Fatigue behaviour of CFRP strengthened open-hole steel plates: Fid-Bau Portal

Fatigue behaviour of CFRP strengthened open-hole steel plates

Wang, Zhi-Yu / Wang, Qing-Yuan / Li, Lihui / Zhang, Ning

AbstractOpen-hole details have gained widely application in bolted connections subjected to fatigue loading. Although the use of carbon fibre reinforced polymer (CFRP) can be efficient in strengthening critically stressed tension area, its benefit in improving the fatigue life of open-hole details has not been extensively evaluated. This paper presents the results of an experimental and finite element analytical study on the fatigue behaviour of CFRP strengthened open-hole steel plates. The merits resulted from CFRP strengthening are investigated and compared with some others from referred open-hole fabrication methods and these with artificial initial cracks or notches as reported in the literature. Typical failure modes, local strain evolution and stiffness degradation behaviour of the test open-hole details are reported. The fatigue life results are evaluated and compared against the design curves of the AASHTO. The results show that the use of single and triple layered CFRP strengthening results in fatigue life enhancement of nearly 20% and 60% respectively in contrast to bare steel open-hole plates. Incorporating the stress ratios allowing for fibrous rupture and steel-adhesive interface failure, the fatigue life of CFRP strengthened specimens can be properly evaluated. Finally, the geometric and configuration parameters of CFRP on the stress concentration of the open-hole details are studied based on finite element modelling. It is demonstrated that the studied stress concentration can be reduced with the increase of the modulus of carbon fibre and the number of CFRP layers. The contribution of the effective width of CFRP to the decrease of stress concentration is also discussed.

Highlights•The CFRP strengthening effect on the fatigue failure modes of open-hole plates is experimentally demonstrated.•The characteristic strain distribution and stiffness of CFRP strengthened open-hole plates are analyzed in details.•The fatigue life improvement effect of CFRP strengthening is discussed from a comparison of life curves related to details.•Proposed model allowing for stress ratios is shown to be effective in evaluating fatigue life enhancement after retrofit.•The influences of CFRP on the stress concentrations of open-hole details are clarified by finite element modelling.