Numerical Investigation of the Shear Buckling and Post-Buckling of Thin Steel Plates with FRP Strengthening

The behavior of thin steel plates under shear loading is governed by early diagonal buckling and subsequent formation of an inclined tension field. This behavior describes the load carrying mechanism in deep steel plate girder webs and steel plate shear walls. Traditionally, steel stiffeners are used on the thin plate in some applications to mitigate out-of-plane buckling and encourage shear yielding, which is preferable and a more stable and energy-dissipating load carrying mechanism. However, the cost and practical difficulties associated with welding these stiffeners, especially on very thin plates and for in-service rehabilitation purposes, are considered as major drawbacks. In this paper, the behavior of thin steel plates strengthened with FRP strips was numerically investigated. FRP wraps were hypothesized to act as an elastic support for the thin steel plate in the early loading stages and as an auxiliary load transfer path in the inelastic tension field action. Numerical investigations were carried out using the finite element method and were divided into two phases; buckling and post-buckling. Elastic eigenvalue analysis for buckling and full inelastic analysis with geometrical and material nonlinearity for the post-buckling phase were carried out. FRP fracture and damage were incorporated in the models. Optimum angle of FRP fibers was studied both for buckling mitigation and post-buckling behavior enhancement. A number of FRP strengthening configurations together with a range of common FRP materials were also employed in the analyses. It was concluded that bonding FRP patches on the steel plate can effectively encourage behavior enhancements, especially given appropriate configuration and material properties.