Comfort-oriented stiffness sensitivity assessment of long-span cable-stayed bridges based on vehicle-bridge coupled vibration analysis

Bridge stiffness is a key factor governing both structural serviceability and vehicle ride comfort in long-span cable-stayed bridges. This study proposes a comfort-oriented stiffness sensitivity assessment framework rather than an inverse stiffness-identification method. The objective is not to uniquely estimate bridge stiffness from ride comfort, but to quantify how prescribed stiffness reductions in major structural components influence bridge deformation and vehicle ride comfort under controlled vehicle-bridge interaction scenarios. Using the Linyu Yangtze River Bridge as a case study, a deterministic traffic flow is established through static-effect equivalence to code-based lane loading, and the influences of stiffness reduction in the main girder, stay cables, and bridge towers on bridge deformation and vehicle ride comfort are systematically investigated. The results indicate that pavement roughness has a dominant influence on vehicle-level ride comfort, whereas global bridge deformation is governed primarily by component stiffness. Different components exhibit different sensitivity characteristics: stay cable stiffness mainly controls the overall vertical deflection of the bridge, main girder stiffness has a more pronounced influence on girder-end rotation and comfort-related vehicle responses, and tower stiffness is closely associated with stability-sensitive global deformation. The proposed framework is therefore not intended to replace conventional load-carrying capacity evaluation, or stiffness identification. Instead, it provides a supplementary vehicle-bridge-interaction response layer that helps determine whether prescribed stiffness variations are mainly reflected in structural deformation, user-perceived vibration, or stability-sensitive response amplification. This information can support component prioritization, deck-serviceability diagnosis, and serviceability-oriented maintenance decision-making for long-span cable-stayed bridges.