SCFs in tubular X-connections retrofitted with FRP under in-plane bending load

Abstract

This paper investigates the stress concentration factors (SCFs) in tubular X-connections retrofitted with fiber reinforced polymer (FRP) under in-plane bending moment. For this aim, a finite element (FE) model was generated and validated using available 13 experimental tests. After that, 276 FE models were created to investigate the effect of the FRP (layer number, orientation, and material) and the connection geometry (β, γ, and τ) on the SCFs. In these models, the contact between the FRP sheets and the steel members (chord, weld, and braces) was modeled. Results indicated that the rise of the FRP sheet number causes a notable drop in the SCFs. Also, the increment of the elastic modulus of FRP along the fibers causes a decrement of the SCF ratios. Moreover, the SCF in an X-connection retrofitted with CFRP can be down to 37% of that of the un-retrofitted connection. Despite the notable efficacy of the FRP sheets on the drop of the SCFs in the X-connections, there is not any study or equation on the X-joints with FRP. Therefore, a precise equation was proposed for quantifying the SCFs in X-connections with FRP. Also, the proposed equation was checked according to the UK DoE acceptance standard.