Hysteretic tests on outrigger truss and its connection with mega column and core tube of the Shanghai Tower

Seismic tests were carried out on the outrigger truss and its connections with mega column and core tube of the Shanghai Tower following the previous monotonic experiments.Three different loading protocols were designed to investigate the effects of various damage accumulation processes on the hysteretic and energy dissipation behaviors of the specimens.Experimental results show that all the specimens fail due to excessive plastic deformation and inelastic local buckling of the web member,as well as fracture at the low chord,while the connecting elements of the outrigger to main structural members develop small plastic strains.The specimens exhibit full hysteretic loops and good ductility.So designed outrigger truss and its connection can meet the requirements for seismic design.The analysis reveals that the damage cumulated under different loading protocols has certain but not very significant effect on the degradation of seismic performance of specimens.About 70% of the energy dissipation in the form of cumulated axial force energy is in the diagonal web member,making it the main energy dissipation member in the outrigger truss.