The vertical load-displacement-capacity response of footings is numerically evaluated in FLAC simulations using embedded stress-strain-strength curves that range from the small-strain shear modulus (G_(max)) to the shear strength (τ_(max)). As strains and loads increase, the modulus is reduced accordingly using a logarithmic function with physically-based parameters, including a reference strain (γ_r = τ_(max) /G_(max)) and strain at failure (γ_f). The ratio of these two strains (x_L = γ_f/γ_r) defines the degree of nonlinearity of the stiffness reduction. An approximate closed-form expression is derived and applied to a case study footing load test.
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