Flexural RC members strengthened with mechanically fastened FRP laminates: Test results and numerical modeling

This paper presents an experimental and numerical investigation aimed at advancing the knowledge of the behavior of reinforced concrete (RC) members strengthened in flexure with Mechanically Fastened (MF) Fiber Reinforced Polymer (FRP) laminates. The test matrix included four MF-FRP strengthened specimens with different combinations of laminate lengths and fastener layouts, a counterpart strengthened with externally bonded (EB) FRP laminate, and a control (unstrengthened) specimen. Test results presented herein emphasize the influence of the partial interaction between RC slabs and MF-FRP laminates on the flexural response arising predominantly from bearing of the fasteners onto the FRP laminate. A finite element procedure was developed to carry out the numerical study, which incorporates nonlinear constitutive models for materials and concrete-FRP interface. For the latter, an accurate and a simplified, conservative bilinear stress-slip model are successfully implemented and verified to evaluate applicability for analysis and design purposes, respectively.