Shear strength

Shear strength is the maximum shear stress a material can withstand before it slides or deforms irreversibly. Its value depends on the material, loading conditions, and failure criterion.

Shear stress: Stress acting parallel to a surface or cross-section. Shear strength is the limiting value of this stress before failure.
Direct shear test: A test that forces a specimen to slide along a predetermined plane while measuring stress. It measures shear resistance by imposing failure along a chosen surface.
Normal stress: Stress acting perpendicular to a surface or cross-section. Normal stress can change shear resistance through confinement or friction.
Tensile strength: The maximum tensile stress a material withstands before breaking or failing. It concerns pulling apart rather than sliding along a plane.
Mohr–Coulomb theory: A failure criterion relating shear strength to normal stress through cohesion and friction. It models how confinement and friction change the shear stress at failure.
Triaxial test: A soil or rock test that applies confining pressure and axial load to a cylindrical specimen. Its controlled confinement reveals how normal pressure affects shear strength.
Strain: A measure of deformation expressed as change in dimension relative to original dimension. Shear strength marks a stress limit, while strain describes the resulting deformation.
Compressive strength: The maximum compressive stress a material withstands before crushing or failing. Compression-driven failure differs from shear-driven sliding, though the stresses can interact.
Tresca yield criterion: A plasticity criterion that predicts yielding when maximum shear stress reaches a critical value. It defines yielding directly by a limiting shear stress, unlike frictional failure models.
Punching shear: A localized failure in which a loaded region pushes through a surrounding material along a shear surface. Concrete slabs are checked against this shear-driven failure around concentrated supports.

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