## 4 Results and Discussion
### Dynamic Response of Bridge  
Figure 8 displays the peak displacements in the middle of the span and shear force at the bottom of the tower with the variation of FCAs and PGRDs. As seen from each row view, the responses of interest vary with FCAs under different PGRDs. It should be noted that when FCA = 15\({}^{\circ}\), the movements on both sides of the sinistral strike-slip fault plane cause the two towers to move backward along the direction of the bridge axis. Yet, when FCA = 165\({}^{\circ}\), the opposite is found in the present study (as shown in Figure 9). Moreover, it is also very noteworthy that the peak response of the structure is almost symmetric in Figure 8, although the FCAs vary from 15\({}^{\circ}\) to 165\({}^{\circ}\) in a symmetrical way because of the symmetry of the examined suspension bridge. In Figure 8a, it can be seen that the transverse displacements of the midspan increase as the FCA increases from 15\({}^{\circ}\) to 90\({}^{\circ}\) and decrease as the FCA increases from 90\({}^{\circ}\) to 165\({}^{\circ}\). Yet, the vertical displacement has the opposite distribution in Figure 8b. A similar phenomenon is found in shear force at the bottom of the tower in Figure 8c,d. That is, there is a greater response in the transverse direction at 90\({}^{\circ}\), while vertical displacement and longitudinal shear force are more sensitive at 15\({}^{\circ}\) and 165\({}^{\circ}\). Figure 8: Peak responses with different FCAs: (**a**) displacement of midspan in transverse direction; (**b**) displacement of midspan in vertical direction; (**c**) shear force of pier bottom in longitudinal direction; (**d**) shear force of pier bottom in transverse direction. Figure 7: Time history of synthetic cross-fault ground motions with different pulse characteristics: (**a–c**) Fling-step effect with PGRDs of 0 m, 0.4 m, 0.8 m, 1.2 m, and 1.6 m, respectively; (**d–f**) Forward directivity effect. Note: FS and FD represent fling-step effect and forward directivity effect, respectively. The displacement response demands of the long-span suspension bridge subjected to strike-slip fault is comprehensively determined by these deformations of soil layers, pier deformation, tower, and girder. For instance, the deformations from three soil layers with a depth of 270 m and tower are responsible for the displacement responses on the top of the 2# tower on Chengdu Bank. Meanwhile, the maximum transverse displacement of the midspan and tower top does not occur at FCA = 90\({}^{\circ}\) but rather at FCA = 165\({}^{\circ}\) because of the asymmetry of the bridge structure and valley terrain and the characteristics of sinistral strike-slip fault. As was found during recent major strong earthquakes, the PGRDs induced by sinistral strike-slip fault varied from tens of centimeters to several meters [4,43]. The faulting-induced dislocation, which affects the responses of fault-crossing bridges through the quasi-static term in the vibration equation of structures in nature, is a crucial factor in influencing the seismic behavior of bridges in the immediate vicinity of active seismic faults. Therefore, it is necessary to study the influence of PGRDs on the responses of long-span suspension railway bridges crossing faults. In addition, FCA = 15\({}^{\circ}\) and FCA = 90\({}^{\circ}\) are two extreme cases for fault-crossing bridges. To save space, these two extreme cases of FCA = 15\({}^{\circ}\) and FCA = 90\({}^{\circ}\) are considered herein to study the influence of PGRDs on the responses of long-span suspension railway bridge crossing faults. As depicted in Figure 10a,c, the transverse displacement of the midspan barely changes with the increase in PGRD, which is attributed to the symmetry of the bridge. The transverse displacement on both sides of the midspan is more sensitive to the increase in PGRD. Particularly when vertically crossing the fault, the displacement at the edge span is almost equivalent to the size of the PGRD.