Abstract
Cope-hole details are widely applied to steel bridges. However, the safety of steel bridges is influenced by the fatigue performance of welded details. So, cope-hole details with flange and web subjected to axial loads were selected as the research object. Based on the basic theory of linear elastic fracture mechanics and the Finite Element Method, the stress intensity factors of cope-holes details were calculated. The influences of geometry size and crack size of the detail on the stress intensity factors were then investigated. The Paris model of fatigue crack propagation predicted the crack propagation life of cope-hole details. Besides, the fatigue limit-state equation was also established to analyse the effect of random variables (such as initial crack size, critical crack size, crack propagation parameter) on the fatigue reliability index. Finally, the recommended value of the detection period was present. The results show that the stress intensity factor gradually increases with the increase of the cope-hole radius, the weld size, the flange plate thickness, the crack length and the web thickness. However, it gradually decreases with the increase of the ratio of the long and short axle to the crack. The predicted number of fatigue cyclic loading required by the fatigue crack depth propagating from 0.5 mm to 16 mm under nominal stress amplitude of 63 MPa is 122.22 million times. The fatigue reliability index decreases with the fatigue growth parameter, the crack shape ratio and the mean of initial crack size increasing, which is relatively sensitive. However, the variation coefficient of the initial crack size has little effect on it. The detection period of cope-hole details is the service time corresponding to the fatigue accumulated cyclic loading of 198.3 million times.
Highlights
The stress concentration phenomenon caused by multiple weld crossover is avoided effectively by using cope-hole details, which has been widely applied in steel bridges
The results show that when cope-hole details were subjected to significant shear stress, the burr grinding had little improvement on the fatigue strength
For cope-hole details in the orthotropic steel bridge deck, the fatigue crack initiation was predicted by critical distance theory (Zhou, Wen, Wang, Zhang, & Du, 2016)
Summary
The stress concentration phenomenon caused by multiple weld crossover is avoided effectively by using cope-hole details, which has been widely applied in steel bridges. For cope-hole details in the orthotropic steel bridge deck, the fatigue crack initiation was predicted by critical distance theory (Zhou, Wen, Wang, Zhang, & Du, 2016). As an essential parameter in fracture mechanics, the stress intensity factor determines the crack growth of the welded details and has a direct effect on the prediction accuracy of the fatigue life (Albuquerque, Silva, de Jesus, & Calçada, 2015; Duchaczek & Mańko, 2015). Based on the basic theory of the linear elastic fracture mechanics, the influence of different corrosion pit size, crack shape and crack depth on the stress intensity factor of welding details were studied. The recommended value of the inspection period for cope-hole details was presented
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