Improving the Dynamic Behavior of Adjacent Buildings with Fluid Viscous Dampers

Explained ways to strengthen structures against lateral dynamic loads can be divided into two broad categories. The first part is the structural systems for controlling seismic displacement and second part is the use of applying systems of control forces. Response mechanism of structures using control systems are improved and greatly reduce the risks of damage caused by earthquakes. Today the use of these control systems in buildings have been increased and it’s important to reduce vibration of structures is felt more than ever. As well as to improve the dynamic behavior of nearby buildings, control systems can be installed between adjacent buildings as activated, semi-active and inactivated systems. The main purpose of this study is the use of control systems in two similar adjacent buildings to reduce the entire system response which will be the analytical study of the impact of viscous dampers to control system performance. In order to analysis of modeling to improve the dynamic behavior of different adjacent buildings connected with dampers, two models of the original sample will be examined in this article. All examples are different from each other and to elicit response analysis and time history software SAP 2000was used. According to the results the effect of fluid viscous dampers for tall buildings compared shorter building, is less. Also, these dampers for adjacent buildings with different heights than buildings with same height are more effective.


Introduction
Many buildings that have not been able to withstand lateral loads and have been broken down and reversal reflects the great importance of the protection of buildings against vibrations.In recent years a large number of people in the world lost their lives in the earthquake and large financial losses have been imposed on as well.The recent earthquakes in Iran, as well as in different parts of the world such as Bam 1382, Azerbaijan in 1391, Turkey in 1999 and Taiwan in 1999 showed that the vibration of structures has been very severe and led to the destruction of buildings.So it can be concluded, in structural design, buildings design to withstand dynamic loads is very important to prevent the destruction of structures.Protection and maintenance of buildings with residents and the equipment inside it is a global priority.Structural engineers aim is to develop safe structures to resist against natural disasters.
Explained ways to strengthen structures against lateral dynamic loads can be divided into two broad categories.The first part is the structural systems for controlling seismic displacement and second part is the use of applying systems of control forces.Response mechanism of structures using control systems are improved and greatly reduce the risks of damage caused by earthquakes.
Today the use of these control systems in buildings have been increased and it's important to reduce vibration of structures is felt more than ever.As well as to improve the dynamic behavior of nearby buildings, control systems can be installed between adjacent buildings as activated, semi-active and inactivated systems.Different control methods and systems for the control of adjacent structures against earthquakes have been done by scientists and engineers or are being done.Hasner et al. (1997) in a study examined the benefits of structural control in reducing unwanted vibration in buildings.They also proposed various control systems for this purpose.Seto (1994) has introduced connecting the adjacent buildings as a practical way to protect and strengthen structures against dynamic loads.He has introduced different strategies for inactivated control systems for tall and short buildings.Gurly et al. (1994) andSojinio et al (1999) also in some studies have addressed the adjacent high-rise buildings with inactivated systems.
Luque and Debaros (1998) and Zhou et al. (1999) examined the connection of high-rise buildings structure to average height ones.Ying et al (2003) studied a stochastic optimal control system for connected adjacent structures.In their study, control systems and structures under stochastic seismic movements were modeled and with energy control of structure, the seismic response of structure and control system dimensions were reduced.They also conducted a numerical study to estimate the reduction capacity of seismic response in connected adjacent buildings.Ney et al. (2001) in a study examined the seismic response of two adjacent and connected buildings by hysterical non-linear dampers under various seismic movements and stated that such dampers are fruitful, even if only on a few floors to be installed.Parametric study and sensitivity analysis to find and insertion the optimal number was done.
Hadi and Owz ( 2009) in a study examined the importance of using fluid viscous dampers to improve the seismic behavior of adjacent structures.They found declines of the last floor displacement, acceleration and shear force response of adjacent structures during seismic stimulation.In their study adjacent structures had been connected in one direction by dampers.Major earthquakes such as Bam, Azerbaijan, Turkey earthquake and others have shown that municipal buildings and buildings are not resistant enough to withstand during earthquake severe shocks.Severe inelastic behavior caused by severe shaking is clearly visible.This inelastic behavior threatens the safety of residents of buildings and facilities and will ultimately lead to the loss of life of many people.
In building constructions, the main purpose is the protection of structures against earthquakes.In recent years, engineers in high-rise buildings have begun to use control systems, such as activated, semi-active and inactivated to reduce seismic response.In buildings with a lot of height, the structures control with this method is difficult.Additionally since high-rise buildings require so much energy, are relatively flexible.Control of interconnected buildings first time was suggested based on the idea of exertion of force on each other.This idea for the first time was proposed in the past three decades by Klein and Halle (1985).They first offered a semi-activated system, which connect two adjacent buildings with the cables by the ability to loosen and tighten (Klein and Halle, 1985).
Christensen and colleagues in 1999 stressed that the idea of adjacent structures connection has been converted from theory into practice and in Japan and America has been considered by engineers (Krystnsvn et al., 1999).

Inactivated Control Systems
In these systems, vibration control agent is placed in the proper location of the structure and practically prior to the stimulation of structures is inactive.Hasnr and colleagues noted in 1994 that inactivated control systems taking the energy resulted from dynamic loading.All inactivated control devices have stiffness and damping to dissipate energy and provide the shift limits of buildings to each other.These systems are characterized by control forces and their fixed specifications.Another advantage of this system is the ability to install again after the earthquake.Song and Dargosh (1997) in a study stated that inactivated control systems, including metallic, fricative, viscoelastic and fluid viscous, massive and regulated fluid dampers.These dampers are installed to strengthen the building against lateral loads (Song and Dargosh, 1997).One of important devices of damper in inactivated control systems is seismic isolators.Varnoteh et al (2007) suggested that the seismic isolator systems can't be used to reduce the displacement of a structure or two adjacent or connected buildings.
Seismic isolators are installed in the foundations of buildings to absorb or reflect some of the energy of earthquake and prevent its transmission to structural elements (Varnoteh et al., 2007).

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Figure 8.A B Tim Figure 11