Probabilistic seismic demand assessment of residual drift for Buckling-Restrained Braced Frames as a dual system

Due to the low postyield stiffness of buckling-restrained braces (BRBs), multistory buckling-restrained braced frames (BRBFs) subjected to earthquakes are prone to lateral deformations and damage concentrations at certain stories, which is deemed a damage concentration effect (DCE). A series of nonlinear pushover analyses and response history analyses are conducted to investigate the key factors affecting the DCE of BRBFs. Two comparisons of the DCE are performed for different types of structures and different beam-to-column connections in the main frame (MF). These comparisons show that BRBFs equipped with BRBs as the main earthquake resistance system have a more serious DCE than the traditional moment-resisting frame or conventional braced frame and that the MF stiffness significantly affects the structural residual displacement and DCE. Then, parametric analyses are performed to investigate the influence of two stiffness distribution parameters (in the horizontal and vertical directions) on the DCE of a 6-story BRBF dual system designed according to the Chinese seismic code. The results show that increasing the MF stiffness and avoiding abrupt changes in the BRB stiffness between stories can effectively mitigate the DCE of BRBFs. Finally, the correlations between various damage performance indices are analyzed. A low statistical correlation between the peak and residual drift responses can be observed in BRBFs. Therefore, it is recommended that the DCE be considered in BRBF design.

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Effects of Frequency Content of Earthquake Ground Motions on Probabilistic Seismic Demand Assessment of Long-Span Bridge Structures

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.255-260.982 ◽

2011 ◽

Vol 255-260 ◽

pp. 982-987

Author(s):

Liang Chen ◽

Jin Song Zhang

Keyword(s):

Ground Motions ◽

Geometric Mean ◽

Response Spectra ◽

Seismic Demand ◽

Frequency Content ◽

Earthquake Ground Motions ◽

Long Span ◽

Long Span Bridge ◽

Demand Assessment ◽

Probabilistic Seismic Demand

Earthquake ground motions were reasonally selected for the nonlinear dynamic time-history analysis conducted for a two-tower long-span cable-stayed bridge. The correlation between frequency content of earthquake ground motions and probabilistic seismic demands reveals that the geometric mean and dispersion of response spectra from earthquake ground motions have significant effects on probabilistic seismic demand assessment of long-span bridge stuctures and these effects are related to the difference of the shape of geometric mean spectra in the important period ranges where cumulative modal mass participation is significant. Response spectra of selected earthquake ground motions should match well with target spectra in the important period ranges. If input ground motions are reasonally selected, analytic results can be obtained more precisely and effectively and more amplitude parameters can be selected as intensity measures.

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Probabilistic Seismic Demand Assessment of Steel Moment-Resisting Frame Buildings with Ordinary and Essential Occupancy Uses

International Journal of Steel Structures ◽

10.1007/s13296-020-00354-0 ◽

2020 ◽

Vol 20 (4) ◽

pp. 1230-1240

Author(s):

Seong-Hoon Hwang ◽

Kyungkoo Lee

Keyword(s):

Seismic Demand ◽

Moment Resisting Frame ◽

Frame Buildings ◽

Demand Assessment ◽

Moment Resisting ◽

Probabilistic Seismic Demand ◽

Steel Moment Resisting Frame

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Seismic Stability of Buckling-Restrained Braced Frames

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.763.924 ◽

2018 ◽

Vol 763 ◽

pp. 924-931 ◽

Cited By ~ 2

Author(s):

Santiago R. Zaruma ◽

Larry A. Fahnestock

Keyword(s):

Elastic Stability ◽

Seismic Stability ◽

Code Design ◽

Braced Frames ◽

Design Strategies ◽

Axis Orientation ◽

Residual Drift ◽

Seismic Force ◽

Story Drift ◽

Buckling Restrained Braced Frames

Buckling Restrained Braced Frames (BRBFs) are widely used as seismic force resisting systems due to their ductility and energy dissipation. However, because of the modest overstrength and relatively low post-yielding stiffness, BRBFs subjected to seismic loading may be susceptible to concentrations of story drift and global instability triggered by P-∆ effects. Due to the use of simplistic methods that are based on elastic stability, current code design provisions do not address seismic stability rigorously and do not consider the particular inelastic response of a system. Design strategies are needed to prevent undesirable seismic response in BRBFs, such as drift concentration and large residual drift. This study used the FEMA P-695 Methodology to evaluate the response of current U.S. code-based BRBF designs and to study the effect on seismic stability of three potential enhancements: strong-axis orientation for BRBF columns, gravity column contribution, and a BRBF-SMRF dual system. Results from nonlinear static and dynamic analyses allowed assessment of seismic behavior. Results from collapse performance evaluation quantify the improvement that is achieved with each alternative and provide a means of comparison.

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