Evaluating post-earthquake strength of steel moment-resisting frames based on fishbone model using acceleration measurements

This paper presents a method of evaluating post-earthquake strength of steel moment-resisting frames based on fishbone model using acceleration data. Fishbone model is a simplified frame model used for simulating the structural behavior of steel moment-resisting frames, and it enables to explicitly identify the stiffness parameters of beams and column bases using model updating approaches. First, the stiffness of column bases and beam ends are identified by the model updating method using incomplete modal data identified from acceleration measurements. Then, the strength parameters of column bases and beam ends are calculated based on the identified stiffness values. Thirdly, post-earthquake strength is assessed through Pushover analyses and Incremental Dynamic Analysis (IDA) of updated fishbone models using OpenSees software. Finally, the practical applicability of the proposed method is investigated through the shaking table tests of a large-scale 3-story, 2-bay steel frame specimen. The results demonstrate that the fishbone model not only is competent to predict the accelerations, displacements, and story drift ratios of the structures but also effectively evaluates the post-earthquake strength of the steel frames. In addition, the fishbone model emerges as a reliable alternative to the conventional concentrated plastic hinge model for the assessment of the strength of steel moment-resisting frames after earthquakes.