Continuum Analysis Approach for Rocking Core-Moment Frames

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

doi:10.1061/(asce)st.1943-541x.0001986

Cited by 25 publications

(12 citation statements)

References 17 publications

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“…Finite difference calculus has been used to study the subject matter as a regular discrete system. An alternative method of analysis based on continuum modeling 50,51 for similar structures could have also been used to solve the same problem with sufficient accuracy for preliminary design purposes. The use of the proposed methodology can be extended to seismic upgrading 52,53 of existing buildings.…”

Section: Discussionmentioning

confidence: 99%

On the analysis of multilevel rocking cores—A bioinspired analogy

Grigorian¹,

Kamizi

2019

Engineering Reports

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This article presents a simple analogy, with practical applications, between the human spine and multilevel rocking cores (MLRCs) under similar loading conditions. The use of energy dissipating rocking cores in general and MLRCs in particular is a relatively new concept for reducing earthquake damage in new and existing buildings. The literature on the subject is rather scant. There are neither official guidelines nor educational materials for practical design of MLRCs. The first step toward rational design of MLRCs is to understand their elastic state static/dynamic behavior as part of a gravity and/or earthquake resisting system. The purpose of the current paper is not to reiterate the merits of various rocking systems but to provide reliable formulae for the preliminary design of simple MLRCs. Suffice to note that the multitude of gap movements in MLRCs results in increased damping and elongated periods of vibrations. Several parametric examples have been provided to demonstrate the applications, the validity, and the simplicity of the proposed solutions. All solutions are exact within the bounds of the theoretical assumptions. All results have been verified by independent computer analysis.

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Section: Discussionmentioning

confidence: 99%

On the analysis of multilevel rocking cores—A bioinspired analogy

Grigorian¹,

Kamizi

2019

Engineering Reports

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“…Wen et al showed that the near‐fault pulse‐like ground motions can also significantly increase the inelastic displacement demand of structures with medium periods. More recently, Rahgozar et al determined the IDRs for the self‐centering controlled rocking systems subjected to far‐field and near‐field pulse‐like ground motions. It is found that the influences of pulse period, predominant period of ground motion, and modeling parameters on the IDRs are significant, whereas the effects of source‐to‐site distance, earthquake magnitude, and site classes are not much significant.…”

Section: The Peak Idrsmentioning

confidence: 99%

“…Most of the existing studies (except Rahgozar et al) are focused on the conventional structures exhibiting the bilinear elastoplastic hysteretic behavior (with zero or positive postyield stiffness). Therefore, they may not provide an accurate estimate of the IDR values for rocking systems exhibiting the self‐centering type FS behavior.…”

Section: The Peak Idrsmentioning

confidence: 99%

“…In future studies, the accuracy of simplified MPA procedure can be further improved by reducing the uncertainty associated with simplifying assumptions. For example, the use of relatively more detailed studies focusing explicitly on the evaluation of the IDRs for rocking systems (e.g., Rahgozer et al) may further improve the response predictions in future. The idea can also be developed further by extending its applicability to various other structural systems exhibiting different hysteretic responses.…”

Section: A Simplified Mpa Procedures For Rocking Wall Structuresmentioning

confidence: 99%

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Prediction of nonlinear seismic demands of high‐rise rocking wall structures using a simplified modal pushover analysis procedure

Najam

Qureshi

Warnitchai

et al. 2018

Structural Design Tall Build

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Summary This study presents a simplified analysis procedure for the convenient estimation of nonlinear seismic demands of high‐rise rocking wall structures. For this purpose, the displacement modification approach used in the nonlinear static procedure of ASCE/SEI 41‐13 is adopted. However, in the current study, this approach is extended to every significant vibration mode of the structure whereas the displacement modifying coefficients for different modes are calculated using the typical flag‐shaped hysteresis behavior of rocking walls. The parameters of this hysteresis behavior are selected to represent rocking walls with a practical range of energy dissipation capacity and postgap‐opening stiffness. The computed peak inelastic‐to‐elastic displacement ratios are presented as mean spectra, which can be used for the convenient estimation of pushover target displacement for every significant vibration mode. The accuracy of proposed procedure is examined using the seismic demands obtained from the nonlinear response history analysis of a 20‐story case study rocking wall structure. Furthermore, a modal decomposition technique is used to determine the individual modal seismic demands. The proposed procedure is found to predict both the combined and the individual modal demands with a reasonable accuracy and can serve as a convenient analysis option for the design and performance evaluation of high‐rise rocking wall systems.

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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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Continuum Analysis Approach for Rocking Core-Moment Frames

Cited by 25 publications

References 17 publications

On the analysis of multilevel rocking cores—A bioinspired analogy

On the analysis of multilevel rocking cores—A bioinspired analogy

Prediction of nonlinear seismic demands of high‐rise rocking wall structures using a simplified modal pushover analysis procedure

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

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