جستجوی مقالات مرتبط با کلیدواژه « میراگر اصطکاکی » در نشریات گروه « عمران »

Considering the increasing use of seismic isolators in the country, which reduce the force on structural members and increase the overall displacement of the structure during an earthquake, it is necessary to create an optimal method for using this system along with reducing the overall displacement of the structure. Also, the use of damper systems reduces the overall and inter-floor movement of the structure during an earthquake. Therefore, it is essential to investigate the effect of using damping systems to optimize seismic isolators. On the other hand, the optimal use of the combination of two damper and isolator systems can be effective in reducing construction costs and repair costs resulting from earthquakes and provides structures with optimal performance. Therefore, in this article, two viscous and frictional dampers as well as isolator were used in high-rise concrete structures with 15 and 20 floors and the combination of these two systems was evaluated in the behavior of the structure. The structures are separated by lead core rubber isolators. The results were studied under three earthquake records of the nearby area. The results showed the positive effect of dampers and separators on the behavior of the structure, and reasonable results were obtained depending on the seismic records used in the article. also, showed the positive effect of the combination of separators and dampers in reducing the amount of relative displacement, roof displacement and base shear. The simultaneous use of damper and isolator in the structures caused a 35% reduction in the base shear of the structures, 47% in the maximum relative displacement and 29% in the displacement of the roof point.

Due to the disadvantages of some existing connections such as the lateral-torsional buckling of RBS connections (Akbari Hamed and Basim, 2020; Akbari Hamed and Bafandeh Nobari, 2021), Saeidzadeh et al. (2022) proposed a novel partial-strength and semi-rigid (Chenaghlou and Akbari Hamed, 2017; Eurocode3, 2005) self-centering connection which eliminates residual drifts and provides more ductility in comparison with existing connections. Considering the stable cycle behavior and the advantages of this connection, in this paper, the structural cyclic behavior of this novel connection was compared with existing connections under the applied quasi-static loading. To this aim, the verified finite element models of four connections including welded moment connection (WMC), post-tensioned strand connection (PTSC), friction damper connection (FDC) and metallic yielding damper connection (MYDC) were considered.

In recent decades , the vibration control of the structures subject to some loads , such as winds and earthquakes , etc . , has been widely expressed. Vibration control, which intends to keep the behavior of a structure within a permissible limit , is utilized in several structures , like bridges , tall buildings , wind turbines , foundations with additional vibrations in industry , and even ordinary structures. In this paper , some of the recent studies on optimal control of the structures are reviewed. In other words , a comprehensive review of articles on the optimal design of different known control systems of each category i.e. , Tuned Mass Dampers (Active , Passive , and Semi - active) , Viscoelastic Dampers and Base Isolation (Passive and Semi - active) , Fluid Viscous Dampers (Passive and Semi - active) and the active Tendons , with special attention to studies performed in the past decades, are presented. Also , due to simplicity , reliability , and maximum energy dissipation of the friction dampers as an energy dissipation device , especially for seismic amplification of the engineering structures , a brief overview of the optimization of the friction dampers is discussed.

The seismic design of buildings ought to be done to decrease the expenses of building repairing after an earthquake. Self-centering systems such as the post-tensioned concrete wall can provide this purpose. In this study, to evaluate the seismic behavior of the post-tensioned concrete wall with friction-based damper (FBD), the proposed system, the post-tensioned concrete wall with energy dissipator (ED) bars, and the concrete shear wall are subjected to the cyclic and nonlinear response history analyses at three, six, and ten-story buildings using OpenSees software. Based on the cyclic analysis, the total energy dissipation coefficients for the post-tensioned concrete wall with FBD in three, six, and ten-story buildings are respectively 1.37, 1.40, and 2.02 times of that obtained for the post-tensioned concrete wall with energy dissipator bars system, and are respectively 1.15, 1.05, and 1.72 times of that achieved for the concrete shear wall system. According to the results of the applied seven earthquake records, the average of the maximum drift in the concrete shear wall system is less than the other systems in the lower floors, and the average of the maximum drift in the upper floors in the post-tensioned concrete wall with FBD is less than the other systems.

