Fluid Viscous Dampers Research Articles

Effectiveness of fluid-viscous dampers for improved seismic performance of inter-storey isolated buildings

The use of fluid viscous dampers (FVDs) together with isolators, frequent in near-fault buildings, is effective in reducing displacements of the isolation layer. Such a hybrid system is also beneficial in the case of inter-storey isolation with the aim of limiting P-Δ effects. However, previous research on base isolation shows that this additional damping may also be detrimental, as inter-storey drifts and floor accelerations may increase.This paper analyses the effectiveness of FVDs for enhanced seismic performance of systems with inter-storey isolation. A seven-floor building, with natural and lead rubber bearings between the second and third levels, was used as a case study, and a multi-objective optimal design was performed to identify the best damper parameters. In particular, time-history analyses with various natural records were carried out and two competing objectives were examined: minimisation of the deflection of the isolation layer and minimisation of the total drift of the superstructure.The results show not only the effectiveness of optimal FVDs but also the fact that their optimal linearity degree depends to a great extent on the non-linear seismic response of the structure, i.e., on the type of earthquake. The simplest design approach, consisting of applying an optimization algorithm for each design accelerogram, did not seem, in this case, to be sufficient to identify the best overall design solution. The design consequences of these findings are discussed.

Seismic Assessment of Response of RC Frame Building with Fluid Viscous Damper

Seismic Assessment of Response of RC Frame Building with Fluid Viscous Damper

Longitudinal Vibration and Its Suppression of a Railway Cable-Stayed Bridge Under Vehicular Loads

The paper is aimed at investigating the longitudinal vibration and vibration reduction of a cable-stayed bridge under vehicular loads with emphasis on the longitudinal resonance. To investigate the phenomenon of longitudinal resonant vibration, the equivalent longitudinal excitation for the bridge deck due to moving vertical loads is approximately expressed as longitudinal loads with a sine-wave form. A formula for estimating the longitudinal resonant speed of the cable-stayed bridge is developed. A long-span cable-stayed railway bridge is considered in the case study to calculate the longitudinal response of the bridge under moving loads at different speeds. The numerical results indicate that the longitudinal resonance for the cable-stayed bridge occurs when the speeds of the moving loads approach the resonant speed predicted by the analytical formula. A fluid viscous damper (FVD) is employed to reduce the longitudinal vibration of the bridge under moving loads. The results show that the longitudinal resonant responses of the cable-stayed bridge can be effectively mitigated by the FVD adopted.

Seismic Performance of Buildings with Viscous Damping Systems Designed by the Procedures of ASCE/SEI 7-16

AbstractThis study investigates the seismic performance of buildings with fluid viscous damping systems designed in accordance with the procedures of ASCE/SEI 7-16. The study examines the effect of...

Advanced scalar intensity measures for collapse capacity prediction of steel moment resisting frames with fluid viscous dampers

Nowadays, passive energy dissipation systems are used in the seismic design of new structures and the retrofit of existing structures. Fluid Viscous Dampers (FVDs) are one of the important types of passive energy dissipation systems. Using FVDs can considerably decrease the seismic demands on structures. In this study, seismic collapse behavior of steel Special Moment Resisting Frames (SMRFs) equipped with FVDs is investigated using different scalar Intensity Measures (IMs). Incremental Dynamic Analysis (IDA) method is applied to determine the collapse capacity, IMcol, values for low- to mid-rise steel SMRFs equipped with FVDs. After determining the collapse capacity, IMcol, values by using each of the IMs, the efficiency and sufficiency of the IMs for predicting the seismic collapse capacity of the structures are investigated. Then, advanced scalar IMs, including the effects of spectral shape and ground motion duration, are proposed to reliably predict the collapse capacity of steel SMRFs equipped with FVDs. The results indicate that the proposed IMs possess high efficiency and sufficiency for collapse capacity prediction of steel SMRFs equipped with FVDs.

