Many existing buildings are irregular in plan or elevation because of asymmetric placement of masonry infills. The stiffness of masonry infill is a considerable value relating to that of the structure. Produced torsion from eccentricity because of infill stiffness leads to extra forces and deformations in structural members and diaphragms. An appropriate alternative to solve this problem especially in existing buildings is using dampers. Dampers can enhance structural performance by reducing seismically induced lateral displacements and by reducing inelastic behavior of beams and columns. In this paper some simple models are used to show structural modeling and a conceptual discussion is presented on the numerical results. An accurate model for masonry infill has been used in structural model. Numerical results show the efficiency and high performance of added dampers to reduce the torsion effects in the structural elements.

In some aerospace vehicles, the tracking sensors which act in a tracking loop as stabilizer are mounted on a two degree of freedom gyro. The gyro must align its rotor axis with the line of sight in order to remove tracking errors. The tracking precision and sensitivity are functions of the gyros performance. One of the main factors in reducing the precision and producing instabilities is nutation vibration. This fluctuating motion, which is a dynamical inherent property of the system, is related to the gyro lateral moment of inertia, the length of gyro and its rotating speed. In order to investigate the capabilities of nutation damper and removing the wobble motion of a freely processing body, this paper analyzes a ring damper partially filled with viscous liquid with taking into account the behavior of the damper and its subsystems. The equations of motion for the dynamical motion of gyro, are obtained using Lagrangian approach, taking into account the friction of dampers and interaction of the liquid with the system equations of motion.

In the Seismic design of Structures, in order to energy damping applied to Structure, when an earthquake occurs, various solutions have been proposed that dampers are also in this category. Due to the relatively simple design and also more economical than other methods of energy dissipations, dampers have been more attention of researchers, In this study, in order to performance improvement of rotational inertia damper, friction and viscous mechanisms added to this type of damper. The experimental sample of rotational friction damper was made in the Urmia university earthquake laboratory and studied in a simple frame. The 8-story structure under Kobe and Tabas will be analyzed to study the effects of made hybrid damper compared with the rotational inertia damper. These intended dampers can be used with different type of braces that embedded in the structure such as Chevron and diameter. At the first in the model studied the 8-story symmetrical structure are modeled in Sap2000. Subsequently the resulting section is modeled in Abaqus2016 to study the effects of different dampers. Experimental laboratory result, is significantly improved Rotational inertia friction damper compared to other friction damper and the loss of their sudden brakes.Also the dynamic responses of structure indicate the reduction of maximum roof displacement and also the base shear of structure. Analytical results indicate that Rotational inertia viscous damper act quickly compared with Rotational inertia friction damper and dissipate the energy applied to structure. But finally Rotational inertia friction damper will behavior better than similar viscous damper.

The present study focusses on the damping force control of shear mode magnetorheological (MR) damper for seismic mitigations. Therefore, the semi-active MR damper which can control the vibration is analyzed both experimentally and numerically. Carbonyl iron is used as the magnetic particle and Castrol Magnetec oil as carrier fluid throughout the study. MR damper is designed and fabricated, and its damping force was evaluated experimentally at 2. 5 A-10 V. Shear mode MR Damper is tested in universal testing machine using time history loading. The model was numerically analyzed using Newmark’ s method for nonlinear system in MATLAB to control the three storey model building frame taken from the literature. The result indicates that 49. 42% reduction in displacement at the second storey and 48. 14% in the third storey, respectively. Maximum reduction was observed when damper was kept in the ground floor. The maximum force observed for the MR Damper is 0. 777 kN.