## 6 Conclusions  
This paper firstly introduced the rubber layer into the SCS composite wall and proposed the SDC wall to optimize the performance of various aspects of this versatile composite wall, including energy absorption, anti-explosion, and impact resistance. A novel connection technology, binding bar working with reinforcement enhancements (steel sheets and sleeves) was developed to compensate for the weakening effect of the rubber layer on the concrete core and to construct the SDC wall. This connection technology along with the introduction of rubber is utilized to allow the SDC wall characterized by the function of energy dissipation and comparable compressive bearing capacity with the SCS wall. A validated FE model was established to simulate the compressive performance of the SDC composite walls. An extensive parametric study was also carried out to optimize the design of the SDC walls. Finally, the bearing capacity formula is proposed to predict the compressive resistance of the SDC composite wall. Based on the numerical results, the following conclusions can be drawn:  
(1) The numerical results proved that compared with the SCS wall, the SDC wall is characterized by comparable ultimate compressive resistance and better ductility. The increase in ductility can be attributed to the cooperation between the embedding rubber layer and reinforcement enhancements. In particular, only embedding the rubber layer in the composite wall failed to increase the ductility. The steel sheets and sleeves provided confinement on concrete core and thus improved the compressive resistance and ductility of the composite wall. (2) From the parametric study, it was found that increasing the thickness of the damping layer can increase the ductility significantly but decrease the ultimate compressive resistance of the SDC wall. When the thickness of the rubber layer was around 2 mm, the SDC wall had a similar compressive bearing capacity of the SCS wall; when the thickness was more than 5 mm, the improving tendency of ductility of the SDC wall became slight. (3) It was observed from the parametric study that (a) increasing both of the thickness of the concrete core and steel plate can offer higher compressive resistance of the SCD wall. However, in terms  
Figure 23: Comparison between numerical results and predictions by proposed methods. of DI ratio, the thickness of the concrete core had less influence while the thickness of steel plates can improve it significantly; (b) increase of the spacing of the binding bars and plate slenderness of the SDC wall can reduce the compressive resistance and the DI ratio; and (c) the diameter of steel sheets has an obvious influence on the ductility of SDC walls. (4) Theoretical models were developed to predict the ultimate compressive resistance of SDC composite walls. The developed models proposed a regression method to determine the weakening effect of the rubber layer on the concrete core and considered reinforcement enhancements by using an equivalent compressive resistance. The proposed design approach was accurately validated against the numerical results. In this paper, compressive behaviors of SDC composite walls with specified cross-sections were investigated numerically and theoretically. The proposed concepts, models developed, and the results obtained are expected to provide meaningful guidance in the design of other composite walls with similar structural characteristics. Further theoretical and experimental studies are needed to cover an extensive range of SDC composite walls under other loading cases. [PERSON] provided the conceptual design of the novel composite wall; [PERSON] and [PERSON] conceived and designed the FE models; [PERSON] and [PERSON] analyzed the data; [PERSON] and [PERSON] wrote the paper. The research is financially supported by the National Natural Science Foundation of China (Grant No. 51708318, 51678322), The International Postdoctoral Exchange Fellowship Program (Grant No. 20190015),Ministry of Science and Technology of China (Grant No.