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Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems, including rigid system (RS), floating system (FS), and passive energy dissipation system (PEDS), is conducted to study the effects of connection configurations on seismic responses and fragilities. Finite element models of bridges are established using OpenSees. A new ground motion screening method based on the statistical characteristic of the predominant period is proposed to avoid irregular behavior in the selection process of ground motions, and incremental dynamic analysis (IDA) is performed to develop components and systems fragility curves. The effects of damper failure on calculated results for PEDS are examined in terms of seismic response and fragility analysis. The results show that the bridge tower is the most affected component by different structural systems. For RS, the fragility of the middle tower is significantly higher than other components, and the bridge failure starts from the middle tower, exhibiting a characteristic of local failure. For FS and PEDS, the fragility of the edge tower is higher than the middle tower. The system fragility of RS is higher than FS and PEDS. Taking the failure of dampers into account is necessary to obtain reliable seismic capacity of cable-stayed bridges. [ABSTRACT FROM AUTHOR]

Shipping impact and wave loads impose dynamic loads on jetties and platforms in the sea, which cause the vibration of structures. Recently, many advanced viscous damper devices have been developed for implementation in structures to diminish structural vibration due to earthquakes or wind. However, the longitudinal configuration of conventional viscous damper devices requires adequate space to locate the damper device within the frame structure, which limits the application of viscous dampers for use in jetties or platforms to dissipate the vibrations imposed by ship impact or wave force. For this reason, in this study, an attempt has been made to develop a new viscous plane damper device applicable in limited space positions where the longitudinal damper device is not able to fit. For this purpose, the initial design for the viscous plane damper device is proposed, and the prototype of the device is manufactured. Then, the performance of the fabricated viscous plane damper is examined through experimental tests by applying cyclic loads using a dynamic actuator. In order to investigate the effect of the diameter and configuration of the piston's orifices, five different diameters for the orifices of 1, 2, 5, 8, and 10 mm are included, and three different distribution configurations of the orifices in the piston plate as Configurations A, B, and C are manufactured and tested experimentally. The lab testing is conducted by applying cyclic loads with different frequencies to evaluate the performance of the developed plane damper device under various load velocities. Accordingly, the dynamic performance of the damper device, including the damping force, effective damping and stiffness and the energy dissipation capacity obtained from the hysteresis response (force–displacement result), is investigated. The results of the experimental tests prove the functionality of the developed device to generate the desired damping force and vibration energy dissipation during applied cyclic loads. Therefore, the new plane damper device can be implemented in any structure to dissipate the effect of imposed vibration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Earthquakes have serious destructive effects on building structures, and effective seismic design is the key to building design. In order to reduce the damage of earthquakes to building structures, seismic design of buildings is based on improved viscous dampers. First, the displacement seismic design was studied and a displacement-based structural seismic model was constructed. In addition, analyzing traditional viscous dampers, an improved viscous damper is adopted based on it. Through equivalent damping expression, a displacement seismic model based on the improved viscous damper is constructed. Finally, two targets, frequent and rare earthquakes, were selected for experimental analysis. In frequent earthquake experiments, the improved viscous damper structure increased the shock absorption rate by 35.65 % compared to the no-structure design. In the shear force comparison, the maximum shear force of the improved viscous damper structure in the HB wave X direction is 2186 KN, which is the smallest shear force among the three structural designs. In a rare earthquake experiment, the maximum value of the floor shear force in the X-direction of the Humbolt bay wave of the proposed improved viscous damper structure was 8696 KN. Compared with other structures, the floor shear force was the smallest. In the comparison of floor displacements, the maximum inter-story displacement in the Humbolt bay wave Y-direction of the proposed improved viscous damper structure is 162 mm, which is the smallest inter-story displacement compared with other structures. In addition, the structure apex displacement was also compared. The structure apex displacement value of the improved viscous damper structure was lower than that of other structures and was in the slight damage range. The overall seismic effect was significantly better than other structural designs. The research content is conducive to optimizing the application effect of viscous dampers and provides technical reference for the seismic design of building structures. [ABSTRACT FROM AUTHOR]

Expansion joints render bridge structures highly vulnerable to damage during strong ground motions. Failures of expansion joints triggered by earthquakes not only jeopardize the post-earthquake serviceability of the bridge but also have a significant impact on the bridge's overall seismic performance. Despite extensive investigations and efforts to integrate these measures into design specifications aimed at mitigating the consequences of relative movements between adjacent bridge spans, major earthquakes have still revealed instances of damage related to expansion joints. On 6 February 2023, strong earthquake sequences occurred in Kahramanmaraş, Turkey, with magnitudes of M7.7 and M7.6. The fault lines and epicenters of these shallow earthquakes were near the city and town centers and caused severe structural damage to buildings and infrastructures. There are approximately 1000 railway and highway bridges in the earthquake-affected region. Although both highway and railway bridges have generally performed well, some bridges experienced structural damage during the Kahramanmaraş earthquakes. A large number of damage on the bridges is due to pounding and opening relative movements in expansion joints. This paper presents a comprehensive seismic evaluation of expansion joint failure mechanisms on bridges without viscous dampers during the 2023 Kahramanmaraş earthquake sequences and an in-depth investigation into the seismic performance of bridge expansion joints equipped with viscous dampers and shock transmission unit devices are implemented utilizing the strong ground motion data collected throughout the earthquake sequences. It can be stated that the near-fault induced significant directivity and fling effects, resulting in notable velocity pulses and permanent tectonic deformations, and that these effects contributed to the failures of expansion joints, viscous damper devices, pot bearings, and shear keys. [ABSTRACT FROM AUTHOR]