Observations of damage to buildings in recent earthquakes indicate that some of the damage was in the area of welded joints.Due to the weakness in the joints, the idea of using a horizontal friction damper using brake pads in bracing openings, especially the chevron frame in steel structures has been proposed Which can be easily replaced after an earthquake.. The purpose of this study is to introduce a new friction damper with low manufacturing and installation costs and high efficiency. This friction device consumes vibrational energy with the help of friction caused by slipping of brake pads on steel surfaces , In this research, the numerical study of the friction damper of the brake pad and also the laboratory study of the materials used in this damper have been done. For this purpose, first a validation based on a laboratory model has been performed in ABAQUS software. In the following, 9 models are numerically studied in ABAQUS software and at the end, the optimal model of selective damping on a braced frame with porch decoration is analyzed. The results show that very high stress concentration occurs in the damping area of the brake pad after the load is applied to the bracing frame and due to the presence of dampers in other elements, including beams and columns, less stress is created than in the case without dampers. Also, among the studied models, the 10 screw model has the highest amount of energy absorption.

By examining the results related to the Northridge earthquakes in 1994 and other destructive earthquakes, it was observed that strengthening the structural members and increasing the length of the welding line of beam-to-column connections in steel structures did not have a suitable seismic performance. After that, to prevent the brittle failure of the connections, the way of forming the plastic joint outside the connection area was investigated and beams with a reduced cross-section were proposed. But less attention has been paid to the use of absorbers in bending frames. The proposed pin-fuse connection, (pin-fuse SBC), is one of the connections that can absorb the incoming forces near the connection through sliding and friction. When an earthquake occurs, the pin-fuses acts through the rotational sliding of the steel surfaces towards each other, the presence of friction between the fuse plates will cause the consumption of the earthquake energy. Frames equipped with pin-fuses, this frame has the ability to absorb high energy through said fuses, it can be used in areas with strong seismic activity. In the model proposed in this research, the intended connection of a real joint near the beam-to-column connection is designed with bean-shaped holes that can rotate and move after reaching an anchorage lower than the connection moment. Therefore, the experimental results of the proposed model under cyclic loads have been investigated and compared with the numerical results of finite elements. These results show that the pin fuse connection after reaching the required limit and due to the removal of the contribution of the web from the bending resistance and the absence of torsional buckling in the beam web and by creating a safe fuse away from the connection of the beam and the column, in addition to the resistance of the fuse pin connection and plasticity has increased by 11% and 6%, respectively, it has been able to reach a relative displacement of up to 9%, which is more than the regulation limit in special bending frames.

In this study, structures equipped with friction dampers under the influence of far-field and near-field earthquakes are investigated. How they slide and vibrate, which includes displacement, velocity and acceleration, is calculated by numerical analysis. And the response of the structure under the effect of far-field and near-field earthquakes on the one hand and also considering the simple friction model of Columbus and the more complete model of velocity-dependent friction (Stribeck friction) is compared. Although the possibility of a far-field earthquake is very likely, but the occurrence of large earthquakes near cities that are near faults is undeniable, and these earthquakes have certain specifications that distinguish them from far-field earthquakes. Some of these specifications are such that if neglected, they will lead to underestimation of the seismic force in the design of structures. Examples of these specifications are fling step effect and the presence of velocity pulse in the component perpendicular to the fault that is caused as a result of the phenomenon of forward directivity.Due to the nonlinear behavior of the damping force (FD), programming has been used to perform nonlinear analytical dynamics. Also, behavioral models in Open Sees software are used to investigate the behavior of Stribeck friction for friction damper and to compare its results with the results obtained from accurate analysis. The results show that simplifications of the sliding friction model, on the one hand, and lack of focus on near-field earthquakes, on the other hand, result in underestimation of displacements, especially in member forces. Considering Stribeck friction, error rate is reduced and results are improved.

This study experimentally examines types of rotational-friction dampers with two slip load and numerically analyze the behavior of a reinforced concrete frame with these dampers under cyclic loading. To this goal, the study will explain the mechanism of proposed damper’s action after the introduction. In the next step, two specimens of rotational-friction dampers with two different slip load are investigated in the laboratory. Using OpenSees software, the proposed behavioral model is validated by experimental results. In the final step, a frame of one-story reinforced concrete that had one bay was analyzed under cyclic loading in four states including (1) without damper, (2) with a rotational-friction damper that had one slip load (RFD), (3) with a rotational-friction damper that had two slip load type S01, and (4) with a rotational-friction damper that had two slip load type S02. The obtained results were discussed and examined after these analyses. The results of the numerical analysis also show that the concrete frame with S01 damper has better seismic performance. This is because its ultimate strength and dissipated energy are respectively 15% and 164% more than the ultimate strength and dissipated energy of the frame without damper, at the last cycle.

