Seismic performance of dual systems coupling moment‐resisting and buckling‐restrained braced frames

Freddi, Fabio; Tubaldi, Enrico; Zona, Alessandro; Dall’Asta, Andrea

doi:10.1002/eqe.3332

Cited by 39 publications

(30 citation statements)

References 45 publications

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“…In the present study, the retrofit is designed independently from a specific seismic hazard, and the base shear of the dissipative system ( V d,1 ) is selected equal to the base shear of the bare frame ( V f,1 ), or in other words, strength proportion coefficient α = V d,1 / V f,1 equals unity, 14,17 hence doubling the base shear resistance of the retrofitted frame. The ductility of the dissipative braces, that is, dissipative device plus elastic brace ( μ d ) is assumed equal to 15.…”

Section: Case Study Structure and Finite Element Modelingmentioning

confidence: 99%

Device uncertainty propagation in low‐ductility RC frames retrofitted with BRBs for seismic risk mitigation

Freddi

Ghosh

Kotoky

et al. 2021

Earthq Engng Struct Dyn

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Passive control systems, such as buckling‐restrained braces (BRBs), have emerged as efficient tools for seismic response control of new and existing structures by imparting strength and stiffness to buildings, while providing additional high and stable energy dissipation capacity. Systems equipped with BRBs have been widely investigated in literature; however, only a deterministic description of the BRBs’ properties is typically considered. These properties are provided by the manufacturer and are successively validated by qualification control tests according to code‐based tolerance limits. Therefore, the device properties introduced within the structure could differ from their nominal design estimates, potentially leading to an undesired seismic performance. This study proposes a probabilistic assessment framework to evaluate the influence of BRBs’ uncertainty on the seismic response of a retrofitted RC frame. For the case study, a benchmark three‐story RC moment‐resisting frame is considered where BRBs’ uncertainty is defined compatible to the standardized tolerance limits of devices’ quality control tests. This uncertainty is implemented through a two‐level factorial design strategy and Latin hypercube sampling technique. Cloud analysis and probabilistic seismic demand models are used to develop fragility functions for the bare and retrofitted frame for four damage states while also accounting for the uncertainty in the property of BRBs. Risk estimates are successively evaluated for three case study regions. The results show that, for the considered case study structure, these uncertainties could lead to an increase of fragility up to 21% and a variation in seismic risk estimates up to 56%.

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Section: Case Study Structure and Finite Element Modelingmentioning

confidence: 99%

Device uncertainty propagation in low‐ductility RC frames retrofitted with BRBs for seismic risk mitigation

Freddi

Ghosh

Kotoky

et al. 2021

Earthq Engng Struct Dyn

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“…In this context, the H2020-SERA project HITFRAMES (Hybrid Testing of an Existing Steel Frame with Infills under Multiple Earthquakes) is aimed on assessing the seismic performance of existing steel frames with masonry infills under multiple earthquakes and the feasibility of retrofitting with buckling restrained braces (BRBs) [14][15][16][17][18]. Among others, the objectives of the HITFRAMES project include: (1) to experimentally assess the seismic performance of nonseismically designed steel frames with masonry infills under earthquake sequences, including the effects of cumulative damage; (2) to evaluate the existing masonry infill models and to develop new calibrated models aimed at describing the behaviour of masonry panels within infilled steel MRFs; and (3) to experimentally evaluate the contribution and effectiveness of BRB-based retrofitting strategies in steel MRFs.…”

Section: Introductionmentioning

confidence: 99%

Preliminary Numerical Analysis of the Seismic Response of Steel Frames With Masonry Infills Retrofitted by Buckling Restrained Braces

