## 5 Conclusions  
The experimental and numerical researches were conducted to investigate the seismic performance of a steel-concrete hybrid supporting structure consisting of RC tubular columns and steel braced truss with A-shaped steel frames. The following conclusions can be drawn:  
1. The FE numerical results of the test model structure were in good agreement with the experimental results, indicating that the proposed FE modeling approaches are reasonable to simulate the seismic behavior of the steel braces truss-RC tubular column hybrid structure. 2. PDTs and FE numerical results showed that the cracks occurred and developed successively on the bottom of column, the lower part of corbel and the upper part of corbel with the increase of PGA. The measured strains showed that the steel truss and diagonal braces did not yield during the PDTs, which coincided with the expected design results. 3. PDTs results showed that the specimen had obvious stiffness deterioration characteristics resulted from the cracks occurring and propagation on RC tubular columns. When PGA was greater than 0.20 g, the speed of stiffness deterioration then slowed. When the PGA came up 0.40 g, the stiffness was about 60% of the initial stiffness. After PGA equaled to 0.80 g, the stiffness was about 41% of the initial value. Correspondingly, with the increase of PGA, the fundamental period and damping ratio increased, while the dynamic magnification factor decreased. 4. The FE numerical results of the prototype structure showed that the first fundamental period was 1.216 s and the corresponding vibration mode was torsion. The period ratio between the first torsion period and the first translation period of this hybrid structure was about 1.02, which was larger than specified limit value of 0.85 in China seismic design code. This indicated that the torsion effect should not be neglected in the design of this kind of hybrid structure. In addition, the numerical results showed that the shear-weight ratio of this hybrid structure is 0.058, which was larger than 0.032, indicating that the shear force distribution of this hybrid structure meets the requirements of the design code. 5. The overall lateral deformation pattern of this hybrid structure was shear mode. The maximum drift ratios of this hybrid structure subjected to different hazard levels of earthquakes were obtained. Under the very rare earthquake, the structure damaged severely, however, the stiffness was still 36% of the initial stiffness and the maximum tensile damage index was about 0.95 which was less than 1, indicating that this hybrid structure could keep upright and not collapse under the severe earthquake. Overall, the RC tubular column-steel braced truss hybrid structure could meet the seismic design requirements with respect to the high-intensity earthquakes. 6. Further analysis is needed in order to propose the performance objectives and the criterion for this peculiar steel-concrete hybrid supporting structure. Moreover, damping and dissipative devices, such as the hysteretic dampers, friction dampers, viscous dampers, or any other dissipative \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Hazard Level (PGA)**} & \multicolumn{2}{c}{**Maximum Lateral Displacement (mm)**} & \multicolumn{2}{c}{**Maximum Drift Ratio (\%)**} \\ \cline{2-7}  & **Top of A-Shaped** & **Top of** & **Top of** & **Top of A-Shaped** & **Top of** & **Top of** \\  & **Frame** & **Truss** & **Column** & **Frame** & **Truss** & **Column** \\ \hline Frequent earthquake (0.07 g) & 36.55 & 28.74 & 28.79 & 0.06 & 0.05 & 0.06 \\ \hline Basic earthquake (0.20 g) & 82.94 & 73.55 & 70.38 & 0.13 & 0.13 & 0.14 \\ \hline Rare earthquake (0.40 g) & 142.49 & 140.91 & 138.85 & 0.22 & 0.26 & 0.28 \\ \hline Very rare earthquake (0.62 g) & 262.12 & 257.28 & 250.93 & 0.40 & 0.47 & 0.50 \\ \hline \end{tabular}
\end{table} 
Table 8: Summary of maximum lateral displacements and drift ratios.