

72. MODULAR TUNED MASS DAMPER UNITS FOR THE SPRING MOUNTAIN ROAD PEDESTRIAN BRIDGE

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.

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White Paper

71. SEISMIC PROTECTION WITH FLUID VISCOUS DAMPERS FOR THE TORRE MAYOR, A 57-STORY OFFICE TOWER IN MEXICO CITY, MEXICO

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.

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Case Study

70. SEISMIC REHABILITATION OF HISTORIC CONCRETE STRUCTURE WITH FLUID VISCO-ELASTIC DAMPERS

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.

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