AbstractViscous dampers commonly mitigate structural vibrations, and various models exist to capture their nonlinear behavior. This article proposes a Hysteretic Maxwell model obtained by evolving the standard Maxwell model to effectively integrate the hysteresis effect. The model entails only a limited number of parameters. The optimized model parameters are identified by fitting model predictions with reported experimental measurements. A numerical case study is conducted, focusing on the longest stay cable of the Rades-La Goulette cable-stayed bridge. Simulation results emphasize the significant improvement of the proposed model over its predecessor, showcasing reductions in both free and forced first-mode vibrations. [ABSTRACT FROM AUTHOR]

Stay cables are becoming slender and their fundamental frequencies are becoming lower with the span of bridges increasing, thus leading to the occurrence of multi-modal vibration under various excitations. As a simple and effective strategy for cable vibration mitigation, the external damper is widely used in practice. However, one damper normally can target only fewer modes and poses limited effects on the control of multi-modal vibration. This paper proposed the use of a joint control system combining a viscous damper and a tuned mass damper for mitigating the multi-modal vibration of stay cables, followed by the optimization methodology of tuning and positioning. The control performance of the joint system was evaluated by numerical simulations. The feasibility of the joint control system was validated by analyzing the results of the comparative study, therefore providing a possible solution to multi-modal and high-modal vibration of stay cables. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study specifically focuses on the damping efficiency of a damped structure with additional viscous dampers. A two-layer steel frame structure with eight sets of viscous dampers is used to conduct a series of seismic simulation shaking table tests, including a non-damped structure without dampers and two damped structures with dampers placed at 1/2 and 1/6 of the beam span, respectively. By conducting these tests, the energy dissipation, force, and displacement of the damper, as well as the parameters of the structure such as floor displacement and acceleration, are obtained. The main damping efficiency indicators of the damped structure are calculated, including the additional damping ratio, inter-story displacement utilization rate, as well as the reduction rate of the vertex displacement and the base shear relative to the non-damped structure. The study shows that the viscous dampers exhibit full hysteresis loops and a strong energy dissipation capacity in the structure. The seismic response of the vertex displacement and base shear in the damped structure is significantly smaller than that in the non-damped structure. Under different seismic levels, including frequent earthquakes, occasional earthquakes, and rare earthquakes, the damping effect of the dampers placed at 1/2 of the beam span is significantly better than that placed at 1/6 of the beam span. For example, the additional damping ratio for the X-direction artificial wave REN is 19% and 11%, 20% and 13%, and 13% and 11%, respectively. The patterns for inter-story displacement utilization ratio, reduction rate of the vertex displacement, and reduction rate of the base shear are similar. The research findings strongly indicate that the damped structure with additional viscous dampers exhibits excellent damping efficiency. In future damping design, designers need to fully consider the placement of viscous dampers within the beam span. [ABSTRACT FROM AUTHOR]

Abstract To mitigate cable oscillations in cable-stayed bridges, a common approach involves using a strategically positioned viscous damper near the cable’s anchorage and bridge deck. However, for longer cables, this method may be insufficient due to installation constraints. In such cases, supplementing the damping system with a high-damping rubber (HDR) damper near the cable’s anchorage point on the bridge tower becomes imperative to enhance the cable’s damping ratio. Conventional designs often overlook crucial factors like viscous damper support stiffness and stay cable bending stiffness when integrating dampers into cable-stayed structures. This study presents findings on achieving an effective damping ratio in stay cables by using both a viscous damper and an HDR damper, considering the influence of viscous damper support stiffness and stay cable bending stiffness. The results indicate that the combined deployment of these dampers achieves a damping efficiency approximately equivalent to the sum of their individual effects. Importantly, decreased viscous damper support stiffness significantly affects the damping effectiveness, leading to a rapid decline in the stay cable’s damping ratio. While stay cable bending stiffness also influences the damping ratio, its impact is relatively less pronounced than that of viscous damper support stiffness. The study outcomes enable a more accurate prediction of the achievable damping ratio for a stay cable with additional components, considering both damper support stiffness and stay cable bending stiffness. Furthermore, the study explores parameters of both the viscous damper and HDR damper, such as the viscous coefficient, loss coefficient, HDR damper stiffness, and damper placement, evaluating their influence on the first damping ratio of the stay cable. The survey results provide valuable insights for determining optimal parameters for both dampers, maximizing the damping efficiency of cable-stayed bridges.

