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Even with strong-column-weak-beam design requirements, story mechanisms have been observed in Moment Resisting Frames (MRF), resulting in concentrated drift demands that can result in severe structural damage to drift-sensitive components. Frame-Spine systems can redistribute demands with building height, but near-elastic higher-mode effects tend to contribute to floor accelerations, affecting damage to acceleration-sensitive nonstructural components. To mitigate this tradeoff, Force-Limiting Connections (FLCs) have been proposed to reduce accelerations through yielding components between the Frame and Spine, thereby limiting the magnitude of the forces. This study examines the sizing and placement of FLCs in a four-story Frame-Spine system using stochastic simulations. The T-shape yielding element dimensions in the FLC were modeled as random variables at each floor, and Monte Carlo simulations were used to explore their effect on drifts and accelerations. Results show the dominant role of the first-story FLC on balancing drifts and accelerations, while upper-story devices offered limited benefit. Design recommendations are provided to constrain first-story yielding element dimensions within effective bounds that reduce peak accelerations relative to the baseline Frame-Spine configuration.
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Force Limiting Connections to Mitigate Accelerations in Moment Resisting Frames with Pinned-Base Spines
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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- Award ID(s):
- 2309829
- PAR ID:
- 10632038
- Publisher / Repository:
- Springer Nature Switzerland
- Date Published:
- Page Range / eLocation ID:
- 958 to 968
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Concentration of drifts due to story mechanisms can lead to severe structural damage and economic loss. Frame-Spine systems have been proposed to mitigate these effects by redistributing drift demands with building height; however, systems can also exhibit near-elastic higher-mode effects, resulting in forces and floor accelerations that remain largely unreduced by inelastic behavior, thereby adversely affecting acceleration-sensitive nonstructural components and occupants. To address near-elastic higher-mode effects, Force-Limiting Connections (FLCs) have been introduced limiting force transfer between the frame and the spine and reducing acceleration demands through controlled yielding components. This study presents observations from full-scale shake-table testing of a four-story Frame-Spine and a Frame-Spine-FLC specimen at E-Defense. Results highlight higher-mode effects under strong shaking, with emphasis on (1) story shear resisted by the spine, (2) force–deformation behavior of the spine-to-frame connections, and (3) vertical distribution of forces. These findings provide experimental evidence of higher-mode participation in Frame-Spine systems and support the development of improved design guidance and controlling mechanisms.more » « less
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Abstract In light of the significant damage observed after earthquakes in Japan and New Zealand, enhanced performing seismic force‐resisting systems and energy dissipation devices are increasingly being utilized in buildings. Numerical models are needed to estimate the seismic response of these systems for seismic design or assessment. While there have been studies on modeling uncertainty, selecting the model features most important to response can remain ambiguous, especially if the structure employs less well‐established lateral force‐resisting systems and components. Herein, a global sensitivity analysis was used to address modeling uncertainty in specimens with elastic spines and force‐limiting connections (FLCs) physically tested at full‐scale at the E‐Defense shake table in Japan. Modeling uncertainty was addressed for both model class and model parameter uncertainty by varying primary models to develop several secondary models according to pre‐established uncertainty groups. Numerical estimates of peak story drift ratio and floor acceleration were compared to the results from the experimental testing program using confidence intervals and root‐mean‐square error. Metrics such as the coefficient of variation, variance, linear Pearson correlation coefficient, and Sobol index were used to gain intuition about each model feature's contribution to the dispersion in estimates of the engineering demands. Peak floor acceleration was found to be more sensitive to modeling uncertainty compared to story drift ratio. Assumptions for the spine‐to‐frame connection significantly impacted estimates of peak floor accelerations, which could influence future design methods for spines and FLC in enhanced lateral‐force resisting systems.more » « less
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ABSTRACT This data paper presents data obtained 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; second, with the Spine connected to the MRF through force‐limiting connections (FLCs). Each specimen configuration underwent earthquake simulations using ground motions with two scale factors. The tests demonstrated the expected benefits of Spines as well as the disadvantage of inducing large floor accelerations in the structure and large shear forces in the Spines. The tests also demonstrated how the FLCs can mitigate these disadvantages. This data paper reports an overview of the tests, data archive structure, and potential use of the data. The data can 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.more » « less
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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.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Book Chapter:
- https://doi.org/10.1007/978-3-031-62884-9_84
