## 15 Conclusions and Future Research Directions  
This comprehensive review has explored the seismic performance of steel-concrete composite structures through multiple perspectives, from component-level behavior to system-wide response strategies. The synthesis of current research reveals both significant advances and critical research gaps that warrant further investigation.  
Properly detailed beam-column joints demonstrate excellent seismic performance, though complex stress distributions at interfaces remain challenging to predict. Future research should develop standardized connection details optimized for varying seismic hazard levels. For composite beams and columns, concrete significantly improves energy dissipation and delays local buckling, with the research needs focused on quantifying long-term performance under repeated seismic events. Composite shear walls offer superior lateral load resistance compared to conventional systems. System-level investigations confirm that properly designed composite structures create redundancy and alternative load paths enhancing structural resilience. Future research should address the optimization of steel-concrete proportions for different building heights and integrate performance-based methodologies with practical construction considerations.  
Modeling techniques have advanced significantly, though computational models still struggle to fully represent composite action at interfaces. Future work should develop efficient models that accurately represent material interface deterioration under cyclic loading, potentially integrating machine learning with physics-based approaches.  
For foundations and bridges, composite construction enhances seismic resistance with improved load transfer characteristics and ductility. Future research should investigate soil-structure interaction under extreme events and develop optimized connection details.  
Progressive collapse studies confirm that composite structures possess inherent robustness against disproportionate collapse. Seismic isolation and energy dissipation devices demonstrate significant reductions in seismic demands when integrated with composite structures. Research should develop adaptive systems responsive to varying earthquake intensities.  
Optimization strategies now effectively balance material efficiency with seismic objectives, while emerging smart materials offer promising directions for adaptive structural response. Future work should incorporate life-cycle considerations and explore integration of monitoring systems with traditional composite structures.  
In conclusion, while substantial progress has been made, significant challenges remain in developing design methodologies that bridge theoretical advancements with practical implementation to enhance the structural resilience of steel-concrete composite structures in seismic regions.  
Conceptualization, P.K. and G.H.; methodology, P.K. and G.H.; investigation, P.K., G.P. and G.H.; resources, P.K. and G.H.; writing--original draft preparation, P.K.; writing--review and editing, G.H; visualization, P.K. and G.H.; supervision, P.K., G.P. and G.H. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
No data were created.  
The authors declare no conflicts of interest.