System-based probabilistic optimization of fluid viscous dampers equipped in cable-stayed bridges

This study presents a methodology to evaluate the optimal parameters of fluid viscous damper for cable-stayed bridges using the system-level fragility assessment approach. Instead of investigating the impact of different isolation devices on the component’s vulnerability separately, this study focuses on evaluating the optimal parameters of fluid viscous damper to achieve the best overall performance of cable-stayed bridge as a system. Numerical model of a cable-stayed bridge with the most common configuration in China is established using OpenSEES that can account for their nonlinear response and uncertainty treatment. A joint probabilistic seismic demand model and Monte Carlo simulation are employed to obtain the system fragility of cable-stayed bridges by accounting for the contribution of multicomponents to the global damage state. The system-level fragility curves and component fragility curves are compared before and after the application of fluid viscous damper with different parameters. The results indicate that a given parameter of the fluid viscous damper may have a negative impact on some components, yet lead to a better performance of the bridge as a system. Thus, in order to obtain comprehensive knowledge of bridge performance and derive the accurate optimal parameters of fluid viscous damper, it is necessary to consider the fragility based on bridge system.

Improving total-building seismic performance using linear fluid viscous dampers

Previous research has revealed that Eurocode-compliant structures can experience structural and nonstructural damage during earthquakes. Retrofitting buildings with fluid viscous dampers (FVDs) can improve interstorey drifts and floor accelerations, two structural parameters that characterize seismic demand. Previous research focusing on FVD applications for improving seismic performance has focused on structural performance. Structural parameters such as interstorey drifts and floor accelerations are often evaluated. Complexities arise as these parameters are often competing objectives. Other studies use damage indices that are influenced by several assumptions to represent performance. The use of repair costs is a more appropriate measure of total-building seismic performance, and avoids these limitations. This study investigates the application of linear FVDs to improve total-building seismic performance considering repair costs. The energy-based method commonly used to calculate damper coefficients is modified to improve its accuracy. The optimal amount of damping with respect to repair costs (estimated using the FEMA P-58 procedure) is identified as 25–45%. This contrasts with a previously suggested optimal damping of 20–25%, based on structural parameters, that is frequently targeted. This study on the damping-repair cost relationship provides insight when selecting levels of damping for structural designs and retrofits. It also highlights that retrofit methods may be enhanced by using repair costs, rather than structural parameters. The FVD buildings significantly reduce both drift-sensitive and acceleration-sensitive damage. Structural damage is also negligible in the FVD buildings: a major step towards achieving building serviceability following an ultimate limit state level earthquake.

Validation of GenEcAm Software Results in Simulation of Seismic Behavior of Buildings Equipped with Damping System

This paper presents the validation process of the GenEcAm program made by the author by comparing the results obtained with this program with the results obtained with the SAP2000 program at the dynamic analysis of a P+10E building equipped with viscous fluid dampers, one on each facade on each level. The results obtained with these two programs are very close, which validates the correctness of the analytical and computational model that underpinned the creation of the GenEcAm program. The GenEcAm program allows the use of 9 theoretical models of hysteresis to simulate seismic behavior of the dampers that equippe the structure of a building.

Analytical and experimental studies on building mass damper system with semi-active control device

A concept of improving an optimum building mass damper (OBMD) system through a semi-active control method for enhancing the efficiency of controlling structural responses is proposed. The proposed concept entails replacing the passive fluid viscous dampers used in an OBMD system with semi-active magnetorheological dampers, thus transforming the system into a novel semi-active OBMD (SOBMD) system for better seismic performance. A numerical model based on the Bouc–Wen model with the interpolation technique was established to represent the behavior of the semi-active magnetorheological dampers. The SOBMD system was then developed on the basis of linear-quadratic regulator method and a continuous-optimal control concept. The damping force in the SOBMD system can be manipulated according to the structural response; therefore, the SOBMD system affords the possibility of improving the displacement or acceleration response compared with the original OBMD system. Both of the numerical analysis and the experimental verification demonstrated the superior seismic mitigation ability of the SOBMD system. Several earthquake events with different characteristics were simulated in a series of numerical analysis to further verify the performance of the proposed SOBMD system. In short, the benefits of both the active and passive control system are successfully combined in the proposed SOBMD system.

Nonlinear dynamic characteristics of a micro-vibration fluid viscous damper

This study is concerned with the nonlinear dynamic characteristics of a micro-vibration fluid viscous damper used in a satellite. When a control moment gyroscope is working, it produces micro-vibrations, which is a disadvantage for imaging equipment. Taking a single-tube micro-vibration fluid viscous damper as our research subject, a nonlinear dynamic model of the micro-vibration fluid viscous damper under harmonic excitation is proposed. Then, the analytical form of the pressure gradient force is derived. Considering the entrance effect in the orifice, the nonlinear elastic force and nonlinear damping force are analyzed. The results reveal that if the entrance effect is not considered, the elastic force and damping force are linear forces. When the entrance effect is considered, the damper has a nonlinear elastic force and a nonlinear damping force. These nonlinear forces are related to the orifice length, diameter, fluid viscosity, excitation amplitude and frequency. In the low-frequency domain, the differences between the two cases are small, while in the high-frequency domain, they are considerable.

