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This paper describes an effective and easy to use displacement-based procedure for seismic design or retrofit of frame structures equipped with hysteretic dampers, taking into account the flexibility of the supporting brace that is usually provided to connect the device to the external frame. The proposed framework leads the designer to the definit...
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... Hysteretic dampers are widely used for seismic passive protection of both new and existing structures [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. According to the European standard EN 15129 [16], hysteretic dampers, which are further classified in steel hysteretic dampers, friction dampers and metal extrusion dampers, belong to the category of Displacement-Dependent Devices (DDDs). ...
... The mechanical properties of each diagonal steel brace and the encased hysteretic steel damper form an in-series system can be expressed as a combination of the properties of the linear elastic brace (B) and of the elasto-plastic damper (D), as shown in Figure 8, where K B and K D are the elastic stiffnesses of the brace and of the damper, V y is the maximum force of the damper, d y, d bd and d 2 are the yield displacement, the design seismic displacement calculated at LLS and the ultimate displacement of the damper at CLS, respectively. Damper ductility µ D , defined as the ratio between d bd and yield deflection d y , for standard steel hysteretic dampers typically ranges between 4 and 16 [1,15,41,43]. The properties of the single damped brace (DB), in terms of stiffness K DB , ductility µ DB , and damping capacity ξ DB , are determined through the Equations (6)-(8), where ratio K B /K D between the stiffnesses of the steel brace and the damper should be taken ≥2 in order to guarantee that the largest part of the deformation of the story is concentrated in the damper [45,46]. ...
... The properties of the single damped brace (DB), in terms of stiffness K DB , ductility µ DB , and damping capacity ξ DB , are determined through the Equations (6)-(8), where ratio K B /K D between the stiffnesses of the steel brace and the damper should be taken ≥2 in order to guarantee that the largest part of the deformation of the story is concentrated in the damper [45,46]. Typical values of µ DB and ξ DB for damped bracing systems according to current practice are reported in Table 1 [15,43,44]. Therefore, in the study, the seismic upgrade of the case study buildings is performed considering damped brace systems characterized by values of ductility µ DB ranging from 3 to 13.5; more specifically, µ DBs equal to 3, 5, 7, 9, 11, and 13.5 are assumed. ...
While the use of steel hysteretic dampers has spread in the last decade for both new and retrofitted constructions, the Italian Building Code (IBC), as well as the Eurocode 8, does not provide specific recommendations for the design and verification of structures equipped with this technology. Due to their strong non-linear behavior, the effectiveness of the design with these systems must be verified through non-linear analyses. Non-Linear Time-History analyses (NLTHAs) are the most reliable method, but they are computationally expensive. The aim of the study is to investigate the reliability of non-linear static procedures, allowed by the IBC as an alternative to NLTHAs, for the analysis of buildings equipped with hysteretic devices provided with high damping capability. A parametric study is conducted on two reinforced concrete residential buildings, typical of the Italian residential heritage, retrofitted with hysteretic braces characterized by different stiffness and ductility values. The retrofit design is verified using non-linear analyses, both static and dynamic, considering either natural or artificial accelerograms, as the IBC deems them as equivalent. Within this work, reference is made only to the IBC; however, given the significant similarity between the IBC and the European code, the outcomes are expected to have a broader impact and to be not limited to the Italian context. Therefore, although this work is a preliminary study, it is believed to offer some initial insights on the topic and serve as the foundation for a more in-depth study that could lead to a regulatory revision on the subject.
... In buildings, traditional buckling restrained braced (BRB) components are employed to resist horizontal forces such as earthquakes or wind loads [1][2][3][4]. When the axial force exceeds the yield load of the BRB components, it undergoes a significant plastic deformation to dissipate the energy, thereby reducing structural damage [5]. However, large residual deformations of post-earthquake structures will increase the cost of structural maintenance. ...
