Supplemental Energy Dissipation Devices Research Articles

3D response simulation of a bridge with a posttensioned base rocking steel pier under sequential loading of traffic loads, braking force, and earthquake excitations

AbstractThis paper presents finite element (FE) investigations of the seismic response of a bridge incorporating a base rocking steel pier. The pier consists of a circular steel tube, circular end plates, posttensioned (PT) tendon(s), and supplemental energy dissipation devices, and is configured to rock at its interface with the foundation. The main characteristic of such a pier is its ability to ensure small residual drifts after undergoing inelastic deformations during cyclic loading. The system has a tendency to close the gap due to the presence of superstructure dead load (DL) and tendon posttensioning force. Using experimental data, the calibration of the FE procedure is done at the material, component, and global system levels. The FE model of a prototype bridge is developed with the rocking pier modelled by continuum elements while superstructure, bearing units, abutment walls and backfill material modelled by discrete elements. The analysis procedure includes the application of one or two earthquake excitations, traffic loads, and braking force. The varied parameters are the diameter‐to‐thickness ratio of the column, presence of a PT tendon, addition of supplemental energy dissipaters (EDs), base plate dimensions, height of ED chairs, and ED strength. The results of dynamic FE studies demonstrate that a bridge utilizing such a pier has the potential to undergo consecutive earthquakes without sustaining significant damage and return to its original position without requiring abutment component stiffness and strength.

Deformation‐based design of seismically isolated bridges

AbstractA performance‐based design procedure is proposed for seismically isolated bridges with/without supplemental energy dissipation devices. Considering multiple performance levels (PLs), the proposed method initially identifies the critical hazard level and “near‐optimal” alternatives of the isolation system. Both performance and economy are evaluated based on the inelastic response of reduced‐degree‐of‐freedom (RDOF) isolation and energy dissipation systems. Nonlinear response history analysis (NLRHA) of the multi‐degree‐of‐freedom (MDOF) system is employed in successive design steps, corresponding to different PLs, to refine the design solution through the control of a broad range of material strains and deformations. The above characteristics aim to deliver a rigorous and broadly applicable design method that reduces the high computational effort characterising complex design frameworks, while addressing identified deficiencies of alternative displacement‐based methods. The efficiency of the proposed design methodology is demonstrated by applying it to an actual bridge that was previously designed for ductile behaviour. Alternative isolation and energy dissipation schemes are investigated. Assessment of the design through NLRHA reveals in all cases enhanced seismic performance and cost reduction in the substructure design, thus rendering base‐isolation an appealing design alternative.

A non-dimensional parametric approach for the design of PT tendons and mild steel dissipaters in precast rocking walls

In recent years, important benefits for the seismic design of precast reinforced concrete wall structures have been obtained from the use of jointed wall-to-foundation connections, where gap openings are permitted, thus resulting in a rocking motion. The lumped rotation at the wall base protects the panels from damage, while gravity loads and unbounded post-tensioned (PT) tendons, designed to remain elastic, re-center the structure after an earthquake, thus solving the problem of residual displacements. External dissipaters, herein partially unbounded mild steel bars, limit the amplitude of lateral displacements providing the required dissipating capacity. The resulting response is characterized by flag-shaped hysteretic loops.The paper investigates the parameters that may influence the design of rocking walls with supplemental energy dissipation devices in the form of mild reinforcing steel and aims to develop a parametric approach for the design of such systems. In this research, an analytical system of non-dimensional equations is developed for the design of PT tendons and dissipaters: location, area and prestressing force of the former, and location, area and unbounded length of the latter. A parametric approach suitable for the design practice is developed. This allows obtaining a simplified, quick, and accurate approach for the selection of PT tendons and energy dissipaters following a performance-based design approach. The procedure has been applied to a selected case study and validated by means of non-linear time history analyses.

Adaptive isolation system combining low-friction sliding pendulum bearings and SMA-based gap dampers

