## 5 Discussion of Test Results
### Dynamic Performance Parameters  
The fundamental frequency \(f_{\rm os}\) and damping \(\xi_{\rm os}\) were estimated for all the test scenarios of Table 2. For each test configuration, the average estimate was then separately collected, based on the available instruments and records. Globally, rather stable predictions were obtained for a given CN#_n_ scenario, with standard deviations less than \(\pm 0.06\) Hz for frequency and \(\pm 0.08\%\) for damping. The mean CN#12 and CN#13 estimates (\(p=0\)), in addition, were taken into account as a reference configuration. According to Figure 9a,c, it is possible to notice that as far as the full set of measurements is considered for the LG + AN panel in bending, a general increase with \(p\) is generally observed for the fundamental frequency \(f_{\rm os}>f_{\rm es}\) and modal damping \(\xi_{\rm os}>\xi_{\rm es}\). In Figure 9b, frequency scatter values are also proposed as a function of \(p\), where:  
\[\Delta_{f}=100\cdot\frac{(f_{\rm os}-f_{\rm es})}{f_{\rm es}} \tag{4}\]  
For reliable investigations, however, the variation of the dynamic parameters with \(p\) can offer only limited information, and multiple features should be necessarily taken into account (i.e., total mass \(M_{p}\) of the occupants, movement type, etc.). Ambient conditions (and their effects on the response of the PVB layers) represent another key aspect for the examined structure. Based on Table 1, for example, major effects were expected at the time of measurements for P#1 estimates, due to a potential decrease of the PVB stiffness resulting from:  
* an increase of P#1 mean temperature (13.2 \({}^{\circ}\)C, in place of 6.5\({}^{\circ}\) of P#2 records);
* a longer life-time of the system (one year apart), with increased ageing phenomena (for the PVB foils but also for the other load-bearing components). Figure 8: Examples of vibration measurements. (**a,c**) Acceleration-time history and (**b,d**) power spectral density functions under random walking traffic. A maximum scatter in the order of \(\Delta_{f}=+15\%\) was obtained (\(p=4\) and \(p=6\)), compared to the empty structure. When \(p>0\), moreover, it can be perceived from Figure 9b that the \(f_{os}\) predictions are minimally affected by the ambient conditions herein investigated. For \(p=1\), even in the presence of a relatively wide range of imposed accelerations, \(\Delta_{f}\) resulted in fact equal to \(+8.08\%\) (P#1) and \(+8.34\%\) (P#2) respectively, giving evidence of mostly negligible time/temperature/humidity effects, for the explored scenarios. This is in line also with the numerical findings reported in [20] for the empty structure, where it was shown that the vibration frequency can be highly sensitive to the stiffness of PVB foils (and hence to the global bending stiffness of the LG + AN section), but also other relevant aspects should be taken into account, like the loss of prestress in the bracing tendons, etc. The higher the ambient temperature (i.e., P#1 \(>\) P#2) and the lower the bending stiffness of the system, hence the lower the expected frequency \(f_{os}\) and the corresponding \(\Delta_{f}\). According to Figure 9b, the added value of the experimental study reported herein is the role of time and humidity. More pronounced ageing phenomena (P#1 \(>\) P#2) and high temperature effects (P#1 \(>\) P#2) were observed to prevail on ambient humidity (P#2 \(>\) P#1). For \(p>1\) (P#1 scenarios), a mean frequency increase up to \(\Delta_{f}=+15\%\) was calculated. Given the same ambient conditions, such a result can be hence mostly justified by the combined number of standing/walking volunteers. This effect is also emphasized in Table 3, where the mean experimental \(\Delta_{f}\) estimates (i.e., average results grouped by \(p\)) are not linearly proportional to \(p\).