Seismic Damage Assessment of Steel Buildings considering Viscoelastic Dampers in Near-Field Earthquake

Abstract

In this study, three flexural steel frames of 4, 8, and 12 floors were investigated. The frames were designed based on the standard guidelines and then subjected to nonlinear dynamic analysis. Damage to structures with the concept of inelastic behavior and, consequently, hysteresis energy is very close. Therefore, it can be said that hysteresis energy at these levels can be a significant criterion for designing or controlling the structure. The high dependence of hysteresis energy on structural damage has caused this concept and new structural design methods to be considered by researchers and engineers. In this research, the first three steel frames of 4, 8, and 12-story with medium bending frame system with statically equivalent method. Then, all frames under the effect of seven near-field accelerometers and seven far-field accelerometers were analyzed nonlinearly and dynamically. The purpose of this study is to investigate the distribution of damage, energy, relative displacement, roof displacement, and base shear in the studied frames. In the following, the necessity of using the reinforcement method to reduce the relative displacement is described based on the regulations, then viscoelastic dampers are used to strengthen and reduce the damage in the frames under study. The results show that despite the uniform distribution of resistance at the height of the floors, the hysteresis and damage distribution diagrams do not follow this distribution and the concentration of energy and damage is observed in one or more floors. Therefore, in order to make the best use of the maximum system capacity, the design of structures based on strength alone does not seem logical and other parameters such as hysteresis energy, which play a major role in structural member damage, should be considered in the design process. Viscoelastic dampers have been used for retrofitting. The results show that this type of damper has a great role in absorbing energy and reducing damage to buildings. By calculating the damage of floors and the damage of the whole structure, it was seen that the level of damage under near-field earthquakes was greater than that in distant earthquakes and also in structures with a higher number of floors. The results show that as the height of the structure increases, the base shear values increase. As dampers are added to the structural layers, the base shear values are highly reduced so that, for 4, 8, and 12 floor frames under distant field earthquakes, 54%, 45%, and 48% decrease, respectively, and near-field earthquakes decrease, by 55%, 68%, and 64%, respectively. Also, the effect of using viscoelastic dampers on reducing the damage of high-altitude frames has been more and shows good performance in reducing the damage under earthquakes in the near area.