Coupled translational-torsional response for SRC frame with special-shaped columns under earthquake

Based on shaking table experiments for a five-floor SRC spatial frame with special-shaped columns, the translational response, torsional response, and translational-torsional response were analyzed. Results indicate that the vibration modes of 1st similar to 4th order are translation in direction X, translation-torsion in direction Y, torsion, and translation in direction Y, respectively. With increase of peak acceleration, the structural plastic deformation gradually increases, which results in natural frequency gradually decreasing. For 0.8 g earthquake, the maximum inter-floor displacement ratio caused by translational-torsional response effect is 1/39. Through analyzing structural torsion effect, it is found that the occasional eccentric translation-torsion effect has little influence on seismic structural performance. In the later stage of loading, with increased lateral displacement, degradation of equivalent torsional stiffness is not obvious, indicating that the structure has good torsional deformation capacity. Finally, considering the torsion effect of column limbs, a theoretical calculation formula about lateral stiffness and internal force are derived.