Seismic performance of alternative risk-reduction retrofit strategies to support decision making

Ligabue, Veronica; Pampanin, Stefano; Savoia, Marco

doi:10.1007/s10518-017-0291-7

Cited by 12 publications

(10 citation statements)

References 15 publications

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“…It is to clarify that, for seismic intensity levels higher than the seismic intensity level adopted for the design of the two structures (i.e., the collapse prevention limit state corresponding to a probability of exceedance of 5% in 50 years), the FE numerical models have assessed, in some cases, the attainment of a collapse condition (i.e., peak element rotation larger than ultimate available rotation or peak interstorey drift ratio (IDR) in one direction larger than 5% or numerical instability or absence of numerical convergence). erefore, as expected, for the seismic intensity levels corresponding to probability of exceedance of 1%, 2%, and 4% in 50 years, the high nonlinear behaviour attained by the FE model of the two structures could provide a slightly less accurate assessment of the building seismic response [33] since this last could be influenced by the hysteretic laws adopted in the FE model [47]. In order to reduce to the minimum the possible effects of numerical instability of the model for some ground motions, the median values of the seismic response have adopted as central values in the Monte Carlo simulation (instead of the mean values usually more influenced by outlier presence) and a proper number of seismic intensity levels, as suggested in FEMA [21], have been assumed.…”

Section: Loss Assessment Analysismentioning

confidence: 64%

“…In the seismic design process, it is quite common to adopt a single q value, which is used for the force-based design of different structural elements assuming implicitly that every element of the structure can be damaged by a design-level seismic event (distributed damage concept). Alternative approaches, for example, based on selective weakening criterion, have been proposed in [31][32][33][34] to drive the degradation mechanism of the structures towards concentrated damage seismic scenarios (concentrated damage concept). All this could provide, in the future, a valid alternative to the distributed seismic damage scenario expected in case of the adoption of the current codes compliant approaches, for the design of new structures.…”

Section: Introductionmentioning

confidence: 99%

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Seismic Performance Assessment of a Multistorey Building Designed with an Alternative Capacity Design Approach

Bovo

Savoia

Praticò

2021

Advances in Civil Engineering

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The actual seismic building codes have a prescriptive nature, and they are principally aimed to guarantee a prescribed life-safety level against a design-level earthquake even if some methods have been proposed to evaluate the seismic performance of a building along its entire service life. Among these, the performance-based seismic design method permits the design of buildings with a more realistic understanding of both risk of life for occupants and economic losses that may occur in future earthquakes. On the other side, the capacity design method, providing criteria to properly spread the inelastic deformation demand between the different structural elements, allows to establish a ductile collapse mechanism avoiding undesired brittle failures. In this context, modern building codes consider the adoption of a single value for the behaviour factor q to be used in the design process. All this should be argued since, especially for buildings characterized by storeys with different uses and occupancy ratios, the adoption of a single value for q could guide the design process to a solution not minimizing the seismic loss. With reference to these aspects, the paper shows the comparison of the seismic responses of a multistorey framed building designed following two different approaches. The first approach, suggested by many international codes, follows the capacity design rules and considers a single value for the behaviour factor valid for the whole building. In this first case, the damage mechanisms could affect, theoretically, every storey of the building. The second approach, proposed here, considers instead the possibility to adopt different behaviour factors to attribute to different storeys. In this way, it is possible to concentrate and localize the most severe earthquake-induced structural damage on (few) storeys, selected by the designers. By means of the seismic performance assessment methodology, the comparison between the two building responses is provided in terms of expected losses during the whole building service life and is reported in terms of both economical loss and human life loss. The results in the paper show that, if different behaviour factors are properly selected for different storeys, the design process can provide a solution characterized by lower values of seismic loss with respect to the case of the design assuming a single-q value.

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Section: Loss Assessment Analysismentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Seismic Performance Assessment of a Multistorey Building Designed with an Alternative Capacity Design Approach

Bovo

Savoia

Praticò

2021

Advances in Civil Engineering

Self Cite

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“…On the other hand, the high seismic vulnerability of existing buildings leads to a great economic impact [5][6][7][8]. In this context, the seismic risk assessment of the existing building heritage and the risk reduction today represent crucial points, having the same importance as the design of new buildings [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Fragility Curves of Existing RC Buildings Accounting for Bidirectional Ground Motion

2022

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In recent decades, the considerable number of worldwide earthquakes caused considerable damage and several building collapses, underlining the high vulnerability of the existing buildings designed without seismic provisions. In this regard, this work analyses the seismic performance of a reinforced concrete building designed without any seismic criteria, characterized by a seismically-stronger and a seismically-weaker direction, such as several existing reinforced concrete-framed structures designed for vertical load only. The case study building was modelled in OpenSees considering a non-linear three-dimensional model, also accounting for the contribution of joint panel deformability on the global behavior. Thirty bidirectional ground motions have been applied to the structure with the highest component alternatively directed along the two principal building directions. Time-history analyses have been performed for eight increasing hazard levels with the aim of evaluating the influence of bidirectional ground motion on structural response and estimating the seismic vulnerability of the building. The seismic performance of the structures are provided in terms of fragility curves for the two principal directions of the building and for different damage states defined according to the European Macroseismic Scale.

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“…Other studies considered applying different retrofitting techniques with varying intervention levels to achieve different performance objectives (e.g. [21], [22]), but only collapse fragility relationships were evaluated.…”

Section: Introductionmentioning

confidence: 99%

Mapping Performance-Targeted Retrofitting to Seismic Fragility Reduction

Aljawhari¹,

Gentile²,

Galasso³

2021

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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This study investigates the improvement in the seismic performance of an archetype reinforced concrete (RC) frame due to varying structural retrofit levels. Specifically, the study attempts to map the increase of the displacement-based global ratio between capacity and life-safety demand (CDRLS) to the reduction of seismic fragility. Such a reduction is characterized by the shift of the median fragility for different structure-specific damage states (DSs). The considered structure does not conform to modern seismic design requirements, and it is retrofitted using various techniques. Advanced nonlinear models are developed for the archetype frame, accounting for potential failure mechanisms, including flexural, joint, and shear failure. Three common retrofitting techniques are investigated, namely RC jacketing, steel jacketing, and fiber-reinforced polymers (FRP) wrapping of columns and joints. Each technique is specifically designed and proportioned to achieve predefined performance objectives (i.e., performancetargeted retrofitting), thus generating many retrofit alternatives. The improvement in seismic performance for the retrofitted frames is first characterized by computing the global CDRLS, which can be obtained using nonlinear pushover analysis combined with the Capacity Spectrum Method. Subsequently, cloud-based nonlinear time-history analyses are performed to derive fragility relationships for the as-built and retrofitted configurations, monitoring the variation in the median fragility for all DSs. Finally, the global CDRLS increase due to retrofitting is correlated with the corresponding shift in the median fragility. A linear trend is found, and it is used accordingly to develop simple models that engineers can implement to provide reasonable estimates for such shift once the global CDRLS is known.

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Seismic performance of alternative risk-reduction retrofit strategies to support decision making

Cited by 12 publications

References 15 publications

Seismic Performance Assessment of a Multistorey Building Designed with an Alternative Capacity Design Approach

Seismic Performance Assessment of a Multistorey Building Designed with an Alternative Capacity Design Approach

Fragility Curves of Existing RC Buildings Accounting for Bidirectional Ground Motion

Mapping Performance-Targeted Retrofitting to Seismic Fragility Reduction

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