Secondary web‐flange interaction in framed‐tube buildings

In the conventional plane‐frame model of framed‐tube buildings, only the primary interaction between the web frame and the flange frame is considered, through vertical shear transfer at corner columns. In addition to this, a secondary interaction takes place due to horizontal shear transfer at each floor level, through the floor slab having high in‐plane rigidity. This interaction causes a discrepancy in member forces of a few bottom and top storeys. A simple modification is suggested in the form of an additional cantilever column connected to the conventional plane‐frame model by axial force transfer members at every floor level. The improved model yields member forces in all the storeys that are very close to those obtained using 3D analysis.