# Pedestrian Comfort Analysis and Parameterized Optimization Design for Raised Floors
## 3 Results
### Model Analysis
#### 3.1.2 Experimental Modal Analysis
Following the installation of the appropriate wall systems on four different types of raised floors, time-domain signals were subsequently measured. Utilizing theoretical modal analysis, the areas most prone to deformation for each floor were pinpointed. Accelerometers were strategically positioned throughout the experiment to track the movement of these critical areas, ensuring comprehensive data collection. This meticulous approach facilitated a deeper understanding of the operational performance of the floors in a practical setting, offering substantial data support for dynamic analysis. The time-domain signal underwent fast Fourier transform to obtain frequency spectrum data ranging from 0 to 500 Hz. The distinct structural characteristics of the four types of raised flooring result in varying natural frequencies. During frequency domain analysis, high frequencies may not significantly contribute to structural analysis. Thus, it is possible to selectively extract appropriate frequency bands for further analysis based on specific requirements. By applying fast Fourier transform to the time-domain signal and utilizing smoothing techniques, Figure 7 displays the processed frequency domain signal. The data acquisition for this study was performed using a state-of-the-art 30-channel LMS Test.Lab analysis system, crucial for extracting resonant frequencies through experimental modal analysis (EMA). Following the collection of analog signals from the sensors, it is imperative to implement appropriate filtering techniques to mitigate the risk of high-frequency aliasing within the defined analysis frequency range. A particularly challenging aspect of this process arises during the conversion of time-domain signals to frequency-domain spectra via the Fourier transform. The Fourier transform presupposes that the recorded signal is either entirely contained within the measured timeframe or is a periodically repeating signal. When these assumptions are met, the transformation yields an accurate representation of the data in the frequency domain. However, in instances where these conditions are not satisfied, signal leakage may occur, leading to significant distortions in the spectral data. To address this issue and minimize distortion attributable to leakage, a harming window was employed as a weighting function in this study. This  
Figure 6: Experimental modal analysis on-site photograph. Figure 7: Experimental modal analysis results. approach effectively adjusts the time-domain signal to more closely align with the periodicity requirements inherent to the Fourier transform, thereby enhancing the fidelity of the resultant frequency spectrum. Through experimental measurements, the first-order vertical natural frequency data of four types of raised floors can be observed in Figure 7. Table 3 presents a comparison between the theoretical modal analysis and the experimental modal analysis results, indicating that there are discrepancies between the two methods. However, the errors are found to be within a reasonable range, affirming the feasibility of the simplification method used in the finite element model and the reliability of the analysis results it provides. The integration of experimental findings with theoretical analysis demonstrates that all four types of raised floors meet the relevant regulations, with a first-order vertical natural frequency exceeding 5 Hz in the walking area. This study delves into the underlying causes of discrepancies between theoretical and experimental modal analyses. One potential contributor to the variations observed during the floor assembly process is the occurrence of procedural inaccuracies. Specifically, there may be slight discrepancies between the actual thicknesses of the floor layers and those prescribed in the design blueprints. Such subtle dimensional deviations can significantly influence the overall stiffness and mass distribution of the floor system, resulting in inconsistencies between experimental outcomes and theoretical predictions.