Fatigue cracking investigation on diaphragm cutout in a self-anchored suspension bridge with orthotropic steel deck

Abstract

To investigate the mechanism of base-metal cracking on diaphragm cutout in a self-anchored suspension bridge with orthotropic steel deck (OSD), multi-scale finite element models were established to obtain stress response at cutout detail under the passage of wheel loads. Fatigue life was evaluated based on nominal stress method and hot-spot stress method. The results indicated that the length of the longitudinal influence line for detail stress to wheel loads approximately equalled to twice the diaphragm spacing. The wheel loading location of maximum stress was the front wheel of middle-axle group 0.3 m from the diaphragm, and the stress was dominated by in-plane stress. The nominal stress was hard to define at cutout detail for high stress concentration, and the hot-spot stress was preferred to fatigue assessment based on S-N curve of FAT125, also nominal stress should be extracted at the location 5.0 mm from cutout edge. Cutout shape of Highway Bridge in Eurocode was suggested, and diaphragm thickness should not be below 12 mm. The cutout cracking was caused by poor cutout shape, thin diaphragm, high truck traffic volume and overloaded wheel loads, while undesirable fabrication control and large residual stress might also contribute to the cracking.

Keywords:

• Orthotropic steel deck
• fatigue
• finite element analysis
• cutout detail
• cracking
• hot-spot stress

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to acknowledge that this work was supported by the National Basic Research Program of China (973 Program) under Grant number 2015CB057701; the National Natural Science Foundation of China under Grant number 51878269; the Communication Science and Technology Project in the Hunan Province of China under Grant number 201522.