Study Of Self-centering Steel Moment Frames

A novel steel structure system having the capacity of self-centering and energy dissipation can solve such problems effectively. This new connection uses bolted top and seat angles, and post-tensioned (PT) high-strength steel strands running along the beam. The PT strands tie the beam flanges on the column flange to resist moment and provide self-centering force. The columns and beams remain elastic while the angles sustain inelastic deformations for the purpose of energy dissipation. After the earthquake, the connections have zero deformation. They can be restored to the original status by simply replacing the angles. This first part of this paper summarizes the recent research on this structural system. The research suggests that the novel structural system is very effective and has high potential for engineering applications.Four full-scale new connections and two connections without self-centering capacity were tested under cyclic lateral load. The connections'strength property, energy-dissipation capacity, the seismic behavior of hysteresis loops as well as angles and posttensioning strands'behavior are investigated. The results show that the connection's prestressing forces determine the connection's self-centering capacity, and angles are important for energy dissipation. Under 5% drift, the columns and beams remain elastic while the angles sustain inelastic deformations. After the loading, the connections have zero deformation. The connection can restore to the original position.A general FEM analysis program called Abaqus 6.9 is adopted to model the 6 test spicemen. The simulated results conrrespond fairly well with the test results and the reason for the deviations are also analyzed. Based on the sumulated results, 9 new connections subjected to cyclic loading. The effects of the prestressing forces, the angles'thickness, and the distance and the amount of the PT strands'on the behaviour of the connections are also investigated. The results show that the connections have an initial stiffness similar to the welded connections, and under 5% drift, the columns and beams remain elastic while the angles sustain inelastic deformations for energy dissipation. After the loading, the connections have zero deformation. They can be restored to the original status by simply replacing the angles.The results from the simulated connections show that Abaqus 6.9 is a quite suitable analysis program for self-centering structures'simulation. So this programe is also adopted to modal tow 4-story, 4-bay and 2-pin frames, called frame-1, which is traditional moment-risistent frame and frame-2, which it self-centering frame, respectively. 22 seimic waves, recommended by ATC-63, are adopted to study the performance of the two frames. The results show that under rare earthquakes frame-1 and frame-2 have similar base share force and frame-1's velocity, acceleration and maximum deformation are smaller than frame-2's, while frame-2's residual deformation is largely reduced compared with frame-1, which shows that frame-2 has a fairly well self-centering capacity.At last, based on the test and simulation results, a brief design and construction process is recommended.