PSI - Issue 78

Enes Krasniqi et al. / Procedia Structural Integrity 78 (2026) 261–268

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(a) (c) Figure 2. (a); Three-dimensional geometry of specimen TR01b with medium anchorage length and no mechanical nut; (b) Three-dimensional geometry of specimen TR02a featuring short anchorage with a mechanical nut and (c)Three-dimensional geometry of specimen TR02b with medium anchorage length and mechanical nut Each model was developed in full three-dimensional geometry, precisely reproducing the physical dimensions and essential details of the test specimens, including the concrete block, embedded threaded steel bar, and any transverse confinement reinforcement. A refined mesh was adopted in the regions around the anchorage zones. Discretisation was performed using linear isoparametric solid elements with full integration schemes to ensure numerical stability and accurate capture of stress–strain responses under nonlinear loading. The final mesh comprised 12.348 finite elements and 15.395 nodes, with an average element size of 0.02 meters in the concrete volume. Mesh refinement was concentrated in critical regions around the anchorage zone and mechanical nut interfaces to accurately simulate stress gradients, crack initiation, and propagation. Boundary conditions were carefully defined to replicate the physical constraints observed in the experimental setup. The base of the concrete specimen was fully restrained to prevent rigid body motions, while axial tensile loading was applied incrementally to the exposed end of the embedded threaded bar. The support conditions were specified using a global coordinate system notation, where “0” represents a free degree of freedom and “1” indicates a fixed restraint. For example, the notation “GLOBAL 0 1 0” signifies that displacement is restrained in the global Y-direction but remains free in the X and Z directions. A graphical representation of the applied boundary conditions is provided in Figure 3, where red areas denote vertical restraints and green areas indicate horizontal constraints. (b)

Figure 3. Visualization of boundary conditions: red indicates vertical fixity, green indicates horizontal constraints.