Analysis on lateral-torsional vibration responses and seismic forces of a steel reinforced concrete frame structure with special-shaped columns

The lateral, torsional, and lateral-torsional coupled dynamic characteristics of a 5-floor solid web spatial frame structure model with steel reinforced concrete special-shaped columns were investigated via 3-dimensional seismic simulation shaking table tests. In addition, the multi-dimensional seismic responses, energy dissipation, structural damage, seismic forces and lateral-torsional coupled vibration behaviors of the structure were comprehensively analysed. The results show that: the corresponding vibration modes of the first 4 orders in turn are: X direction translation, Y direction lateral-torsional coupled, torsion, and Y direction translation. As the seismic intensity increases, the free vibration frequency of the frame structure and the acceleration amplification coefficient decline gradually, the plastic deformation of the structure develops continuously, the internal damage of the structure gradually accumulates, the energy dissipation of the earthquake increases continuously, and the cumulative hysteretic energy of the structure is rapidly increased with stepped characteristic. After the effect of 0.80g PHGA earthquake, the maximum value of inter-story drift ratio caused by the coupling effect of lateral-torsional vibration is 1/39, which exceeds the limit requirement of elastic-plastic inter-story drift ratio, and the damage index of the frame structure based on the deformation and energy parameter model is 0.56. Comparing with the general torsional effect of the model structure, the impact of an accidental eccentric torsion on the seismic performance of the model structure is small, and its accidental relative eccentric distance is less than 0.1. According to the analysis of the model torsional stiffness and seismic force, at the later stage of loading, the inter-story equivalent torsional stiffness degeneration is not distinct, which shows that the structure has high seismic performance and torsional deformation capacity. © 2019, Editorial Office of Journal of Vibration and Shock. All right reserved.