Load transfer mechanism of pretension injection bolts

between the bolt and hole with resin. Injected bolts were tested at TUD in oversized holes of composite floor systems for application in a reusable parking garage. The latest Eurocode3 (EN1993-1-8_2021) provides a design resistance formula for an injected bolt with pretension. Its resistance is the sum of bearing and slip resistance, Fs,Rd+Fb,Rd,resin. While this simplified formula conveys the fundamental principles of assumed force distribution, an investigation by FEA is presented in the paper to check if the frictional and bearing resistance can be simply added.It is expected that the bolt preload may change due to the deformation of the spliced plate, which may affect the slip resistance. In addition, the calculation of bearing resistance depends on factors including geometric configurations of the bolt's shank in the hole and material properties of the resin. Consequently, our investigation intends to refine the calculation methodology. By employing analytical methods, we explore the interaction between frictional force (Fs,Rd) and bearing force (Fb,Rd,resin) while considering the effects of varying pressures on the resin and geometric factors.The paper addresses injection bolt behaviour under preload and aspires to provide a more accurate and reliable calculation method for assessing the tensile resistance of injection bolts with preload in practical applications. The pretension and deformation of bolts, as well as the distribution of bearing stress and plastic deformation of the resin, are considered to determine the resistance distribution of tensile load applied on a double lap joint. Improved design guidelines for engineers and designers can enhance the safety and efficiency of structural connections that use injection bolts by better understanding the complex interaction of forces and variables involved in the joint.