Finite Element Analysis of the Seismic Performance of Self-Centering Rocking Frame with Column Mid-Height Uplift System

The controlled rocking steel frame with column-base uplift system not only improves the seismic performance of the structure but also increases the overturning moment generated by second-order effects， thereby increasing the risk of structural overturning and limiting the full utilization of its structural seismic performance. To address these limitations， this paper proposes a controlled rocking steel frame with column mid-height uplift system. This system features a liftable rocking form with relaxed constraints at the mid-height of the ground-floor columns， causing the upper and lower segments of the columns to bend in opposite curvatures. This creates a reverse bending point at the column's mid-height， reducing the rocking of the upper structure under seismic actions， consequently mitigating the risk of structural overturning. Utilizing the finite element software OpenSEES， a finite element model for controlled rocking steel frames with column mid-height uplift system was developed. Based on this model， time-history analyses under minor， moderate， major， and extreme seismic events were performed for four structural configurations： the steel frame structure， the braced-steel frame structure， the self-centering rocking frame with column-base uplift system， and the self-centering rocking frame with column mid-height uplift system. The seismic performance of these structures was compared and analyzed based on the maximum inter-story drift ratio， top-story displacement response， inter-story drift concentration factor， residual inter-story drift ratio， and the distribution of plastic hinges. The analysis results indicated that the rocking frame with column mid-height uplift system demonstrated superior control over the maximum inter-story drift ratio， top-story displacement， and residual inter-story drift ratio compared to the other structures. Additionally， it optimized the plastic hinge development pattern of the ssystem during earthquakes， providing a higher safety margin against strong seismic actions.