A new damage identification method in beam to column connections and column base connections of steel frame

In the present study, an effective method for damage detecting in beam to column connections and column to the ground connections is presented. Rotational springs are used to model the joints (beam to column and column to the ground) of the steel frame. After finite element modeling of the studied frames in Matlab software environment, modal analysis was performed. To identification of joint damages, an optimization problem formulated to identify location and severity of damages. A new optimization algorithm called moth-flame algorithm with high accuracy and speed is used to solve this problem. The joint damages modeled through the reduction of the rotational stiffness factors. To show the performance of presented approach, two frames consist of a four-story steel frame and a nine-story steel frame have been investigated. In the studied frames, damage was assumed at the beam to column connections and column to the ground connections and then the severity and location of damage at the assumed joint were identified by the proposed method. The results indicated that the proposed method is robust to detect damage in beam to column connections and column to the ground connections that can accurately identify the location and severity of damage at the joints.