NUMERICAL EXPERIMENT FOR SHEAR KEY JOINT BEHAVIOUR SIMULATION IN ARCH DAMS: PART 1 – INVESTIGATING THE INFLUENCE OF THE KEY SHAPE AND ANGLE

Nonlinear behavior of contraction joints in arch dams, such as joint opening and sliding caused by hydrostatic pressure and temperature variations, can affect the dam’s serviceability. Furthermore, strong seismic events can additionally alter the response in dynamic conditions, impacting the natural period and stress redistribution in the arches and cantilevers. In order to enhance structural integrity with additional shear strength, shear key elements are usually installed along these joints. However, traditional modeling with the actual shear key geometry results in complex analyses. This paper presents a novel approach for simulating shear key behavior by modifying the flat joint concept in ADAD-IZIIS software. The method introduces additional tangential stiffness to the flat joint's stiffness matrix to simulate shear resistance derived from the key geometry. The model uses a uniaxial constitutive law for nonlinear behavior in normal and Coulomb's friction law in the tangential direction. This paper presents the first part of a comprehensive study examining the influence of the key shape and angle through numerical experiments using refined FE models of flat, beveled, and unbeveled shear key joints. The additional tangential force Fτ,add is calculated by increasing the initial modulus of elasticity En,τ in the local shear direction as Enτ,add=kad*En,τ. The coefficient kad, representing additional tangential stiffness, is derived from the experimental analyses. Results indicate that the shape and angle of the key greatly influence the element's shear resistance. Unbeveled shear key joint increases tangential stiffness by approximately 60%, while the beveled joint by 23% compared to the flat joint. Although tangential stiffness minimally affects the extreme joint openings at the top edge, the unbeveled joint significantly reduces openings along the joint length. This research confirms that the modified approach effectively simulates nonlinear behavior by incorporating the complex geometry of the shear key joint.