# Structural Health Monitoring for Prefabricated Building Envelope under Stress Tests
## 2 Materials and Methods
### Materials  
The materials adopted for the research activities were:  
* InComEss components--the research was based on component development within the InComEss project [27] concerning the FOS MonadGator. The FOS MonadGator is based on a low-energy consumption solution for data gathering and transmission of the InComEss system architecture. The FOS MonadGator needs 3.3 V to be powered.
* On-market sensing solutions for SHM:
* FBG for FOS to monitor stress conditions of facade. The selection of FBG is based on well-established sensors on the market. The InComEss project did not expect to investigate and develop FBG solutions. The FBG used for this research was a fiber type SM1250B, with a length of 9 mm, a reflectivity of 45%, and 3 dB bandwidth of 0.16 nm. The FBG coating is a fiber polyamide.
* Sensors in the field of structural health monitoring to monitor stress conditions of facade to collect data not collectible from FBG, such as the following:
* Accelerometers--On the external side of the facade prototypes, a triaxial accelerometer PCB 354C03 is integrated with IP66 characteristics and a compact dimension of 27 \(\times\) 21 \(\times\) 11 mm. It is feasible to be integrated into the facade ventilated cavity. On the internal side, the selected accelerometers are monoaxial sensors model PCB 352C33 with no IP66 characteristics and dimensions of 18 \(\times\) 11 \(\times\) 17 mm;
* Strain gauge-based force washers--the selected model was the K-KMR+200K-01M5-Q with connectors D-SUB HD 15 polis, and the monitoring system was MX840, 8 channels. This washer has a nominal force of 200 kN based on the standard force applied to facade stresses. Force washers are connected to commercial data collectors.
* Monitoring systems for data collection:
* FBG interrogator MonadGator, in which the wavelength range is 1575-1582 nm; noise level: \(\sigma\) < 1 pm; sampling speed: 2 kHz; FBG's per channel: 1; and the number of channels available is 1;
* FBG interrogator switchgator, in which wavelength range is 1516-1583 nm; noise level: \(\sigma\) < 1 pm; sampling speed: 19.23 kHz; FBG per channel is 8; and the available number of channels is 8;
* NI 9234 for accelerometer monitoring;
* For the strain gauge-based force, it was the QUANTUM X MX840B monitoring system.
* Prefabricated facade--a unitized facade system for multifractional facades is selected to improve solutions in the same product development.
* Method statement for testing activities conducted in a laboratory environment to validate facade system modules based on EN 13830:2015 [16] and EN 14019:2016 [38] for curtain walling--impact resistance--performance requirements, as referenced in Appendix A. These tests involved the use of a fan positioned at 600 mm and rain-simulating nozzles targeting facade joints, delivering a continuous flow rate of 2 L/min-sqm at 400 mm from the facade. To replicate rain in a controlled laboratory setting, a system employing nozzles at typical joint locations on the facade was used. Two types of rain tests were conducted:
* Dynamic Rain Test: this test simulates wind gusts, generating pulsating pressure variations every 3 s, fluctuating between 750 Pa and 250 Pa to mimic the dynamic nature of wind-induced pressure changes.
* Static Rain Test: this test aimed to assess behavior under constant rain conditions, maintaining a constant pressure of 600 Pa throughout the test duration.
* In Appendix A also includes the fail/pass criteria for each parameter.