Metallic Dampers Research Articles

Development of a novel rotational metallic damper as a dissipative connector in rocking steel core systems: Cyclic behavior and seismic demand

Rocking systems with stiff rocking cores have been proposed as a promising solution for mitigating concentrations of story drift and enhancing structural seismic resilience. This study introduces a novel rotational metallic damper, termed the rotational steel rod damper (RSRD), developed for use in rocking steel core systems to improve energy dissipation capacity. The configuration, working mechanism, and application of the RSRD in rocking steel core systems are described. Three critical energy-dissipating elements, low-yield-point steel rods with different edge shapes, were isolated from the RSRD and tested to validate the efficacy of an optimal hourglass shape, defined through cubic equations, in enhancing low-cycle-fatigue performance. Two RSRD specimens were then tested and analyzed, focusing on failure modes, cyclic behavior, rotational strength, and energy dissipation. Both specimens demonstrated positive and stable hysteretic performance and energy dissipation capacity, with maximum equivalent viscous damping ratios of 0.51 and 0.53. Subsequently, structural models of seven steel frames were developed in OpenSees for case studies. Nonlinear response history analyses were performed under 20 ground motion records scaled to DBE and MCE levels. Dynamic behaviors, particularly the seismic demand on RSRDs, were examined. Numerical results confirmed the efficacy of the RSRD in mitigating inter-story drift. The location of the pivoting point of the rocking core significantly influenced the rotational demand on the RSRD. The proposed RSRD presents an innovative energy-dissipating alternative for the development of rocking steel core systems.

Improving the Behavior of Reinforced Concrete Frame Using an Innovative Metallic Shear Damper

ABSTRACTDespite the advantages of reinforced concrete (RC) frame, they are susceptible to damages under seismic loading. This is due to the fact that the main elements of the RC frame carry the gravity load in addition to the lateral loading. So imposed seismic energy is dissipated through the two ends of the beam, making the repair of the element complicated due to the gravity load. Although adding concentrically braced frames (CBFs) improves the lateral strength and stiffness, the ductility of the system is reduced. This shortcoming is due to the susceptibility of the diagonal elements to buckling. To do so, in this paper, an innovative metallic damper was investigated numerically and parametrically. The damper compound of the shear plate is surrounded by two HSS sections at two ends. The damper pertains to simplicity of construction and implementation. Also, the required equation to design and prediction of the system is presented. To investigate the behavior of the system, dynamic (to consider its suitable performance against seismic expiation) and static analyses (to determine the structural parameters) were carried out. Results revealed that the HSS section used as flanges for the shear plate not only improves the behavior of the plate but also contributes to resisting the applied load. Also, the reduction of the length to the height ratio of the damper enhances the stiffness and strength and stiffness. Subsequently, the variable Ф was defined as the ratio of the strength of the flanges to the web plate that affects the response of the damper. Although raising the Ф reduced the stiffness and ultimate strength, it is suggested to design dampers with Ф > 2 to achieve suitable overstrength in accordance with economical aspects. Also, time‐history analysis indicated that the proposed damper prevents the buckling of the CBF elements and improves the energy‐dissipating capacity of the system.

Study on unseating prevention for multi-union long simply supported girder bridges under near-fault ground motions

Girder shifting is a common form of seismic damage for girder bridges. Unseating could occur when the displacement of the girder is too large, especially for bridges near faults, because the velocity impulse effect leads to greater displacement responses of structures. Setting metal dampers between girders and piers is a useful way to control the seismic behavior and reduce the risk of unseating. Since metal dampers are inevitably exposed to the erosive service environments, their mechanical properties may degrade due to corrosion. In this paper, a U-shaped metal damper made of stainless steel instead of mild steel (i.e., U-shaped stainless steel damper, which could be named simply as USSSD) is proposed and applied to the seismic reduction design of girder bridges. First, the finite element model (FEM) of the USSSD is built by the ABAQUS, and its force-displacement relationship is obtained based on the skeleton curve, which is fitted by the trilinear kinematic strengthening model. Then, a multi-union long simply supported girder bridge is taken as an example. The FEM of the adopted bridge is established via the Midas Civil to verify the seismic mitigation effect of the proposed USSSD excited by near-fault ground motions. The numerical analyses demonstrate that the unseating may occur without the use of the USSSDs. The relative displacement between the girder and pier is effectively controlled by the USSSDs, and the reduction is more than 50 %. When the bridge is equipped with the USSSDs, both the curvature ductility coefficient of the pier bottom and the maximum drift of the pier tip increase by a limited amplitude, which do not cause additional damage to the piers.