Shake Table Testing of a Low Damage Steel Building with 2-4 Displacement Dependent (D3) Viscous Damper

To improve seismic structural performance, supplemental damping devices can be incorporated to absorb seismic response energy. The viscous fluid damper is a well-known solution. However, while they reduce displacement demand, they can increase overall base shear demand in nonlinear structures as they provide resistive forces in all four quadrants of force-displacement response. In contrast, Direction and Displacement Dependent (D3) viscous fluid dampers offer the opportunity to simultaneously reduce structural displacements and the total base-shear force as they only produce resistive forces in the second and fourth quadrants of a structural hysteresis plot. The research experimentally examines the response of a half-scale, 2-storey moment frame steel structure fitted with a 2-4 configuration D3 viscous fluid damper. The structure is also tested with conventional viscous dampers to establish a baseline response and enable comparison of results. Dynamic experimental tests are used to assesses the base shear, maximum drift and residual deformation under 5 different earthquakes (Northridge, Kobe, Christchurch (CCCC), Christchurch (CHHC), and Bam ground motion). Response metrics including base shear, the maximum structural displacement, and peak structural accelerations are used to quantify performance and to assess the response reductions achieved through the addition of dampers. It is concluded that only the 2-4 device is capable of providing concurrent reductions in all three of these structural response metrics.

High-Performance Computer-Aided Optimization of Viscous Dampers for Improving the Seismic Performance of a Tall Steel Building

Using fluid viscous dampers (FVDs) has been demonstrated to be an effective method to improve seismic performance of new and existing buildings. In engineering applications, designs of these dampers mainly rely on trial and error, which could be repetitive and labor intensive. To improve this tedious manual process, it is beneficial to explore more formal and automated approaches that rely on recent advances in software applications for nonlinear dynamic analysis, performance-based evaluation, and workflow management and the computational power of high-performance, parallel processing computers. The optimization design procedure follows the framework of Performance Based Earthquake Engineering (PBEE) and uses an automatic tool that incorporates an optimization engine and structural analysis software: Open System for Earthquake Engineering Simulation (OpenSEES). An existing 35-story steel moment frame is selected as a case-study building for verification of this procedure. The goal of the retrofit design of FVDs is to improve the building’s seismic behavior that focuses on avoiding collapse under a basic-safety, level-2 earthquake (BSE-2E). The objective of the optimization procedure is to reduce the building’s total loss under a BSE-2E event and optimal damper patterns will be proposed. The efficiency of the optimization procedure will be demonstrated and compared with a manual refinement procedure.

Critical Evaluation of Behavior of an Mdof System Subjected to Seismic Excitation Using Fluid Viscous Damping in Specific Context to its Response Reduction

Critical Evaluation of Behavior of an Mdof System Subjected to Seismic Excitation Using Fluid Viscous Damping in Specific Context to its Response Reduction

Seismic Response Evaluation of High-Rise Building with and Without Fluid Viscous Damper

The major lateral load of the high structures is the earthquake load. In the high rise buildings, the structural response increases exponentially in response to earthquake load. Therefore, the damping has significant function in design of Earthquake Resistant High Structures, which can decrease the response of the structure when exposed to lateral loads. The energy produced by earthquake will be absorbed by these devices and the load acting on the main structure of the building will reduce significantly. The fluid viscous dampers are used to dissipate energy and lessen the response of reinforced concrete buildings. The main function of structure is to carry the lateral loads and transmit them well to the foundation. The lateral loads enjoined on the structures are dynamic in nature, which cause vibrations in the structure. In the current study, the responses of the structures having square plans with different cross-sections are analyzed by the software ETABS 2015 based on the consideration of Fluid Viscous Damper. The results of numerical examples show that fluid viscous damper (250) can reduce the response of the structures effectively, including the base shear of the buildings, and the structures with square columns performs perfect and have good earthquake resistant characteristics when compared to structures with rectangular columns regardless of the flooring plan.

