Mitigating interfacial stresses in strip-bonded beams by appending end-anchored unbonded segments

Abstract

Bonding strips is widely used for the strengthening of structures. This paper addresses the challenge of stress concentration in the strip-strengthened beams, where interfacial stresses at the end of the strip are usually large enough to causes premature brittle debonding failure. Lengthening bonded strips and thickening adhesive layer are effective solutions to decrease the stresses but sometimes difficult to implement. For example, obstacles under the beam may stop the strip from being lengthened with bonding. This paper proposes a feasible solution for this case that is extending the strip without bonding and then fixing it with additional anchors at the end. Analytical expressions are derived for interfacial stresses in strip-bonded beams with the end-anchored unbonded segment (EAUS). The deformation coordination relationship between EAUS and the beam is considered. The anchor bolts are analogous to elastic foundation beams to obtain their shear stiffness which will greatly influence the tension at the strip end. The theoretical results are then verified by finite element simulations. Moreover, parameter studies are performed to explore the effects of various strengthening configurations such as the length of the bonded and unbonded segments on interfacial stresses. The investigations show that the presence of the EAUS could substantially alleviate the concentration of interfacial stresses. The findings of this study provide a new approach on how to control stress concentration in the strip-strengthened beams.