Dload

*Dload - Distributed load

*Dload, <option>
<element set name>, <Load label>, [additional parameter]

This option defines a distributed load acting on the faces of the element set <element set name> with a defined load magnitude. Except of [additional parameter] all sub-keywords are mandatory.

• <option>

  Specify how the load should be applied. The load can either be applied:

  • instantaneously (without any temporal delay) using <option> = instant

  • linearly increasing with step time (0% of the prescribed magnitude are applied at the beginning of the step and 100% at the end of the step time) using <option> = ramp

  • using a user defined amplitude defined prior to the step definition using <option> = Amplitude = <amplitude name>

  • user-defined <option> = user. The user has to supply the user_load.o file (see user loads)

• <element set name>

  Element set to which the load should be applied

• <Load label>

  Load label defining the direction of action of the external distributed load. Currently available are:

  • Pi:

    Distributed loads acting perpendicular to the element face i (where i is the face label). The subsequent line then reads:

    <element set name>, Pi, <Magnitude>

  • Di:

    Distributed loads acting in global direction Dir={1,2,3} on element face i (where i is the face label). The subsequent line then reads:

    <element set name>, Di, Dir, <Magnitude>

  • SWPi:

    Distributed load acting perpendicular to the element face i compensating (positive) pore-water pressure by its deadweight (e.g. to simulate the flooding of slopes). The magnitude of the load is calculated such that the (only positive) pore water pressure acting on the surface is compensated. The subsequent line then reads:

    <element set name>, SWPi

  • HPi:

    Hydrostatic pressure (elevation-dependent) acting perpendicular to the element face i. The vertical direction \(h\) is assumed to be the \(z\)-direction in 3-D and axisymmetric models and the \(y\)-direction in 2-D models and the distribution of initial pore water/air pressure is assumed to vary piecewise linearly with this vertical coordinate. The subsequent line then reads:

    <element set name>, HPi, <Magnitude 1>, h1, <Magnitude 2>, h2

  • COMPLIANTi:

    The compliant base boundary condition is used to impose a seismic signal at the bottom of the FE model and at the same time damping downwards propagating waves by applying equivalent viscous forces. The distributed force acts in global direction Dir to the element face i to which the force is applied. The <Magnitude> is defined as \(\rho \cdot c_{p,s}\) of the underlying material, where \(\rho\) is the density and \(c_{p,s}\) is the wave speed (\(c_s\) for shear waves and \(c_p\) for compression waves) The subsequent line then reads:

    <element set name>, complianti, <Dir>, <Magnitude>

    This corresponds to the \"implicit\" implementation, where the current velocity \(v\) is used to calculate the viscous stress.

  • COMPLIANT0i:

    The compliant base boundary condition is used to impose a seismic signal at the bottom of the FE model and at the same time damping downwards propagating waves by applying equivalent viscous forces. The distributed force acts in global direction Dir to the element face i to which the force is applied. The <Magnitude> is defined as \(\rho \cdot c_{p,s}\) of the underlying material, where \(\rho\) is the density and \(c_{p,s}\) is the wave speed (\(c_s\) for shear waves and \(c_p\) for compression waves) The subsequent line then reads:

    <element set name>, compliant0i, <Dir>, <Magnitude>

    This corresponds to the "explicit" implementation, where the velocity \(v_0\) from the previous (converged) time step is used to calculate the viscous stress.