Recent studies demonstrated that high-frequency earthquakes have the most effect on the economic losses during seismic events. However, code-based seismic design criteria mainly aim to provide the occupants' life safety. In this regard, code-compliant structures may result in significant economic losses during their life span. These damages contribute to the higher repair costs and lengthy functional disruptions of these structures. Improving the seismic behaviour of the structures by control devices could be one of the most efficient solutions. On this subject, applying fluid viscous dampers (FVDs) is an economical and reliable method. Optimizing the properties of these devices contributes to more efficient seismic behaviour of the structures. In this study, the key design parameters of viscous dampers, including damping coefficient and velocity exponent, are considered as optimization variables to achieve minimum life cycle cost (LCC) using the genetic algorithm (GA). To investigate the efficiency of the proposed approach, four-, eight- and twelve-story structures in high-seismic regions are investigated to consider different assumptions. The Endurance Time method (ETM) is adopted to conduct nonlinear analysis due to its high computational cost-efficiency and reliability. The results show that the nonlinear viscous dampers would decrease the total seismic loss of the structures by up to 40% in comparison with linear dampers. The optimal amount of velocity exponent is also obtained as a function of variation with the height and seismic region of the structures. [ABSTRACT FROM AUTHOR]

To mitigate cable oscillations in cable-stayed bridges, a common approach involves using a strategically positioned viscous damper near the cable's anchorage and bridge deck. However, for longer cables, this method may be insufficient due to installation constraints. In such cases, supplementing the damping system with a high-damping rubber (HDR) damper near the cable's anchorage point on the bridge tower becomes imperative to enhance the cable's damping ratio. Conventional designs often overlook crucial factors like viscous damper support stiffness and stay cable bending stiffness when integrating dampers into cable-stayed structures. This study presents findings on achieving an effective damping ratio in stay cables by using both a viscous damper and an HDR damper, considering the influence of viscous damper support stiffness and stay cable bending stiffness. The results indicate that the combined deployment of these dampers achieves a damping efficiency approximately equivalent to the sum of their individual effects. Importantly, decreased viscous damper support stiffness significantly affects the damping effectiveness, leading to a rapid decline in the stay cable's damping ratio. While stay cable bending stiffness also influences the damping ratio, its impact is relatively less pronounced than that of viscous damper support stiffness. The study outcomes enable a more accurate prediction of the achievable damping ratio for a stay cable with additional components, considering both damper support stiffness and stay cable bending stiffness. Furthermore, the study explores parameters of both the viscous damper and HDR damper, such as the viscous coefficient, loss coefficient, HDR damper stiffness, and damper placement, evaluating their influence on the first damping ratio of the stay cable. The survey results provide valuable insights for determining optimal parameters for both dampers, maximizing the damping efficiency of cable-stayed bridges. [ABSTRACT FROM AUTHOR]