Gutiérrez‐Urzúa¹,

Freddi²,

Sarno³

et al. 2021

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

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Existing steel moment-resisting frames in several seismic regions worldwide are often characterised by high vulnerability to earthquakes due to insufficient local and/or global ductility. Nowadays, it is of paramount importance to assess their response under strong motions and provide cost-effective retrofitting strategies. Amongst others, the seismic behaviour of these frames is often strongly affected by the presence of masonry infills which, from one side, if adequately distributed, beneficially contribute to the seismic resistance of the structure providing stiffness and strength to the frame, from the other side often experience a brittle behaviour and are very vulnerable to seismic actions. To this end, the H2020-INFRAIA-SERA project HITFRAMES (i.e., HybrId Testing of an Existing Steel Frame with Infills under Multiple Earth-quakeS) experimentally evaluated a case study building representative of non-seismically designed European steel frames with masonry infills and investigated a possible retrofit strategy. This paper takes advantage of the experimental results of the HITFRAMES project to calibrate numerical models in OpenSees of a case study building which is analysed as bare, infilled and retrofitted frame with buckling-restrained braces (BRBs). The impact of masonry infills and BRB-retrofit is investigated by comparing the response of models with different configurations.

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“…Buckling Restrained Braces (BRBs) have proven to be effective in improving the seismic performance of existing and new Moment Resisting Frames (MRFs) [1][2][3]. Such devices can be included within diagonal steel bracing connected to the existing frame contributing to the strength and stiffness of the existing structures by providing a parallel truss-like force path for the seismic lateral load imposed on the building hence forming a dual system [4]. In addition, the stable hysteretic behaviour provided by the BRBs largely contributes towards the increase of the energy dissipation capacity of the structure [2,5].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…When properly designed, the MRF can provide restoring forces to counteract the residual drifts related to the yielding of BRBs [4]. Additionally, the Buckling Restrained Braced Frame (BRBF) can contribute towards the reduction of the floor accelerations arising from higher modes effects [4,13] and can limit the damage in the MRF [8]. Nonetheless, the efficiency of this dual system (i.e., MRF + BRBF) is function of the relative properties of the MRF and the BRBF; therefore, the sizing of the bracing system plays a significant role in the effectiveness of the retrofitting scheme.…”

Section: Introductionmentioning

confidence: 99%

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Seismic Performance of Steel MRFS Retrofitted With Brbs: Influence of the Design Decisions for the Devices

Gutiérrez‐Urzúa¹,

Freddi²

2021

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

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Buckling Restrained Braces (BRBs) represent an effective strategy for the seismic retrofit of existing steel Moment Resisting Frames (MRFs), as they contribute to increase the strength, stiffness and energy dissipation capacity of the frame. Nonetheless, the design choices made during the retrofit process have a significant impact on the performance of the structure. For example, the inclusion of 'large' BRBs (i.e., high yielding strength and stiffness) may contribute to limit the deformation demands in the MRF; nonetheless, it may also induce large forces in the beams and columns of the existing structure. On the other hand, the inclusion of 'smaller' BRBs (i.e., low yielding force and stiffness), while allowing reaching the required safety requirements, may not be able to protect the MRF from damage. Additionally, the sizing of the BRB elements has an influence on the seismic demand parameters affecting the global performance of structural and non-structural components (i.e., peak and residual drifts, as well as storey accelerations). The present study investigates the impact of the design choices in the seismic performance of a retrofitted three-storey case-study frame by considering three retrofit options. The case-study MRF for the bare frame and the three retrofit configurations are modelled and numerically investigated in Opensees by monitoring local damage states (e.g., damage in BRBs, beams, columns, panel zones). First, a comparison is made in terms of non-linear static analyses to identify the deficiencies of the structures. Then, a fragility analysis is carried out through Incremental Dynamic Analyses (IDAs) accounting for the influence of the recordto-record variability. Finally, a comparison is made in terms of local and global Engineering Demand Parameters, by developing fragility curves for the components, for storey drifts and accelerations.

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Seismic performance of dual systems coupling moment‐resisting and buckling‐restrained braced frames

Cited by 39 publications

References 45 publications

Device uncertainty propagation in low‐ductility RC frames retrofitted with BRBs for seismic risk mitigation

Device uncertainty propagation in low‐ductility RC frames retrofitted with BRBs for seismic risk mitigation

Preliminary Numerical Analysis of the Seismic Response of Steel Frames With Masonry Infills Retrofitted by Buckling Restrained Braces

Seismic Performance of Steel MRFS Retrofitted With Brbs: Influence of the Design Decisions for the Devices

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