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As a typical passive energy dissipation device, the fluid viscous damper (FVD) is widely utilized for structural vibration control. However, performance degradation in FVDs has been highlighted, particularly concerning the gap effect resulting from the imperfect installation and insufficient fluid. This study proposes three analytical models to characterize the gap property in the hysteresis behavior of FVDs, including the Gap model (G. model), the Equivalence model (E. model), and the Stiffness Degradation model (S. model). The purpose of the G. model is to reproduce the zero-force platform in the hysteresis curve. The E. model and S. model are both simplified models, aiming to consider the gap effect by altering the damping coefficient, velocity exponent, and stiffness based on the energy and maximum force equivalence principles. Shake table tests of a single-degree-of-freedom system are carried out to validate and assess the effectiveness and accuracy of these three methods. The results indicate that the gap effect will significantly degrade the vibration mitigation performance of FVDs, and hence it needs to be considered in simulations. The displacement and force obtained using the G. model under distinct loads highly correspond to the experimental results. By adopting the simplified models, satisfactory results can be derived with a lower implementation cost. Among them, the E. model is more appropriate when subjected to harmonic loads, while the S. model is suggested for cases under seismic excitations. [ABSTRACT FROM AUTHOR]

In the study, the change in the required gap distance with the use of fluid viscous damper-(FVD) in adjacent reinforced concrete buildings compared to traditional fixed-base models was examined. Additionally, the adequacy of the required gap distance recommended respect to the provisions of the Turkish Building Earthquake Code-(TBEC-2018) was examined. For this purpose, 3- and 7-story residential buildings with conventional fixed-base and FVD dampers were modelled. Nonlinear behavior for structural elements and FVD dampers was considered. A total of 44 nonlinear time history analysis was carried out for the conventional model with fixed-base and with FVD dampers adjacent model, using 11 ground motion pairs selected as spectrum compatible. As a result of the analysis, it was calculated that the use of FVD damper reduced the required gap distance by average of 43.6% compared to the fixed-base model. Additionally, it was determined that while the gap distance recommended in TBDY-2018 was 32.7% insufficient for fixed base buildings, was 42.2% remained on the safe side with the use of FVD. In this respect, it has been concluded that the use of FVD dampers can be an effective alternative to prevent or reduce the effects of pounding for existing or new adjacent buildings. [ABSTRACT FROM AUTHOR]

Deformations, accelerations, shear forces, and energy demands are normally utilized to evaluate the performance of steel frames equipped with fluid viscous dampers (FVDs). This study aims to quantify damage indices (DI) and their distributions along the structural height for steel frames (3, 6, 9, and 20 stories) equipped with FVDs. The damage model incorporating both deformation and hysteretic plastic energy is adopted to quantify damage developed in structures. A set of 20 pairs of ground motions is used to perform nonlinear time history analyses. Influences of structural property and FVD features (supplementary damping ratio $${\xi _{add}}$$ and velocity power $$\alpha $$) on DI are investigated. The results show that FVDs with lower α would reduce DI. However, nonlinear FVDs lead to higher DI compared to linear ones when $${\xi _{add}}$$>30%, particularly for 9- and 20-story structures. Nonlinear FVDs ($$\alpha \lt 1$$) are more effective than linear ones in reducing DI during low-intensity earthquakes. The results further demonstrate that the distribution of DI along the structural height is mostly determined by structural properties, FVD characteristics, ground motion intensity, and the type of damage model used.

Global approval of the use of fluid viscous dampers to control the buildings response against dynamic loadings is growing. The idea behind incorporating additional dampers is that they will reduce most of the energy that is transmitted to the building during shaking event. The objective of this work is to identify and enhance the design parameters that control the nonlinear behaviour of fluid viscous damper subjected to sinusoidal excitation. For this, a numerical model of the flow inside the dissipater has been carried out based on finite volume method. A novel approach has been adopted to simulate elastic behaviour of the fluid, taking into account its compressibility by using the Murnaghan equation of state. A comparison between the calculations of the proposed model and the experimental tests was carried out. The model proved to be sufficiently accurate. A fluid flow analysis was then conducted to fully understand the internal mechanism of the damper. A parametric study was then performed by varying aspects such as dimensions, geometric relationships between components and fluid properties in order to better understand their effect on the non-linear behaviour of the device. The results highlight the relationship between the parameters governing the shear thinning behaviour of the fluid and the non-linearity exponent of the damper. This makes it possible to better control the non-linear behaviour of the device by selecting the appropriate silicone oil and the appropriate geometric dimensions of its components.

