Pseudo-dynamic test of CFST lattice columns with flat lacing tubes

Based on quasi-static tests, a pseudo-dynamic test of two 1/8-scaled concrete-filled steel tubular (CFST) lattice columns with flat lacing tubes was performed. The seismic records from the Wenchuan 2008 Earthquake and Kobe 1995 Earthquake were used as input ground motions. Seismic performance including deformation, strength, stiffness, and energy dissipation of the CFST lattice columns was studied with earthquakes and main aftershocks of different intensities. The results show that the CFST lattice columns with flat lacing tubes had good seismic performance. The structure was in an elastic state when subjected to the intensity 8 frequent, basic, rare, and extremely rare earthquakes. Under the intensity 9 rare earthquakes, the CFST column limbs yielded, and the structure entered the elastoplastic working state. With the increase in the peak ground acceleration, the strain of the steel tube at the bottom and the maximum response displacement at the top were both significantly increased. The plastic hinge region at the bottom of the CFST limb did not form a yield ring until the end of the test, and there was no apparent structural damage. The main aftershock aggravated the cumulative damage of the structure, and the structural stiffness degradation phenomenon was obvious. After experiencing one main shock (intensity 9 rare) and two equal-strength aftershocks, the elastic stiffness of the structure was reduced by about 50% compared with the initial elastic stiffness, while the maximum response displacement increased by 41%. Through the calculation of the strength and deformation of CFST lattice columns under various seismic conditions, it is further shown that this type of structure has sufficient strength reserves and good deformability and can still maintain a certain bearing capacity after many strong earthquakes. CFST lattice columns have a great application prospect in bridge engineering in high-intensity areas in China.