Analysis of shear lag and floor damage degree assessment in steel bundled-tube structure

A series of calculation models were designed and made to analyze the energy dissipation of structure and floor damage under rare earthquake, in order to investigate the shear lag phenomenon of steel bundled-tube and its effects on structure design. Based on the finite elements analysis models, elastic analysis under wind load and frequent earthquake and elasto-plastic time history analysis under rare earthquake were used. The calculating data were used to analyze distribution of plastic energy dissipation along story and influence of shear lag with different depth of beams. Relationship between shear lag and floor damage was also studied. The calculation method of floor damage degree was proposed by analysis of harmful displacement angle and plastic energy dissipation of floors. The floor damage degree was quantitatively evaluated. The results show that the 1/3 height range of the lower part of steel bundled-tube structure is shear sensitive region. Increasing depth of spandrel beams in this region can get the same space working effect as increasing depth of all spandrel beams. It is important to avoid stress mutation and severe shear lag in one region during improving the shear lag in another region. Representative value of columns non-uniform stress coefficient which can reflect shear lag of floor has similar distribution patterns to plastic energy dissipation in the section of vertical set back. The calculated floor damage factors agree with the damage phenomena. The proposed formula based on the normalized two parameter model of displacement and plastic energy dissipation can be used to evaluate the floor damage degree of steel bundled-tube structure quantitatively. © 2018, Editorial Office of Journal of Building Structures. All right reserved.