# Progressive Collapse Analysis of SRC Frame-RC Core Tube Hybrid Structure
## 5 Conclusions  
In this paper, a 3-D finite element model was first built with the OpenSees software to simulate the behavior of SRC frame-RC core tube hybrid buildings under sudden component removal. The method and principle for the modeling techniques and progressive analysis are described in detail. The model also incorporates non-linear material characteristics and non-linear geometric behavior. A 1/5 scaled, 10-story 3-bay model was built for the validation of the proposed modeling method. The numerical results are presented and compared to experimental data, a good agreement is obtained. Using the proposed model, the progressive collapse analysis under loss of key components and seismic waves input were conducted. The following conclusions can be drawn within the limitation of the current study presented in this paper.  
Even though the progressive collapse is a rare event when subjected to only the loss of a column or shear wall, the possibility of progressive collapse should not be neglected. When the seismic wave was entered into the component removed model, especially the model under the loss of shear wall scenario, DCR of the adjacent beams significantly increased. For the SRC frame-RC core tube hybrid structure, the possibility of progressive collapse increases with the increase of earthquake intensity, especially under the loss of shear wall scenario.  
In this paper, the portion of shear assumed by the frame in case 5 is more than double of that in case 1 under a seismic wave. A loss of the W5 seriously weakened the carrying capacity of the core tube. Under the same general conditions, removal of a shear wall is the most likely to cause progressive collapse, and then next likely is removal of a corner column, and lastly removal of a side column. In addition, removal of a shear wall without opening is more likely to cause progressive collapse than the shear wall with opening.  
When subjected to the loss of component and earthquake, the internal forces will be redistributed between the frame and core tube and the frame is responsible for more load. The concept of multi-lines of seismic defense is reflected in SRC frame-RC core tube hybrid buildings. The core tube plays a role as the first line of defense against progressive collapse, the second line of collapse resistance is provided by the frame.  
All authors substantially contributed to this work. [PERSON] and [PERSON] were the scientific coordinator of the research, designed the experimental campaign and analyzed the results. [PERSON] supervised all the research and revised the results. [PERSON] and [PERSON] contributed on the experimental tests. All authors helped with the writing of the paper and give final approval of the version to be submitted and any revised versions.  
The research presented in this paper was funded by Natural Science Foundation of Hubei Province of China (Grant No. 2016 CFB604), Natural Science Foundation of China (Grant Nos. 51108041, 51378077), Science Foundation of the Education Department of Hubei Province of China (Grant No. D20161305), and it is grateful for their support.  
It is very grateful for the supports from [PERSON].  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multirow{2}{*}{**Beam Number**} & \multirow{2}{*}{**Seismic Wave**} & \multicolumn{2}{c}{**Average Bending**} & \multirow{2}{*}{**Portion (\%)**} & \multirow{2}{*}{**DCR**} \\  & & & **Moment/kN-m** & & \\ \hline \multirow{8}{*}{5 (W2)} & \multirow{8}{*}{B5} & HOLLYWOOD & 715.00 & 47.59 & 1.47 \\  & & ELCENTRO & 1026.25 & 44.52 & 2.11 \\  & & NRIGDE & 1502.50 & 46.33 & 3.09 \\  & & Artificial wave & 1430.00 & 50.87 & 2.94 \\ \cline{2-5}  & \multirow{8}{*}{B8} & HOLLYWOOD & 787.50 & 52.41 & 1.62 \\  & & ELCENTRO & 1278.75 & 55.48 & 2.63 \\ \cline{1-1}  & & NRIGDE & 1740.00 & 53.67 & 3.58 \\ \cline{1-1}  & & Artificial wave & 1381.25 & 49.13 & 2.84 \\ \hline \hline \end{tabular}
\end{table}
Table 14: _Cont._