Global approval of the use of fluid viscous dampers to control the buildings response against dynamic loadings is growing. The idea behind incorporating additional dampers is that they will reduce most of the energy that is transmitted to the building during shaking event. The objective of this work is to identify and enhance the design parameters that control the nonlinear behaviour of fluid viscous damper subjected to sinusoidal excitation. For this, a numerical model of the flow inside the dissipater has been carried out based on finite volume method. A novel approach has been adopted to simulate elastic behaviour of the fluid, taking into account its compressibility by using the Murnaghan equation of state. A comparison between the calculations of the proposed model and the experimental tests was carried out. The model proved to be sufficiently accurate. A fluid flow analysis was then conducted to fully understand the internal mechanism of the damper. A parametric study was then performed by varying aspects such as dimensions, geometric relationships between components and fluid properties in order to better understand their effect on the non-linear behaviour of the device. The results highlight the relationship between the parameters governing the shear thinning behaviour of the fluid and the nonlinearity exponent of the damper. This makes it possible to better control the non-linear behaviour of the device by selecting the appropriate silicone oil and the appropriate geometric dimensions of its components. [ABSTRACT FROM AUTHOR]

The combined viscous-steel damping system is a passive energy dissipation device consisting of a fluid viscous damper and a steel yielding damper in series. However, many viscous dampers installed in structures have been suffering from severe oil leakage. This study aims to assess the influence of the leaked viscous damper on the seismic performance of the combined system. Cyclic tests were conducted on the viscous damper with different leakage levels to obtain its degraded hysteretic performance. The modeling method of the leaked viscous damper was proposed according to the experimental result. The locking behavior and seismic mitigation effectiveness of the combined system suffering from oil leakage were investigated based on a single-degree-of-freedom system. The result reveals that (i) The leaked viscous damper cannot generate damping force at the beginning of the reverse movement of its piston, which is reflected in the hysteretic curves as a "gap" phenomenon. (ii) The proposed modeling method can accurately simulate the damping characteristics of the leaked viscous damper. (iii) In spite of the leakage severity, the combined system possesses reliable locking behavior and decent vibration mitigation effectiveness under earthquakes. (iv) The combined system is superior to the viscous damper in mitigating seismic-induced displacement when suffering from oil leakage. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) provides a powerful tool for investigating complicated fluid flows. This paper aims to study the applicability of CFD in the preliminary design of linear and nonlinear fluid viscous dampers. Two fluid viscous dampers were designed based on CFD models. The first device was a linear viscous damper with straight orifices. The second was a nonlinear viscous damper containing a one-way pressure-responsive valve inside its orifices. Both dampers were detailed based on CFD simulations, and their internal fluid flows were investigated. Full-scale specimens of both dampers were manufactured and tested under dynamic loads. According to the tests results, both dampers demonstrate stable cyclic behaviors, and as expected, the nonlinear damper generally tends to dissipate more energy compared to its linear counterpart. Good compatibility was achieved between the experimentally measured damper force-velocity curves and those estimated from CFD analyses. Using a thermography camera, a rise in temperature of the dampers was measured during the tests. It was found that output force of the manufactured devices was virtually independent of temperature even during long duration loadings. Accordingly, temperature dependence can be ignored in CFD models, because a reliable temperature compensator mechanism was used (or intended to be used) by the damper manufacturer. [ABSTRACT FROM AUTHOR]

Seismic isolation has been widely accepted as one of the techniques that can be used to protect structures during earthquake ground motions. However, some challenges still exist such as the optimal control of excessive isolator shear strains imposed by some ground motions. The main purpose of this study was to assess the effects of building height variation and earthquake ground motion type on the optimal performance of the seismic isolation using lead core rubber bearing (LCRB). Nonlinear time history analysis for building models of various storeys isolated by LCRB and exposed to different real earthquakes was performed. To achieve this, the equations governing the motion of the isolated three different building models were presented, and an approach for solving the equations while taking into consideration of the optimized mechanical properties of the LCRB was developed. The LCRB performance was measured in terms of elastomer shear strains, derived after an optimal criterion leading to reliable substructure and superstructure responses was reached. The results showed that the combined effects of the earthquake type and building height significantly affect the substructure responses (maximum isolator displacement, energy dissipation capacity, maximum isolator force) and the superstructure responses (storey shear forces, storey drifts, floor displacements, and floor accelerations), which in some cases lead to a need for adding a fluid damper. In this regard, an attempt to couple the LCRB with nonlinear fluid viscous damper was made, and the performance of the hybrid was assessed. It was generally found that the hybrid can positively improve the substructure responses, thereby reducing the unwanted large elastomer shear strains without adversely affecting the superstructure responses. [ABSTRACT FROM AUTHOR]

Fluid viscous dampers (FVDs) have shown their efficiency as energy-dissipating systems, reducing the effects induced on structures by dynamic loading conditions like earthquakes and winds. In this paper, the evolution of this technology is reviewed, with a focus on the current trends in development from passive to semi-active and adaptive systems and an emphasis on their advances in adaptability and control efficacy. The paper examines the implementation of semi-active FVDs such as electrorheological, magnetorheological, variable stiffness, and variable damping dampers. These devices have a high potential to mitigate the vibrations caused by earthquakes of different intensities. In addition, adaptive FVDs are presented. As semi-active devices, the adaptive ones can adjust their behavior according to the dynamic excitations' intensity; however, they are able to do that autonomously without the use of any external equipment. [ABSTRACT FROM AUTHOR]