A comparative experimental and numerical study on the shear and flexural mechanism of an innovative butterfly-damper

In this paper, the behavior of an innovative metallic damper made of butterfly plates (with shear or flexural mechanisms) to improve the behavior of the CBF system is considered. These dampers can provide similar seismic resistant properties but concentrate most damage in the damper region during a seismic event. This has considerable practical utility in the construction industry and can allow quick replacement of these dampers (instead of replacing braces) after damage without impacting the serviceability of the building. To consider the behavior of the proposed dampers, experimental and numerical as well as parametrical studies were carried out. Experimental results indicated that both shear and flexural dampers pertain to stable hysteresis loops although the flexural damper showed a better ultimate rotation. However, experimental and numerical results revealed that the shear damper's ultimate strength, stiffness, and energy dissipating capacity reached >3.58, 4.59, and 14.56 times greater than flexural dampers. Results indicated that the response of the dampers is related to the slenderness and that the allowable slenderness was suggested for the design of the dampers.

Mechanical behavior and seismic control performance of a metallic torsional damper for flexible structures

The use of metallic dampers is an effective way to reduce seismic responses and dissipate excessive vibration energy for civil structures. Conventional metallic dampers employed energy dissipation by plastic deformation under bending or shear modes are hard to design, and may cause uniform distribution of stress in the metallic components. In this paper, employing the high plastic deformation capacity of aluminum materials, a metallic torsional damper using a gear and rack device (MTDGRD) is proposed to enhance the control effectiveness for the structural response reduction under earthquakes. The static mechanical behavior and energy dissipation of aluminum metallic components under torsional deformation are experimentally studied. Moreover, the configuration and working principle of the proposed damper are introduced. The dynamic behavior of the proposed damper is experimentally studied. For precise modeling in simulations, the elastic-plastic theory of torsional deformation is used to derive the mechanical model of the proposed damper and the model accuracy is validated by experimental data. Finally, numerical simulations under different seismic ground motions controlled by a proposed MTDGRD are compared to that controlled by a conventional tuned mass damper (TMD) for a 10-floor flexible structure. The results show that aluminum 6061# of the energy dissipation capacity is higher than aluminum 1060#. The dynamical tests show that the loading frequency and operational cycles have very limited effect on mechanical behavior and energy consumption capacity of the MTDGRD. The proposed dynamic mechanical model of the MTDGRD has considerable accuracy in numerical simulations and seismic control simulations show the better performance of the proposed damper in reducing structural displacement responses than the conventional TMD with a mass ratio of 0.5 %.

Seismic behavior of CFDST frame with metallic dampers: Damage-controlled design and performance assessment

Current investigations on performance-based seismic design of structures generally employed story drift as performance objectives. However, the story drift could only partially reveal the global damage of a structure and not control the damage of important components. In order to control the damage of various components in a structure, this paper proposed a new damage-controlled seismic design method using the Park & Ang indexes of components. Firstly, the Park & Ang damage index was simplified as an equivalent ductility damage index for various components. The energy balance concept was used to observe the hysteretic energy demand which was subsequently distributed to all stories. Thus, the components of each story could be designed based on their damage indexes under design-based and maximum-considered earthquakes. Four concrete filled double skin tubular (CFDST) moment resisting frames equipped with metallic dampers with various layouts were designed based on the proposed design method. Time history analyses on these four structures were performed after validating the accuracy of nonlinear model by Opensees. Analysis results showed that the components in four structures exhibited expected damage states as illustrated by the design method. It also verified that proposed seismic design method was effective to control the damage of various components, which was beneficial for protecting the important components in a structure by setting low damage indexes for them. The seismic design method and analysis results also provided a reference for the design of moment resisting frame with energy devices.

Development and application of out-of-plane deformable X-shaped brace for energy dissipation and thermal stress mitigation: An experimental and numerical study

Exoskeleton systems are increasingly employed in both new and existing buildings to enhance seismic performance. Addressing the critical challenges of energy dissipation and thermal stress mitigation in these systems, an out-of-plane deformable X-shaped energy dissipation brace (OPD-XEDB), integrating an out-of-plane X-shaped brace with a shear-type metallic damper, was proposed in this study. A seismic design methodology for OPD-XEDB was firstly developed, ensuring effective energy dissipation of the damper before any potential brace buckling. Following this methodology, two specimens, exhibiting distinct failure modes of damper shear fracture and brace buckling, were designed and subjected to quasi-static loadings to explore their energy dissipation mechanisms. Upon these experimental results, a numerical model incorporating buckling and pinching behaviors was proposed and calibrated, effectively capturing the hysteretic responses of the specimens. This model was then employed in a comprehensive numerical analysis, validating the effectiveness of design methodology and determining the optimal specifications for the OPD-XEDB in a prototype building. Ultimately, thermal analysis and nonlinear time history analysis were conducted on the prototype building. The thermal analysis proved the effectiveness of the OPD-XEDB's out-of-plane configuration in mitigating thermal stress by out-of-plane deformation, significantly mitigating thermal stress in braces and interconnected moment frames by 96.59–96.66 %. The time history analysis revealed that the dampers in OPD-XEDBs dissipated 11.6–23.2 % of total seismic energy, effectively preventing substantial buckling in the X-shaped braces. This energy dissipation mechanism led to a remarkable 79.7 % reduction in steel consumption for post-earthquake retrofitting, thereby significantly enhancing the seismic resilience of the primary structure.