Additional damping provided by a viscous damper (VD) may not be sufficient to mitigate the wind-induced vibration of long cables. In this paper, the damping properties of the hybrid application of a VD and a tuned mass damper (TMD) on a taut cable are studied. The VD-TMD-cable system's characteristic equation is formulated by using complex modal analysis. The modal properties of the VD-TMD-cable system are subsequently discussed. Then, a damper optimization principle is introduced. When optimizing the cable single mode, based on the damper optimization principle, the effects of the damper parameters of the VD and TMD on the damping ratio of the optimized cable mode are investigated. Furthermore, a damper optimization method for cable multimode vibration mitigation is proposed. Finally, case studies are presented to verify the effectiveness of the damper optimization method. It is shown that the hybrid application of the VD and TMD can significantly improve the damping ratios of the cable multimode. The hybrid application approximates the superposition of separate applications if cable lower modes are optimized and outperforms the superposition of separate applications for cable higher modes if cable higher modes are optimized. The optimum modal damping ratios can be obtained efficiently by the proposed damper optimization method for cable multimode vibration mitigation to satisfy the damping requirement. This paper proposes a damper optimization method of the hybrid application of a viscous damper and a tuned mass damper for a bridge taut cable multimode vibration mitigation. To overcome the difficulty involved in the actual implementation of the hybrid application, the authors provide a practical solution based on the findings of this paper, which is to set the optimum conditions of the viscous damper and tuned mass damper for the longest cables of each group, while setting the suboptimum conditions of the viscous damper and tuned mass damper's for the other cables of each group as long as the modal damping ratios meet the target damping ratio. To achieve this, the following steps are required to be taken: First, select adjacent cables with the similar properties as one group. Second, optimize viscous damper and tuned mass damper parameters for the lower and higher modes of the longest cable in one group, respectively. Third, set the viscous damper and tuned mass damper's configuration parameters of the other cables in the group equal to the optimum viscous damper and tuned mass damper's configuration parameters of the longest cable. Check whether the damping ratios of the considered modes of the other cables in the group meet the target damping ratio; if not, just try adjusting the cable modes optimized by the viscous damper and tuned mass damper, which means actually adjusting the viscous damper and tuned mass damper's installation locations of these dampers to meet the target damping ratio. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFST) arch bridges have a high center of gravity and a substantial mass, resulting in a discernible seismic response. Consequently, long-span CFST arch bridges must retain exceptional seismic performance and appropriate seismic control design. In this study, the dynamic response and seismic performance of a unique swallow-type CFST arch bridge when subjected to longitudinal earthquake forces were analyzed using numerical simulation methods. The displacement and axial force response results and their laws of the key bridge components were obtained. Taking into account seismic checking calculations, two damping measures were proposed for the CFST arch bridge, as the relative displacement of the girder end exceeded the allowable value specified. The appropriate design parameters for viscous dampers and lead shear dampers were examined. Additionally, the seismic performance of these dampers was verified through a shaking table test using a 1:16 scale model. The findings indicated that when subjected to Wenchuan Wolong wave action, the relative displacement between the steel box girder and the concrete girder of the bridge was significantly larger, leading to girder end pounding. The limit values were surpassed by 32.5% and 50%, when subjected to the uniform and traveling wave excitations, respectively, thus indicating that the expansion joint was the most vulnerable component. Following the selection of optimal parameters for the dampers, the dampers exhibited the capability to mitigate seismic and pounding impacts. Long-span CFST arch bridges with dampers were found to effectively reduce the seismic response of the skewback strain and vault, as well as the relative displacement of the girder ends. Furthermore, the average maximum damping rates achieved by the viscous damper and the lead shear damper reached 44.9% and 44.6%, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Shipping impact and wave loads impose dynamic loads on jetties and platforms in the sea, which cause the vibration of structures. Recently, many advanced viscous damper devices have been developed for implementation in structures to diminish structural vibration due to earthquakes or wind. However, the longitudinal configuration of conventional viscous damper devices requires adequate space to locate the damper device within the frame structure, which limits the application of viscous dampers for use in jetties or platforms to dissipate the vibrations imposed by ship impact or wave force. For this reason, in this study, an attempt has been made to develop a new viscous plane damper device applicable in limited space positions where the longitudinal damper device is not able to fit. For this purpose, the initial design for the viscous plane damper device is proposed, and the prototype of the device is manufactured. Then, the performance of the fabricated viscous plane damper is examined through experimental tests by applying cyclic loads using a dynamic actuator. In order to investigate the effect of the diameter and configuration of the piston’s orifices, five different diameters for the orifices of 1, 2, 5, 8, and 10 mm are included, and three different distribution configurations of the orifices in the piston plate as Configurations A, B, and C are manufactured and tested experimentally. The lab testing is conducted by applying cyclic loads with different frequencies to evaluate the performance of the developed plane damper device under various load velocities. Accordingly, the dynamic performance of the damper device, including the damping force, effective damping and stiffness and the energy dissipation capacity obtained from the hysteresis response (force–displacement result), is investigated. The results of the experimental tests prove the functionality of the developed device to generate the desired damping force and vibration energy dissipation during applied cyclic loads. Therefore, the new plane damper device can be implemented in any structure to dissipate the effect of imposed vibration.

In the present paper, the impacts of viscous dampers on controlling the vibrations imposed on seismic vibrations are evaluated using descriptive methods. To this end, the library method and other research related to viscous dampers and their impacts on controlling external excitation such as earthquakes have been used. ETABS software was used for modelling the structures. Also, nonlinear dynamic analysis was used for seismic analysis of the structures. Based on the findings, using viscous dampers are effective to improve seismic parameters of structure and to decrease displacement, speed, base shear, and velocity. On the other hand, viscous fluid dampers can strengthen the structure and its performance during severe earthquakes and can be applied in newly constructed structures. The impact of a passive viscous damper on reducing the seismic response of the structures is found significant at the confidence level of 90%. Reduction of energy of structure hysteresis because of the nonlinear behaviour of members using dampers is proved to be significant at the confidence level of 80%. The results reveal that the lateral resistance of an EBF with a short joint can be 4/5 to 9 times more than the lateral resistance of an MRF, that the behaviour coefficient of fifteen-story EBF considered 6/5-7/75, concluded that the length of the bray does not have an impact on the behaviour coefficient of these frames. [ABSTRACT FROM AUTHOR]

Expansion joints render bridge structures highly vulnerable to damage during strong ground motions. Failures of expansion joints triggered by earthquakes not only jeopardize the post-earthquake serviceability of the bridge but also have a significant impact on the bridgeâs overall seismic performance. Despite extensive investigations and efforts to integrate these measures into design specifications aimed at mitigating the consequences of relative movements between adjacent bridge spans, major earthquakes have still revealed instances of damage related to expansion joints. On 6 February 2023, strong earthquake sequences occurred in KahramanmaraÅ, Turkey, with magnitudes of M7.7 and M7.6. The fault lines and epicenters of these shallow earthquakes were near the city and town centers and caused severe structural damage to buildings and infrastructures. There are approximately 1000 railway and highway bridges in the earthquake-affected region. Although both highway and railway bridges have generally performed well, some bridges experienced structural damage during the KahramanmaraÅ earthquakes. A large number of damage on the bridges is due to pounding and opening relative movements in expansion joints. This paper presents a comprehensive seismic evaluation of expansion joint failure mechanisms on bridges without viscous dampers during the 2023 KahramanmaraÅ earthquake sequences and an in-depth investigation into the seismic performance of bridge expansion joints equipped with viscous dampers and shock transmission unit devices are implemented utilizing the strong ground motion data collected throughout the earthquake sequences. It can be stated that the near-fault induced significant directivity and fling effects, resulting in notable velocity pulses and permanent tectonic deformations, and that these effects contributed to the failures of expansion joints, viscous damper devices, pot bearings, and shear keys.