The flag-shaped hysteretic behavior of Shape Memory Alloys (SMAs) can be conveniently used for developing efficient isolation systems, providing energy dissipation without implying residual displacements. This work presents a base isolation layout that combines low-friction curved surface sliders (CSSs) with SMA gap dampers (SMAGDs). The proposed SMAGDs are formed by a group of SMA wires placed in parallel with the CSS isolation system and connected to it through a sliding pin and a slotted ring in order to accomplish the “gap damper” feature. Based on this installation configuration, SMAGDs introduce additional stiffening and energy dissipation to the isolation system only when the displacement of the CSS exceeds a certain threshold or gap displacement dgap, while not being engaged for lower displacements. Consequently, the system exhibits a phased behavior, meaning that its reaction force depends on the amplitude of the displacement. This is particularly convenient for limiting seismic displacements while avoiding at the same time undesirable effects such as high structural accelerations and poor re-centering capability exhibited by alternative systems at low-intensity excitations, e.g. systems based on high-friction CSSs or combinations of CSSs with traditional supplemental energy dissipation devices. The paper describes a preliminary design procedure and the evaluation of the seismic performance of the proposed CSS + SMGAGD system. A leading design parameter of the SMAGDs is the overall cross-sectional area of the SMA wires, which is designed here through a direct displacement based procedure, by introducing some reasonable assumptions for the definition of the linear equivalent mechanical properties of CSS, SMAGD and combined CSS + SMAGD system. This performance-oriented design procedure is aimed at achieving a target displacement demand of the combined CSS + SMAGD system under the maximum credible design earthquake. A parametric study comprising a variety of CSS and SMAGD properties reveals that the proposed isolation layout is suitable to limit the maximum displacement under ultimate limit state earthquakes, providing at the same time satisfactory energy dissipation along with high re-centering capability, and outperforms both low-friction CSSs and high-friction CSSs.

Dynamic Analysis of Heavily Damped Structures with Supplemental Energy Dissipation Devices

ABSTRACT A structure supplemented with dampers may be over-critical damped as a result of more deformations in higher modes. Over-critical modal damping can significantly decrease structural displacements but also increase absolute accelerations and consequently the seismic forces. In dynamic analyses, undamped and complex mode superposition approaches are always employed due to their efficiency. However, the critical and over-critical damping issues are normally ignored because of more complexities introduced in the calculation of mode vectors. Particularly, the critical damping can result in the defectiveness of non-classically damped systems such that the analysis methods aforementioned become invalid. In this paper, a generalized complex mode superposition method is developed without the limit of modal damping. Orthogonality conditions among under-critical, critical, and over-critical damped modes are firstly constructed based on the linear algebra theory and the generalized complex mode superposition method is derived in time domain. Then, this approach is further extended to frequency domain and associating with the response spectra. The implementation and effectiveness of the proposed methods are presented in numerical examples. The results show that the over-critical damped modes have a remarkable effect on the structural response, particularly for the low stories.

Vibration Control Devices for Building Structures and Installation Approach: A Review

Retrofit and structural design with vibration control devices have been proven repeatedly to be feasible seismic hazard mitigation approach. To control the structural response; supplemental energy dissipation devices have been most commonly used for energy absorption. The passive control system has been successfully incorporated in mid to high rise buildings as an appropriate energy absorbing system to suppress seismic and wind-induced excitation. The considerable theses that are highlighted include vibration control devices, the dynamic behavior of devices; energy dissipation mechanism, devices installation approach and building guidelines for structural analysis and design employing vibration control devices also, design concern that is specific to building with vibration control devices. The following four types of supplemental damping devices have been investigated in this review: metallic devices, friction devices, viscous fluid devices, and viscoelastic devices. Although numerous devices installation techniques available, more precisely, devices installation approaches have been reviewed in this paper, including Analysis and Redesign approach (Lavan A/R), standard placement approach, simplified sequential search algorithm, and Takewaki approach.

Probabilistic Assessment of Upgraded Rocking Cores-Moment Frames with Supplemental Self-Centering Energy Dissipation Devices

ABSTRACT An upgraded rocking cores-moment frame (RCMF), aimed to improve the RCMF from life safety to seismic resilience, is proposed in this article by equipping the rocking cores with replaceable self-centering energy dissipation devices. Its seismic performance is assessed within a probabilistic framework, which treats maximum interstory drift ratio (MD) and residual interstory drift ratio (RD) as a combined engineering demand parameter. Results indicate that the upgraded RCMF demonstrates an outstanding performance in reducing MD, RD and their corresponding deviations, mitigating the drift concentration, especially in eliminating the RD, which highlights its potential to achieve seismic resilience.