Development and experimental study of a novel rotational metallic damper

As passive control technology advances and building forms become increasingly diversified, traditional axial and shear dampers may no longer meet diverse structural application requirements. This paper introduces a novel rotational metallic damper, i.e. rotational steel rod damper (RSRD), as an alternative engineering solution. The RSRD comprises three steel plates rotating around a central pin and four low yield point steel rods as energy dissipators. The input seismic energy can be dissipated in the form of plastic rotation of the RSRD. Initially, the structural form, working mechanism, and design approach of the RSRD are presented. Subsequent cyclic quasi-static tests on two RSRD specimens under varied loading protocols demonstrated satisfactory energy dissipation capacity, with an equivalent viscous damping ratio exceeding 0.47. The cyclic behavior, rotational strength, and cumulative plastic deformation capacity are discussed following the tests. A finite element (FE) analysis on the RSRD using ABAQUS is conducted to further investigate its performance. A comparison between the hysteretic behavior and failure mode of tested and simulated results is presented to validate the FE model. Additionally, two new structural forms, with linear and arc-shaped weakening on the steel rod, are simulated and compared with the original. FE results indicate that the arc-shaped weakening of the steel rod effectively avoids plastic strain concentration, showcasing superior low-cycle-fatigue performance. Finally, nonlinear time history analyses on two RC frames, with and without RSRD, reveal that structural and non-structural damage can be controlled under the maximum considered earthquake (MCE) by utilizing RSRDs.

The cumulative plastic deformation demand for buckling restrained braces imposed by the strong motions in the 2023 Türkiye earthquake sequence

The Türkiye earthquake sequence on February 6, 2023, was featured by the closely located earthquake doublet of Mw 7.8 and Mw 7.5. The consequent strong ground motions are supposed to be able to impose high demands on the ultra-low-cycle fatigue performance of metallic dampers in buildings, including the widely used buckling restrained braces. This study evaluates the cumulative plastic deformation (CPD) demands on buckling-restrained braces (BRBs) in multi-story buildings imposed by the strong ground motions in the 2023 Türkiye earthquake doublet. Thirty-two records of the highest peak ground accelerations were selected from the strong motion database. Among them, eight captured the ground motions during both events, and the rest only captured the shaking of either of the events. The CPD demands on the BRBs in reinforced concrete frames with various fundamental periods, brace-to-frame stiffness ratios, and BRB ductility ratio are calculated by nonlinear time history analyses and are summarized in the form of enveloped spectra of CPD ratios at constant ductility. The results show that the CPD demands on BRBs increase with smaller brace-to-frame stiffness ratios and larger BRB ductility ratios. The enveloped CPD demands are several hundreds of times the nominal yield deformation of the BRB, which are much higher than the CPD demands for the calibration tests of BRBs stipulated by AISC 341 in the US.

Effect of U-Shaped Metallic Dampers on the Seismic Performance of Steel Structures based on Endurance-Time Analysis

Seismic performance of steel moment-resisting frames is investigated through the incorporation of U-shaped metallic dampers. The primary objective is to assess the effectiveness of these dampers in mitigating seismic responses by utilizing various analysis techniques. Two representative structural configurations (5 and 10-story) are studied in both damped and undamped states to reveal the impact of dampers on seismic response reduction. The study utilizes the endurance time analysis (ETA) method, known for its efficiency in evaluating structural seismic performance. To validate the analysis results, a benchmark comparison is made through nonlinear time history analysis (NTHA). Incremental dynamic analysis (IDA) is also conducted to assess structures’ intensity measures with respect to their damage intensity index. The findings demonstrate that U-shaped metallic dampers substantially reduce inter-story drift and story shear forces. Importantly, a close alignment between the results obtained from ETA and NTHA underscores the reliability of the former in assessing seismic performance with supplemental damping devices.

