Study the correlation of natural frequency and damage index of 2D steel EBF-vertical shear link

Study of damage index of Eccentrically Braced Frame-Vertical Shear Link (V-EBF) was performed. The study was part of the research of damage index of several types of seismic resistance of steel structure. Three different stories of the V-EBF were taken from the preceding experimental study conducted by other researchers. Monotonic and semi-cyclic pushover analysis was carried out by using OpenSees software to get the parameters needed to determine the damage index which was calculated according to Park Ang's theory. The index is measured as a sum of deformation per-cycle and the energy absorption. The study found that the natural frequency of the structure decrease with the increasing of structural damage. The reduction of natural frequency from the initial condition to the third damage is 70.79%, 71.68%, and 62.13% of the one, two and three stories of The V-EBF structure, respectively. The study observed the critical limit where the damage index begins to increase drastically, followed by a decrease of the natural frequency. It occurred when the ratio of natural frequency to the initial frequency was in the range of 43% to 59%.