In order to enhance the self-centering capacity of steel frame structures after earthquakes and reduce the tubes of traditional double-tube or triple-tube SC-BRB, an innovative single-tube self-centering buckling restrained brace (ST-SC-BRB) is proposed in this paper. Firstly, the structural configuration of the ST-SC-BRB component was described. Then, cyclic tests were conducted on one small-scaled BRB and one ST-SC-BRB with the same core steel plate. The test results indicate that the ST-SC-BRB specimen exhibits an excellent self-centering ability compared to the conventional BRB. However, their energy-dissipation capacities are still determined by the core steel plate. In addition, time–history analyses were conducted to evaluate the seismic performance of steel frame structures with BRBs and ST-SC-BRBs. The results suggest that the ST-SC-BRBs can effectively reduce the residual deformation of steel frame structures after earthquakes and contribute to the self-centering capacity of the steel frame structures. Finally, the influence of design parameters of ST-SC-BRB components on the seismic performance of steel frame structures was discussed. It is confirmed that the initial stiffness of the ST-SC-BRB component significantly influences the seismic response of the structure, while the self-centering ratio of the ST-SC-BRB component is a crucial factor in determining the residual deformations of the structure.
... Figure 1 illustrates a typical TMD installation on an existing RC chimney. The choice of TMDs as a retrofitting solution for historical RC chimneys is motivated by their proven effectiveness in mitigating structural vibrations under seismic loads (Donà et al., 2021;Faiella & Mele, 2019;Gill et al., 2017;Kazemi et al., 2021;Matta, 2021;Miranda, 2021;Nuzzo et al., 2019;Pu et al., 2018;Puthanpurayil et al., 2016;Rakicevic et al., 2012;Ruiz et al., 2016;Zeng et al., 2021;Zhou et al., 2021). The decision to focus on TMDs is rooted in their ability to efficiently reduce top displacement, base shear, and base moment in such structures. ...
In the late 1950s, driven by economic development and environmental considerations, industrial plants began utilizing reinforced concrete (RC) for chimney construction, lacking specific earthquake-resistance provisions. However, RC chimneys exhibit an inelastic response and a potential for brittle collapse under seismic loads. Rebuilding these chimneys is unattractive, given their symbolic importance within the community and the growing emphasis on sustainability, material recycling, and environmental resilience. In response to this need, we explore the performance of seven historic RC chimneys retrofitted with Tuned Mass Dampers (TMDs). This study considers the nonlinear material properties of concrete and steel rebars subjected to five European earthquakes. The TMDs’ effectiveness is evaluated by their impact on top displacement, base shear, and base moment. Additional aspects, such as equivalent damping and mode changes, are scrutinized. Through a parametric investigation, we analyze the influence of slenderness ratio, taper ratio, height, and vertically distributed mass on chimney response to earthquakes. Notably, the slenderness ratio emerges as a crucial factor affecting mass ratio, optimizing TMD parameters, base shear, and base moment. Interestingly, geometrical features appear to have minimal impact on equivalent damping.
Furthermore, examining energy dissipated by TMDs reveals their contribution to increased elastic damping energy in chimneys, concurrently reducing kinetic and hysteretic (inelastic) energies. Elastic damping energy involves dissipation through inherent system elasticity, while hysteretic damping encompasses energy dissipation due to material damping effects. This research sheds light on the potential of TMDs in enhancing the seismic resilience of historic RC chimneys and provides insights into the key parameters influencing their performance.
... 2 design objectives can be satisfied at specific seismic intensities. The structural performance indices include the magnitude of responses [11][12][13][14][15][16][17][18], the reduction ratio of responses owing to the dampers [19][20][21][22][23][24][25][26], the damping ratio supplemented to a structure by dampers [27][28][29], the additional energy dissipated by dampers [30], the peaks of transfer functions [31], and life-cycle costs [32]. ...
... The distribution of the VED storage stiffness was determined using the stiffness proportional criterion. Similar assumptions were adopted by Nuzzo et al. [12] and Xie et al. [20]. Unlike the above methods, which considered the displacement response as the design objective, Habibi et al. [30] established another method targeting the additional energy dissipation provided by EDDs, where the distribution of the damper energy dissipation at different stories was determined by the modal energy profile. ...
