Probabilistic loss assessment of curved bridges considering the effect of ground motion directionality

Abstract

This study aims to assess, in a probabilistic manner, the effect of seismic excitation direction on the performance of a 638 m‐long, 12 span prestressed concrete bridge with significant curvature in plan on the basis of overall monetary repair loss. By means of a large number of nonlinear dynamic analyses, the optimum intensity measure (IM) was selected from a pool of twenty candidates considering the impact of seismic excitation direction. Next, the variability of bridge loss with respect to the seismic incidence angle under different groups of earthquake intensities was obtained. Finally, the applicability of combination rules for the seismic performance of curved bridges was evaluated based on the multidirectional loss assessment results. Meanwhile, the effects of seismic excitation direction and earthquake intensity on the evaluation of combination rules were also revealed. Results indicate that velocity‐related or/and structural‐dependent IMs are more appropriate for the probabilistic seismic demand analysis of curved bridges. It is also notable that the total bridge loss gradually turns out to be independent of the seismic excitation direction as the seismic intensity increases and the damage develops throughout the structure. Additionally, the widely used 100/30 and 100/40 rules may lead to an unconservative estimation for the loss of the curved bridge. The above findings highlight the necessity of addressing the issue of ground motion directionality in a rigorous probabilistic manner and pave the way for further research on qualifying the influences of geometric configuration, material parameters, soil type and the consequent soil‐structure interaction effect.

Influence of directionality of spectral‐compatible Bi‐directional ground motions on critical seismic performance assessment of base‐isolation structures

“…The directionality parameter of the ground motions in GM1 becomes zero by definition, while those in GM2 almost retain the directionality properties of the 18 original records. The difference of the average values of the directionality parameter (𝛼 𝑤 ) and that of the major axis orientation (𝜃 𝑤 ), defined in Equations ( 8) and (9), between GM2 and the original ground motions are less than 0.1 and 20 • , respectively, as shown in Figure 10(A) and (B). One evident outlier in the average major axis orientation was seen in the No.…”

“…It is clearly seen that the bidirectional trajectory of accelerations, the directionality parameter, and the orientation of major axis are significantly affected after the spectral-matching operation, in this case, especially, in long period range. As a consequence, the average major axis angle, see Equation (9), is also significantly affected. However, this change will not affect the observations and conclusions obtained in simulation results of Section 6.1, since GM1 and GM2 satisfy their respective requirements in the current study, namely GM1 with unidirectional nature (having a zero directionality parameter) and being spectrum-compatible and GM2 with bidirectional nature (having a nonzero directionality parameter) and being spectrum-compatible.…”

“…The directionality effect of bidirectional ground motions is defined as the characteristics of ground motion along all possible orientations and their influence on the seismic performance assessment. The effects of the incident angle of bidirectional ground motions have received comprehensive investigations 5–10 . For example, the study for symmetric and asymmetric single‐/multistory buildings 11,12 indicated that the critical direction of a ground motion does not necessarily coincide with the direction of the maximum‐direction spectrum (computed at the building's first mode period) or the fault‐normal spectrum.…”

“…The effects of the incident angle of bidirectional ground motions have received comprehensive investigations. [5][6][7][8][9][10] For example, the study for symmetric and asymmetric single-/multistory buildings 11,12 indicated that the critical direction of a ground motion does not necessarily coincide with the direction of the maximum-direction spectrum (computed at the building's first mode period) or the fault-normal spectrum. The orthogonal effect of bidirectional ground motions on structural responses has also been investigated in a number of studies by scaling the amplitude of the component perpendicular to a specified strong axis.…”

Seismic Fragility Assessment of Cable-Stayed Bridges Crossing Fault Rupture Zones

“…Four limit states are considered, namely slight, moderate, extensive, and complete. For the pylon sections, the value of each damage state proposed by Feng [61] is adopted in this study. Figure 10 illustrates the moment-curvature curve for a pylon section.…”