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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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This content will become publicly available on July 13, 2027
Higher-mode response of Frame-Spine and Frame-Spine-FLC specimens tested at E-Defense shake table
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.
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- Award ID(s):
- 2309829
- PAR ID:
- 10657016
- Publisher / Repository:
- 13th National Conference on Earthquake Engineering (13NCEE)
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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