## 4 Analysis of Structural Uncertainty
### Analysis of Structural Uncertainty
For the curvature of the pylon bottom, the peak compressive strength of confined concrete and concrete bulk density have the greatest impact, which reaches 69.8%, then followed by the peak strain of confined concrete, with an influence of 66.8%. The influence of damping ratio is 59.0%, and that of pylon-section size and height are 44.8%. Meanwhile, the effect of the peak strain of unconfined concrete and peak compressive strength of unconfined concrete are 22.7% and 20.9%, respectively. Furthermore, the influence of other parameters is less than 5%, except for that of the bearing friction coefficient, which has an influence of 10.8%. For the parameters that affect the bearing displacement, according to their impact, they are concrete bulk density, which is 10.8%. Figure 15: Sensitivity of SFDP under transverse ground motion. (**a**) Curvature sensitivity of pier bottom (**b**) Displacement sensitivity of pier top (**c**) Cable force sensitivity (**d**) Main girder angle sensitivity (**e**) Curvature sensitivity of pylon bottom (**f**) Bearing displacement sensitivity. density, peak strain of confined concrete, damping ratio, friction coefficient of bearing, peak compressive strength of confined concrete and component size with influences of 77.2%, 69.2%, 41.7%, 39.%, 33.1% and 28.9%, respectively. Other parameters have little influence on the bearing displacement, and come to less than 10%. In addition, the influence of cable force is nearly consistent with the that of under longitudinal ground motions, showing the same characteristics with low sensitivity. The sensitivity Tornado diagram of SFDP affected by random parameters under a transverse earthquake is shown in Figure 16.  
From Figures 13-16, it can be seen that the cable force has a very low sensitivity to parameter variation. Compared with the influence of random parameters on the SFDP under longitudinal and transverse earthquakes, the friction coefficient of bearing, concrete bulk density, damping ratio, peak compressive strength of confined concrete, component size and peak strain of confined concrete have great influences on the dynamic response of high-speed railway extradosed cable-stayed bridges. These are followed by the parameters of strength and strain of unconfined concrete, the impact of which on the bridge cannot be ignored. The influence of other parameters is slightly insignificant. In other words, the effects of material properties and cross-section should be fully considered for nonlinear dynamic time-history analysis. For example, the fiber section involving the concrete compressive strain and strain should be considered. Therefore, accurate calculation of material parameter characteristics and accurate simulation of structural characteristics are the prerequisites for ensuring accurate and reliable calculation results. For the influence of structural size, the cross-section and pylon height are considered in this paper, for which the error in the bridge dynamic response cannot be ignored. From the point of view of engineering, bridge construction control needs to be strengthened to ensure accuracy of structure size. The research shows that structural uncertainty has a greater impact on the dynamic response of high-speed railway extradosed cable-stayed bridges than that of the traditional static parameter sensitivity analysis. Therefore, it is necessary to clarify the influence of random parameters on the bridge dynamic response, and to explore the relationship between seismic demand and random structural parameters. This is of theoretical and practical significance to clarify the bridge seismic functional damage. Additionally, it is the basis for the subsequent seismic fragility analysis of the bridge. Figure 16: SFDP sensitivity of Tornado Diagram under transverse earthquake.