Use of fluid viscous dampers in structural control: a case study

This study focuses on the assessment of the buildings dynamic response under wind loads. It is known that any structure inherently dissipates and absorbs energy due to external loads thanks to the combination of its deformability, strength and flexibility. An improvement of this capacity could be achieved using fluid viscous dampers, concentrating mainly on their nonlinear behaviour; a case study will illustrate the major impact of these devices on a RC tall building, subjected to wind turbulence. Wind have a great impact on the dynamic response of tall buildings, with its dynamic and random nature, it plays an important role in the design of civil structures. In this paper, the simulation of wind time histories is discussed, in order to fully cover all wind components to end up with proper results.

Direct displacement based design of hybrid passive resistive truss girder frames

An innovative Hybrid Passive Resistive configuration for Truss Girder Frames (HPR-TGFs) is introduced in the present study. The proposed system is principally consisting of Fluid Viscous Dampers (FVDs) and Buckling Restrained Braces (BRBs) as its seismic resistive components. Concurrent utilization of these devices will develop an efficient energy dissipating mechanism which is able to mitigate lateral displacements as well as the base shear, simultaneously. However, under certain circumstances which the presence of FVDs might not be essential, the proposed configuration has the potential to incorporate double BRBs in order to achieve the redundancy of alternative load bearing paths. This study is extending the modern Direct Displacement Based Design (DDBD) procedure as the design methodology for HPR-TGF systems. Based on a series of nonlinear time history analysis, it is demonstrated that the design outcomes are almost identical to the pre-assumed design criteria. This implies that the ultimate characteristics of HPR-TGFs such as lateral stiffness and inter-story drifts are well-proportioned through the proposed design procedure.

Use of fluid viscous dampers in structural control: a case study

Use of fluid viscous dampers in structural control: a case study

Verification of an energy-based design procedure for seismic retrofit of a school building

A viable design criterion of supplemental damping strategies for seismic retrofit of frame structures, recently proposed by the first author (Terenzi, 2018), is applied in this paper to a school building in Florence dating back to the early 1980s. The building is composed of two portions, with reinforced concrete and steel frame structure, respectively. Similarly to several other buildings of the same period, the structure is infilled by heavy reinforced concrete panels interacting with the frame elements under horizontal loads. A careful reconstruction of the structural characteristics of the constituting members, based on the original design documentation and on-site testing campaigns, highlighted specific drawbacks in current state, related to a remarkable degration of the materials and a poor performance of several elements. The retrofit solution considered in this study consists in removing the infill panels and replacing them with a set of dissipative braces incorporating fluid viscous dampers as protective devices. The design is carried out by the sizing criterion mentioned above, targeting an elastic structural response up to the maximum considered earthquake normative level.

Transverse failure modes and control strategies of super long-span cable-stayed bridge under extreme earthquake

This work is focused on the failure modes and control strategies of a trial designed super long-span cable-stayed bridge (Abbr. CSB) with a main span of 1400 m under various seismic intensities, exploring the key characteristic of the failure modes of super high tower. Then several control strategies, such as the use of conventional viscous fluid dampers (Abbr. VFDs) and a new combination strategy comprising sacrificial inelastic links and conventional VFDs, are presented for the failure modes improvement and the seismic damage mitigation of the CSB under extreme earthquake (PGA = 1.0 g). It is found that the super high tower experiences an unexpected failure mode with double plastic hinges that shows a new characteristic on the tower failure in the transverse direction, which is different from that of the short- and medium-span cable-stayed bridge during earthquake excitation. Whereas the piers show a typical and expected flexural failure mode with only one plastic hinge in the transverse direction. Although conventional control strategies using the optimal VFDs can help to significantly reduce the seismic damage of the CSB, they cannot entirely make the tower satisfy seismic control targets. It is also observed that the new combination strategy can successfully improve the failure mode and seismic damage of the CSB that satisfies seismic control targets, the effects of proposed combination strategy on the CSB are superior to those of the convention control strategy with the optimal VFDs.

Multiobjective Design of Supplemental Seismic Protective Devices Utilizing Lifecycle Performance Criteria

AbstractThe cost-effective design of seismic protective devices considering multiple criteria related to their lifecycle performance is examined, focusing on applications to fluid viscous dampers. ...