A novel damage evaluation method for exposed column bases (ECBs) affecting the seismic properties of low-rise steel moment-resisting frames (MRF)

Exposed column base (ECB) connections are widely used in low- and mid-rise steel moment-resisting frames (MRFs). In this study, we investigated the impact of ECB damage on the overall seismic properties of low-rise MRFs. A novel method was proposed to evaluate the post-earthquake conditions of steel frame structures based on the coupling coefficient (CC). Using only the strain gauge data of the columns in the bottom storey, a method using a modified CC was adopted to classify the degree of damage by estimating the residual capacity of the MRF and predicting the future seismic response under specific intensity levels of hypothetical earthquakes, considering both the structural and non-structural components. The limit values of CC were obtained by solving the deduced equations. Finite element analyses were conducted to validate the proposed method. The method was applied for calculating the test data of a four-storey MRF tested at the E-Defense shaking table facility. Four loading cases comprising six groups of monitored data in the X- and Y-directions were used in this study. A comprehensive and systematic evaluation result was eventually obtained, and the accuracy of the method was validated.