Seismic behavior of prestressed concrete filled steel tubular lattice tower subjected to combined compression-bending-torsion

Prestressed concrete filled steel tubular (CFST) lattice tower is an innovative application to combine prestress and CFST composite structure to onshore tall wind turbines. In order to explore the seismic behavior of prestressed CFST lattice tower under a complex load state, there was pseudo-static testing carried out for prestressed four-chord CFST lattice columns under compression-bending-torsion combined load. The hysteretic performance of the specimens was analyzed by obtaining the failure mode, load-displacement hysteretic curve, energy dissipation, stiffness degradation, variation of strands stress and steel strain. The influence of prestress on seismic behavior of CFST lattice chords was investigated from prestress loss rate. Results showed that: the inclined battens of CFST lattice columns were seriously damaged with or without strands, while the inclined battens of non-prestressed specimen were damaged first and then the CFST chords. The existence of inclined battens had a great influence on the structural stiffness, while the application of strands significantly affected the initial stiffness and structural ductility of the prestressed specimen, but did not have any significant effect on ultimate bearing capacity. Post-tensioned strands could protect the main bearing chords and reduced the cracking of concrete in the tension area under the coupling action of compression, bending, and torsion.