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1. Shake Table Testing of a Frame-Spine System with Force-Limiting Connections

   Fahnestock, Larry; Sause, Richard; Ricles, James; Simpson, Barbara; Kurata, Masahiro; Okazaki, T; Kawamata, Y; Tao, Z; Duke, J; Rivera, D; et al (January 2022, 12th National Conference on Earthquake Engineering (12NCEE))

   A novel structural system is being developed collaboratively by researchers from the United States and Japan to protect essential facilities, such as hospitals, where damage to the building and its contents and occupant injuries must be prevented and where continuity of operation must be maintained. The development is focusing on new construction, but it also has potential for use in seismic retrofit of deficient existing buildings. The new system employs practical structural components, including (1) flexible steel moment frames, (2) stiff steel elastic spines and (3) force-limiting connections (FLC) that connect the frames to the spines, to economically control building response and prevent damaging levels of displacement and acceleration. The moment frames serve as the economical primary element of the system to resist a significant proportion of the lateral load, dissipate energy through controlled nonlinear response and provide persistent positive lateral stiffness. The spines distribute response evenly over the height of the building and prevent story mechanisms, and the FLC reduce higher-mode effects and provide supplemental energy dissipation. The full-scale shake-table testing of a building with the Frame-Spine-FLC System, which represents a hospital facility and includes realistic nonstructural components and medical equipment, validated the functionality of the structural system. 

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2. Full-scale stability evaluation of a frame-spine system with force-limiting connections

   Fahnestock, Larry; Sause, Richard; Ricles, James; Simpson, Barbara; Kurata, Masahiro; Okazaki, Taichiro; Kawamata, Yohsuke; Tao8, Zhuoqi; Duke, Jessica; Rivera, David; et al (January 2021, Structural Stability Research Council (SSRC))

   A new seismic-resilient structural system is being developed to protect buildings, their contents, and occupants during major earthquakes. This economical system is intended for essential facilities, such as hospitals, where damage to the buildings and contents and occupant injuries must be prevented and where continuity of operation is imperative. The primary components of the Frame-Spine-FLC System are: (1) steel base moment-resisting frames designed and detailed to behave in the inelastic range and dissipate energy, (2) stiff and strong elastic spines designed to remain essentially elastic to redistribute seismic demands more uniformly over the building height, and (3) force-limiting connections (FLC) that connect the frame to the spines to provide a yielding mechanism that limits acceleration demands. An international team, including three U.S. universities, two Japanese universities and two major experimental research labs, is collaborating on this project and recently conducted full-scale shake-table testing at the E-Defense facility in Miki, Japan. The test building represents a hospital facility and includes realistic nonstructural components and medical equipment. This paper provides an overview of the shake-table testing program and presents preliminary results that demonstrate the seismic stability response of the Frame-Spine-FLC System and the overall viability of the new concept. 

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3. U.S.-Japan Collaboration for Shake Table Testing of a Frame-Spine System with Force-Limiting Connections

   Fahnestock, Larry; Sause, Richard; Ricles, James; Simpson, Barbara; Kurata, Masahiro; Okazaki, Taichiro; Kawamata, Yohsuke; Tao, Zhuoqi; Duncan, Jessica; Rivera, David; et al (January 2021, 17th World Conference on Earthquake Engineering, 17WCEE)

   Conventional lateral force-resisting systems can provide a stable, ductile response but also experience significant inelastic demands, rendering repairs impractical or uneconomical. Thus, there is a need for novel structural systems that protect structural and nonstructural components to reduce post-earthquake repairs and downtime. A U.S.-Japan research team – including three U.S. universities, two Japanese universities, and two major experimental research labs – is developing a structural solution to reduce peak drift and acceleration demands, thereby protecting buildings, their contents, and occupants during major earthquakes. The primary components of the system are: (1) steel base moment-resisting frames designed and detailed to behave in the inelastic range and dissipate energy, (2) stiff and strong elastic spines designed to remain essentially elastic to redistribute seismic demands more uniformly over the building height, and (3) force-limiting connections (FLC) that connect the frame to the spines to provide a yielding mechanism that limits acceleration demands. This economical earthquake-resilient system is intended to be used in essential facilities, such as hospitals, where damage to the buildings and contents and occupant injuries must be prevented and where continuity of operation is imperative. The system was recently tested at full scale at the E-Defense shake-table facility in Miki, Japan. This paper provides an overview of pre-test numerical simulations, shake-table test setup and instrumentation, and preliminary test results. 

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4. Force Limiting Connections to Mitigate Accelerations in Moment Resisting Frames with Pinned-Base Spines

   https://doi.org/10.1007/978-3-031-62884-9_84  

   Duncan, Jessica; Astudillo, Bryam; Sause, Richard; Ricles, James; Fahnestock, Larry; Simpson, Barbara; Kurata, Masahiro; Kawamata, Yohsuke; Okazaki, Taichiro; Tao, Zhuoqi; et al (January 2024, Springer Nature Switzerland)

   Mid-rise moment resisting frames (MRF) which utilize supplemental pinned-base spines (spine) to prevent the formation of story mechanisms experience higher mode accelerations at near elastic spectral values. Force Limiting Connections (FLC) can be introduced to reduce the floor accelerations from the higher mode responses while having small impact on first-mode response and maintaining the story mechanism prevention from the spine. Results from nonlinear response history analysis (NRHA) of a 4-story MRF-Spine system show how floor accelerations for higher modes are reduced with the addition of FLC placed between the MRF and spine. Peak effective pseudo accelerations are utilized to show how pseudo spectral accelerations are reduced by the introduction of FLC. Full-scale testing of the 4-storyMRF-Spine structure supports the numerical results of theMRF-Spine andMRF-Spine-FLC numerical analyses. These results show the potential benefits of adding FLC to MRF-Spine systems. 

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5. E-Defense shake-table test data:Subtitle

   https://doi.org/10.17603/ds2-e159-v458  

   Fahnestock, Larry; Qie, Yi; Astudillo, Bryam; Duncan, Jessica; Tao, Zhuoqi; Okazaki, Taichiro; Sause, Richard; Ricles, James; SIMPSON, BARBARA; Kurata, Masahiro; et al (January 2025, Designsafe-CI)

   This dataset contains data from E-Defense shake-table tests of a full-scale, steel moment-resisting frame (MRF) supplemented with spines. Herein, the spines were pin-based columns with sufficient stiffness and strength to distribute plastic deformation evenly over the height of the MRF. The specimen was tested under two configurations: first, with the spine rigidly connected to the MRF; and second, with the spine connected to the MRF through Force-Limiting Connections (FLCs). The two structural systems were subjected to two ground motions adjusted to two different scales. The tests highlighted the expected benefits of spines as well as their drawbacks of inducing large floor acceleration in the MRF and large shear forces in the spines themselves. The tests also highlighted how the FLCs can mitigate such drawbacks of spines. The data may be used, for example, to reproduce the observations presented by the authors, to compare the dynamic response of the specimen with building specimens tested in other shake-table test programs, to validate numerical models against the measured specimen response, or to formulate classroom exercises on system identification of linear and nonlinear systems. 

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