The number of extensive studies on the implementation and performance of passive control systems in RC structures has recently increased. A fluid viscous damper as an energy dissipating device was proved to improve the energy absorption capacity of the structure subjected to severe earthquakes by reducing displacement and acceleration responses. Therefore, this paper is intended to investigate the seismic behavior of low-rise, mid-rise, and high-rise RC structures utilized with fluid viscous dampers subjected to pulse-like and non-pulse-like earthquakes. As a part of the study, a parametric investigation of the damper's performance will be performed using different combinations of damping coefficient (C) and damping exponent (α) since these two constants remarkably change the damping force and hence the performance of the viscous damper. In addition, this paper will study and compare the behavior of low-rise, mid-rise, and high-rise buildings. Finally, the performance of fluid viscous damper on the different RC structures will be discussed and reported in this study. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic analysis of a long-span double-deck suspension bridge subjected to random traffic loading using a Finite Element (FE) model. During this study, the influence of various traffic parameters, such as vehicle speed, traffic volume, traffic weight, and the location of the passing girder, on the longitudinal movement of the girders was investigated. The results reveal that schemes with double girders passing can lead to greater longitudinal displacement of the girder as compared to a long-span bridge with a single passing girder. However, the incorporation of fluid-viscous dampers at the ends of the girders significantly reduces the displacement range of each node. For instance, at the left end of the bridge, the original model (without dampers) exhibits a displacement range of approximately 0.01–0.056 m, whereas the constrained model (with dampers) shows a range of 0.025–0.033 m. A quantitative analysis demonstrates that higher damping coefficients (or smaller damping exponents) can further mitigate the girder's movement. [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.)

After the catastrophic destruction of the October 2005 Kashmir earthquake, the first building code of Pakistan was developed in 2007. The sole purpose of the building code of Pakistan (BCP) was to incorporate advancements in earthquake-resistant design to fortify structures and ensure the safety of citizens against future seismic events. After 2007, the BCP was not revised till 2021 to include the changes over time. However, the recently updated version of BCP 2021 highlights that the seismicity of many regions in Pakistan is high, which is not truly reflected in the BCP 2007. Therefore, the advancements in earthquake-resistant design due to the growing concerns about the potential risks of seismicity in the region have been incorporated into the updated version of the BCP. However, there are concerns among researchers that many structures designed on the 2007 code may need seismic fortification. Therefore, the current study focuses on the seismic fortification of existing systems that were developed using previous codes. Non-linear viscous fluid dampers are used to improve the seismic resilience of existing structures. This study compares the seismic performance of an existing reinforced concrete building with and without non-linear viscous dampers and subjected to a non-linear dynamic analysis. The performance of the building is evaluated in terms of story displacement, story drift, story acceleration, and energy dissipation mechanisms. Adding the non-linear fluid viscous dampers in the structure caused a decrease in the inter-story drift by around 31.16% and the roof displacement was reduced by around 36.58%. In addition to that, in a controlled structure, more than 70% of energy was dissipated by the fluid viscous dampers. These results indicate that adding the non-linear fluid viscous dampers to the existing structure significantly improved the vibration performance of the system against undesirous vibrations. The outcomes of this study also provide a very detailed insight into the usage of non-linear viscous dampers for improving the seismic performance of existing buildings and can be used to develop effective strategies to mitigate the impact of seismic events on already built structures. [ABSTRACT FROM AUTHOR]

Earthquakes are enormous natural disasters that increase the energy within the structural system, causing catastrophic destruction. Various control systems, such as passive, active, hybrid, and semi active control systems, can be used to dissipate this unwanted energy. The fluid viscous damper is one such dissipation device used in this study. The goal of this project is to use a fluid viscous damper to lessen the seismic response of the Symmetrical and unsymmetrical G+9 structure in ETABS2017. To obtain the seismic response with and without a fluid viscous damper, ETABS2017 was used to analyse symmetrical and unsymmetrical structures with and without a fluid viscous damper. The analysis takes into account nonlinear temporal history, which is derived using fast nonlinear analysis of Electro data. The position and function of dampers are discussed in this study. For seismic evaluation of buildings with and without fluid viscous dampers, the equivalent static approach and response spectrum method are utilised. The structure was examined utilizing ETABs 2017 programming, with seismic zone IV and medium soil (Type II) according to IS 1893-2016. The structure’s exhibition is assessed utilizing story removal, story shear, story float, and modular periods and frequencies. The objective of this study is to about the consequences of static and reaction range examination in both longitudinal and cross over bearings for damper development with and without damper structure.

Fluid viscous dampers (FVDs) have shown their efficiency as energy-dissipating systems, reducing the effects induced on structures by dynamic loading conditions like earthquakes and winds. In this paper, the evolution of this technology is reviewed, with a focus on the current trends in development from passive to semi-active and adaptive systems and an emphasis on their advances in adaptability and control efficacy. The paper examines the implementation of semi-active FVDs such as electrorheological, magnetorheological, variable stiffness, and variable damping dampers. These devices have a high potential to mitigate the vibrations caused by earthquakes of different intensities. In addition, adaptive FVDs are presented. As semi-active devices, the adaptive ones can adjust their behavior according to the dynamic excitations’ intensity; however, they are able to do that autonomously without the use of any external equipment.