This article presents the analysis of a damping fluid deficiency in a torsional vibration viscous damper. The problem is analysed both qualitatively and quantitatively. Experimental results are presented, showing what happens to the damper in a situation where the design of the housing is inadequate and the inertia forces prevent the formation of an oil film. In addition, the article deals with the problem of the proper design of the oil channel and the dimensions required to enable the damper to operate reliably. The results of the article may be useful to the constructors of torsional vibration viscous dampers for marine engines.

Recent studies showed that while code-compliant structures can generally protect the safety of the occupants, they may exhibit extensive damages during strong earthquake events. On the other hand, structures are generally designed to satisfy the seismic code requirements with the least initial cost regardless of their life cycle cost. In recent years, value-based design has been considered as an effective alternative for code-based design procedures. In this method, as well as the initial cost of the structure, a comprehensive consequence modeling is performed in the design process. In this paper, for the first time, a value-based design optimization method is developed for seismic enhancement of existing RBS steel frames using nonlinear viscous dampers. The efficiency of the method is demonstrated through 4-, 8-, and 12-story frames designed for low, medium, and high earthquake intensity levels, while the life cycle costs are evaluated using FEMA P-58. A time-based approach is carried out to consider different earthquake events and their corresponding probability of occurrence in a specific range of intensities. For dynamic analysis of the structures, the Endurance Time (ET) method is adopted to significantly reduce the computational costs while providing accurate results. The Genetic Algorithm (GA) is then used to optimize the damping coefficient of the viscous dampers for minimum life cycle cost. The results, in general, indicate the efficiency of the proposed method in increasing the total economic value of the studied structures with the least additional cost. It is shown that shorter structures and those designed in high-seismic risk regions benefit more from using optimized viscous dampers, leading to up to 42% lower life cycle costs. The results of this study should prove useful in more efficient strengthening design of existing steel frames. [ABSTRACT FROM AUTHOR]

This paper presents the investigation results of a base-isolated RC frame-shear wall structure located in Luding County, Sichuan Province, China, which was damaged by a Ms 6.8 earthquake on September 5, 2022. This recently constructed school office building was about 9 km away from the epicenter. The isolation layer of this building consists of 54 rubber bearings and 12 viscous dampers. These viscous dampers or their connections failed during the earthquake, and the limit state included connection breaking or global buckling of the damper. Also, the superstructure suffered some minor damage. To investigate the cause of structural damages, a nonlinear time-history analysis is conducted using the ground motions recorded by four seismic stations close to the building. The onsite investigation and numerical simulation results revealed the possible reasons for the failure. [ABSTRACT FROM AUTHOR]

In order to study the creep viscoelastic-plastic mechanical behavior of asphalt mixture, the Maxwell model is used as the basic model, and the fractional order calculus operator theory is used to construct the fractional order viscous body to replace the Newton body in the basic model. The nonlinear viscous damper is introduced and connected in series with the foundation model. The damage variable is defined, the damage evolution is carried out according to the Lemaitre equivalent strain principle, and the fractional creep model of asphalt mixture considering aging damage is obtained. The model parameters are solved, the parameter sensitivity is analyzed, and the damage evolution is carried out. The creep data of asphalt mixture are identified by using the model, and compared with the empirical model to verify the feasibility and rationality of the model. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a frequency domain-based analytical framework for seismic performance of viscously damped outrigger systems. Based on a core–outrigger–damper–column simplified model, the global dynamic stiffness matrix is assembled from the core modeled as a Timoshenko beam, damped outriggers as complex rotational stiffness comprising outriggers, dampers, and perimeter columns, and inherent damping using Leung's theory and modal damping construction. A general numerical method combining Wittrick-Williams algorithm and Newtonian iteration is developed to study the dynamic characteristic of such systems with multiple damped outriggers. The fast Fourier transformation (FFT) and the inverse Fourier transformation (IFFT) are then integrated with the principle of potential energy to obtain the equivalent nodal force and thus the time history response by transformations between time and frequency domains. Finally, the stochastic analysis is conducted via the transfer function resulting from the global stiffness matrix with the stochastic seismic excitation following Kanai-Tajimi spectrum. The proposed approach is verified by comparison with the finite element method through a case study of a tall building implemented with viscously damped outriggers. This study shows that the proposed analytical framework could serve as a powerful tool for evaluating the performance of viscously damped outrigger systems. [ABSTRACT FROM AUTHOR]

