University of Tabriz Journal of Civil and Environmental Engineering 2008-7918 53 111 2023 08 23 Investigation of the Performance of CFRP and GFRP Wraps on Improving the Nonlinear Static Behavior of Tubular X-Joints Investigation of the Performance of CFRP and GFRP Wraps on Improving the Nonlinear Static Behavior of Tubular X-Joints 189 200 13872 10.22034/jcee.2021.47839.2069 FA Pooya Rezadoost Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran. Hossein Nassiraei Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran Seyed Ahmad Neshaei Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran. Journal Article 2021 09 08 Tubular structures are made of hollow steel members with circular cross-sections and connecting them is one of the major challenges in their design. So far, some techniques to improve the performance of tubular connections have been proposed. Most of these methods can only be used for structures during the fabrication, but there are only a few techniques that can be applied during both fabrication and operation. Due to the successful experience of using composite materials for the repair and retrofitting of structures, special attention has now been paid to examining the efficacy of these materials in offshore structures.<br />In this research, the effect of CFRP and GFRP wraps on the ultimate strength and deformation of tubular X-joints under compressive load is investigated. For this purpose, the results of the finite element (FE) models were validated with several available experimental tests. After that, the nonlinear static behavior of tubular X-joints strengthened with FRP was studied. In these FE models, the contact between the FRP layers and the steel members (chord, weld, and braces) was considered. Also, the weld profile in the brace/chord intersection was modeled. Tubular structures are made of hollow steel members with circular cross-sections and connecting them is one of the major challenges in their design. So far, some techniques to improve the performance of tubular connections have been proposed. Most of these methods can only be used for structures during the fabrication, but there are only a few techniques that can be applied during both fabrication and operation. Due to the successful experience of using composite materials for the repair and retrofitting of structures, special attention has now been paid to examining the efficacy of these materials in offshore structures.<br />In this research, the effect of CFRP and GFRP wraps on the ultimate strength and deformation of tubular X-joints under compressive load is investigated. For this purpose, the results of the finite element (FE) models were validated with several available experimental tests. After that, the nonlinear static behavior of tubular X-joints strengthened with FRP was studied. In these FE models, the contact between the FRP layers and the steel members (chord, weld, and braces) was considered. Also, the weld profile in the brace/chord intersection was modeled. https://ceej.tabrizu.ac.ir/article_13872_402a30d00fd48c9a2c5518aa10b457a9.pdf