Quantification of seismic performance factors for self‐centering controlled rocking special concentrically braced frame

Rahgozar, Navid; Moghadam, Abdolreza S.; Aziminejad, Armin

doi:10.1002/tal.1279

Cited by 34 publications

(21 citation statements)

References 33 publications

(49 reference statements)

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“…The mean value of residual roof drift for the RCBF and RZBF is 0.0014 and 0.00016 radians, which showed the reliable self-centering behavior of these frames. This result is identical with the result of past researches [40,43,44]. They presented that the residual roof drift for fixed base frame is 46 and 54 times larger than the residual roof drift for rocking frame under DBE and MCE earthquakes, respectively.…”

Section: Roof Drift Ratio and Residual Driftsupporting

confidence: 90%

“…Also, RCBF experiences first damage at higher drifts comparing with CBF system, resulting in better seismic performance in terms of drift ratio and residual drift as presented in different experimental and analytical studies [10,40]. Recent studies presented that RCBFs like rocking concentrically braced frame [10,41,42], dual rocking frames [31,43,44], using multiple rocking joint through the height of the frame [11], rocking braced frames with energy dissipating elements and various story numbers [45] and tension-only concentrically braced frames with rocking core [46] are able to decrease damage under severe earthquakes and enhance the seismic performance of ordinary CBFs in terms of uniform distribution of inter story drifts. Huang et al showed that RCBFs are economically better systems comparing to CBFs for low and mid-rise building under severe earthquakes [47].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Seismic Performance of Improved Rocking Concentrically Braced-frames with Zipper Columns

Sarand¹,

Jalali²

2020

Period. Polytech. Civil Eng.

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Concentrically braced frames (CBFs) as one of well-known stiff and common lateral force resisting systems often show limited ductility capacity under severe earthquakes. This study proposes rocking zipper braced frame (RZBF) to improve the drift capacity of CBFs which is based on combination of rocking behavior and zipper columns. In the RZBF system, rocking behavior permit the braced frame to uplift during the earthquake and then restoring force induced through post-tensioned bars self-center the frame to its initial state.Also, zipper columns can decrease the concentration of damage by distributing the unbalance force at the mid bay over the frame's height. To assess the performance of RZBF, a comparison study is carried out considering CBF, rocking concentrically braced frame, zipper braced frame and RZBF. For this purpose, some frames structures are designed and nonlinear time history analysis conduct under a set of earthquake records. Seismic responses such as roof drift ratio, gap opening at the column-base interface, forces of top story braces and post-tensioned bars are taken into consideration. The results show that the proposed RZBF has better performance among the others and zipper columns can improve the behavior of rocking systems.

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Section: Roof Drift Ratio and Residual Driftsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Evaluation of Seismic Performance of Improved Rocking Concentrically Braced-frames with Zipper Columns

Sarand¹,

Jalali²

2020

Period. Polytech. Civil Eng.

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“…In recent years, self‐centering earthquake‐resisting systems (SC‐ERSs) have been developed to provide a sustainable system through directing seismic damage to replaceable devices. Figure a shows examples of rocking and stepping self‐centering systems including single or coupled stepping braced frames, pin‐supported rocking frame or wall, rocking precast concrete wall, and self‐centering timber frames . These lateral resisting systems are generally composed of bounded or unbounded posttensioning (PT), replaceable energy dissipation (ED) devices, rigid strut beam, bumper, and special diaphragm connections.…”