In this study, a novel hybrid self-centering system is introduced. This system consists of self-centering systems and Pall friction dampers. The design methodology of hybrid self-centering systems is developed and some examples of the designed hybrid self-centering are presented. Hybrid self-centering systems not only have the capability of dissipating energy but can also remove or arrange residual drifts of structures. In fact, hybrid self-centering systems can maintain design target residual drifts (zero or any) during lateral loading similar to the pure self-centering system and have the benefits of high capacity energy dissipation of Pall friction dampers. The hybrid self-centering system is developed for seismic resilience in terms of economic benefits, ready-to-use after the earthquake event, and practical fabrication. To evaluate the proposed design method, different low- to high-rise (3-, 6-, 9- and 12-story) buildings are selected from the literature, redesigned based on the proposed method, and then subjected to cyclic loading. Results are presented in terms of the cyclic response, residual drift and energy dissipation capacity of structures. Results indicate that the proposed design equations precisely meet the target structural performance (target residual drift) of the hybrid self-centering system and this system is obviously a superior system compared to the pure self-centering or Pall system.

Post-tensioned coupled shear wall system is characterized by good seismic specifications like a self-centering capability and an ability to sustain large nonlinear lateral deformations with little damage and negligible residual deformation. In this system, the coupling beam is not embedded into the walls, and coupling of concrete walls is performed by posttensioning beam to the walls using unbonded post-tensioning (PT) steel strands. In this paper, the seismic behavior of hybrid coupled wall systems with post-tensioned steel coupling beam was investigated experimentally. In order to dissipate seismic energy and reduce displacements of system, two friction dampers were used in the beam-to-wall connection region. To study the behavior of the system, a friction damper was first tested at different frequencies; then, four 2/3-scale posttensioned hybrid coupled wall sub-assemblages equipped with friction dampers were tested subjected to reversed-cyclic lateral loading. Each sub-assemblage included a half-length steel coupling beam and the adjacent concrete wall region at a floor level. The test specimens consisted of one control specimen without friction damper and three specimens equipped with friction dampers with various damper normal forces and different initial beam post-tensioning (PT) steel stresses. The test results showed that the system had very good lateral stiffness, strength, and ductility with little damage up to 8% lateral drift. The nonlinear deformation in this system occurs because of the gap opening at the beam-to-wall interface. The friction damper uses these gap opening displacements to provide supplemental energy dissipation. Friction dampers provide considerable energy dissipation at the system, while the self-centering capability of the system remains. The restoring effect of the post-tensioning steel strands causes closing the gap upon unloading and provides a self-centering behavior and flag-shaped hysteresis loops for specimens equipped with friction dampers. Based on the test results, the system, even after a severe earthquake, suffers limited damage and requires little repair.

In this study a new hybrid energy dissipation device is developed by combining two friction dampers (auxiliary and main fuse) in series to be used for seismic control of two different earthquake intensities. Compared with the conventional friction dampers, the new hybrid damper has an advantage in that only auxiliary fuse (with low sliding force) is activated for moderate earthquakes and both fuses work simultaneously for strong earthquakes. Cyclic loading tests of the combined hybrid dampers are carried out to evaluate their seismic energy dissipation capability. The obtained experimental force- displacement indicates proper details of the new damper to create two performance level. Finite element analyses of the test specimens are also carried out for comparison, which had good agreement with the test results. Force displacement characteristics, Energy dissipation and equivalent viscous damping are also derived and good agreement has been found with code requirement for displacement dependent dampers. Also, it is demonstrated, engaging the main fuse with non-loaded pretention bolts, strength losses of hybrid damper in subsequent cycles are limited compared to the common friction dampers which can be called “resurrection-type” behavior of the main fuse in the main shocks.

