Dual earthquake resistant frames

Structural control through energy dissipation systems has been increasingly implemented internationally in the last years and has proven to be a most promising strategy for earthquake safety of the structures. The control concept is based on the integration of passive damping devices within the structure for the necessary energy dissipation and the elastic response of the primary system. Adaptable dual control systems (ADCS) presented in this paper, consist of tension-only bracing members with closed circuit and a hysteretic damper of steel plates. The implementation of ADCS in frame structures enables a dual function of the component members, leading to two practically uncoupled systems, i.e. the primary frame, responsible for the static vertical and horizontal forces and the bracing-damper mechanism, for the earthquake forces and the necessary energy dissipation. ADCS are investigated and compared in their energy dissipation behavior for three differing configurations of the bracing-damper mechanism. In all cases the hysteretic damper utilizes effectively the relative displacements between its connection joints, i.e. a bracing and a primary frame's member, through its own yielding deformations for the necessary energy dissipation. In the present paper parametric dynamic analyses of the SDOF system's responses have been performed, based on three representative international earthquake motions of differing frequency contents. A nonlinear link parameter, defined as the ratio of the stiffness to the yield force of the hysteretic damper, DR, characterizes the behavior of the controlled systems in each configuration. Optimum DR values are proposed for each system configuration in achieving high energy dissipation capacity, while preventing possible increase of the maximum base shear and relative displacements. Keywords Adaptable Systems, Earthquake Resistance, Frame Structures, Passive Control. Language: en

Conventional approaches in seismic design dissipate most of the energy input by the earthquake through plastic deformations in regions of the main structure that also support the gravity loads. This involves important damage spread throughout the structure. Innovative approaches based on the use of energy dissipation devices (EDDs) apply a completely different strategy. The EDDs release the main structure from dissipating energy and limit its responsibility to only (or mainly) sustaining the gravity loads as the building deforms laterally. The seismic capacity of the structure is entrusted entirely (or mainly) to EDDs. Ultimately, the usefulness of EDDs is fully acknowledged, but their use in Europe is still very incipient. Two impediments to the widespread implementation of EDDs would be the lack of requirements, or else the over-conservative requirements of code provisions for the seismic design of structures with EDDs. This presentation introduces the concept of a buildings with energy dissipation systems and briefly reviews recent research on this topic. Finally, the procedures for verifying buildings with energy dissipation systems that have tentatively been adopted in the draft-new-Eurocode 8 are explained.KeywordsEnergy dissipation devicesHysteretic damperPerformance based designEnergy based designEurocode 8

The objective of the present study is to investigate a new energy dissipation system that combines the positive stiffness of the resetting passive stiffness damper (RPSD) with the negative stiffness of a passive negative stiffness device (PNSD). The displacement-based adjustable stiffness and energy dissipation (D-BASED) system can be designed to have independent damper stiffness and energy dissipation. Equations for modeling the RPSD and PNSD components of the D-BASED system are presented, along with an approach for designing the PNSD component. The results of laboratory experiments on a small-scale prototype D-BASED system are provided for validation of the concept. Numerical simulations are performed for the D-BASED system installed in the isolation layer of a five-story base-isolated building subject to a suite of near-field earthquake ground motions. The performance of the D-BASED system with the same net stiffness, but different levels of energy dissipation, is compared with that of the RPSD alone. It is shown that increasing the RPSD- and PNSD-component stiffness in the D-BASED system results in a reduction in the peak base drift compared to the RPSD, while limiting the building story drifts. Furthermore, it is shown that increasing the RPSD- and PNSD-component stiffness generally does not lead to an increase in the peak total force transmitted to the foundation. The D-BASED system is also found to yield smaller peak story drifts and foundation forces compared to a passive linear fluid viscous damper for a long-period base-isolated building.

Viscoelastic damper is an effective passive damping device, which can reduce the seismic response of the structure by increasing the damping and dissipating the vibration energy of structures. It has a wide application prospect in actual structural vibration control because of simple device and economical material. In view of the poor seismic behaviors of assembled frame structure connections, various energy dissipation devices are proposed to improve the seismic performance. The finite element numerical analysis method is adopted to analyze relevant energy dissipation structural parameters. The response spectrum of a 7-story assembled frame structure combined the ordinary steel support, ordinary viscoelastic damper, and viscoelastic damper with displacement amplification device is analyzed. The analysis results show that the mechanical behavior of assembled frame structure with ordinary steel supports are not significantly different from those without energy dissipation devices. The assembled frame structure with viscoelastic damper has better seismic performance and energy dissipation, especially for the viscoelastic damper with displacement amplification devices. The maximum value of inter-story displacement angle decreases by 32.24%; the maximum floor displacement decreases by 31.91%, and the base shear decreases by 13.62% compared with the assembled frame structures without energy dissipation devices. The results show that the seismic fortification ability of the structure is significantly improved, and the overall structure is more uniformly stressed. The damping structure with viscoelastic damper mainly reduces the dynamic response of the structure by increasing the damping coefficient, rather than by changing the natural vibration period of the structure. This paper provides an effective theoretical basis and reference for improving the energy dissipation system and the seismic performance of assembled frame structures.