Section: Introductionmentioning

confidence: 99%

Equivalent linear model for fully self‐centering earthquake‐resisting systems

Rahgozar

Moghadam

2018

Structural Design Tall Build

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Modern rocking and stepping cores have been known as the efficient self-centering earthquake-resisting systems (SC-ERSs). The current article proposes an approximate equivalent linear (EL) model for rapid estimation of the SC-ERS displacement. An equivalent damping ratio and effective stiffness are formulated for flag-shaped hysteresis of a fully SC-ERS. The approximate EL model is first established using secant stiffness and Jacobsen's damping model. Nonlinear response history analyses are carried out to compare exact and approximated peak displacements. Findings reveal that EL analysis of the SC-ERS based on Jacobsen's damping leads to underestimation of the maximum inelastic displacement. Accordingly, a new optimal damping formula is proposed using a genetic algorithm and nonlinear regression analyses. The improved EL model is validated by practical examples, and the results show acceptable accuracy in design-level displacement estimation. KEYWORDS equivalent linear model, flag-shaped hysteresis, optimization analysis, secant stiffness, selfcentering systems, viscous damping model 1 | INTRODUCTIONOn the basis of the traditional ductility-based design concept, structural members allow for sustaining of uniform damage. Nevertheless, buildings experience severe damage following a large earthquake, which lead to socioeconomic losses due to business downtime and repair costs. In recent years, self-centering earthquake-resisting systems (SC-ERSs) have been developed to provide a sustainable system through directing seismic damage to replaceable devices. Figure 1a shows examples of rocking and stepping self-centering systems including single or coupled stepping braced frames, [1][2][3][4][5][6][7][8] pin-supported rocking frame or wall, [9][10][11] rocking precast concrete wall, [12][13][14][15] and self-centering timber frames. [16,17] These lateral resisting systems are generally composed of bounded or unbounded posttensioning (PT), replaceable energy dissipation (ED) devices, rigid strut beam, bumper, and special diaphragm connections. Regardless of the SC-ERS components, a flag-shaped hysteresis is representative of their total seismic responses. Figure 1b depicts a sample of push-pull curves of the system characterized by uplift ( F up − Δ up ) and yield ( F y − Δ y ) parameters along with postyield stiffness (α) and ED index (β). Prior to unloading the system ( F d − Δ d ), the response is generally composed of three main branches. In the first branch that terminates when the system is uplifted, the SC-ERS has a large initial elastic stiffness and behaves as conventional buildings. Nevertheless, in the second branch, the system stiffness is reduced and sways on its foundation, which leads to the system yielding point. The yielding point is the beginning of the third branch with the hardening stiffness of α. Note that geometric nonlinearity is controlled using PT and ED devices. Accordingly, the PT cable provides adjustable restoring forces, and the ED device produces required ED capacity during the unloading ph...

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“…Some collapse assessment studies have been completed previously on CRSBFs , which have shown that they can provide acceptable collapse prevention characteristics based on the FEMA P695 methodology . The study by Ma et al.…”

Section: Introductionmentioning

confidence: 99%

“…Some collapse assessment studies have been completed previously on CRSBFs [3,9,10], which have shown that they can provide acceptable collapse prevention characteristics based on the FEMA P695 methodology [11]. The study by Ma et al [3] used an elastic model to evaluate one three-storey building, two six-storey buildings and one nine-storey building with a constant response modification factor of R D 8, and ED and PT parameters selected within a direct displacement-based design framework.…”

Section: Introductionmentioning

confidence: 99%

Collapse risk of controlled rocking steel braced frames with different post‐tensioning and energy dissipation designs

Steele

Wiebe

2017

Earthq Engng Struct Dyn

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Summary Controlled rocking steel braced frames (CRSBFs) are low‐damage self‐centring lateral force resisting systems. Previous studies have shown that designing the energy dissipation (ED) and post‐tensioning (PT) in CRSBFs using a response modification factor of R=8 can prevent collapse of structures during earthquakes beyond the design level. However, designers have unique control over the hysteretic behaviour of the system, even after the response modification factor is selected. Additionally, recent studies have suggested that CRSBFs could also be designed using R>8 while still satisfying performance limits. This paper examines how the response modification factor and the design of the ED and PT influence the collapse performance of CRSBFs with three and six storeys where collapse occurs because of over‐rotation of the base rocking joint. In addition, the influence of using an additional rocking joint above the base to mitigate higher‐mode forces is evaluated for a 12‐storey frame. A total of 18 different designs are considered for the three buildings using different ED and PT design parameters, including different response modification factors. A suite of 44 ground motions is scaled until at least 50% of the records cause collapse, and fragility curves are generated using the truncated incremental dynamic analysis curves. The results from two different assessment methodologies show that the parameters selected have a marked influence on the collapse performance of a CRSBF. Nevertheless, even CRSBFs designed using R>8 or without supplemental ED can have acceptably low probabilities of collapse, provided that the frame members are designed to remain elastic. Copyright © 2017 John Wiley & Sons, Ltd.

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Quantification of seismic performance factors for self‐centering controlled rocking special concentrically braced frame

Cited by 34 publications

References 33 publications

Evaluation of Seismic Performance of Improved Rocking Concentrically Braced-frames with Zipper Columns

Evaluation of Seismic Performance of Improved Rocking Concentrically Braced-frames with Zipper Columns

Equivalent linear model for fully self‐centering earthquake‐resisting systems

Collapse risk of controlled rocking steel braced frames with different post‐tensioning and energy dissipation designs

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