# Structural Health Monitoring for Prefabricated Building Envelope under Stress Tests
## 1 Introduction  
The building environment's increasing reliance on smart technologies opens up opportunities for a deeper understanding and consequent service operations of building performance within the so-called Intelligent Building [1; 2]. The relevance of data-driven approaches within the smart built environment is consolidating dynamic control for energy optimization and occupant well-being within building automation [3; 4]. This field involves the continuous and real-time assessment of a structure's structural integrity, allowing for the early detection of potential issues such as deterioration, damage, or unforeseen structural changes. In the dynamic and ever-changing urban environment, where buildings are subjected to diverse loads, environmental conditions, and unforeseen events, structural health monitoring (SHM) serves as a proactive measure to mitigate risks and enhance the resilience of structures [5]. By leveraging advanced sensing technologies, data analytics, and monitoring systems, SHM empowers engineers and stakeholders with valuable insights, enabling timely interventions, maintenance, and, ultimately, the optimization of overall performance and safety. In recent years, both civil construction and the building sector have explored the utilization of sensing technologies for SHM embedded in their structure [6; 7]; in particular, focus has been given to the SHM of bridges [8; 9]. However, the integration of sensors into non-load-bearing structures, such as a curtain wall facade, represents an increasing topic that needs to be further investigated. Indeed, this component faces the risk of sudden breakage, vulnerability to severe weather conditions, and unexpected collisions. These variables present significant obstacles to maintaining the longevity and dependability of these architectural elements. Recent research focused on the SHM of glass curtain walls of a super-high-rise building by integrating thermocouples in a real building to monitor the temperature distribution [10] with the aim of avoiding thermal shock or monitoring the wind effect on a single-layer cable net with modern curtain walls [11]. SHM sensors in no-load-bearing building components are also useful for analyzing the actual behavior of buildings and the relationship between the building response and the damage caused by earthquakes [12]. Moreover, other solutions for facade SHM could be investigated without directly integrating sensors within the facade; indeed, the study conducted by Brell-Cokcan and Co. investigated the possibility of developing an automated system that scans the facade surface through a projector light with the aim of detecting defections and alerting the automized components' replacing system positioned at the facade perimeters [13]. Investigating sensing solutions embedded in prefabricated facades becomes a perspective opportunity, as demonstrated by the exploration of smart applications for other building applications [14; 15]. Indeed, as the interface between the internal and external environments, building envelopes serve as invaluable indicators of a building's structural health. For these reasons, compliance with regulatory standards, such as EN 13830 [16] and CWCT's 'Standard for Systemized Building Envelopes'-Part 8 Testing-Section 8.12.2 [17], is compulsory. Therefore, performing a mock-up validation is required to ensure the facade's functional efficacy and safety. The validation process, outlined in detail in Table 11 and reported in Appendix A of these standards, provides a systematic sequence of steps for conducting the validation phase. Each parameter critical to the facade's performance and safety undergoes evaluation within this framework. Structural integrity and functioning are scrutinized to guarantee compliance with established benchmarks.