Dynamic response of non-classically damped structures via reduced-order complex modal analysis: Two novel truncation measures

The Caughey-O’Kelly condition, which defines a specific property of the damping matrix with respect to the mass and stiffness matrix, is violated in several cases of interest in earthquake engineering (e.g. seismic base isolation, supplemental energy dissipation devices, etc.). In these circumstances, non-classically damped systems are associated with complex-valued natural modes of vibration, and the complex modal superposition approach can be invoked as a generalization of the real-valued classical modal analysis to decouple the equations of motion and to compute the earthquake response. In analogy to the classical modal analysis, measures that quantify the error resulting from truncating up to a certain mode are desirable, especially for structures with hundreds or thousands of degrees of freedom. The concept of modal participating mass ratio, widely used in classical modal analysis, is no longer applicable to non-classically damped systems. The authors introduce here two novel measures related to a generalized modal mass ratio and to a modal dissipation ratio of each mode in the complex modal analysis framework. These two real-valued measures, whose sum is equal to one when all the modes are present, should be simultaneously considered to anticipate the importance of each mode in the complex modal superposition approach. Therefore, they are useful to determine the number of modes to retain in a reduced-order model. These two measures and the novel concepts are illustrated through some simple numerical examples of free vibration response and earthquake response of non-classically damped systems, including structures equipped with fluid viscous dampers and base-isolated buildings.

Seismic Upgrade of an Existing Tall Building Using Different Supplemental Energy Dissipation Devices

AbstractThe feasibility and cost-effectiveness of various retrofit techniques to improve the seismic performance of an existing 35-story steel building are examined. Three types of supplemental ene...

Design and performance of autonomous chevron-brace systems with elastomeric-dampers for steel frames

This paper presents an innovative use of natural rubber pads for seismic control of multistory low- and medium-rise steel braced frames. Such pads have always been used as supplemental energy dissipation devices in structures that already have their own and independent seismic force resisting system. This paper investigates the use of such devices in series with chevron braces as an autonomous seismic force resisting system, which provides not only additional damping to the structure but also a period shift. The damping and isolation material is a fiber reinforced natural rubber exhibiting strong nonlinear dependence with respect to strain. First, a design procedure based on numerical studies is illustrated for a typical one-story building. Pseudo-linear models of the structures are used for the final evaluation of the seismic response. Cyclic tests on a full scale frame were conducted to calibrate the models and showed the reliability of the autonomous rubber-based system under full loading and real assembly conditions. Then a 1/3-scale 3-story chevron braced steel frame with and without rubber devices was used to evaluate the seismic performances of the system. The application was studied numerically and experimentally through shake table tests of the 1/3 reduced-scale model at different seismic intensities. Results show the efficiency of the system to significantly reduce linear seismic forces induced on the structure without devices. Control of displacements is also achieved but is highly dependant on the initial value of damping in the structure without devices.

등방성 이력형 강재댐퍼를 이용한 RC 라멘조 아파트건물의 지진응답 개선

수동형 제진장치를 이용하는 제진구조는 수년간 개발이 지속되고 있으며, 1990년대 중반이후로 여러 나라들에서 실무적인 적용이 빠르게 증가되고 있다. 국내의 경우 이러한 제진장치 중 강재이력형 댐퍼가 비교적 저렴한 비용과 설치와 관리가 용이하다는 이유로 건물의 내진설계를 위하여 보편적으로 많이 적용되고 있다. 이 논문에서는 건물의 지진응답을 개선하기 위하여 적용된 소위 카고메댐퍼로 불리우는 등방성 강재이력형 댐퍼(Isotropic Hysteretic Metallic Damper, IHMD)의 유효성에 대한 해석적인 사례연구를 제시하고 있다. 연구대상 건물은 18층 규모의 철근콘크리트 라멘조 아파트건물로 해석결과를 통하여 IHMD의 실효성을 실증적으로 보여주고 있다. 해석결과는 IHMD가 건물의 지진응답을 줄일 수 있는 매우 효과적인 방법임을 검증하고 있다. Passive energy dissipation systems for seismic applications have been under development for a number of years with a rapid increase in implementations starting in the mid-1990s in many countries. A metallic hysteretic damper has most commonly been used for seismic protection of structures in domestic area because they present high energy-dissipation potential at relatively low cost and easy to install and maintain. This paper presents an analytical case study of the effectiveness of isotropic hysteretic metallic damper(IHMD) called Kagome as a passive dissipative device in reducing structural response during seismic excitation. An eighteen-story RC framed apartment building is studied with and without IHMD. Results demonstrate the feasibility of these techniques for seismic mitigation. The inclusion of supplemental passive energy dissipation devices in the form of IHMD proved to be a very effective method for significantly reducing the seismic response of the building investigated.