This study specifically focuses on the damping efficiency of a damped structure with additional viscous dampers. A two-layer steel frame structure with eight sets of viscous dampers is used to conduct a series of seismic simulation shaking table tests, including a non-damped structure without dampers and two damped structures with dampers placed at 1/2 and 1/6 of the beam span, respectively. By conducting these tests, the energy dissipation, force, and displacement of the damper, as well as the parameters of the structure such as floor displacement and acceleration, are obtained. The main damping efficiency indicators of the damped structure are calculated, including the additional damping ratio, inter-story displacement utilization rate, as well as the reduction rate of the vertex displacement and the base shear relative to the non-damped structure. The study shows that the viscous dampers exhibit full hysteresis loops and a strong energy dissipation capacity in the structure. The seismic response of the vertex displacement and base shear in the damped structure is significantly smaller than that in the non-damped structure. Under different seismic levels, including frequent earthquakes, occasional earthquakes, and rare earthquakes, the damping effect of the dampers placed at 1/2 of the beam span is significantly better than that placed at 1/6 of the beam span. For example, the additional damping ratio for the X-direction artificial wave REN is 19% and 11%, 20% and 13%, and 13% and 11%, respectively. The patterns for inter-story displacement utilization ratio, reduction rate of the vertex displacement, and reduction rate of the base shear are similar. The research findings strongly indicate that the damped structure with additional viscous dampers exhibits excellent damping efficiency. In future damping design, designers need to fully consider the placement of viscous dampers within the beam span.

Strong earthquake can cause larger structural response of bridge, resulting in the interaction between structures and the surrounding water to generate hydrodynamic pressure. Taking a deep-water long-span suspension bridge in a reservoir area as the research object, longitudinal viscous dampers are set between the towers and beams for structural shock absorption, the interaction of water and the bridge tower is considered in the form of additional mass and calculated using the analytical method. By establishing four different structural system analysis models, the effects of hydrodynamic pressure on the earthquake response of long-span suspension bridge and the aseismic performance of damper are studied. The results show that the hydrodynamic pressure further enlarges the structural displacement and internal force response of the suspension bridge under the earthquake. The greater the depth of the bridge tower into the water, the more obvious of enhancement effect. The viscous damper can reduce the longitudinal displacement and structural internal force of the suspension bridge in the form of additional anti-seismic damping. However, under the influence of the seismic hydrodynamic pressure, the working hysteresis area of the damper increases, the maximum increase of damping force is 2.21%, and the maximum increase of displacement is 8.33%. Therefore, when viscous damper is adopted for deep-water bridge, the influence of seismic hydrodynamic pressure on its performance should be considered so as to avoid over-limit damage. [ABSTRACT FROM AUTHOR]

At present, dampers are widely used in the field of energy dissipation in engineering structures. However, when the displacement and velocity output of dampers are not significant under small and medium-sized earthquakes, it is difficult for a damper to fully exert its energy dissipation capacity. The use of toggle-brace mechanisms in the structure is an effective method to solve the above problems, and the effect of toggle-brace-viscous dampers (referred to as TBVDs) in the structure can be reflected by a magnification factor (referred to as Mf). Therefore, it is particularly important to study the calculation method for the Mf of TBVD. Domestic and foreign scholars have achieved certain results in the study of the calculation method for the Mf of TBVD, and the corresponding calculation formula for the Mf has been proposed. Given the existing research results, this article conducts the following work: analyzing the shortcomings of existing methods for calculating the Mf of TBVD, proposing an improved method for calculating the Mf of viscous dampers, comparing the accuracy of existing and improved algorithms, and analyzing the calculation results to provide practical suggestions for engineering applications. [ABSTRACT FROM AUTHOR]

Stay cables of several cable-stayed bridges with a span of nearly 1000 m are confronted with the simultaneous actions of low-mode rain-wind induced vibration and high-mode vortex-induced vibration. It is difficult to effectively reduce these two kinds of cable vibrations by installing one damper at the end of the stay cable. In this paper, the effectiveness of two dampers attached at the lower end of the stay cable, including viscous dampers and viscous inertial mass dampers, is investigated by the finite difference method. First, the stay cable was simplified as an inclined cable with sag, and equation of motion governing the stay cable attached with two dampers was derived. This equation was then numerically solved by the finite difference method. Second, taking Cable A30 of the Suzhou-Nantong Yangtze River Bridge as a reference, a series of numerical simulations were carefully conducted to obtain the damping ratios of the first fifty modes. The results show that it is impossible to enhance the damping ratios of all of the concerned modes up to the minimum target value only by installing a single viscous damper or a single viscous inertial mass damper at the end of the stay cable. However, two viscous dampers installed at the lower end of the cable (l 1/ l = 2%, l 2/ l = 5%) can overcome the shortcoming of a single viscous damper or viscous inertial mass damper to enhance the damping ratios of the first 34 modes up to the minimum target value (0.5%). In general, the optimized relative location of the two dampers (l 2/ l 1) should be near 2. The optimized ratio of the damping coefficients (η 1/ η 2) should be lower than l 2/ l 1, and the lower limit of η 1/ η 2 is determined by the minimum target values for modal damping ratios. Moreover, it appears that a lower installation position of two viscous dampers can realize the mitigation of higher modes even up to the 40th ∼ 50th modes. [ABSTRACT FROM AUTHOR]