The establishment of a simple engineering rule for predicting the fatigue failure of concrete has been pursued over the past decades. An energetic approach to the matter seems to be an attractive option that many researchers have embraced. In the present work, the authors attempt to contribute to the establishment of such a rule. In particular, the energy dissipation of confined concrete subjected to shear cyclic loading is studied and quantified. For this purpose, a microplane fatigue model recently introduced by the authors, referred to as MS1, is used. It aims to capture the fundamental inelastic mechanisms driving the tri‐axial stress redistribution within a material zone during the fatigue damage process in concrete. To this end, the fatigue damage evolution is linked to a measure of cumulative inelastic shear strain at the microplane level, reflecting the accumulation of fatigue damage due to internal shear/sliding between aggregates at subcritical pulsating load levels. To isolate the dissipative mechanism mentioned above, test configurations with dominant shear stress seem to be more appropriate. In the present work, a punch‐through shear test (PTST) FE model is used to induce shear‐dominated stresses and strains along the ligament of a specimen. Numerical studies are first presented to evaluate the behavior and energy dissipation at the elemental interface level. The interface is introduced in the MS1 microplane material model, which is capable of reproducing the concrete behavior under monotonic, cyclic, and fatigue loading with consistent set of material parameters. Quantification of the energy dissipation for each introduced dissipative mechanism is performed at each microplane and integrated via a well‐established homogenization scheme to evaluate the macroscopic energy dissipation. Later, an analysis of the energy dissipation of the PTST process zone is performed for cyclic loading under two different subcritical cyclic load amplitudes.

For a square tubular T-joint under axial loading, failure occurs easily along the weld toe because high stress concentration exists in this region. This phenomenon can be used to explain why brittle fracture is dominant when the joint is subjected to cyclic loading, such as faigue loading or earthquake loading. To improve the seismic resistance of a square tubular joint, collar plate can be used to reinforce the joint connection. However, the aseismic behaviour of the collar- plate reinoforced tubular joint must be assessed because only the increase of the load carrying capacity can not guarantee the capacity of energy dissipation for this joint under seismic loading. Through both experimental investigation and finite element analysis, the hysteretic behaviour of square tubular T-joints with or without collar-plate reinforcement is studied. The hysteretic curves, the ductility ratio and the energy dissipation index are all analyzed. Based on the obtained results, it is found that a square tubular T-joint with collar-plate reinforcement can dissipate more energy before failure compared with the corresponding un-reinforced one. Therefore, the reinforced T-joints are more capable in resisting earthquake loading.

This paper proposes a variable structure (VS) control algorithm, with which a system can be stabilized by switching the system control input among a set of simple feedback control laws. Each feedback control law is easy to be designed because it uses only one element of the state variable with a fixed positive or negative feedback gain. For an n-order system, 2n feedback control laws are needed to realize the proposed VS control. The concept of the sliding sector is used in the paper to show that there exists an area for each feedback control law, inside which a Lyapunov function decreases with the control law although the system may not be stabilized by it alone. It is shown that a common Lyapunov function for all control laws exists for a controllable system, i.e., for any state in the state space, there exists at least one control law among those laws mentioned above such that the system state is inside the sliding sector of the system with the corresponding control law. Thus a hybrid-type control rule of the variable structure control system is designed to switch the control input to the control law, which ensures the decrease of the common Lyapunov function. The proposed VS control system is quadratically stable. Simulation results are given to show the convergence of the proposed VS control system.

While the construction of civil engineering is developing towards the direction of higher height, larger span and more complex structure, structural vibration control technology has gradually become one of the most effective technical means to resist strong earthquakes and hurricanes due to its safety, economy and effective characteristics. This summary includes the following three parts: 1. Concept and Principle of Structural Vibration Control. Based on the basic principles of structural dynamics and earthquake engineering, the control mechanism of vibration reduction and base isolated structure is explained. 2. Classification and Basic Performance of Structural Vibration Control. The vibration control technology of building structures is divided into energy dissipation and vibration reduction technology, frequency modulation technology and isolation technology. The basic performance of these technologies is analyzed. 3. Development and Current Situation of Structural Vibration Control. Based on the analysis of current situation, the research of new high-performance damping device, the improvement of current design theory and method of vibration control are considered as the development trends in near future.

Passive energy dissipation devices have been proved to be effective and low-cost means of structural control, and a variety of dampers have been developed over the past decades. Hysteretic dampers with hardening post-yielding stiffness have multiphased energy dissipation characteristics because of their hardening behavior, which can compensate for stiffness loss and postpone the collapse of damaged structures. In this article, a hysteretic model is proposed for hysteretic dampers with hardening post-yielding stiffnesses, and a formula is derived for equivalent yield strength expressed by the additional damping of the structure. A procedure is developed for displacement-based seismic design that transforms the relatively complex damping into an acceptable yield strength. A numerical example is only presented for demonstrating the design process and simply validating the proposed method. The results show that the proposed procedure is easy to implement and could produce adequate hysteretic dampers with hardening post-yielding stiffness hardening behavior. The maximum displacement responses of the existing structure retrofitted using the proposed procedure satisfy the expected performance objective well. Thus, this procedure could be an alternative to seismic retrofitting for structures with energy dissipation systems.