Design and evaluation of seismic strengthening techniques for reinforced concrete frames with soft ground story

This paper presents a design procedure and analytical evaluation of two strengthening techniques to improve the seismic performance of the existing non-ductile RC frames with soft-story at the ground story level. The first technique, termed as column retrofit (CR), uses only partial steel jacketing (or caging) to enhance the lateral strength and plastic rotational capacities of the deficient columns at the ground story level. The later technique, termed as full retrofit (FR), considers the aluminum shear links as supplemental energy dissipation devices in addition to the strengthened ground story columns. Steel collector beams and chevron braces are used to transfer the lateral load from the RC frame to these dissipating devices. Performance-based plastic design approach is used to proportion various elements of the strengthening techniques. Nonlinear static and dynamic analyses are carried out to evaluate the performance of the existing and the strengthened frames. The main parameters investigated are (a) interstory drift, (b) residual drift, (c) yield mechanism, (d) energy dissipation, and (e) lateral strength. The FR frame effectively controlled the drift response by avoiding the soft-story collapse because of the significant energy dissipation in the shear links. Moreover, the FR frame achieved the desired yield mechanism without exceeding the design target drift level.

Parametric analysis of optimum isolator properties for bridges susceptible to near-fault ground motions

This paper examines the selection of optimum isolator properties, namely characteristic strength, Qd, and post-elastic stiffness, kp, for bridges located in near-fault regions. First, a two-phased sensitivity analysis is conducted to evaluate the influence of bridge, isolator, and near-fault ground motion parameters on optimum levels of Qd and kp based on minimizing maximum isolator displacement and force. In the first phase of sensitivity analyses, a screening via design of experiments principles is performed to assess the statistical significance of various parameters on the optimum isolator properties. The second phase includes rigorous sensitivity analyses to assess the trends in optimum Qd and kp as a function of the bridge, isolator, and near-fault ground motion parameters. Next, nonlinear time history analyses of typical seismically isolated bridges are conducted for a suite of near-fault ground motions across a range of values of the identified parameters to enable the development of parametric equations for optimum Qd and kp to minimize isolator force or displacement. The parametric equations are validated using an alternate suite of near-fault ground motions. Furthermore, the dispersion about the predictive equations are quantified and assessed. It is observed that the developed equations produced reasonable estimates of optimum isolator properties with a relatively consistent dispersion across the modeling parameters. Moreover, it is observed that for near fault ground motions with high intensity and strong directivity, supplemental energy dissipation devices are required to minimize the isolator displacements.

Energy Dissipation Systems for Vibration Control of Framed Buildings: A Review

In conventional structural design, the stiffness and energy absorption mechanisms are combined in a single system, and the structure is allowed to deform inelastically. Experience with recent earthquakes has shown that the economical penalty associated with repairing conventionally designed structures can be significant. Situations also exist in which the conventional design approach is not appropriate. When a structure must remain functional after an earthquake, as is the case of important lifeline buildings (such as hospitals) the conventional design approach focusing on only life safety is inappropriate. For such cases, the structure must be designed with sufficient strength so that inelastic action is either prevented or minimised. But this approach is very costly. Moreover, in such structures, special precautions need to be taken to safeguarding against damage or failure of important occupational and functional systems, which are needed for continuing serviceability. Use of supplemental energy dissipation devices that can dissipate a large proportion of the vibration energy can be a viable option to safeguard the occupational and functional systems. An examination of the behavior and effects of these systems considers the distribution of energy within a structure. During a seismic event, energy is input into a structure. This input energy is transformed into both kinetic and potential (strain) energy, which must be either absorbed or dissipated. There is always some level of inherent damping, which dissipates energy from the system and therefore reduces the amplitude of vibration until the motion ceases. The structural performance can be improved if a larger portion of the input energy can be absorbed, not by structure itself, but by some type of supplemental energy-dissipating devices. This paper presents a review on energy dissipation system for vibration control of framed buildings.

Damping coefficients for near-fault ground motion response spectra

Damping coefficients are frequently used in earthquake engineering as a simple way to adjust the pseudo-acceleration or displacement response spectra associated with a viscous damping ratio of 5% to the higher values of viscous damping needed for design of structures equipped with base isolation and/or supplemental energy dissipation devices. In this study, damping coefficients for the single-degree-of-freedom system subjected to near-fault ground motions are calculated for a large range of periods and damping levels. The results indicate that damping coefficients proposed in design codes and previous studies, based primarily on far-field ground motion records, tend to not be conservative for near-fault seismic excitations. A new approach is recommended for the derivation of damping coefficients appropriate for engineering analysis and design in the immediate vicinity of the earthquake fault. This includes the normalization of the period axis with respect to the duration of the ground velocity pulses recorded in the near-fault region. The pulse duration is controlled by the rise time on the fault plane and scales directly with earthquake magnitude.