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & 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 force of the viscous fluid damper is negatively related to its temperature. • The proposed analytical model can obtain accurate real-time force and temperature. • Long-term and high-intensity loads amplify the thermo-mechanical coupling effect. • The damping ratio is more sensitive to the coupling effect than responses. The fluid viscous damper (FVD) is a typical passive energy dissipation device applied to civil engineering structures for vibration control. However, the heat generated during its operation will alter the properties of the fluid, thereby affecting the damping force. This study explores the thermo-mechanical coupling effect on the performance of the FVD. A theoretical model is developed based on fluid dynamics and thermodynamics to reflect the interaction between the real-time damping force and temperature of the FVD. Computational fluid dynamics (CFD) simulations are performed to investigate the impact of the thermo-mechanical coupling effect on the hysteresis performance of the damper and validate the proposed calculation method. The dynamic behavior and vibration mitigation effectiveness of the FVD considering the thermo-mechanical coupling effect are examined based on time history analysis on a single-degree-of-freedom and a multi-degree-of-freedom system. The results indicate that the increased temperature will lead to a reduction in the damping force, while the degraded force will in turn slow the temperature rise. Long-duration and high-intensity excitations can significantly amplify the impact of the thermo-mechanical coupling effect, thus it is essential to be considered in designing dampers for loads in the service stage and major earthquakes. The thermo-mechanical coupling effect on the supplemental damping ratio of the damper is greater than that on structural response control effectiveness, thereby it cannot be neglected when the damping ratio is used as the design criterion for FVDs. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic analysis of a long-span double-deck suspension bridge subjected to random traffic loading using a Finite Element (FE) model. During this study, the influence of various traffic parameters, such as vehicle speed, traffic volume, traffic weight, and the location of the passing girder, on the longitudinal movement of the girders was investigated. The results reveal that schemes with double girders passing can lead to greater longitudinal displacement of the girder as compared to a long-span bridge with a single passing girder. However, the incorporation of fluid-viscous dampers at the ends of the girders significantly reduces the displacement range of each node. For instance, at the left end of the bridge, the original model (without dampers) exhibits a displacement range of approximately 0.01–0.056 m, whereas the constrained model (with dampers) shows a range of 0.025–0.033 m. A quantitative analysis demonstrates that higher damping coefficients (or smaller damping exponents) can further mitigate the girder’s movement.

Fluid viscous dampers (FVDs) are the key energy dissipation devices for long-span suspension bridges, and their leakage poses a threat to the stable and reliable operation of bridge restraint systems. Therefore, this paper proposed an FVD fluid leakage diagnosis method based on girder longitudinal displacement monitoring data. First, the longitudinal vibration equation of the main girder under traffic loads was derived to reveal the displacement characteristic of girder-end motion. On this basis, considering that different displacement components under traffic loads are coupled and transient analysis directly utilizing traffic loads as the excitation is complicated and inefficient, an analysis framework focusing on the influence mechanism of FVD leakage on quasi-static displacement was established. Second, an equivalent mechanical model for simulating the hysteresis relationship of leaked FVD was proposed and verified. Then, the influence of variations in the location, number, leakage level and parameters of the leaked FVD on the quasi-static displacement was studied. Third, the equivalent traffic load (ETL) indicator was constructed to characterize the traffic volume. Furthermore, a quasi-static cumulative displacement and ETL correlation model, which can effectively eliminate the interference of traffic flow variations, was proposed for the leakage diagnosis of FVD. Finally, the proposed method was verified by real suspension bridge monitoring data. The results demonstrated that the proposed method can effectively detect a mild increase in the girder-end cumulative displacement due to FVD fluid leakage. • Proposed and validated an equivalent model for simulating the hysteresis relationship of leaked FVD. • The influence of leaked FVD locations, numbers, leakage levels and parameters on vehicle-induced GECD was revealed. • An online diagnosis method was established to realize the condition monitoring of FVD leakage in operation. • The effectiveness is verified by case study of an actual in-service suspension bridge. [ABSTRACT FROM AUTHOR]

The ability of structural elements to absorb input energy through inelastic deformation and supplemental damping is a primary factor in determining structural damage during earthquake excitation. This study proposes an energy methodology for the seismic evaluation of single-degree-of-freedom (SDOF) systems, considering the effect of fluid viscous dampers (FVDs). The FVD is characterized by supplemental damping ratio, ξ a d d , and velocity power α. A computer algorithm is developed for the numerical simulation of SDOF systems using nonlinear time history analysis, which is verified through a number of validation examples. This study focuses on issues related to input and hysteretic energies (E I and E H) with particular emphasis on near-field records and their interrelationship with seismic response demand, which is defined as non-dimensional indices for SDOF systems without FVD and those equipped with FVD. The energy indices (ζ and γ) are the ratios of input and hysteretic energies to maximum displacement demand, respectively. The results show that the natural period T n , ductility level μ , ξ a d d , and α have a significant effect in the determination of energy spectra (E I and E H) . The non-dimensional ζ is a more stable and reliable indicator than γ to quantify the damage potential of ground motion. Finally, the observations of the energy approach provided in this study indicate that it can be used as a useful tool for developing energy-based guidelines for structures incorporating FVDs. [ABSTRACT FROM AUTHOR]

