Influence of the design objectives on the seismic performance of steel moment resisting frames retrofitted with buckling restrained braces

Abstract

Buckling restrained braces (BRBs) represent an effective strategy for the seismic retrofit of existing steel moment resisting frames (MRFs), as they contribute to increasing the strength and ductility capacity of the structure. However, current design strategies do not provide recommendations on how the performance increase is achieved. Prioritising either the increase of strength or ductility capacity has an impact on the damage evolution and affects the overall performance of the structure. A low increase of strength typically requires larger exploitation of the ductility capacity (i.e., damage) of the existing structure, while a high increase of strength produces a significant increase of stiffness, which is often accompanied by an increase of the seismic demands that may limit the effectiveness of the retrofitting solution. The present study assesses the impact of these decisions on the overall performance of steel MRFs retrofitted with BRBs. For this purpose, two MRFs with several BRB retrofitting configurations are used as case study structures. Finite Element Models are built in OpenSees and assessed through Incremental Dynamic Analyses to account for the record‐to‐record variability. Fragility relationships are derived based on local Engineering Demand Parameters (EDPs) to describe structural and non‐structural damage, as well as path‐dependent damage indicators (i.e., residual drifts and cumulative ductility in BRBs). A comparison of the overall performance of the structures is carried out in terms of risk estimates for a high seismicity location.

Influence of corrosion on failure modes and lifetime seismic vulnerability assessment of low‐ductility RC frames

“…The use of global EDPs has several advantages, and, amongst others, they synthetically describe the structural response containing the computational effort involved in the analysis of complex models. Alternative strategies include the definition of the DSs of the structure directly considering local EDPs at member and/or section-level, for example, rotation, strength of cross-sections, and material strains [24][25][26][27][28] or the use of DS thresholds adopted from standard guidelines. 29 However, the direct use of local EDPs is usually too computationally demanding, while the use of code-based DSs for low-ductile non-seismically designed RC frames may lead to under-prediction of failure probability, in particular when the considered structure is undergoing material aging and time-dependent structural degradation.…”

Shaking table tests and numerical analysis of RC coupled shear wall structure with hybrid replaceable coupling beams

“…Moreover, dissipative devices can be used as structural fuses to concentrate damage so that they can be easily replaced, and structures can return to a fully functional condition within a relatively short time interval after the earthquake, hence promoting seismic resilience. 4,5 In this context, several innovative construction technologies (e.g., supplemental damping devices, [6][7][8] structural fuses, 9 seismic isolation systems, 10,11 rocking, [12][13][14] and self-centering systems [15][16][17][18] ) have been proposed in recent years for the development of seismic-resilient structures, hence minimizing the consequences of extreme seismic events.…”

Assessment of Non-Linear Analyses of RC Buildings Retrofitted with Hysteretic Dampers According to the Italian Building Code

“…These systems are characterized by constitutive behavior which is mainly dependent on displacement. Among DDDs, steel hysteretic dampers are the most popular devices for the seismic protection of ordinary structures, such as school, residential and industrial buildings, as proved by the large number of studies and applications [17][18][19][20][21][22][23][24][25], thanks to their good damping capacity and predictable behavior combined with ease of manufacturing and installation [26][27][28][29]. Focusing on the Italian scenario, recommendations on anti-seismic devices are given in Chapter 11 of the Italian Building Code, the IBC [30,31].…”

“…However, in spite of the increasing spread of hysteretic dampers for both new and retrofitted buildings [17][18][19][20][21][22][23][24][25], the IBC [30,31] does not provide specific recommendations for the analyses of structures provided with such devices but refers to the general provisions for buildings in seismic areas. The same consideration is valid also referring to the European design code [39].…”