Modeling of bracing dampers in steel buildings under seismic loading

This paper focuses on modeling and effectiveness of the manufactured dampers when used in steel buildings. The concept is to protect the building from the damaging effects of earthquake by introducing a manufactured damper instead of the traditional bracing. Two types of manufacture dampers, namely Pure Manufactured Dampers and Viscoelastic Manufactured Dampers, have been considered in this paper. Structural characteristics of manufactured dampers (i.e., stiffness and damping) have been derived based on a macroscopic point of view. Where the stiffness is defined based on the slope of the diagonal line of the hysteretic loop and the damping is derived from the area of hysteretic loop of tested damper. This study has been using viscous model to simulate the behavior of Pure Manufactured Dampers and Viscoelastic Manufactured Dampers. Based on comparison of predicated behavior with analytical results, one can conclude that the viscous model simulate behavior of Viscoelastic Manufactured Dampers with larger accuracy if compared with Pure Manufactured Dampers. As damping of manufactured dampers is generally greater than the damping of traditional materials, then the resulting damping matrix for the whole structure could be classified as a nonclassical damping. Accuracy of the mode superposition method when applied to a structure with manufactured dampers has been checked. Where, approximated results of mode superposition method have been compared with the more accurate results of the direct integration method. It has been noted that the mode superposition method has different levels of accuracy depending on the relation between the fundamental frequency of structure and the dominate frequency of the earthmotion. Effectiveness of the above two types of manufactured dampers have also been assessed based on comparing them with traditional bracings. Different ratios of stiffness for manufactured dampers have been used during this assessment in order to separate the effects of stiffness from the effect of damping for the manufactured dampers. Effectiveness have also been assessed as a function of building height where it has been found that rate of efficiency of manufactured damper is inversely proportional with the height of building. Finally, effectiveness of the two damper types have been assessed for different earthmotion, where it has been found that the effectiveness depends on the relation between the fundamental frequency of the structure and the dominate frequency of the earthmotion.