The seismic requirements of piers with fixed bearings (the fixed pier) for continuous girder bridges are relatively high, while the potential seismic capabilities of piers with sliding bearings (the sliding piers) are not fully utilized. To solve this contradiction, a new type of winding rope shock absorption device activated by a fluid viscous damper (WRD-D) was proposed. The WRD-D was installed on the top of the sliding piers, and the both ends of a fluid viscous damper were connected to the superstructure by winding ropes. During an earthquake, the damping force rises with the increase of relative speed between the sliding piers and the superstructure, activating the WRD-D and producing large frictional resistance, subsequently causing the sliding piers and the fixed pier to bear the seismic load cooperatively. In this study, the working mechanism of the WRD-D was researched. The shaking table test of a scaled continuous girder bridge model employing the WRD-D was conducted. The test results reveal that the WRD-D can effectively reduce the seismic requirements of the fixed pier and the superstructure displacements. [ABSTRACT FROM AUTHOR]

Under near-field ground motions, fluid viscous dampers (FVDs) are effective in controlling deck longitudinal displacement but lead to the increase of bending moment and shear force at tower base. Negative stiffness (NS) devices are introduced in combination of FVDs for the bridge. The NS devices lengthen the fundamental vibration period of the bridge to reduce the spectrum acceleration whereas FVDs introduce extra damping to the bridge system to reduce the deck displacement. After implementing NS devices, designers have more options of designing FVDs for seismic control of the cable-stayed bridges while maintaining the design requirements under near-field seismic excitations. [ABSTRACT FROM AUTHOR]

After the catastrophic destruction of the October 2005 Kashmir earthquake, the first building code of Pakistan was developed in 2007. The sole purpose of the building code of Pakistan (BCP) was to incorporate advancements in earthquake-resistant design to fortify structures and ensure the safety of citizens against future seismic events. After 2007, the BCP was not revised till 2021 to include the changes over time. However, the recently updated version of BCP 2021 highlights that the seismicity of many regions in Pakistan is high, which is not truly reflected in the BCP 2007. Therefore, the advancements in earthquake-resistant design due to the growing concerns about the potential risks of seismicity in the region have been incorporated into the updated version of the BCP. However, there are concerns among researchers that many structures designed on the 2007 code may need seismic fortification. Therefore, the current study focuses on the seismic fortification of existing systems that were developed using previous codes. Non-linear viscous fluid dampers are used to improve the seismic resilience of existing structures. This study compares the seismic performance of an existing reinforced concrete building with and without non-linear viscous dampers and subjected to a non-linear dynamic analysis. The performance of the building is evaluated in terms of story displacement, story drift, story acceleration, and energy dissipation mechanisms. Adding the non-linear fluid viscous dampers in the structure caused a decrease in the inter-story drift by around 31.16% and the roof displacement was reduced by around 36.58%. In addition to that, in a controlled structure, more than 70% of energy was dissipated by the fluid viscous dampers. These results indicate that adding the non-linear fluid viscous dampers to the existing structure significantly improved the vibration performance of the system against undesirous vibrations. The outcomes of this study also provide a very detailed insight into the usage of non-linear viscous dampers for improving the seismic performance of existing buildings and can be used to develop effective strategies to mitigate the impact of seismic events on already built structures.

When a structure is subjected to earthquake forces, vibrations are setup in the structure leading to severe damages to the structure and results in loss of property and life. Now a days, keen attention is given to research and development of vibration control devices to mitigate the seismic effects. The present duty of civil engineer is to discover earthquake resisting design approach to reduce structural damages. The basic technology used to protect the structure from damaging earthquake effects is "base isolation". The base isolation system decouples the super-structure from the substructure by means of flexible devices through which seismic energy is dissipated. In the present context G+15 storey structure situated in zone V is modeled and analyzed using ETABS-2017 software by providing different base isolation systems namely a) RC structure having fixed base b) RC structure with Fluid Viscous Damper (FVD) and Lead Rubber Bearing (LRB). Response of the structure is studied in terms of story displacement, story drift, base shear, natural time period and design lateral forces. It is found that the provision of Fluid Viscous Damper (FVD) and Lead Rubber Bearing (LRB) in a same structure shows better performance in story displacement, base shear, story drift, natural time period and design lateral forces as compared to fixed base model. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design 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.)

