Fatigue performance of orthotropic steel decks in a wide steel-box girder

To investigate the fatigue performance of an orthotropic steel deck (OSD1) in a long-span highway suspension bridge with a wide steel-box girder, a finite element analysis (FEA) and a model test were conducted. The fatigue stress characteristics and stress-influence surface of typical fatigue details of the OSD were investigated. An equivalent full-scale fatigue test model with eight U-ribs was tested under five million load cycles. The nominal-stress method and linear elastic fracture mechanics (LEFM) were employed to evaluate the fatigue performance of the OSD. The results demonstrate that the fatigue details near the hanger side have relatively large stresses. The stresses of symmetrical details in one U-rib are in the opposite compression and tension states due to deflection of the wide diaphragm, which is unfavourable for fatigue performance. The stress-influenced surfaces indicate the different multi-vehicle effects for fatigue details. The measured tension stresses near the rib-to-deck welds and rib-to-diaphragm connections changed significantly at 2.25 and 3.0 million cycles, respectively. After 5 million cycles, the measured crack lengths in these details were 130 and 45 mm, respectively. The model's overall deformation performance is hardly affected by the fatigue cracks. According to the damage-accumulation principle, the assessment of the fatigue lives of rib-to-deck and rib-to-diaphragm details were 92.3 and 114.2 years, respectively. The existing recommended fatigue design class would clearly overestimate the fatigue life of rib-to-deck details of the OSD in a wide steel-box girder. According to the LEFM, these fatigue lives were 98.6 and 138.7 years, respectively.

Automated summary

The fatigue performance of an orthotropic steel deck in a long-span highway suspension bridge with a wide steel-box girder was investigated. Results showed that fatigue details near the hanger side had relatively large stresses and symmetrical details were affected by deflection of the wide diaphragm. The stress-influenced surfaces were different for fatigue details due to multiple vehicle effects.