Application of toughened epoxy-adhesives for strengthening of fatigue-damaged steel structures

• Published in: Construction & building materials 2021-03, Vol.275, p.121579, Article 121579
• Main Authors: Kasper, Yann, Albiez, Matthias, Ummenhofer, Thomas, Mayer, Christoph, Meier, Tobias, Choffat, Fabien, Ciupack, Yvonne, Pasternak, Hartmut
• Format: Article
• Language: English
• Subjects: Adhesive; Bridges; Epoxy; Experiment; Fatigue; FRP; Steel; Strengthening
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2020.121579

•A common and a toughened EP adhesive are compared using standardized experiments.•Toughened EP adhesive fulfils high toughness, strength and stiffness requirements.•Woehler curves are determined for steel-CFRE bonds under bridge-typical stresses.•Adhesively bonded CFRE reinforcements increase the service life up to 7.9 times.•Full scale specimens validate the positive influence of the reinforcement. The average condition of German road bridges has deteriorated significantly in recent years. Steel bridges often show fatigue crack at points of increased stress concentrations. For increasing the remaining service life, effective reinforcement methods for reducing the crack growth are of increasing importance. Adhesively bonded reinforcements show many advantages compared to screwed or welded reinforcements, as the components are not damaged by heat input or drill holes. In this paper, a common EP adhesive and a toughened EP adhesive are characterised and compared by means of standardized experimental investigations. Due to the dynamic loading and the service temperatures occurring in steel bridges, the toughened EP adhesive is especially suitable for the strengthening application and is therefore prioritized for further experimental investigations. Due to the pre-stressing of the CFRP (Carbon Fiber Reinforced Plastics)-lamellas, the creep resistance of the bonded joint is of central importance. Creep tests show that the expected creep deformations are in irrelevant orders of magnitude. Fatigue tests on centre-notched steel specimens using the toughened EP adhesive in combination with CFRP lamellas show great potential for decreasing the crack tip stress and therefore increasing the remaining service life. With a reinforcement on both sides with pre-stressed plates, up to 7.9 times the remaining service life can be determined in comparison to unreinforced specimens.