... According to the Italian Building Code "NTC-2018" [25,26], the dynamic response of steel or RC frames including dissipative braces can be predicted through two different calculation methods: (1) "Method-A", which is based on the theory of ductility for nonlinear systems [27] and the use of a behaviour factor to quantify the deformation demand [28,29]; and (2) "Method-B", using the Displacement-Based Design (DBD) procedures originally developed by Priestley et al. in 2007 [30], which is based on the definition of the effective (or secant) stiffness and the equivalent viscous damping of the braced frame [31,32]. ...
A refined design procedure for the seismic retrofit of warehouses or, more generally, single-storey RC frames bounded by "drift-sensitive" masonry infills and glazed curtain walls, is proposed in this paper by means of hysteretic braces. The calculation method is based on displacement-based design (DBD) procedures in which both the as-built frame and the dissipative braces are modelled through simple linear equivalent SDOF systems arranged in parallel. In this regard, with respect to the provisions of the Italian Building Code, two refinements are introduced: (1) the definition of two performance targets tailored to the protection of glazed curtain walls (among most expensive non-structural components) and to ensure an acceptable level of damage level for masonry infills; and (2) the adoption of a more accurate formulation for the estimation of the equivalent viscous damping developed both by the main frame and the dissipative braces. The refined design method is applied to a case-study building and the achievement of the performance targets is verified through NLTH analyses.
... For instance, Cardone (2014) presented the displacement limits and performance displacement profiles for the direct displacement-based assessment of existing bridges. Nuzzo et al. (2019) proposed a simplified probabilistic loss assessment methodology that builds on a direct displacement-based framework. Welch et al. (2014) described an effective and easy to use displacement-based procedures for seismic design or retrofit of frame structures equipped with hysteretic dampers, taking into account the flexibility of the supporting brace which is usually provided to connect the device to the external frame. ...
In recent years, various passive energy dissipation devices have been gradually applied to structural vibration control. Hysteretic dampers with hardening post-yielding stiffness (HDHPSs) could solve the problem of insufficient stiffness after the ordinary friction damper enters into its yield state, and realize multi-level seismic objectives and multi-stage energy dissipation. For hysteretic dampers with hardening post-yielding stiffness, computational formula of its resistance is given in this paper based on Wen-Gap connecting element, and the calculation formula of its equivalent yield strength is derived combining with the energy theory, which is verified by SAP2000 software. A 12-story steel frame with a weak story was strengthened by using HDHPSs and the dynamic performances of three frames are compared by using the connection element method proposed in this paper. The results show that the proposed formula of equivalent yield strength matches well with the numerical simulation results, which could provide a reference for seismic design of structures installed such dampers. The connection element method proposed in this paper is feasible to analyze the dynamic performances of structures with hardening post-yielding stiffness. The frame installed HDHPSs could effectively control the maximum displacement, which could meet the requirement of displacement performance target. This paper has certain reference significance for structural retrofit of existing structures.
... Finally, the results depend on the skill of the designer. All of this has discouraged the wide-scale application of supplemental energy dissipation devices in current practice and stimulated the development of effective design procedures [54][55][56][57][58][59][60][61][62][63][64][65][66]. To avoid the trial and error analysis, Guo and Christopoulos [67] presented a performance spectra-based method for structures equipped with passive supplemental damping devices (including both hysteretic and viscous dampers). ...