To investigate the use of vibration control systems in fatigue damage mitigation for welded beam-to-column connections in steel high-rise buildings, cases of both a single connection under constant amplitude cyclic loading and multi-connections in a high-rise building under the stochastic wind, with and without the fluid viscous damper (VFD) and the tuned mass damper (TMD), are discussed respectively. The finite element analysis and the fatigue assessment are conducted so that the mitigation effect, the effect of technical parameters and the conditions of both high-cycle fatigue and low-cycle fatigue are all discussed. The results show that the VFD and the TMD systems are both effective in the mitigation of local fatigue damage along with the structural displacement for both cases. The VFD generally has a better mitigation effect than the TMD and it starts to take effect instantly with the external loading, but it causes a phase difference in structural responses, while the situation of the TMD is quite the opposite. The displacement and the local stress show similar and synchronous mitigation trends so that the damping systems can be designed based on either of them. The VFD should be designed with a smaller damping exponent and a larger damping coefficient in a braced installation form, while the TMD can be designed using the optimal parameters. The optimized VFD layout plan is that VFDs are placed between the two connections with large relative displacement and relative velocity on higher floors and these two connections with VFDs should be near to the targeted connection. The negative fatigue damage mitigation mainly stems from insufficient lateral support force so that the direct installation of VFDs may result in a negative fatigue damage mitigation effect in the connections with limited lateral support.

In this paper, an optimization approach for the seismic retrofitting of inelastic moment resisting frames (MRFs) equipped with nonlinear fluid viscous dampers (FVDs) and negative stiffness devices (NSDs) is presented. The goal of the optimization is to minimize a cost‐related objective function, which accounts for the cost of the supplemental FVDs and NSDs. The mechanical properties and the topological layout of both the FVDs and NSDs are considered as design variables and simultaneously optimized during the optimization process. A loss estimation analysis is utilized as a performance constraint, where the PEER framework is adopted. The structural response is evaluated using a nonlinear time history analysis (NTHA), which accounts for the nonlinear behavior of the MRF elements, FVDs, and NSDs. The optimization problem is formulated using differentiable functions only, making it suitable for an efficient gradient‐based optimization solution scheme. The gradients are efficiently derived using the adjoint sensitivity analysis approach. Two numerical examples show the robustness and efficiency of the presented methodology, where the optimized design relies on NSDs and FVDs in both examples. [ABSTRACT FROM AUTHOR]

Direct displacement-based design (DDBD) method is one of the most effective methods for performance-base design of structures that has been also employed to design structures controlled by fluid viscous damper (FVD). In previous studies, a modified DDBD has been developed to apply the higher mode effects as well as difference between spectral velocity and pseudo-spectral velocity on the design velocity of FVD. To this end, two constants were defined to correct the damping coefficient of FVD that these correction constants had been determined in a non-classical and iterative manner. In this study, a new classical method is proposed for determining these constant such that no iteration is required in DDBD. In order to be able to introduce this design approach as a reliable framework, its performance is validated under different sets of earthquake records and this design approach is also developed for structures controlled by nonlinear FVD. Steel moment-resisting frames with different numbers of stories have been designed using this method. For comparison, structures have been also designed based on DDBD proposed in previous researches. The results show that DDBD approach improved in this study is capable to achieve the design performance level under different sets of earthquake records and this design approach has more effective performance than previous design methods. Performance of steel moment-resisting frames equipped with nonlinear FVD also shows excellent performance of this design approach in achievement of desirable performance level. Therefore, DDBD approach proposed in this study can be introduced as a new classical and reliable framework because of its simplicity and excellent performance under different sets of earthquakes. [ABSTRACT FROM AUTHOR]

A self-anchored suspension bridge balances forces internally without external anchorage requirements, making it suitable for sites where anchorages would be difficult to construct. It often adopts either a full-floating or a semi-floating tower-girder connection system, which may result in large displacement responses along bridge longitudinal direction during earthquakes. This study investigated the efficacy of using the fluid viscous damper (FVD) for seismic control of a single-tower self-anchored suspension bridge. First, the energy dissipation behaviors of the FVD under sinusoidal excitations were studied. It revealed that besides the damper parameters (i.e. damping coefficient and velocity exponent) of an FVD itself, the energy dissipation capacity also relies on the characteristics of external excitations. Therefore, optimum damper parameters added to a structure should be determined on a case-by-case basis. Parametric study was then carried out on the prototype bridge, which indicated a tendency of decreasing the longitudinal deck/tower displacements and tower forces with increasing damping coefficient C and decreasing velocity exponent α. Compared with the linear FVD, the nonlinear FVD with a smaller velocity exponent can develop more rectangular force-displacement loops and thus achieve better energy dissipation performance. With selected optimum damper parameters (i.e. C = 3 0 0 0 kN ⋅ m − 0. 3 s 0. 3 and α = 0. 3) for the two FVDs added between the deck and the tower, the longitudinal deck and tower displacements could be reduced by 54%, while the peak bending moment and shear force at the tower base could be reduced by 30% and 19%, respectively. It is concluded that the nonlinear FVD can provide a simple and efficient solution to reduce displacement responses of self-anchored suspension bridges while simultaneously reducing the bending moment and shear force in the tower. [ABSTRACT FROM AUTHOR]

