## 4 Time History Analysis
### Displacement Response  
Figures 18-21 illustrate the distribution of inter-story drift ratios of the CSSC multi-floored grain warehouse structure under four representative earthquake records. Overall, with the increase in ground motion intensity, the inter-story drift ratios under all grain-loading conditions exhibit an upward trend. The maximum drift ratio consistently appears at the second floor, indicating that this level is the critical region for lateral deformation control within the structure.  
Figure 19: Inter-story drift under El Centro ground motion.  
Figure 17: Structural acceleration responses under different ground motions.  
Figure 18: Inter-story drift under Wenchuan ground motion.  
Grain-loading configuration has a pronounced influence on the distribution of inter-story drift. The FFF and FFE scenarios consistently exhibit the highest inter-story drift ratios under all earthquake records, with the most prominent deformation occurring at the first and second floors. Although upper-floor grain storage increases the overall structural stiffness, the concentration of grain mass in the middle and upper levels generates substantial inertial forces during seismic excitation. This intensifies the stress demand on the lower structural components, leading to greater inter-story deformation. In contrast, the EEE condition, characterized by a reduced total structural mass, results in significantly lower inertial forces and a correspondingly weaker seismic response. For most earthquake records, the inter-story drift at the second floor remains low in the EEE scenario, and although some top-floor amplification is observed in specific cases, the overall deformation pattern remains relatively uniform.  
Further comparison reveals that, relative to the EEE condition, the second-floor inter-story drift ratio in the FFF condition increases by 74.33%, 192.41%, 87.27%, and 151.61% under the Wenchuan, El-Centro, Chi-Chi, and Hector Mine records, respectively. These results further confirm the substantial impact of grain mass distribution on structural seismic response and underscore the necessity of accounting for deformation concentration at lower levels under full-storage conditions in the structural design of multi-floored grain warehouses.  
The displacement time history curves of the second floor are shown in Figure 22, where significant differences in both overall response and peak displacement can be observed across different grain-loading scenarios. In the EEE condition, where no grain is stored on any floor, the total structural mass is substantially reduced, resulting in lower inertial forces. Under identical seismic excitation, the reduced inertial demand leads to a lower stress level  
Figure 21: Inter-story drift under Hector Mine ground motion.  
Figure 20: Inter-story drift under Chi-Chi ground motion.  
within the structure, thereby weakening the accumulation of nonlinear deformation effects and effectively limiting the displacement response.  
In summary, the structural responses in terms of both acceleration and displacement under different earthquake records exhibit consistent trend characteristics. Acceleration responses are primarily concentrated at the top of the structure, indicating a tendency for vibration amplification in the upper levels and revealing a pronounced whipping effect. In contrast, displacement responses are characterized by the maximum inter-story drift ratio occurring at the second floor, highlighting that the lower structural components experience the most significant shear deformation during seismic excitation. The displacement analysis results suggest that the combined effects of grain loading and seismic action are unfavorable to structural performance. However, across all grain-loading scenarios, the inter-story drift ratios remain within the limits specified by the design code. Even under the most critical condition--full storage (FFF)--the CSSC multi-floored grain warehouse structure still demonstrates sufficient safety reserves.