<p>This study proposes a new energy dissipation system in which a steel slit damper is applied to an energy dissipation devise using lever arms as the displacement amplification mechanism. It is characterized by utilization of small lever arms. The brace members in the proposed system do not buckle because the brace can maintain tensile axial force by introducing initial tension, which allows the use of small diameter rods. Cyclic loading test results are presented to reveal that the proposed energy dissipation system could perform adequately. The experimental results demonstrated that all the specimens yielded in the small story drift angle and thereby had high energy dissipation ability. The loading tests confirmed that the stiffness and strength of the system can be controlled by the amplification factor of the lever arm and the slit damper configuration.</p>

There are already approximately 5,000 structures in the world, located in over 30 countries, that have been protected by seismic isolation (SI), energy dissipation (ED) and other modern seismic vibration passive control (SVPC) systems. The number of such applications is increasing everywhere more and more. It has been confirmed that, in each country, the extension of the use of the SVPC systems is conclusively influenced by earthquake experience, the availability of specific design rules and the features of those adopted. With regard to application, Japan has consolidated its worldwide leadership, with over 3,000 seismically isolated buildings, many others protected by ED systems and several isolated bridges & viaducts. Second is now the P. R. China, with 610 isolated buildings and 45 with dampers, in addition to numerous isolated bridges & viaducts. The Russian Federation is third for the number of isolated buildings, which are approximately 600. In the USA, due to the very penalizing design code in force for SI of buildings, there are at present only a few new applications of this kind (an overall number of approximately 200 was reported), although the US isolated buildings are mostly quite important, half being retrofits; on the contrary, the use of SI for bridges & viaducts and that of ED for buildings are more popular in the USA. At present (April 2008), Italy (which remains the worldwide leader as regards the application of the SVPC systems to cultural heritage and keeps a key role also as to the number and importance of bridges & viaducts protected by such systems) is at the fifth place, at least for the number of isolated buildings already open to activity: they are 51, besides others protected by other SVPC systems. There, thanks to the new national seismic code (enforced in May 2003), there has been a significant recent increase of building application and design of the SVPC systems. With regard to the use of such systems in other countries, Italy is now followed by Taiwan, France (including its Martinique island), New Zealand and Armenia. In addition, significant applications also concern: Canada in North America; Mexico in Central America; Chile and Venezuela in South America; Turkey, South Korea and Indonesia in Asia; and Greece, Cyprus, Portugal and Macedonia in Europe. More recently, the installation of the aforesaid systems also began in further countries, such as Argentina, Israel, India and Iran. Devices manufactured in Italy have been frequently used even abroad. Finally, to be stressed are the somewhat increasing use of SI in nuclear and high risk chemical plants (e.g. the liquefied natural gas tanks) and the already significant application of the SVPC systems to cultural heritage, in particular in Italy

Seismic resilient rocking shear wall with dual self-centering energy dissipation system: Introduction and A preliminary study

The increasingly demanding performance requirements trigger the development of new devices to eliminate the limitations concerning the post-earthquake performance of available seismic protection systems. The prerequisite for economical earthquake-resistant bridges is the structures’ capacity to absorb and dissipate a large amount of seismic energy. A widely considered strategy for enhancing this capacity is through the use of passive energy dissipation systems for seismic protection of structures. It has been known that majority of the available energy dissipation systems are non-usable after a major earthquake, which increases the risk of collapse during an aftershock. The focus of the current study is given to introduce a new type of passive energy dissipation device with a pending patent that is testified to have an improved energy dissipation capacity without suffering any damage while absorbing energy. Thus, the proposed damper does not require an immediate expensive replacement and keeps its operational capabilities and effectiveness during aftershocks. The paper presents the dynamic performance tests of the first full-scale prototype of the damper that eventually prove it to be a promising design with an improved energy dissipation capacity and stable behavior during and after the dynamic event.

The synchronization phenomenon is common to many natural mechanical systems. Joint friction and damping in humans and animals are associated with energy dissipation. A coupled oscillator model is conventionally used to manage multiple joint torque generations to form a limit cycle in an energy dissipation system. The coupling term design and the frequency and phase settings become issues when selecting the oscillator model. The relative coupling relationship between oscillators needs to be predefined for unknown dynamics systems, which is quite challenging problem. We present a simple distributed neural integrators method to induce the limit cycle in unknown energy dissipation systems without using a coupled oscillator. The results demonstrate that synergetic synchronized oscillation could be produced that adapts to different physical environments. Finding the balanced energy injection by neural inputs to form dynamic equilibrium is not a trivial problem, when the dynamics information is not priorly known. The proposed method realized self-organized pattern generation to induce the dynamic equilibrium for different mechanical systems. The oscillation was managed without using the explicit phase or frequency knowledge. However, phase, frequency, and amplitude modulation emerged to form an efficient synchronized limit cycle. This type of distributed neural integrator can be used as a source for regulating multi-joint coordination to induce synergetic oscillations in natural mechanical systems.

Seismic retrofit of spherical liquid storage tanks with energy dissipative devices