In this paper to increase the efficiency of direct displacement based design (DDBD) in designing structures equipped with viscous dampers (VDs), a method has been proposed to determine optimal distribution of VDs. The proposed method has been based on defining an optimization problem which minimizes the sum of damper coefficients to achieve the required equivalent viscous damper. To solve the optimization problem the distributed genetic algorithm (DGA) has been applied. To illustrate the method, three 2, 5 and 20 story steel frames equipped with linear VDs and designed using DDBD, have been considered and optimal placement of VDs has been determined. The controlled structures using uniform distribution (UD) and optimal distribution (OD) of VDs subjected to ten artificial earthquakes compatible with design spectrum and nonlinear time history analysis has been conducted. Results show that to achieve the same equivalent viscous damping for both uniform and optimal distributed VDs distribution, using OD has reduced significantly the sum of dampers coefficient (up to 30%) as well as the maximum damping force(up to 24%). Also evaluating the performance of controlled structures under different artificial records has shown that using OD has led to less control system cost while both distributions has similar performance.

Summary: An optimization approach for the seismic design of yielding moment‐resisting frames (MRFs) with nonlinear fluid viscous dampers (FVDs) is presented. As the optimal design of new buildings is addressed, no parameters are set a priori, and the properties of both the structural elements and the dampers are simultaneously optimized. The goal of the optimization is to minimize the cost of the system (structure + dampers), while code requirements and performance constraints are considered. The performance of the structure is evaluated using a nonlinear time history analysis (NTHA), accounting for the nonlinear behavior of both the MRF elements and the added FVDs. The optimization problem is first formulated as a mixed‐integer problem suitable for a solution by zero‐order optimization. Then, the problem is reformulated in a continuous differentiable form and solved using an efficient gradient‐based optimization approach. This is done by utilizing discrete material optimization (DMO) functions to achieve a good initial design for the cross‐sections and the FVDs. This initial design accounts for the important aspects of design, some directly and some indirectly. The responses of interest are computed using a probabilistic approach while considering ensembles of ground motions. Numerical examples show the robustness of the presented methodology and its efficiency demonstrated on a five‐story MRF and a real‐scale irregular nine‐story MRF. [ABSTRACT FROM AUTHOR]

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Bridges are the lifelines of disasters in earthquake areas. Therefore, it is very necessary to ensure the safety and traffic function after earthquake. Seismic isolation refers to install external energy dissipation devices or external energy input devices in specific parts of engineering structures. There are certain differences in longitudinal and transverse seismic responses of multi-span continuous beam bridges by changing the seismic dynamic characteristics or dynamic effects of structures. It is difficult to achieve the purpose of seismic isolation in both horizontal directions using isolation devices alone. The rubber deformation ability of lead rubber bearings can effectively insulate, and the yield energy consumption ability of its lead core can effectively consume the seismic energy for damping. The horizontal resistance is very small under the creep load, and the stiffness decreases rapidly after yielding under the strong dynamic earthquake load; meanwhile, the seismic energy is dissipated by the hysteresis of bearing. Fluid viscous damper is a velocity-dependent energy dissipation device, which produces viscous damping force, provides strong restoring force for components, and has a good limit function. This process will also dissipate the seismic energy, so as to reduce the structural earthquake response. Using these two methods together, the horizontal seismic responses of multi-span continuous beam bridges can be effectively controlled at the same time. Based on this idea, this article takes a high-speed multi-span continuous beam bridge with equal section as the engineering background, and uses dynamic time history analysis method to discuss the seismic isolation effect of lead rubber bearings and fluid viscous dampers. [ABSTRACT FROM AUTHOR]

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Purpose: The paper is an attempt to evaluate the efficiency of passive control techniques such as base isolation system (e.g. Lead/Rubber Bearing) and fluid viscous dampers subjected to earthquake ground motions and underground blast-induced vibrations. Two moment-resisting steel frame buildings are analyzed to evaluate the structural responses under dynamic excitations. The effect of vertical irregularity on the performance of passive control techniques in mitigating the responses of the building is also studied. Methods: Non-linear dynamic analysis has been conducted on regular and irregular steel structures. The study investigates the effect of isolation period on the structural responses. The isolators are designed based on the design procedures developed by various researchers. The technical specifications of fluid viscous dampers have been selected from M/s Taylor Devices, USA. Results: The structural responses and energy dissipated by these control techniques is evaluated and a comparative study is also carried out amongst control techniques under blast and seismic excitations. Conclusions: Both the selected passive control techniques have proved to be very effective in reducing the structural responses and forces induced in the building owing to ground-induced vibration. [ABSTRACT FROM AUTHOR]

