## 5 Numerical Analysis and Results
Figure 11: Comparison of base-isolated and non-isolated structures, considering the linear and nonlinear behaviour. Comparison of hysteresis loops of the base isolators for different standoff distances under the blast load: (**a**) Fixed-base systems; (**b**) Base-isolated systems. Figure 12: Plastic hinge formations in the base-isolated and non-isolated structures: (**a**) Plastic hinge formations for A-A and 1-1 Axis, at T = 0.1 s on non-isolated structure; (**b**) Plastic hinge formations for A-A and 1-1 Axis, at T = 0.1 s on base-isolated structure (Pink joints: Immediate occupancy, Blue joints: Life safety, Red joints: Collapse). column and beam sections as a result of the explosion. The plastic rotations of the columns and beams of seismic isolated and fixed-base structures, which would be caused by vehicle explosion effects at different distances, were calculated and compared according to the TBEC 2018 damage limit values (Figures 13 and 14). When the rotation rates of the beams were compared, it was observed that although less rotation occurred in seismic isolated structures for the first storey compared to the fixed-base structures, more rotation occurred in the seismic isolated structure for R\({}_{\text{G}}\) = 10 m compared to the fixed-base structure for the second storey. However, there was no significant difference between two different building systems for R\({}_{\text{G}}\) = 15 m. When the third storey beams were evaluated, it was seen that there was no difference between seismic isolated and fixed-base structures. The reason for this is that the explosion causes local damage and, as the number of storeys increases, the effects of the explosion decrease as the distance increases. When comparing performance analysis 1 and 2 for beams, all of the beams were in the limited damage zone for R\({}_{\text{G}}\) = 15 m, while part of the beams reached a controlled damage level for the first and second storeys for R\({}_{\text{G}}\) = 10 m.  
Figure 13: Plastic rotations for distances 10–15 m at beams for non-base isolated and base isolated: (**a**) Performance analysis 1; (**b**) Performance analysis 2. When the rotation ratios of the columns were compared, it was observed that although less rotation occurred in seismic isolated structures compared to fixed-base structures for the first storey, more rotation occurred in the seismic isolated structure for R\({}_{\rm G}\) = 10 m compared to the fixed-base structure for the second storey. However, when the rotation rates occurring in the first storey columns were examined, it was observed that high rotation rates were formed that would lead the fixed-base structure to the collapse zone. For R\({}_{\rm G}\) = 15 m, high rotations occurred in the rigid bonded system in the first storey columns, while the seismic isolated building columns remained at limited damage level. As a result of the performance analyses, both structures were in the state of collapse under the effect of 227 kg TNT in performance analysis 1 (R\({}_{\rm G}\) = 10 m). On the other hand, in performance analysis 2 (R\({}_{\rm G}\) = 15 m), the seismic isolated structure was at the advanced damage level, while the non-seismic isolated structure was in the state of collapse under the effect of 227 kg TNT. In Figure 15, 'IO' indicates immediate occupancy, 'LS' indicates  
Figure 14: Plastic rotations for distances 10–15 m at columns for fixed-based and base-isolated systems: (**a**) Performance analysis 1; (**b**) Performance analysis 2.  
life safety, 'CP' indicates collapse prevention, and 'C' indicates collapse. The percentage of exceeding performance limits has been expressed as an exceedance of these limits. Consequently, performance analyses of seismic isolated and non-isolated structures were conducted to examine the nonlinear behaviour of seismic isolated and non-isolated structures under explosion effects, and to examine the behaviour of structural members.