During earthquakes, extended pile‐shaft–supported bridges in laterally spreading ground can undergo inelastic deformations, especially in their embedded portions. Following earthquakes, it is critical to assess damage to these difficult‐to‐inspect portions and determine whether vehicles can safely pass bridges. This paper aims to identify optimal aboveground engineering demand parameters (EDPs) that are readily measurable after earthquakes and have high‐quality probabilistic associations with post‐earthquake load‐carrying capacity of bridges as well as underground difficult‐to‐inspect EDPs. For this purpose, an experimentally validated bridge‐soil‐foundation model considering liquefaction‐induced lateral spreading is adopted and subjected to ground‐motion time histories in the transverse direction. Subsequently, pushdown analyses are performed to assess the post‐earthquake vertical load‐carrying capacity of bridges. Metrics such as efficiency, practicality, and measurability are established and examined for EDPs. Results show that residual column drift ratio is the optimal EDP for load‐carrying capacity assessments, whereas maximum column drift ratio best predicts pile demands. Furthermore, developed probabilistic relationships between residual and maximum column drift ratios will assist in preliminary post‐earthquake evaluation of bridges for damage assessment and posting decisions.

In current practices, the elastic design principle for the seismic design of pile foundations is an overly conservative strategy. In this regard, cyclic lateral loading tests were conducted to investigate the seismic failure mechanism and ductile behaviors of elevated RC pile-cap foundations. Two six-pile specimens with different aboveground heights were constructed and embedded in a single layer of cohesionless soil. Hysteretic characteristics and observed damages of the pile groups were presented, together with the corresponding soil pressure and pile curvature responses. From the test results, the sequence and positions of the pile plastic hinges were established. Ultimate limit states of the pile groups were determined according to test data, as well as numerical analysis results. Test results revealed a ductile flexural failure mode for both specimens. Plastic hinges were detected first at the top of outer piles, then underground at a depth of 4–6 times the section width. A displacement ducti...

Potential scouring scenarios around the foundations of bridges that pass over water could have adverse effects on the seismic response of both the site and the structures. In this study, a two-step methodology is proposed to estimate the seismic response of pile-supported structures accounting for these effects. The first step was to calculate the seismic response of the free field and obtain the acceleration and displacement responses of the site considering the effects of scouring on ground motions. The second step was to perform seismic analysis on the pile-supported structure on the basis of a simplified model, using the acceleration response of the free field as a uniform input along the pile nodes. The responses of four different input motion choices were compared to determine the best choice for the seismic analysis of bridges with scour in their foundations. To validate the accuracy of the proposed approach, the results were compared with an integrated soil-pile-structure numerical model and with shake table test data. It was found that the simplified method could effectively estimate the bending moments of the pier and piles, as well as the acceleration response of the superstructure and pile cap. It was shown that the best input motion choice for the simplified model was to use the ground acceleration response of the free field after scouring.

A key challenge for estimating seismic response of piles and soils in liquefied and laterally spreading ground is the efficient prediction of local loosening phenomenon (shear localization) at the interlayer between the liquefied loose sand and the overburden crust. To this end, a simplified finite-element (FE) model was developed. In the soil model, a soft interlayer element with a thickness and corresponding low reference shear modulus was developed to represent the shear localization phenomenon. The proposed FE models were then used to simulate centrifuge tests of a single pile, a two-pile group, and a six-pile group in sloping liquefiable profiles that lead to lateral spreading. Predicted results of the shear-localization-induced soil lateral spreading displacement, as well as the structural response, agree reasonably well with the test records, indicating that the proposed FE model is capable of approximating the seismic responses of soil and piles in liquefied and laterally spreading ground....