By gradual change in structural design methods from strength based to performance based methods, typical existing frames could not satisfy the criteria of latter methods and if structures are designed by applying all related criteria, it will be an uneconomical design. Main problem in typical frames is imbalance between stiffness and ductility. To prevent large drifts, structures should have sufficient lateral stiffness and in order to absorb earthquake energy they must have high ductility. The goal of this research is to study the seismic performance of rigid and semi-rigid steel frames and the effects of adding friction dampers to such structures. In this paper, semi-rigid connections are supposed to yield and dissipate energy like dampers. For this purpose, 5-story building frames are designed in four cases including bare moment frame, moment frame with friction damper, bare semi-rigid frame and semi-rigid frame with friction damper. Dynamic time-history analyses are carried out applying three earthquake records. By observing the results of numerical analyses of structures, one can find out that semi-rigid frame with friction damper have the best performance among studied frames. Obtained results show that using friction damper in the moment frame with semirigid connections compared to the case with rigid connections, maximum first story displacement and base shear decrease respectively 7 and 20%.

Friction dampers are one of the most widely used types of energy absorbing devices to control vibrations and to reduce the structural responses subjected to dynamic loads. The most important parameter of the design of these devices is slip load of the damper. The proper selection of this parameter has an important effect on the seismic behavior of the structures equipped with friction dampers. Several different methods have been proposed in the literature to determine the slip load [1-3]. Among them، the best known is based upon the development of design slip-load spectra [1، 4]. In this paper، a new method for the selection of the slip load of the dampers in different stories of the moment resisting building frames is proposed so that a uniform height-wise distribution of ductility demand is achieved. Results of the proposed method are compared with the usual design method using design slip-load spectra.

Abstract: Considering the seismicity of most of the areas in Iran, it is inevitable to confront the earthquake because of its major property and life damages. Therefore researchers put a great effort on designing and strengthening against earthquake. The researches conducted so far for improving the reinforced concrete structures using different types of steel braces and analytical studies and widespread experiments has been done for confronting destructive effects of earthquake on structures, results show the proper effectiveness of different mechanisms of inactive seismic control of structures as an efficient option for confronting the earthquake forces. Of different control methods, using friction damper could be counted as one of the best methods for improving the seismic behavior of current structures, as it uses a simple mechanism and doesn’t need specific materials or technology. By using friction dampers both the rigidity and the structure’s hysteresis energy loss ability is increased. These dampers by their inelastic behavior in different points of the structure cause the loss of incoming energy of earthquake. Also in high importance structures, by selecting the proper design parameters, it is possible to prevent the main structural members to enter the inelastic behavior limit which causes local damages to some parts of them or minimize that. This system was first introduced by Pall and March in 1982. The mechanism of this system is creating slippage friction surfaces at the intersection of braces. For building frames, these dampers could be used in crossed tension bracing, single diagonal bracing and Chevron bracing. The first model of pall friction damper was tested in chevron bracing against earthquake in Eaton Building in Canada. The purpose of this study is to investigate the role of Pall friction dampers in reducing structural response during the earthquake. Therefore, modeling of the damper is based on the model used by the Pall Corporation in Eaton Building. The functioning of this damper is by generating friction under lateral shear force which causes the movement of the damper and generation of slippage in it. Therefore, three concrete moment frames with 5, 8 and 10 stories, have been designed according to the Iranian National Codes. Using SAP2000, v14, several static nonlinear analyses were done to get the performance point of frames on the basis of the capacity spectrum method. Adding chevron braces to the mid span, the target displacement of frames were determined. Considering the fact that none of the braced moment frames satisfied the Life Safety criteria under Design Based Earthquake, Pall friction dampers have been added to the frames and static nonlinear analysis were done by several slip loads such as 1%, 10%, 25%, 50%, 75% and 100% of frame weights. Evaluation showed that in optimum slip Load, the performance level of the frames improves.

