# Progressive Collapse Analysis of SRC Frame-RC Core Tube Hybrid Structure
## 4 Progressive Collapse Analysis
### Nonlinear Static Analysis
#### 4.4.2 The Results from Case 2 to Case 5  
Table 10 shows the force condition of beams under the other cases. It can be seen that the DCRs are less than 2.0. Due to the structural symmetry, the difference between the DCRs of B1 and B4 is small in case 2. In case 3, the DCR of B5 is larger than the DCRs of B1 and B2. Similar to the case 1, B5 is closer to the core tube than B1 and B2, and the more load is transferred to B5 by the portion of 48.77% while the load is transferred to B1 and B2 by the portion of 20.02% and 32.21% respectively. In case 4 and case 5, B5 and B8 are directly linked to the core tube. Due to the structural symmetry, there is a small difference between the DCRs of B5 and B8, and the DCR of B5 is larger than the DCR of B8 in case 4, but the relationship is reversed in case 5. From the results of the above cases, it can be seen that the closer to the core tube, the more affected the beam gets.  
Figure 16 shows the lateral displacement of the structure in different case. The maximum displacements are 22.5 mm, 12.50 mm, 7.80, 5.70 mm respectively. Moreover, the \(\theta_{\text{max}}\) is still smaller than the specified limitation. From case 1 to case 5, in terms of the number, the displacements of 9 th floor are the maximum, the maximum displacements and the difference between the maximum value in X-axis and Y-axis showing a decreasing trend. In cases 1, 2 and 4, the maximum values on the X-axis are larger than that on the Y-axis. This means that the removal of C1, C2 and W1 make the ability of structure to resist deformation weaker mostly in X direction. On the contrary, in cases 3 and 5, the removal of C3 and W2 make the ability of structure to resist deformation weaker mostly in Y direction.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & **Beam** & \multirow{2}{*}{**Direction**} & **Bending** & \multirow{2}{*}{**Portion (\%)**} & **Average** & \multirow{2}{*}{**DCR**} \\  & **Number** & & & **Moment/kN-m** & & **Value (\%)** & \\ \hline \multirow{4}{*}{2 (C2)} & B1 & Positive & 213.75 & 33.79 & \multirow{4}{*}{50} & 0.44 \\  & B1 & Negative & \(-\)428.75 & 66.21 & & 0.88 \\ \cline{1-1}  & B4 & Positive & 418.75 & 67.39 & \multirow{4}{*}{50} & 0.86 \\ \cline{1-1}  & B4 & Negative & \(-\)207.50 & 32.61 & & 0.43 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Force condition of beams in cases 2, 3, 4 and 5.  
Figure 15: Displacement of structure in case 1.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & **Beam** & \multirow{2}{*}{**Direction**} & **Bending** & \multirow{2}{*}{**Portion (\%)**} & **Average** & \multirow{2}{*}{**DCR**} \\  & **Number** & & & **Moment/kN-m** & & **Value (\%)** & \\ \hline \multirow{4}{*}{1 (C1)} & B4 & Positive & 110.00 & 15.69 & \multirow{4}{*}{20.06} & 0.23 \\  & Negative & \(-\)202.50 & 24.43 & & 0.42 \\ \cline{1-1} \cline{2-6}  & B8 & Positive & 280.00 & 39.92 & \multirow{4}{*}{45.23} & 0.58 \\  & Negative & \(-\)418.75 & 50.53 & & 0.86 \\ \cline{1-1} \cline{2-6}  & B10 & Positive & 311.25 & 44.39 & \multirow{4}{*}{34.71} & 0.64 \\ \cline{1-1}  & Negative & \(-\)207.50 & 25.04 & & 0.43 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Force condition of beams in case 1.