The effectiveness of the semi-active control strategies using fluid viscous dampers (SAFVDs) for seismic mitigation of reinforced concrete (RC) elevated liquid storage tanks is investigated. Three control algorithms are employed for regulating the damping coefficient of the SAFVDs: (1) Passive-OFF, (2) Passive-ON, and (3) Clipped Optimal Control (COC). The uncontrolled response of the tank is compared with those installed with SAFVD of different control algorithms. Focus is also placed on various positions of the dampers, viz., dampers installed at alternate levels (Configurations I, II, IV, and V) and at all levels (Configurations III and VI) of the staging. A discrete two-mass model for the liquid and multi-degree-of-freedom system for the staging, installed with the dampers, is developed for the RC elevated liquid storage tanks. The response of the broad and slender tanks is studied, for which the ratios of the height of the liquid to the radius of the container are 0.5 and 2.0, respectively. The time-history response of the elevated tank is evaluated for eight different earthquake ground motions, including near- and far-field earthquakes. A MATLAB code was developed to solve the coupled differential equations of motion of the system using the state-space approach. Key parameters, viz., convective displacement, rigid mass displacement, base shear, overturning moment, and damper force, are evaluated. The results show that all the control systems considered herein are beneficial in reducing the seismic responses. The frequency response function for the uncontrolled and semi-actively controlled liquid storage tank in frequency domain exhibits significant response reduction, highlighting the effectiveness of the SAFVDs. The structural response is effectively controlled using the SAFVDs with Passive-OFF (valve closed) and COC algorithms. The COC algorithm employed in this study is a promising candidate for the seismic mitigation of RC elevated liquid storage tanks using the semi-active control. [ABSTRACT FROM AUTHOR]

The effectiveness of passive vibration control devices used to retrofit multi-storied steel buildings during their design life is investigated under the dynamic forces induced by earthquake and wind. The passive vibration control devices include steel bracing, viscous and viscoelastic dampers. The buildings without and with the retrofitting devices are modelled as multi-degree of freedom (M-DOF) systems, with inertial masses lumped at each floor level. The governing differential equations of motion for the uncontrolled and controlled buildings are solved using Newmark's time marching scheme. The obtained dynamic responses for the buildings exposed to the earthquake- and wind-induced forces are subsequently compared. It is concluded that upon retrofitting, the modified dynamic properties, such as modal frequencies and damping ratio play an active role to attract forces during the two hazards, which in turn influences the response reduction achieved. It may be worth noting that the buildings retrofitted for earthquake tend to attract more forces under wind load and vice versa. Therefore, a retrofit strategy providing beneficial effects against a particular hazard may prove to be catastrophic for the other, which underlines the need for careful selection of the retrofit solution and design for a structure considering such multi-hazard scenario. [ABSTRACT FROM AUTHOR]

Highlights • A dimension-reduced explicit method is proposed for nonlinear time-history analysis. • Sensitivity analysis with respect to the parameters of viscous dampers is conducted. • Statistical moments of responses and their sensitivities are obtained with MCS. • A MMA-based optimization method is developed for stochastic optimal design. • Stochastic optimal design of viscous dampers is carried out for a suspension bridge. Abstract Nonlinear fluid viscous dampers have been widely used in energy-dissipation structures. This paper is devoted to the stochastic optimal design of viscous dampers for large-scale structures under non-stationary random seismic excitations. The optimization problem is formulated as the minimization of the standard deviation of a target displacement component subjected to the constraint on the standard deviations of damping forces of viscous dampers, and the method of moving asymptotes (MMA), a gradient-based optimization method, is employed to solve the optimization problem involved. An effective dimension-reduced explicit method is first proposed for fast nonlinear time-history analysis of structural responses and the corresponding sensitivity analysis with respect to the parameters of viscous dampers, in which only a small number of degrees of freedom associated with the viscous dampers need to be considered in the iteration scheme, leading to extremely low computational cost in the nonlinear analysis. Then the proposed dimension-reduced explicit method is further used to conduct sample analyses with high efficiency in Monte-Carlo simulation (MCS) so as to obtain the statistical moments of critical responses and the relevant moment sensitivities required in the process of optimal design. To demonstrate the feasibility of the proposed method, the stochastic optimal design of viscous dampers is carried out for a large-scale suspension bridge with a main span of 1688 m, and the mean peak values of critical responses with the optimal parameters of viscous dampers are finally obtained for the design purpose of the bridge. [ABSTRACT FROM AUTHOR]

Summary: The purpose of this study is to perform a seismic assessment of the moment resistant steel structures enhanced with viscous dampers where the dampers are degraded due to possible leak of viscous fluid. This paper proposes a design procedure based on corrected response spectrums as a result of seismic assessments based on nonlinear time series analyses on three‐, five‐, and seven‐story steel frame structures denoted as “generic structures.” The proposed design procedure is a seismic displacement‐based design methodology for buildings with viscous dampers as passive energy dissipation systems. Prior literature on these types of structures often overlook the viscous dampers degradation due to the fluid leak. In this paper, in order to study these effects, a target displacement is specified at first and the lateral forces and required stiffness are obtained. The effectiveness of the proposed procedure is verified with the collapse fragility curves of the generic structures according to the ASCE 7‐10 and displacement‐based design methodology. The results show that the structures designed based on proposed procedure demonstrate acceptable performance with degrading dampers. [ABSTRACT FROM AUTHOR]