Residual shear performance and surrogate-assisted model updating of in-service prestressed concrete hollow slab beams

Prestressed concrete hollow slab (PCHS) beams are widely used in highway bridges, but their structural performance may degrade over time due to repeated traffic loading and environmental exposure. In this study, static load tests were carried out on four full-scale in-service PCHS beams removed from an existing bridge to investigate their residual shear behavior. The effects of shear span-to-depth ratio and pre-existing cracks on stiffness, shear capacity, crack development, and failure mode were examined. The test results showed that specimens with larger shear span-to-depth ratios exhibited greater deflections and lower stiffness, while pre-existing diagonal cracks significantly reduced stiffness, ultimate load capacity, and ductility compared with beam containing mainly transverse cracks. Most specimens failed due to bond deterioration between the prestressing strands and concrete, accompanied by strand slippage and crushing of the bottom concrete region. Furthermore, to establish a calibrated numerical model that accurately reproduces the measured structural responses, a surrogate-assisted inverse updating framework was developed. A series of ABAQUS solid-element analyses were performed to generate parameter–response data for training a kriging surrogate model. The surrogate model was then combined with constrained optimization to identify the effective structural parameters from measured structural responses. The updated models reproduced the experimental load–displacement behavior with good accuracy, with relative errors in ultimate load of −0.1%, + 10.9%, and −6.7% for Specimens S1, S3, and S4, respectively. The proposed framework provides an efficient tool for finite element model (FEM) calibration and structural assessment of aging PCHS bridges.