Cyclic behavior of carbon steel and austenitic stainless steel hollow laminated viscoelastomer-filled steel tube damper under unidirectional and bidirectional loadings

The hollow laminated viscoelastomer-filled steel tube damper (HLVSTD) is a metallic damper with stable working performance and excellent energy dissipation capability. It can exhibit equal mechanical performance in any single horizontal direction based on the geometric features of the circular shape. However, the impact of carbon steel tube material, stainless steel tube material and bidirectional loading on the mechanical behavior of HLVSTD remains unclear. The objective of this study is to analyze the mechanical performance of HLVSTD under bidirectional loading conditions using carbon steel tubes and austenitic stainless steel tubes, which are commonly utilized in China. Experimental tests were conducted using both unidirectional loading and bidirectional loading to comprehensively assess the performance. The results indicate that, under unidirectional and bidirectional loading, HLVSTDs made from both carbon steel and austenitic stainless steel tubes exhibit stable hysteresis curves. In comparison to the carbon steel tube HLVSTD, the counterpart with an austenitic stainless steel tube demonstrates higher equivalent stiffness, ultimate force, energy dissipation and low-cycle fatigue performance. Moreover, HLVSTDs under bidirectional loading exhibit a similar trend in mechanical performance compared to those under unidirectional loading. Regardless of whether the tube material is carbon steel or austenitic stainless steel, the cumulative displacement and cumulative energy under bidirectional loading were found to be twice as much as those observed under unidirectional loading, which demonstrates the excellent mechanical performance of HLVSTD under bidirectional loading.

Seismic fragility assessment of the innovative and optimal box-shaped dampers in steel frame structures

Box-shaped dampers (BSDs) are newly introduced, innovative, and low-cost metallic dampers installed along the diagonal members of the frames. Dissipating the input energy by continuously forming plastic hinges, BSDs prove to possess the potential to serve as a fuse during earthquakes. Nonetheless, little literature exists on the seismic response of the BSD-equipped steel frames. Hence, this study aims to evaluate the seismic performance of steel frames equipped with BSDs. First, the failure mechanism and shape effects of these dampers were investigated using non-linear finite element analysis (FEA) in ABAQUS. Using the results obtained from the FEA, the incremental dynamic analysis (IDA) is utilized to determine the vulnerability of BSD-equipped frames during earthquakes. In this regard, IDA analysis was performed on 5- and 10-story steel frames equipped with BSDs, and the fragility curves of the frames were extracted, followed by calculating the structures' collapse margin ratio (CMR). Furthermore, the obtained results were compared to that of traditional X-braced frames. The results revealed that the BSD-equipped frames display better performance compared to that of the X-braced frames, indicating that these dampers can replace the conventional bracing systems for structural strengthening.

Shaking table test of a controlled rocking reinforced concrete frame with column-end hinge joint

A controlled rocking reinforced concrete frame with column-end hinge joint (CR-RCFC) is proposed, in which the pure hinged joints are adopted, the post-tensioned (PT) tendons are arranged in the columns to provide lateral stiffness and self-centering capacity, and the inter-story metal dampers are utilized to dissipate earthquake energy and control displacement response. Based on the quasi-static cyclic tests of the CR-RCFC, the rotation stiffness of the joint was obtained. Shaking table tests were carried out on the 1/3-scale CR-RCFC and conventional reinforced concrete frame (RCF) test models. The test results are studied in terms of damage observations, dynamic characteristics, peak floor accelerations, peak inter-story drifts, and force changes in the PT tendons. The results indicated that the CR-RCFC can effectively protect concrete members from damage even under rare earthquakes. Meanwhile, the CR-RCFC can significantly reduce the acceleration response compared with the RCF, and the metal dampers can effectively control the displacement response.

Investigating the seismic response of chevron braced frame equipped with a replaceable sandwiched fused damper

This paper proposes a new replaceable metallic damper called a Sandwiched Fuse Damper (SFD) to enhance the seismic performance of chevron braced frame. The proposed damper decreases the damage level and increases the deformation capacity of braced frames. To investigate the cyclic behavior of the proposed damping system, experimental tests were carried out on two 1/2-scaled chevron-braced frames equipped with the SFD and a conventional chevron-braced frame for comparison. Test specimens were one-bay single-story chevron braced frames execrated from the bottom story of a prototype three-story building. The experimental results showed that the SFD-braced frames possessed stable hysteresis loops, a large deformation and excellent energy dissipation capacities. The results also indicated that the ductile flexural-yielding of fuses governed the failure of SFD-braced frames. Besides, it was found that the ductility, energy dissipation, and deformation capacity of SFD-braced frames were 2, 4.73, and 4.59 times larger than that of the conventional chevron-braced frame.

