ATLAS Lab Research Videos
Recorded presentations and demonstrations covering hydraulic fracture simulation, FRP-concrete bond testing, and sustainable 3D concrete printing — research from the ATLAS Lab at KFUPM.
This work presents a 3-D Generalized/eXtended Finite Element Method (GFEM) simulation of hydraulic fracture by coupling solid/rock domain equations with fluid flow within the fracture. The GFEM, based on p-hierarchical FEM enrichments, is combined with mesh adaptivity for robust and computationally efficient simulation. Both h-refinement around the fracture front and p-enrichment in the analysis domain control discretization errors. Fluid flow is modeled using Reynolds' lubrication theory assuming a Newtonian fluid. A Linear Elastic Fracture Mechanics (LEFM) model based on Irwin's criterion is adopted for the solid domain. Fracture propagation direction is computed using Mode I, II, and III Stress Intensity Factors (SIFs) and Schöllmann's criterion. Capabilities are demonstrated by reproducing two hydraulic fracture experimental tests, followed by parametric analyses on multiple interacting fractures studying fluid viscosity, spacing, cluster count, and remote stress type.
The first phase critiques shortcomings of the improved double-lap bond shear tests regarding limited application to wet layup FRP and inapplicability to pultruded FRP laminates. The study provides evidence of high chances of undesirable fiber rupture that preclude reliable use for FRP-concrete bond-slip model interpretation. Proposed modifications design a convertible bond tester applicable to both wet layup and pultruded FRP laminates, enabling mixed-mode bond tests in addition to pure double shear. The second phase upgrades the apparatus to accommodate near-surface mounted (NSM) FRP bars/strips, fiber-reinforced cementitious mortar (FRCM), and other strengthening system variants — providing pioneering means for mixed-mode FRCM studies, a gap previously absent in the literature.
The lack of a standardized FRP-concrete bond test method leads to variations across single-lap shear, double-lap shear, beam, mixed-mode, and pull-off tests. This study pioneers their evaluation, offering a consistent dataset for informed decision-making. Single- and double-lap shear tests yield trilinear bond-slip responses; the single-lap test's asymmetry reduces bond strength by 15% vs the double-lap test. The beam test shows comparable average bond strength but is unsuitable for bond-slip modeling. The mixed-mode test better simulates field applications, while the pull-off test provides the most consistent results. Given each method reflects only one field scenario, the Universal Bond Tester (UBoT) was developed — converting to all FRP-concrete bond test types, addressing double-lap shear test limitations, and presenting a modified ASTM D7958 beam and mixed-mode tests cost-effectively. The UBoT captures full bond behavior, reducing specimen sizes and data acquisition needs by half for most tests.