O‌n‌e o‌f t‌h‌e m‌o‌s‌t e‌c‌o‌n‌o‌m‌i‌c‌a‌l a‌n‌d f‌a‌s‌t w‌a‌y‌s i‌n r‌e‌h‌a‌b‌i‌l‌i‌t‌a‌t‌i‌o‌n i‌s t‌h‌e u‌s‌e o‌f e‌n‌e‌r‌g‌y d‌i‌s‌s‌i‌p‌a‌t‌e‌r‌s i‌n t‌h‌e f‌o‌r‌m‌a‌t o‌f a‌d‌d‌i‌t‌i‌o‌n‌a‌l d‌a‌m‌p‌e‌r‌s. T‌h‌e f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r i‌s ac‌o‌m‌m‌o‌n d‌a‌m‌p‌e‌r u‌s‌e‌d i‌n a w‌i‌d‌e r‌a‌n‌g‌e o‌f a‌p‌p‌l‌i‌c‌a‌t‌i‌o‌n‌s, d‌u‌e t‌o i‌t‌s d‌y‌n‌a‌m‌i‌c b‌e‌h‌a‌v‌i‌o‌r a‌n‌d m‌a‌n‌n‌e‌r o‌f w‌o‌r‌k‌i‌n‌g. I‌n t‌h‌i‌s p‌a‌p‌e‌r, w‌e w‌i‌l‌l d‌i‌s‌c‌u‌s‌s t‌h‌e e‌f‌f‌e‌c‌t‌s o‌f t‌h‌e u‌s‌e o‌f a m‌o‌u‌n‌t‌e‌d f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r a‌t t‌h‌e j‌u‌n‌c‌t‌i‌o‌n o‌f a c‌h‌e‌v‌r‌o‌n b‌r‌a‌c‌e w‌i‌t‌h a f‌l‌o‌o‌r b‌e‌a‌m. F‌o‌r t‌h‌i‌s p‌u‌r‌p‌o‌s‌e, t‌w‌o f‌r‌a‌m‌e‌s w‌e‌r‌e d‌e‌s‌i‌g‌n‌e‌d, a b‌a‌r f‌r‌a‌m‌e a‌n‌d a‌n e‌q‌u‌i‌p‌p‌e‌d f‌r‌a‌m‌e, w‌h‌i‌c‌h i‌s o‌f t‌w‌o t‌y‌p‌e‌s: s‌a‌m‌e a‌n‌d s‌t‌o‌r‌y s‌h‌e‌a‌r r‌a‌t‌i‌o d‌i‌s‌t‌r‌i‌b‌u‌t‌e‌d. T‌h‌e m‌o‌s‌t i‌m‌p‌o‌r‌t‌a‌n‌t p‌a‌r‌t o‌f f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r d‌e‌s‌i‌g‌n i‌s d‌e‌t‌e‌r‌m‌i‌n‌a‌t‌i‌o‌n o‌f o‌p‌t‌i‌m‌u‌m s‌l‌i‌p l‌o‌a‌d. S‌o, f‌r‌a‌m‌e‌s e‌q‌u‌i‌p‌p‌e‌d w‌i‌t‌h a d‌a‌m‌p‌e‌r i‌n a d‌o‌m‌a‌i‌n o‌f d‌i‌f‌f‌e‌r‌e‌n‌t s‌l‌i‌p l‌o‌a‌d‌s w‌e‌r‌e a‌n‌a‌l‌y‌z‌e‌d u‌s‌i‌n‌g P‌e‌r‌f‌o‌r‌m 3D. A‌n‌d t‌h‌e l‌o‌a‌d w‌i‌t‌h t‌h‌e l‌e‌a‌s‌t a‌n‌s‌w‌e‌r o‌f t‌h‌e s‌t‌r‌u‌c‌t‌u‌r‌e w‌a‌s c‌h‌o‌s‌e‌n a‌s t‌h‌e o‌p‌t‌i‌m‌u‌m s‌l‌i‌p l‌o‌a‌d o‌f t‌h‌e d‌a‌m‌p‌e‌r. A‌f‌t‌e‌r d‌e‌s‌i‌g‌n‌i‌n‌g t‌h‌e d‌a‌m‌p‌e‌r, t‌i‌m‌e h‌i‌s‌t‌o‌r‌y a‌n‌a‌l‌y‌z‌e‌d e‌a‌c‌h o‌f t‌h‌e b‌a‌r f‌r‌a‌m‌e‌s a‌n‌d e‌q‌u‌i‌p‌p‌e‌d f‌r‌a‌m‌e‌s. T‌h‌e r‌e‌s‌u‌l‌t‌s o‌f t‌h‌e a‌n‌a‌l‌y‌s‌e‌s o‌f t‌h‌e t‌w‌o f‌r‌a‌m‌e‌s, i‌n‌c‌l‌u‌d‌i‌n‌g a‌b‌s‌o‌l‌u‌t‌e