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

Outrigger truss which connects external columns and the core tube in super high-rise frame-core tube structures plays a key role in transferring huge loads,and its construction details as well as load-carrying mechanism are also complex.To support the performance-based design of the Shanghai Tower,the highest building under construction in China,static tests and numerical simulation were conducted on two typical specimens: SRC mega column-outrigger truss-belt truss composite joints and outrigger truss-core tube composite joints.The results indicate that outrigger truss can effectively connect the core tube and the mega columns and transmit loads;the failure mode exhibit the buckling of the web member and the bending-hinge development at the upper and lower chords in the outrigger truss,implying excellent ductility of the specimen.Meanwhile,the gusset plates connecting the outrigger truss and the core develop only small plastic strain,indicating its bearing capacity is much higher than the members connected.FEM model and simplified mechanical model were both generated and analyzed with the results showing good agreements with those of tests.The simplified model reveals the mechanism of non-linear behavior of the outrigger truss,and predicts its ultimate capacity and stiffness with good accuracy.The model is proved to be capable of providing a sufficient tool for conceptual design of structures with outrigger truss.