# Structural Health Monitoring for Prefabricated Building Envelope under Stress Tests
## 1 Introduction
Indeed, by adhering to these standards, the industry demonstrates a commitment to upholding safety and operational standards in curtain wall facade construction ensuring safety of curtain wall facades, mitigating risks, and safeguarding the well-being of occupants. The standards also defined assessing criteria for each test paraments for verified the facade behavior during each test. These criteria, reported in Table 11 of Appendix A, determine the test pass or failure limit values. Within this scientific and technological context focused on facade applications, this research investigates the possibility of defining a kit of conventional and multi-parameter sensors integrated within the building envelope to monitor its behavior during performance tests. During the research, the kit is validated with the aim of demonstrating its effectiveness and replicability for structural health monitoring of building envelopes. Therefore, an analysis of conventional sensors was conducted to determine the most suitable ones. Fiber Optic Sensors (FOS) featuring Fiber Bragg Gratings (FBGs) [18; 19] are examined with the goal of demonstrating potentialities and limitations for their application in building envelopes. Together with FBG sensors, the possibility of integrating conventional devices was investigated; therefore, vibration sensors and force washers have been explored to monitor structural conditions [20]. Numerous research works have not only considered the use of accelerometers to detect the impact of weathering and external forces on buildings for structural analysis, to monitor the behavior in infrastructure [21] and historical building behavior [22], or to quantify the seismic damage in building structure [23], but also for the identification and verification of possible structural damage because of the stresses imposed on the structure under investigation by performing a modal analysis before and after the events [24]. In fact, modal parameters can be used to evaluate the safety condition of a structure and assess structural health based on modal parameters [25]. [PERSON] et al. [9]demonstrated that temperature is an important factor that affects the natural frequency of the bridge, and it is not negligible. Therefore, the temperature must be controlled in order to not consider a variation in frequency only due to temperature change as a damage indicator. Strain gauge-based force washers have also been considered as commercial sensors to monitor bolt irregularities [26]. This research focuses on monitoring the structure behavior during the performance of the standard compliance tests for wall curtain facades; the temperature variation results in a few degrees between days since they were accelerated tests, and thus they were performed in short duration even if the temperature is monitored during the performance of the test. In line with these research and technological scenarios, the EU-funded InComEss project [27] aims to define a stand-alone solution for SHM using Piezoelectric Energy Harvesting Systems (PE-EHS) for facade monitoring [28], and this paper presents the structural health monitoring sensing solutions within the InComEss architectural system [29]. The architectural design of the InComEss system is geared towards harnessing the potential of Piezoelectric Energy Harvesting Systems (PE-EHS) to supply energy to a fiber optic sensor, MonadGator. This interrogator reads data from FBG and communicates with a Power Conditioner Circuit (PCC) seamlessly integrated with a Printed Circuit Board (PCB) powered by a locally implemented Supercapacitor (SC). The connection between the PCC/PCB, an Internet of Things (IoT) gateway, and a cloud-based IoT monitoring platform facilitates data collection and analysis. The overarching objective is to showcase the practicality of Wireless Sensor Networks (WSNs) for structural health monitoring (SHM). Based on the InComEss system architecture conceptualization, the PE-EHS and FBG sensors are designed to demonstrate their integrability within a prefabricated facade.