Abstract
This paper investigates the fatigue behaviour of out-of-plane gusset welded joints strengthened with carbon fibre reinforced polymer (CFRP) laminates. Two notches were introduced at the weld toes adjacent to longitudinal plate ends to simulate the initial damage. Variables including the stress range, single- or double-sided strengthening and modulus of CFRP materials were considered. It was found that both cracks propagated under fatigue loading. All the specimens fractured along one predefined notch when the fatigue crack reached a certain length while the other crack also grew to some extent. Test results showed that the addition of composite materials significantly prolonged the fatigue life of specimens by as much as 1.28 to 8.17 times. Double-sided bond and ultra-high modulus CFRP materials led to a better strengthening efficiency. Thereafter, a series of numerical analyses were performed to study the stress intensity factor (SIF) and crack opening displacement (COD). Local debonding around the crack tip at the adhesive-steel interface was taken into consideration. Finally, the fatigue life of all the specimens was evaluated based on the linear elastic fracture mechanism (LEFM) theory and the predicted results agreed well with the experimental data.
Highlights
Due to the combined effect of loading and environmental conditions, structural members are observed to deteriorate during their service life
Experimental results demonstrated that carbon fibre reinforced polymer (CFRP) materials could effectively extend fatigue life and retard crack propagation of defective specimens, and the retrofitting efficiency was highly dependent on bond configuration, CFRP stiffness, prestress level and initial damage degree [4,5,6,7,8,9]
Fatigue design criteria for strengthening metallic beams with CFRP materials were proposed [23,24], which extended the understanding of CFRP-repaired steel beams
Summary
Due to the combined effect of loading and environmental conditions, structural members are observed to deteriorate during their service life. Experimental results demonstrated that CFRP materials could effectively extend fatigue life and retard crack propagation of defective specimens, and the retrofitting efficiency was highly dependent on bond configuration, CFRP stiffness, prestress level and initial damage degree [4,5,6,7,8,9]. Yu et al [34] investigated fatigue crack propagation of steel plates with longitudinal weld attachments strengthened by CFRP laminates on one side using the boundary element method. To the best knowledge of the authors, there have no attempt to perform a fatigue analysis using numerical simulation on out-of-plane gusset welded joints with two cracks strengthened with composite materials. This paper tested eight out-of-plane gusset welded joints under tensile fatigue loading, and variables including the stress range, single- or double-sided strengthening and modulus of CFRP laminates were considered. The fatigue life was predicted based on the numerical results by the linear elastic fracture mechanism (LEFM) theory
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