Investigation of Nonlinear Seismic Behavior of High-rise Reinforced Concrete Buildings and their Improvement by Viscoelastic Dampers

Owing to the destruction of high-rise buildings during recent earthquakes, the use of a structural system of reinforced concrete moment frame with viscoelastic damper causes a loss of seismic energy and consequently reduces lateral displacement. In this study a high-Rise, 20-Storey, three-dimensional reinforced concrete frame with 8 Models, of which 4 models with moment frame structural system and 4 models with moment frame + viscoelastic damping system in two directions of X, Y located in the high seismic zone (A=0.3g) on the soil type III is considered. The aim of the present study is to investigate the horizontal lateral displacement (absolute and relative) of the stories, the base shear of frames under gravity loads, and lateral loads of the earthquake.  In order to modeling the viscoelastic materials, the Kelvin-Voigt model and to determine damping ratio(ζ) of frames with viscoelastic damper, stiffness coefficient (Kv) and damping coefficient (Cv) of viscoelastic dampers, the modal strain energy method have been applied. For seismic analysis of models without and with dampers, dynamic analysis of nonlinear time history via direct integration and modal (FNA) methods have been utilized, respectively.  Geometric modeling of all frames was done using the SAP2000-V15 software. The results indicate that with increasing span length (model 2 compared to model 1 and model 4 compared to model 3) and increasing the height of stories (model 3 compared to model 1 and Model 4 compared to model 2), the maximum absolute lateral and relative displacement of stories, and base shear along with X, Y without and with viscoelastic damper have an increasing trend. Also, the maximum percentage increase of the mentioned models with damper compared to without damper along with X, Y has decreased