Despite significant progress in research and development of aluminum shear panels in recent decades, their implementation for seismic retrofit of existing reinforced concrete (RC) buildings can still be significantly extended. Their application is limited by the general lack of relatively simple and effective design criteria and proper guidelines. This paper develops a design method for the seismic retrofit of reinforced concrete buildings using aluminum multi-stiffened shear panels as dampers. Both the nonlinearity in the structure and the dampers-structure interaction are considered to give an optimal distribution of the shear panels over the height of the building. The analytical laws refer to dissipative aluminum shear panels recently tested and analyzed by the authors. The proposed procedure has been described in detail. Its applicability has been demonstrated by analyzing two typical RC buildings having drift capacity-to-demand ratios ranging from 0.505 to 0.624. The design value of the panel-to-frame stiffness ratio has been found to range from 0.594 to 1.432 as a function of the lateral stiffness of the existing building. The verification of the proposed procedure has been carried out by checking the validity of the design assumptions. The first one (i.e., the mode shapes remain the same before and after retrofit) has been checked using the modal assurance criterion that gives values ranging from 0.992 to 0.998. The second one (i.e., uniform yield drift distribution over the building height) has been checked by comparing the yield drifts with their average value giving a standard deviation ranging from about 11 to 15%. The effectiveness of the design method has been finally validated through nonlinear time-history analysis for different seismic accelerograms and hysteresis models. The results show that the seismic retrofit design procedure is effective in significantly reducing inter-story drift (maximum inter-story drift ratio demands ranging from 1.04 to 2.07%) thus satisfying the acceptance criteria of the building, and avoiding drift concentration and consequential weak story collapse.
... In view of this, the system failed to protect partitions and infills, which started to be damaged below this acceleration level due to their typical interaction with the structural skeleton [6]. At the same time, the activation of the steel dissipators occurred for the subsequent highest acceleration peaks helped substantially protect the RC structure, with light-to-moderate plasticizations of the most stressed beams and columns [3][4][5], consistently with typical performance capacities of several types of metallic dampers [7][8][9][10]. ...
A balanced performance improvement of the constituting structural members, infills and partitions is a fundamental requirement in seismic retrofit design of frame buildings. In order to pursue this objective, the response of the non-structural elements must be accurately simulated, so as to evaluate their damage evolution and the correlation with the response of the structural skeleton. In the study presented in this article, diagonal no-tension struts with multilinear “pivot”-type hysteretic behaviour are adopted as substitute elements for masonry infill and partition panels. A trilinear axial force–displacement backbone curve is generated for the equivalent struts and transformed in the lateral force-drift curve of the panels. The latter is then scanned in terms of sequential performance limits and ranges. This model is demonstratively applied to a real case study, i.e. a reinforced concrete frame building damaged by the 2016 Central Italy earthquake, although a retrofit intervention had been carried out a few years before. Based on the results of the time-history assessment analyses in its original conditions, an alternative retrofit solution is proposed, consisting in the incorporation of dissipative braces equipped with pressurized fluid viscous dampers. This technology was selected for its high-damping capacity, as well as for the prompt activation of the constituting devices starting from the early stages of the building seismic response. The verification analyses developed in retrofitted configuration for the main shock records of the 2016 earthquake confirm this property, showing slight damage only in a small number of partitions—instead of the diffused moderate-to-irreparable damage actually surveyed in the building partitions and infills—and safe response of all structural members.
... Another important drawback of damped braces is the increase in internal forces in the structural elements that surround these dissipative systems, which often need local strengthening, especially at connections that are particularly sensitive to stress concentration [2,7,31,32]. Moreover, the stiffening effect of these braces decreases the vibration period of structures, causing an increase in horizontal forces at the foundation level [30]. ...
... Moreover, the stiffening effect of these braces decreases the vibration period of structures, causing an increase in horizontal forces at the foundation level [30]. This requires further expensive interventions to strengthen the foundations of the main frame [7,[30][31][32][33]. ...
... Among the various types of current hysteretic dampers [24,[29][30][31][32][33][34][35][36], buckling-restrained braces (BRBs) are perhaps the most popular system and are used for both new and retrofitted structures [2,[37][38][39]. BRBs dissipate seismic energy through the inelastic deformation of a mild steel core confined in a rigid metal sleeve, which provides buckling resistance and allows the development of large and stable hysteretic loops with an almost symmetric hysteretic behavior [37,38,[40][41][42][43], providing an equivalent damping ratio on the order of 20% to 40%. ...
