Influence of fortification intensity on structural performance and material dosage of frame-tube structures

To determine the effect of fortification intensity on the mechanical properties and amount of material used in reinforced concrete frame-tube structures, high-rise buildings over 100 m in height that were either built or being built were researched. 12 models of high-rise office buildings ranging from 150 m to 300 m in height and with different seismic intensities were analyzed, with respect to their period ratios, shear-weight ratios, stiffness-weight ratios, earthquake and wind-load influences, and the costs of steel and concrete for different fortification intensities. The results show that for the Jinan International Finance Center Landmark Tower, with increasing fortification intensity, the natural vibration period of the structure decreases, the torsion period lags behind the vibration period, the torsional effect reduces, and the shear-weight ratio significantly increases. Structures with low fortification intensities are greatly influenced by gravity as a second-order effect and their entire stability becomes the main safety control factor. The influence of earthquake action increases with increased fortification intensity. In the region with seismic fortification intensity 6 (0.05 g), steel consumption for buildings over 200 m in height increases significantly and in the intensity region 8 (0.20 g), steel consumption has linear growth with height. The concrete dosage in unit area in intensity region 6 (0.05 g) is close to that in intensity region 7 (0.10 g), and increases by about 19% in intensity region 8 (0.20 g). As such, the influence of fortification intensity is significant with respect to structural material dosage.