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Viscous dampers have proven to be effective in enhancing the seismic performance of existing structures. Despite this, there is still a need for rapid and simplified design methods and formulae for viscous dampers that can take into account the elastic–plastic performance of structures. This study introduces a retrofit design method for existing structures using viscous dampers, based on the concept of uniform damping ratio (UDR), with the aim of fully utilizing each damper. The UDR concept assumes that each damper in the structure provides the same UDR when subjected to seismic excitations of identical intensity. In this method, the first step involves defining the equivalent damping ratio (EDR) of the damper. Then, based on the capacity spectrum of the structure, the response mitigation ratio can be determined, which helps to determine the additional EDR required from the dampers. Once the UDR and additional EDR from the viscous damper have been determined, the parameters of the dampers at each story can be rapidly obtained. To demonstrate the effectiveness of this method, a six-story reinforced concrete frame was utilized as a benchmark structure. A comparison between this UDR-based approach and a traditional design approach was also conducted. The study findings reveal that the UDR concept enables the maximum utilization of energy dissipation capacity of viscous dampers installed in the structure, leading to a more effective and economical design approach. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The traveling wave and slope amplification effects should be considered in the shaking table test of large-span structures in mountain areas. Based on the structural characteristics and site conditions of a large-span structure in a mountain area, this paper designed a high-rise steel frame structure with viscous dampers through finite element analysis to amplify seismic waves with a time delay. Then, the original structure and steel frame models with a similarity ratio of 1/40 were made for shaking table tests. The test results showed that a high-rise steel frame structure with reasonable viscous dampers could delay and amplify seismic waves, and the scaled model of the structure could play the same role in shaking table tests. Meanwhile, by comparing the seismic responses of large-span structural models in mountain areas before and after the amplification of seismic wave delays, it was found that the delay and amplification of seismic waves had little impact on the acceleration response of the structure. In contrast, the seismic wave delay played a dominant role in the change in the structural displacement response. [ABSTRACT FROM AUTHOR]

Residual vibrations in machine tools hamper accuracy and productivity. The attenuation of residual vibrations has been an industrial concern for decades. Meanwhile, the residual vibrations' vibration pattern reveals that the support foundation's damping capabilities predominantly influence them. Therefore, inserting dampers in any other location on a machine tool (such as a machine column) is ineffective. Hence, the scope of inserting the damper into the machine foundation needs to be verified. However, conventional machine mounting systems (concrete foundation and rubber mounts) equally respond to all variable inputs. Both these flocks resulted in inadequate dampening and perhaps poor accuracy. This paper provides a first-generation model of a semiactive-viscous damper (ERF damper-foundation) with tunable damping facilitating machine installation. Controlled experimentation by exposing the developed damper foundation to excitations of medium duty lathe machine confirms its effectiveness and obtains over 48% attenuation compared to a conventional concrete foundation.

In the case of cable-stayed bridges with very large spans of over 400m, the common engineering practice at the national level requires the placement of vibration mitigation devices in the form of external dampers (usually of the viscous type). The main disadvantage of this solution is due to the relative positions of these devices along the cable, which are very close to the edge, in a zone where their influence on the cable is minimal.

Abstract A new model reduction method is presented for moment‐resisting frames with viscous dampers. The proposed method considers (1) the interactive effect of added damping between the horizontal‐vertical directions and (2) the direct effect with regard to the vertical direction different from the conventional static condensation method. When brace‐type dampers are treated, these effects cannot be neglected originally. The proposed method gives a better correspondence of the fundamental eigenmode with that of the non‐reduced moment frame than the static condensation method. In addition, the proposed reduced model can accurately evaluate the maximum interstory drifts of the non‐reduced moment frame. The proposed model reduction method is formulated in the frequency domain. The frequency dependency of the stiffness matrix and the damping matrix of the reduced model is investigated. The influences of the added damping matrix by viscous dampers on the natural circular frequencies, the damping ratios and the participation vectors are also investigated. Finally, it is demonstrated through a numerical example that the displacement‐based optimization of the damper allocation can be accurately and rapidly conducted by using the reduced models throughout the optimization process.