The paper presents the experimental characterization, the formulation of a numerical model, and the evaluation, by means of non-linear analyses, of a new friction damper conceived for the seismic upgrade of existing building frames. The damper dissipates seismic energy through the friction force triggered between a steel shaft and a lead core prestressed within a rigid steel chamber. The friction force is adjusted by controlling the prestress of the core, allowing the achievement of high forces with small dimensions, and reducing the architectural invasiveness of the device. The damper has no mechanical parts subjected to cyclic strain above their yield limit, thereby avoiding any risk of low-cycle fatigue. The constitutive behavior of the damper was assessed experimentally, demonstrating a rectangular hysteresis loop with an equivalent damping ratio of more than 55%, a stable behavior over repeated cycles, and a low dependency of the axial force on the rate of displacement. A numerical model of the damper was formulated in the OpenSees software by means of a rheological model comprising an in-parallel system of a non-linear spring element and a Maxwell element, and the model was calibrated on the experimental data. To assess the viability of the damper for the seismic rehabilitation of buildings, a numerical investigation was conducted by performing non-linear dynamic analyses on two case-study structures. The results highlight the benefits of the PS-LED in dissipating the largest part of seismic energy, limiting the lateral deformation of the frames, and controlling the increase in structural accelerations and internal forces at the same time.
... Italy, Greece and Romania are the European countries with the highest seismic risk and reinforced concrete (RC) frame structures are among the most recurrent typologies in these regions [1]. For this reason, seismic upgrading of RC buildings has emerged as a main research area [2][3][4][5], and in recent years a number of technologies and design procedures have been investigated for the retrofit of RC structures, including the use of supplementary energy dissipation systems [6][7][8][9][10][11][12][13][14][15][16]. ...
... However, also steel structures designed before the publication of modern regulations (e.g., AISC 341-16 [17], ASCE 7-16 [18], EN 1993-1-1 [19], EN 1998-1 [20]) have been reported to suffer local and global collapses as a consequence of earthquakes [21][22][23][24][25][26][27]. Braces equipped with energy dissipation devices have proved to be effective in reducing the seismic demand for both RC [6][7][8][9][10][11][12]15] and steel structures [26][27][28][29][30][31][32][33][34][35][36][37][38][39], and the most updated codes (e.g., [17,18,20]) have incorporated general guidelines for the design of dissipative braces in new constructions, with the goals of limiting the lateral displacement and dissipating most of the seismic energy in auxiliary devices, avoiding any damage to the gravity-load resistant system [33,[39][40][41][42]. ...
... Most of the procedures proposed in the literature [6][7][8][9][10][11]39,[43][44][45] for dimensioning dissipative braces are based on the Direct Displacement-Based Design (DDBD) method [45], in which a "substitute" single degree of freedom (SDOF) model is used to replace the real multi-degree of freedom (MDOF) structure. The design of the dissipating system is performed to achieve, for a given seismic intensity level, a specified performance objective, expressed for example as a specific target displacement [11]. ...
Supplementary energy dissipation has proved to be an effective way of protecting structures from the disastrous effects of earthquakes and has been used in the last decades both in new and in existing constructions. In this regard, various procedures for the design of the damping system for the seismic retrofit of buildings have been formulated over the years, mainly focused on reinforced concrete (RC) constructions, which represent the largest part of the existing stock in many seismic-prone countries. The study deals with the assessment of a displacement-based design procedure for proportioning the damping system recently proposed in the literature for RC framed buildings, with the goal of establishing a good practice for the application of the procedure to steel buildings as well. The method was applied to three case-study frames, regular in plan and in elevation, which were assumed as being representative of old structures designed without consideration of seismic requirements. The retrofit was performed by using chevron braces equipped with dampers with an elastic-perfectly plastic behavior. The method aimed at defining the properties of the dampers to achieve a target performance in terms of the maximum lateral deflection for a specific level of seismic intensity. The effectiveness and reliability of the proposed procedure was eventually assessed by evaluating the seismic performance of the upgraded steel structures in static and dynamic non-linear analyses.
