Structural Diagnostics and Assessment of the Current Condition of the 40-Year-Old Railway Viaduct

Abstract In this study, an integrated nondestructive testing and finite element analysis approach is proposed for assessing a 40-year-old steel railway viaduct with an orthotropic deck. Visual NDT revealed numerous structural defects, most notably a discontinuous butt weld in the deck plate. To evaluate its structural consequences, onsite monitoring was carried out: strain gauges measured stress increments in the riveted crossbeam joint directly beneath the defective weld, whereas displacement transducers tracked relative deck plate movements during four representative locomotive passages. The monitoring revealed an unexpected stress distribution, with peak increases reaching 24.7 MPa in the bottom cover plate and 12.5 MPa in the upper plate. A global linear beam‒shell model was used to verify the ultimate and service limit states, confirm the fatigue limit exceedance, pinpoint the cross-beam joint as the governing hot spot, and clarify why no failure has occurred despite the faulty weld. The study’s novelty lies in a subsequent local investigation: a local solid‒shell model of the riveted joint, reproducing rivet clamping and incorporating contact and material plasticity. Under the representative load case, this model predicted stresses of 22.1 MPa (bottom plate) and 11.0 MPa (upper plate), deviating by only 10.5–12.0% from the measured values when the clamping force was neglected. Parametric analyses demonstrated that including the clamping force increases the discrepancy to 22.4–36.8%, suggesting that the stress distribution observed in the joint may stem from rivets installed at an insufficient temperature, which reduces their effective clamping ability. The integrated monitoring–modeling approach, therefore, not only quantifies the residual capacity of a flawed structure but also identifies manufacturing-related causes of unexpected stress behavior, guiding targeted maintenance and retrofit decisions.