Development of analytical modeling for an energy-dissipating cladding panel

Modern earthquake-resistant design aims to isolate architectural precast concrete panels from the structural system so as to reduce the interaction with the supporting structure and hence minimize damage. The present study seeks to maximize the cladding-structure interaction by developing an energy-dissipating cladding system (EDCS) that is capable of functioning both as a structural brace, as well as a source of energy dissipation. The EDCS is designed to provide added stiffness and damping to buildings with steel moment resisting frames with the goal of favorably modifying the building response to earthquake-induced forces without demanding any inelastic action and ductility from the basic lateral force resisting system. Because many modern building facades typically have continuous and large openings on top of the precast cladding panels at each floor level for window system, the present study focuses on spandrel type precast concrete cladding panel. The preliminary design of the EDCS was based on existing guidelines and research data on architectural precast concrete cladding and supplemental energy dissipation devices. For the component-level study, the preliminary design was validated and further refined based on the results of nonlinear finite element analyses. The stiffness and strength characteristics of the EDCS were established from a series of nonlinear finite element analyses and are discussed in detail in this paper.

Performance of a Damage-Protected Highway Bridge Pier Subjected to Bidirectional Earthquake Attack

Recent earthquakes such as Loma Prieta, Northridge, and Kobe have demonstrated a need for a new design philosophy of bridge piers that avoids damage in order to ensure postearthquake serviceability and reduce financial loss. Damage avoidance design (DAD) is one such emerging philosophy that meets these objectives. DAD details require armoring of the joints; this eliminates the formation of plastic hinges. Seismic input energy is dissipated by rocking coupled with supplemental energy dissipation devices. In this paper the theoretical performance of a DAD bridge pier is validated through bidirectional quasi-static and pseudodynamic tests performed on a 30% scale specimen. The DAD pier is designed to rock on steel–steel armored interfaces. Tension-only energy dissipaters are used to increase tie down forces and further reduce dynamic response. The seismic performance of the DAD pier is compared to that of a conventional ductile pier. Results show that one can have 90% confidence that the DAD pier will survive a design basis earthquake without sustaining any damage, whereas for the conventional design substantial damage is sustained.

Fuzzy logic control of bridge structures using intelligent semi-active seismic isolation systems

Passive supplemental damping in a seismically isolated structure provides the necessary energy dissipation to limit the isolation system displacement. However, damper forces can become quite large as the passive damping level is increased, resulting in the requirement to transfer large forces at the damper connections to the structure which may be particularly difficult to accommodate in retrofit applications. One method to limit the level of damping force while simultaneously controlling the isolation system displacement is to utilize an intelligent hybrid isolation system containing semi-active dampers in which the damping coeffic ient can be modulated. The effectiveness of such a hybrid seismic isolation system for earthquake hazard mitigation is investigated in this paper. The system is examined through an analytical and computational study of the seismic response of a bridge structure containing a hybrid isolation system consisting of elastomeric bearings and semi-active dampers. Control algorithms for operation of the semi-active dampers are developed based on fuzzy logic control theory. Practical limits on the response of the isolation system are considered and utilized in the evaluation of the control algorithms. The results of the study show that both passive and semi-active hybrid seismic isolation systems consisting of combined base isolation bearings and supplemental energy dissipation devices can be beneficial in reducing the seismic response of structures. These hybrid systems may prevent or significantly reduce structural damage during a seismic event. Furthermore, it is shown that intelligent semi-active seismic isolation systems are capable of controlling the peak deck displacement of bridges, and thus reducing the required length of expansion joints, while simultaneously limiting peak damper forces. Copyright © 1999 John Wiley & Sons, Ltd.

Supplemental Damping for Improved Seismic Performance

The results of several studies on the effects of supplemental viscous damping on the response of elastic and elasto-plastic single-degree-of-freedom systems are used to provide insight to the effects of large damping on the earthquake response of buildings and the interpretation of studies reporting the equivalent damping and increased stiffness characteristics of specific types of supplemental energy dissipation devices. Extension to multi-story buildings is discussed briefly. Conversion of the properties of viscous, viscoelastic, friction, and metallic yield device characteristics to equivalent viscous damping are proposed. Specific recommendations for the incorporation of the effects of supplemental energy dissipation devices in the code design process are given.