# Structural Health Monitoring for Prefabricated Building Envelope under Stress Tests
## 5 Conclusions  
The data-driven approach presented in this paper unlocks a deep understanding of how building envelopes respond to various stresses, including wind, seismic activity, material strain, temperature changes, and other dynamic loads. The research conducted demonstrated the potential of various sensor types for SHM in building envelopes. Considering the nature of different environmental events, a multivariant approach is the best solution for SHM. The facade, in this case, overcame all standard tests, but the different sensors detected minimal structural variation. Modal analysis is useful even if a critical event has been registered and allows for printing the status of the structure in a specific time frame. The final considerations on the obtained results are as follows:  
* From the modal analysis point of view, the maximum deviation of the natural frequencies experienced is 1.2% between the structure status at the beginning and at the end of the certification tests. * This was also confirmed by the monitoring accelerometers and observing the power spectra of the time histories registered during rain (static) between day 1 and day 2 (Figure 16, where the shift towards lower natural frequency is evident)
* Force washers evidenced that between day 1 and day 2, the bolts undergo loosening, especially concerning the bolt registered by the sensor installed on channel 2 (a decrease in the tension of that bolt of about 8% was registered). * Integration of FBGs into building envelopes for temperature monitoring prevents thermal shock damage, offering compact size and multiplexing capabilities. FBGs also excel in strain, ensuring longevity and structural integrity, with potential applications in facades to improve safety during the entire life of the structure. The achieved results demonstrate that sensing facade for SHM can open new approaches in the following: preventive maintenance schedules within the building envelope, identifying potential issues before they become critical, thereby reducing downtime and costs and minimizing environmental impact, reducing unnecessary repairs and interventions by prioritizing targeted maintenance based on data-driven insights; prioritizing retrofitting requirements directing resources towards facade areas most in need of improvement for enhanced safety; guiding design improvements integrating real-world performance data into future building designs for increased resilience and sustainability. For future works, a threshold that identifies and detects anomalies will be studied for each variable. In addition, it is also necessary to optimize sensor placement, with a particular focus on integration within the facade, finding a balance between aesthetic harmony, sensor monitoring, and maintenance. Sensor integration should be conducted during manufacturing activities, with the aim of inserting them into the aluminum profile cavity and isolated chamber within double-glazed panels. Other applications could be investigated, such as embedding Fiber Bragg Gratings (FBGs) for temperature monitoring in glass PVB components during the glass lamination phase, aiming to prevent thermal shock glass defects and guarantee aesthetic harmony in the building envelope. Additionally, integrating FBGs for strain monitoring in structural silicone, which are responsible for supporting hundreds of kilograms of glass in minimal space, can ensure the facade's safety and serviceability. Conceptualization, A.P. and L.V. ; methodology A.P. and L.V. ; software, M.T.C. and G.P. ; validation, A.P. and L.V. ; formal analysis, A.P., L.V. and M.M. ; investigation, A.P., L.V. and G.M.R. ; resources, A.P., L.V., F.B., V.D., M.T.C. and G.P. ; data curation, A.P., L.V., V.D., M.T.C. and G.P. ; writing--original draft preparation, A.P. and L.V. ; writing--review and editing, A.P., L.V., F.B., M.M., G.M.R., V.D., M.T.C. and G.P. ; visualization, L.V., F.B., V.D., M.T.C. and G.P. ; supervision, A.P. ; project administration, A.P. ; funding acquisition, A.P.