Experimental Investigation on Cyclic Performance of Rotation‐Based Metallic Damper

Experimental Investigation on Cyclic Performance of Rotation‐Based Metallic Damper

Seismic retrofitting of RC frames combining metallic dampers and limited strengthening with FRP/SRP applying energy-based methods

Strengthening with advanced composite materials (i.e. Fiber Reinforced Polymer laminates, FRP, and Steel Reinforced Polymer spikes, SRP), or adding passive devices (metallic dampers) have been used separately for seismic retrofitting RC frames. On the one hand, using only FRP/SRP may prove insufficient and cost prohibitive. On the other hand, installing hysteretic dampers in an existing frame that lacks a minimum quasi-elastic deformation capacity can jeopardize the efficiency of the metallic dampers, leading to devices of excessive size and cost. This study investigates combining limited FRP/SRP strengthening with the addition of metallic dampers to attain a cost-effective strengthening scheme. This paper elucidates the structural variables involved in such a hybrid solution and the desirable range of their values through an energy-based method. The validity of the proposed method and formulation is assessed through numerical simulations conducted on a RC frame subjected to far-field and near-fault earthquakes.

Development and Investigation of the Hysteretic Behavior of an X-Shaped Metal Damper with an Oblique Angle

To investigate the hysteretic behavior of an X-shaped metal damper (XMD) with an oblique angle, cyclic loading tests were carried out on nine specimens, including two XMDs without buckling-restrained devices, four XMDs with stiffening ribs, and three XMDs with cover plates as references. The test results showed that the oblique angle could effectively increase the stiffness, strength, and energy dissipation of the XMD. When the oblique angle of an XMD with stiffening ribs increased from 0° to 30° at the applied displacement of 8.4 mm, the mean strengths and cumulative energy dissipation of specimens increased by about 80.77% and 80.57%, respectively. Although asymmetric hysteretic loops were also observed in specimens with an oblique angle and buckling-restrained devices, stable hysteretic curves were obtained. This indicated that the stiffening ribs and cover plates can effectively constrain the buckling behavior of XMDs. Additionally, the mean strengths of specimens with stiffening ribs were a little higher than those of specimens with cover plates. Subsequently, the finite element analysis models of the XMDs were proposed, in which the metal plasticity model considering isotropic and kinematical hardening was used to model the material properties of steel, and the simulation results matched well with the test results. Finally, the theoretical calculation method was proposed to predict the elastic stiffness of specimens, and the theoretical elastic stiffness matched well with the test results.

Experimental Study on Energy Dissipation Performance of SPA Shear Plate Metal Damper Based on Jacket Platform

Aiming at the problem of excessive vertical vibration caused by seismic primary waves in jacket structures located in seismic zones in China, a new type of shear plate metal damper with upper and lower elliptical openings (SPA) is proposed in this paper. The seismic model test is carried out to compare the shear plate metal damper with three traditional opening forms, central elliptical opening, single row opening, and double row opening, and the hysteretic curve, skeleton curve, and cyclic hysteretic energy dissipation capacity are analyzed. The results show that the energy dissipation performance of the new shear plate metal damper with upper and lower elliptical openings proposed in this paper is better than that of the other three types of dampers.

Seismic performance of a novel hemisphere-based rocking hinge realizing self-centering damage-free bridge system

The rocking column with post-tensioned (PT) strands is shown able to provide satisfactory self-centering capacity for bridge systems after earthquakes. However, local damage to concrete at the rocking interface and consequent losses of PT force may occur during ground motions. To minimize the local damage and facilitate the construction procedure, this paper proposes a novel hemisphere-based rocking hinge (HRH) at the rocking interface. For the columns with the proposed HRH, self-centering capacity is provided by PT strands, and energy dissipation is supplied by oval-shaped metal dampers. Hemispheres are adopted to achieve pre-determined rotation center, as well as reduce stress concentration and avoid local damage to the rocking interface. The construction of the HRH is first described, followed by an analytical model characterizing the hysterical behavior of the column with this HRH. The analytical model is then numerically validated using models developed by both the Abaqus and the OpenSees softwares. Accordingly, a design procedure is presented for columns utilizing this HRH, achieving damage-free and self-centering seismic performance. Finally, the HRH is implemented in an illustrative bridge, and its efficiency is verified by comparing the seismic responses with the conventional RC bridge. Results show that the HRH bridge possesses an excellent self-centering capacity and is able to maintain operational even after a major earthquake.

Numerical study of metallic dampers’ effect on seismic performance of concrete frames

Numerical study of metallic dampers’ effect on seismic performance of concrete frames