Summary: Tall buildings suffer from low inherent damping and high flexibility. Therefore, a core‐outrigger system is often used to stiffen such buildings. A modified form, known as the damped outrigger system, wherein vertically oriented dampers are installed between outriggers and perimeter columns, has been recently developed to supplement the damping. This paper studies the efficacy of a viscously damped outrigger system through dynamic analysis of a 60‐story tall building subjected to nonconcurrent earthquake and wind excitations. Two ground motion sets (100 accelerograms) are used for the former and wind tunnel test data for the latter. Effects of three building parameters, namely, (i) the core‐to‐column stiffness ratio, (ii) the outrigger location, and (iii) the damper size, on the dynamic characteristics and seismic and wind responses are evaluated. Effects of damper nonlinearity on seismic and wind responses are also investigated considering energy‐equivalent nonlinear viscous dampers. Finally, the optimum values of these parameters are determined. For example, the optimum outrigger location is found to be between 0.6H to 0.9H, where H is the height of the building. The results also show that the damped outrigger system significantly outperforms the conventional one for seismic excitation, and it is very effective in reducing the wind‐induced floor accelerations, provided the parameters are chosen appropriately. [ABSTRACT FROM AUTHOR]

In order to study the influence of soil-structure interaction (SSI) on the dynamic response and vibration reduction control of transmission tower-line system under wind load. According to the actual project, the transmission tower-line system model and the pile-soil-transmission tower-line system model were established, and then the transmission tower-line system considering the SSI effect under the soft soil condition and the transmission tower-line system with rigid foundation were carried out respectively. Vibration response analysis. Multiple viscous dampers were installed on the transmission tower considering the SSI effect to control the wind-induced vibration of the transmission tower. The research results show that: after considering the SSI effect, the displacement response of the transmission tower increases significantly, in which the maximum displacement and the root mean square value of the representative node of the tower body increase by 64.73% and 79.09%, respectively. The axial force response of the tower body and tower legs decrease. When the damping coefficients are the same, the damper with a velocity index of 0. 3 has the best effect on the wind vibration control of the transmission tower. When the velocity index is the same, the larger the damping coefficient is, the smaller the displacement response of the tower top and the axial force response of the tower body element are. When the velocity index is 0.3 and the damping coefficient is lower than 30 000 kN·(s/m) 0.3, the difference in the displacement control effect of dampers with different damping coefficients on the top node of the tower is obvious, and when the damping coefficient is less than 15 000 kN·(s/m) 0.3, the dampers with different damping coefficients have obvious differences in the axial force control effect of the tower unit. [ABSTRACT FROM AUTHOR]

To mitigate longitudinal vibration of long-span railway suspension bridges, a Combined Viscous-Steel Damping System (CVSDS) is put forward in this paper. In the CVSDS, the viscous damper is expected to work under train braking and frequent earthquakes, while the steel damper can resist rare earthquakes. Moreover, a fuse-lock device is proposed to work as the switch between the aforementioned two dampers. The working mechanism of the CVSDS was introduced. The locking function was verified by static test, and the vibration reduction efficiency of the proposed system was validated through numerical method. The results show that the combined system is efficient. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new hybrid system consisting of wood shear walls, concrete columns, bracing system, and viscous damper devices is introduced in this paper. A benchmark wood building is adopted here as a case study, and different configurations of the new hybrid system are applied on it in order to investigate its seismic performance under some near-fault ground motion records. The performance base design method is used to design the considered models. In order to make the models comparable, their performance levels are considered to be identical. Detailed finite element models are built in OpenSees software to conduct nonlinear static and dynamic analyses. The parametric study is done to optimize the viscous damper system parameters. At the end, the damage potential of the models is investigated through their fragilities. The results demonstrate the high potential of the proposed system in improving the seismic performance of the mid-rise wood buildings. It is also observed that the good behavior of the system is achieved when the viscous damper coefficient and its supporting tendon cross-sectional area is dependently increased. [ABSTRACT FROM AUTHOR]

Precast structures have become increasingly popular in recent years. However, the low seismic capacity of prefabricated structures is still a fraught issue in high seismic intensity regions. This paper aims to improve the structural seismic capacity of a precast concrete frame by employing a viscous damper. Two precast concrete frame specimens, with and without viscous dampers (PCFV and PCF), were produced and subjected to dynamic reversed cyclic loading tests. The experimental results showed that the viscous damper could improve the dynamic bearing capacity of the frames. [ABSTRACT FROM AUTHOR]

Vibration measures can be taken at three main locations: the vibration source, the propagating part, and the radiating part. However, measures at the vibration source are often difficult to implement, and countermeasures at the radiating part are inefficient. Therefore, measures at the propagation part are expected. For measures at the propagation part, the technique of structural intensity (SI) is used, which is effective in understanding the propagation path. Then, we attempt to reduce the vibration by a viscous damper layout based on the SI distribution. In this paper, the most effective layout for vibration reduction is presented for 2 and 3 DOF systems. As a result, it was found that adding a damper on the response side is effective. For beam system, the relationship between the ratio of change of SI and the velocity was also discussed. Based on these findings, a method for identifying the damper location by SI is newly proposed, and its effectiveness is verified.

Abstract In this study, a model for the evaluation of a building's resilience and recovery time is proposed, and a new method is developed for the optimal viscous damper placement for a targeted resilience. The features of this model are as follows: 1) building components are categorized into systems in view of their functionality, 2) recovery time is regarded as a function of the damage to building components and human resources for repairing the components, 3) the model is applicable to structural design. This design method uses a type of real‐coded genetic algorithm (GA). The effective use of a constraint on the sum of the added damper damping coefficients enables an efficient search for the solution.