In the realm of bridge seismic engineering, precast segmental column (PSC) bridges have gained popularity for their use in accelerated bridge construction (ABC), owing to their sustainability and superior component quality. However, previous research on these structures has significant shortcomings. Most studies have concentrated on the seismic behavior of individual PSCs without considering the effects of soil-structure interaction (SSI) and have typically relied on uniform or surface-only ground motion inputs. This failure to account for depth-varying multi-support ground motions (DMGMs), which arise from soil layer filtering and amplification, has resulted in inaccurate predictions of seismic responses and fragility, ultimately complicating reliable seismic design.
To address these gaps, a research team from Dalian University of Technology, Beijing University of Technology, and CSSC Windpower Development Co., Ltd. has published a study titled “Seismic Performance Assessment of a Precast Segmental Column Bridge Considering Soil−Structure Interaction and Depth-Varying Multi-Support Ground Motion Inputs.” This study introduces a thorough method for assessing the seismic performance of PSC bridges, using a traditional monolithic column (MC) bridge as a reference point.
The study encompasses several key components:
- Model Development: Utilizing OpenSees, the researchers created 3D finite element models for both PSC and MC bridges. The PSCs were represented using nonlinear beam-column elements for segments, ZeroLengthSection elements for joints (lacking tensile strength), and CorotTruss elements for prestressing tendons, ensuring that the initial stiffness was comparable to that of MCs. SSI effects were modeled through p-y, t-z, and Q-z soil springs, which also considered the effects of pile groups.
- DMGM Generation: Employing one-dimensional wave propagation theory and a spectral representation method, the researchers synthesized DMGMs by integrating site transfer functions that accounted for conditions like porous soil water saturation and empirical coherence loss functions. The results indicated significant variations in peak ground acceleration (PGA) and time histories at various pile depths, underscoring the need for DMGM inputs.
- Seismic Response Analysis: Under 20 sets of DMGMs scaled to 0.3g, 0.6g, and 0.9g PGA, nonlinear time history analyses demonstrated that neglecting SSI could underestimate the peak pier drift ratio (PDR) by between 9.93% and 12.28%. Additionally, using uniform excitation underestimated peak PDR by 7.02% to 9.94%, as it failed to consider out-of-phase vibrations between supports. Ignoring DMGMs resulted in an overestimation of peak PDR by 3.68% to 8.19%, as it relied on amplified surface motions for all soil springs. Overall, PSC bridges showed a significantly smaller residual PDR (ranging from 74.54% to 86.78% less) compared to MC bridges, attributed to the restoring forces of prestressing tendons, although the peak PDR was 1.04% to 12.66% larger due to a lower capacity for energy dissipation.
- Fragility Analysis: Using a bivariate lognormal distribution that considered both peak and residual PDR, the seismic fragility curves indicated that ignoring SSI could lead to a 12.45% overestimation of fragility median PGA. Similarly, uniform excitation overestimated it by 11.96%, while neglecting DMGMs underestimated it by 7.89%. The fragility of PSC bridges was found to be comparable to that of MC bridges, but their post-earthquake recoverability was superior due to smaller residual displacements, with median PGA differences reaching up to 12.70% for moderate damage.
The study, authored by Yucheng Diao, Chao Li, Hongnan Li, Huihui Dong, and Ertong Hao, provides critical insights into the seismic design of PSC bridges, highlighting the importance of accounting for both soil-structure interaction and depth-varying ground motions. The full text can be accessed at: https://doi.org/10.1007/s11709-025-1214-3.
