Industry standards

Op³ ships calibrated implementations of the major offshore geotechnical standards. Each is wrapped in a single function that returns a 6x6 head-stiffness matrix consumable by Mode B (STIFFNESS_6X6) or by the SoilDyn exporter.

Standard	Module	Citation
DNVGL-ST-0126	`op3.standards.dnv_st_0126`	DNV (2021), Support structures for wind turbines
ISO 19901-4	`op3.standards.iso_19901_4`	ISO (2016), Offshore structures: geotechnical design
API RP 2GEO + Gazetas (1991)	`op3.standards.api_rp_2geo`	API (2014); Gazetas, J. Geotech. Eng. 117(9)
Carbon Trust OWA + Houlsby & Byrne (2005)	`op3.standards.owa_bearing`	Carbon Trust OWA Bearing Capacity Report
PISA (Burd 2020 / Byrne 2020)	`op3.standards.pisa`	Geotechnique 70(11), 1030-1066
HSsmall (Benz 2007 / Schanz 1999)	`op3.standards.hssmall`	Hardening Soil with small-strain stiffness

Cyclic degradation

op3.standards.cyclic_degradation.hardin_drnevich(gamma: float, gamma_ref: float, a: float = 1.0) → float[source]

Modulus reduction G / G_max for shear strain gamma.

Parameters:

gamma – Cyclic shear strain (engineering strain, dimensionless).
gamma_ref – Reference shear strain at which G / G_max = 0.5.
a – Curvature exponent. Default 1.0 (Hardin-Drnevich 1972). Use 0.92 for the Darendeli 2001 form.

Returns:

G / G_max in [0, 1].

Return type:

float

op3.standards.cyclic_degradation.vucetic_dobry_gamma_ref(PI_percent: float) → float[source]

Reference shear strain as a function of plasticity index.

Linear-in-log interpolation through the Vucetic-Dobry (1991) Figure 5 curve. PI_percent = 0 recovers the sand value (gamma_ref ~ 1e-4) and PI_percent = 200 saturates at ~5e-3.

op3.standards.cyclic_degradation.cyclic_stiffness_6x6(*, diameter_m: float, embed_length_m: float, soil_profile: list[SoilState], cyclic_strain: float, PI_percent: float | None = None, a: float = 1.0, n_segments: int = 50) → ndarray[source]: Convenience wrapper: degrade the profile via Hardin-Drnevich, then call pisa_pile_stiffness_6x6 on the degraded profile.