d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t, s‌t‌o‌r‌y s‌h‌a‌r‌e, i‌n‌p‌u‌t, s‌t‌r‌a‌i‌n a‌n‌d d‌i‌s‌s‌i‌p‌a‌t‌e‌d e‌n‌e‌r‌g‌y, a‌x‌i‌a‌l f‌o‌r‌c‌e o‌f c‌o‌l‌u‌m‌n‌s, h‌i‌n‌g‌e‌s a‌n‌d i‌n‌e‌l‌a‌s‌t‌i‌c p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e l‌e‌v‌e‌l‌s, w‌e‌r‌e c‌o‌m‌p‌a‌r‌e‌d. T‌h‌e r‌e‌s‌u‌l‌t‌s s‌h‌o‌w t‌h‌a‌t t‌h‌e u‌s‌e o‌f a d‌a‌m‌p‌e‌r i‌n t‌h‌e s‌a‌m‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n c‌o‌u‌l‌d r‌e‌d‌u‌c‌e s‌t‌o‌r‌y d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t b‌e‌t‌w‌e‌e‌n 47.28 t‌o 60.71 p‌e‌r‌c‌e‌n‌t, a‌n‌d s‌t‌o‌r‌y s‌h‌e‌a‌r r‌a‌t‌i‌o c‌o‌u‌l‌d r‌e‌d‌u‌c‌e s‌t‌o‌r‌y d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t b‌e‌t‌w‌e‌e‌n 60.7 t‌o 69.29 p‌e‌r‌c‌e‌n‌t. F‌u‌r‌t‌h‌e‌r‌m‌o‌r‌e b‌r‌a‌c‌e s‌h‌e‌a‌r f‌o‌r‌c‌e i‌n t‌h‌e s‌a‌m‌e d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n r‌e‌d‌u‌c‌e‌s 28.7%, w‌h‌i‌l‌e, i‌n s‌h‌e‌a‌r r‌a‌t‌i‌o d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n, r‌e‌d‌u‌c‌e‌d 52.3%. A‌l‌l t‌h‌e a‌b‌s‌o‌r‌b‌e‌d e‌n‌e‌r‌g‌y i‌s r‌e‌d‌u‌c‌e‌d a‌n‌d d‌i‌s‌s‌i‌p‌a‌t‌e‌d e‌n‌e‌r‌g‌y i‌s i‌n‌c‌r‌e‌a‌s‌e‌d. A‌l‌t‌o‌g‌e‌t‌h‌e‌r, t‌h‌e s‌h‌a‌r‌e‌s o‌f i‌n‌p‌u‌t a‌n‌d s‌t‌r‌a‌i‌n e‌n‌e‌r‌g‌i‌e‌s i‌n t‌h‌e b‌a‌r f‌r‌a‌m‌e i‌n c‌o‌m‌p‌a‌r‌i‌s‌o‌n w‌i‌t‌h t‌h‌e e‌q‌u‌i‌p‌p‌e‌d f‌r‌a‌m‌e a‌r‌e r‌e‌d‌u‌c‌e‌d. B‌e‌c‌a‌u‌s‌e o‌f t‌h‌e n‌o‌n‌l‌i‌n‌e‌a‌r b‌e‌h‌a‌v‌i‌o‌r t‌r‌a‌n‌s‌m‌i‌s‌s‌i‌o‌n o‌f s‌t‌r‌u‌c‌t‌u‌r‌e m‌e‌m‌b‌e‌r‌s t‌o t‌h‌e d‌a‌m‌p‌e‌r‌s, t‌h‌e n‌u‌m‌b‌e‌r o‌f h‌i‌n‌g‌e‌s i‌s r‌e‌d‌u‌c‌e‌d n‌e‌a‌r‌l‌y t‌o z‌e‌r‌o. I‌n m‌o‌s‌t c‌a‌s‌e‌s, t‌h‌e e‌q‌u‌i‌p‌p‌e‌d f‌r‌a‌m‌e‌s w‌i‌t‌h s‌a‌f‌e‌r i‌n‌d‌i‌c‌e‌s s‌h‌o‌w h‌i‌g‌h‌e‌r l‌e‌v‌e‌l‌s o‌f p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e.

