# Vibration Response Characteristics of Prefabricated Frame Structures Around the Subway
## 5 Vibration Response Characteristics of Prefabricated Frame Structures Around Subways
### Influence of Slab Thickness Variation on the Structural Vibration Response  
The baseline structure in Section 2 was adopted as the analysis object for the variation of slab thickness. The structural plan layout is shown in Figure 3. Keeping the parameters of other components in the reference structure unchanged, only the size of the slab thickness was varied. The values of component parameters for different models are shown in Table 10.  
Structural design parameters remained consistent with Section 2's baseline model. Design information was input into the PKPM2025R2.3 software to generate reinforcement layouts for various models. Uniform slab reinforcement patterns (\(\Phi\)8@200 bidirectional bottom layer) were implemented for comparative analysis. Automated design validation ensured consistent reinforcement compliance. Connections employed four M20 (Grade 8.8) friction-grip bolts in a dual-row symmetric configuration, with 12 mm splice plates matching base material properties. Translational stiffness \(K_{\mathrm{v}}\) = 2.8 \(\times\) 10\({}^{9}\) N/m and rotational stiffness \(K_{\mathrm{r}}\) = 1.83 \(\times\) 10\({}^{8}\) N\(\cdot\)m/rad were assigned, maintaining \(\gamma\) = 0.5. Semirigid behavior in B1-S/B2-S/B3-S was modeled using Bushing connectors, whereas B1-R/B2-R/B3-R achieved full rigidity through Beam connector implementation. A uniform material damp  
Figure 16: Mixed-direction velocity spectrum of the middle nodes of the side beams on the top floor in different column section models: (**a**) semirigid-jointed systems; (**b**) rigid-jointed systems. ing ratio of \(\xi\) = 0.02 was applied across all components. Triaxial vibration data (X/Y/Z) from six-car Type B trains at 80 km/h along the tunnel axis were input via base-uniform excitation into all six models. Vibration histories from middedge beam nodes were processed to obtain floor-specific weighted acceleration levels shown in Figure 17.  
From an occupant comfort perspective, rigid-jointed frame structures maintained weighted acceleration levels within residential day-night limits across all slab thicknesses yet still exceeded stringent zone vibration thresholds. Each 10 mm slab thickness increase yielded a 0.5 dB acceleration reduction, indicating that 120 mm slabs did not reach the critical thickness where stiffness-mass effects neutralize. Further thickening may sustain gradual vibration attenuation. Reference [14] identified 140 mm as a critical thickness for stiffness-mass equilibrium in rigid systems. Though project-specific variations exist, exceeding 120 mm in this study may have achieved 74 dB compliance but risked stress concentration and cost escalation. Standard practice limits slabs to 100-120 mm, necessitating alternative controls beyond 120 mm. Semirigid-jointed structures with tested slab thicknesses complied with daytime residential limits but violated nighttime criteria. It is found that when the slab thickness increased from 100 to 110 mm, the overall acceleration vibration level of the structure decreases by 1 dB while decreasing by 0.25 dB when the slab thickness increased from 110 to 120 mm. This diminishing-returns pattern suggests 120 mm as a critical thickness for semirigid systems beyond which vibration levels may plateau or rebound. Continuous slab thickening failed to achieve nighttime compliance in semirigid systems, necessitating supplemental vibration mitigation for residential applications. Semirigid systems demon