T‌o‌r‌s‌i‌o‌n h‌a‌s b‌e‌e‌n r‌e‌c‌o‌g‌n‌i‌z‌e‌d a‌s a m‌a‌i‌n f‌a‌i‌l‌u‌r‌e m‌o‌d‌e i‌n p‌a‌s‌t e‌a‌r‌t‌h‌q‌u‌a‌k‌e‌s. O‌n‌e e‌f‌f‌i‌c‌i‌e‌n‌t m‌e‌t‌h‌o‌d o‌f r‌e‌d‌u‌c‌i‌n‌g e‌a‌r‌t‌h‌q‌u‌a‌k‌e e‌f‌f‌e‌c‌t‌s i‌s t‌h‌e a‌p‌p‌l‌i‌c‌a‌t‌i‌o‌n o‌f e‌n‌e‌r‌g‌y d‌i‌s‌s‌i‌p‌a‌t‌i‌o‌n d‌e‌v‌i‌c‌e‌s, s‌u‌c‌h a‌s d‌a‌m‌p‌e‌r‌s. F‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s a‌r‌e a‌m‌o‌n‌g t‌h‌e s‌i‌m‌p‌l‌e‌s‌t e‌n‌e‌r‌g‌y d‌i‌s‌s‌i‌p‌a‌t‌i‌o‌n d‌e‌v‌i‌c‌e‌s. A‌l‌t‌h‌o‌u‌g‌h t‌h‌e‌r‌e i‌s m‌u‌c‌h r‌e‌s‌e‌a‌r‌c‌h o‌n t‌h‌e u‌s‌e o‌f f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s i‌n s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s, t‌h‌e‌r‌e a‌r‌e f‌e‌w‌e‌r s‌t‌u‌d‌i‌e‌s r‌e‌p‌o‌r‌t‌e‌d o‌n a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s. R‌e‌s‌u‌l‌t‌s o‌f t‌h‌o‌s‌e l‌i‌m‌i‌t‌e‌d p‌a‌s‌t s‌t‌u‌d‌i‌e‌s s‌h‌o‌w t‌h‌a‌t t‌h‌e p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e o‌f f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s i‌n t‌h‌e c‌o‌n‌t‌r‌o‌l o‌f t‌o‌r‌s‌i‌o‌n i‌n a‌s‌y‌m‌m‌e‌t‌r‌i‌c s‌t‌r‌u‌c‌t‌u‌r‌e‌s i‌s c‌o‌n‌s‌i‌d‌e‌r‌a‌b‌l‌e. T‌h‌e a‌i‌m o‌f t‌h‌i‌s i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌i‌o‌n i‌s t‌o d‌e‌t‌e‌r‌m‌i‌n‌e e‌f‌f‌e‌c‌t‌i‌v‌e p‌a‌r‌a‌m‌e‌t‌e‌r‌s a‌n‌d t‌h‌e‌i‌r r‌a‌n‌g‌e o‌f e‌f‌f‌e‌c‌t‌i‌v‌e v‌a‌l‌u‌e‌s f‌o‌r t‌o‌r‌s‌i‌o‌n‌a‌l c‌o‌n‌t‌r‌o‌l o‌f a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s b‌y f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s. F‌o‌r t‌h‌i‌s p‌u‌r‌p‌o‌s‌e, s‌t‌e‌e‌l b‌u‌i‌l‌d‌i‌n‌g‌s h‌a‌v‌e b‌e‌e‌n m‌o‌d‌e‌l‌e‌d a‌n‌d a‌n‌a‌l‌y‌z‌e‌d b‌y O‌p‌e‌n‌S‌e‌e‌s. T‌h‌e a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s i‌n t‌h‌i‌s s‌t‌u‌d‌y a‌r‌e a‌s‌s‌u‌m‌e‌d t‌o b‌e c‌l‌a‌s‌s‌i‌f‌i‌e‌d a‌s m‌a‌s‌s e‌c‌c‌e‌n‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s. T‌h‌e‌s‌e m‌o‌d‌e‌l‌s a‌r‌e s‌y‌m‌m‌e‌t‌r‌i‌c, w‌i‌t‌h r‌e‌s‌p‌e‌c‌t t‌o s‌t‌i‌f‌f‌n‌e‌s‌s a‌n‌d s‌t‌r‌e‌n‌g‌t‌h d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n, a‌n‌d t‌h‌e‌i‌re‌c‌c‌e‌n‌t‌r‌i‌c‌i‌t‌y i‌s d‌u‌e t‌o t‌h‌e‌i‌r a‌s‌y‌m‌m‌e‌t‌r‌i‌c m‌a‌s‌s d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n. D‌i‌f‌f‌e‌r‌e‌n‌t l‌e‌v‌e‌l‌s o‌f m‌a‌s‌s e‌c‌c‌e‌n‌t‌r‌i‌c‌i‌t‌y a‌r‌e c‌o‌n‌s‌i‌d‌e‌r‌e‌d i‌n p‌a‌r‌a‌m‌e‌t‌r‌i‌c s‌t‌u‌d‌i‌e‌s. D‌a‌m‌p‌e‌r p‌l‌a‌c‌e‌m‌e‌n‌t‌s a‌r‌e i‌n‌v‌e‌s‌t‌i‌g‌a‌t‌e‌d t‌o i‌d‌e‌n‌t‌i‌f‌y t‌h‌e‌i‌r o‌p‌t‌i‌m‌u‌m d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n i‌n h‌a‌v‌i‌n‌g t‌h‌e ‌a‌r‌g‌e‌s‌te‌f‌f‌e‌c‌t i‌n r‌e‌d‌u‌c‌i‌n‌g t‌h‌e a‌d‌v‌e‌r‌s‌e e‌f‌f‌e‌c‌t o‌f t‌o‌r‌s‌i‌o‌n i‌n a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s. T‌h‌e c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s o‌f f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s a‌r‌e a‌l‌s‌o c‌h‌a‌n‌g‌e‌d t‌o c‌o‌v‌e‌r a w‌i‌d‌e r‌a‌n‌g‌e o‌f r‌e‌a‌l‌i‌s‌t‌i‌c v‌a‌l‌u‌e‌s. A‌l‌s‌o, c‌o‌n‌s‌i‌d‌e‌r‌e‌d i‌n p‌a‌r‌a‌m‌e‌t‌r‌i‌c s‌t‌u‌d‌i‌e‌s, a‌r‌e t‌h‌e p‌r‌o‌p‌e‌r‌t‌i‌e‌s o‌f b‌r‌a‌c‌e‌s, w‌h‌i‌c‌h a‌r‌e c‌o‌n‌n‌e‌c‌t‌e‌d t‌o t‌h‌e f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s. T‌h‌e e‌f‌f‌e‌c‌t‌s o‌f t‌h‌e‌s‌e p‌a‌r‌a‌m‌e‌t‌e‌r‌s h‌a‌v‌e b‌e‌e‌n e‌v‌a‌l‌u‌a‌t‌e‌d, n‌o‌t o‌n‌l‌y i‌n o‌p‌t‌i‌m‌u‌m p‌l‌a‌c‌e‌m‌e‌n‌t, b‌u‌t, a‌l‌s‌o, i‌n t‌h‌e v‌a‌l‌u‌e o‌f t‌h‌e s‌l‌i‌p l‌o‌a‌d o‌f f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s. T‌h‌e r‌e‌s‌u‌l‌t‌s s‌h‌o‌w t‌h‌a‌t t‌h‌e u‌s‌e o‌f r‌e‌s‌u‌l‌t‌e‌d o‌p‌t‌i‌m‌u‌m d‌i‌s‌t‌r‌i‌b‌u‌t‌i‌o‌n a‌n‌d t‌h‌e r‌e‌c‌o‌m‌m‌e‌n‌d‌e‌d c‌h‌a‌r‌a‌c‌t‌e‌r‌i‌s‌t‌i‌c‌s o‌f f‌r‌i‌c‌t‌i‌o‌n d‌a‌m‌p‌e‌r‌s c‌a‌n c‌o‌n‌t‌r‌o‌l t‌o‌r‌s‌i‌o‌n i‌n a‌s‌y‌m‌m‌e‌t‌r‌i‌c b‌u‌i‌l‌d‌i‌n‌g‌s.

In this paper، the hybrid friction-yielding damper in the center of X-braced steel frame for dissipating seismic energy and its design methodology are introduced. Due to their relative simplicity and easy application with no need for any special material or technology، this high performance system have gained more attention compared to other means of energy dissipation devises. The advantage of failure localization at circular damper cause this system can be used for rehabilitation of existing building whose slender braces designed based on tension forces only. Possibility of Prompt installation of new ones after strong earthquake is another advantage of this simple system.

Studying the behavior of asymmetric structures in past earthquakes shows that torsion was one of the main factors of failure of the buildings. One of the methods of reducing the responses of a structure is using energy dissipation devices. The main contribution of this study is determining of effective parameters and their values of friction dampers load to reduce the adverse effects of torsion in stiffness eccentric structures. For this purpose steel building models have been analyzed in OpenSees program for various stiffness and strength eccentricity and different distribution and properties of frictional dampers. Finally the responses of the structure have been compared for different cases of damper distribution and change in effective parameters that influence suitable distribution and optimum slip load of frictional dampers.