1. Geotechnical spring specification

Additional to the Arbitrary system data group.

This data group is used to specify geotechnical springs in the global X-Y plane suitable for modeling cyclic geotechnical data with degradation. The stiffness of the spring is degraded based on the secant stiffness to ultimate resultant displacement from initial position.

The applied damping calculates damping force based on the following model

\(\mathrm {F=C(d)\times |\dot {d}|^P\times sign(\dot {d})}\)

where - \(\mathrm {F}\): damping force - \(\mathrm {C}\): damping coefficient (strain / displacement dependent) - \(\mathrm {d}\): spring displacement - \(\mathrm {\dot {d}}\): velocity of attached node - \(\mathrm {P}\): exponent for strain velocity (P >= 1)

Note that the degradation of the geotechnical spring will dissipate some energy in the cycles where the spring is updated.

1.1. Data group identifier, one input line

GEO SPRINg SPECification

1.2. Number of geotechnical springs, one input line

NGEOSPR

  • NGEOSPR: integer > 0: Number of geotechnical springs

The following input lines are repeared NGEOSPR times.

1.3. Spring ID

SPRING-ID

  • SPRING-ID: character(8): Spring ID. Must be unique.

1.4. Spring localization and properties

4 or 5 input lines, depending on the damping model selected,

LINE-ID ISEG INOD

  • LINE-ID: character(8): Line identifier

  • ISEG: integer: Local segment number within line

  • INOD: integer: Local node number within segment

RLEN

  • RLEN: real, default: 0: Relative length, for scaling of results only

FORCE1 DISP1 .... FORCEn DISPn

  • FORCE1: real: Force corresponding to DISP1. First value must be zwero. \([\mathrm {F}]\)

  • DISP1: real: Displacement correcponding to FORCE1. First value must be zwero. \([\mathrm {L}]\)

  • FORCEi: real > 0: Force corresponding to DISPi. \([\mathrm {F}]\)

  • DISPi: real > DISP_i-1: Displacement correcponding to FORCEi. \([\mathrm {L}]\)

IDMP EXPDMP

  • IDMP: integer >= 0: Damping coefficient code

    • = 1: Constant damping coefficient

    • = N: Table with N pairs of damping coefficient / Displacement to be specified.

  • EXPDMP: real >= 0: Exponent for displacement velocity (Z = 1). Dummy if IDMP = 0.

No more input in this data group if IDMP = 0

1 line of input if IDMP = 1:

DAMPGEO

  • DMPGEO: real > 0: Displacement independent damping coefficient

1 line of input with IDMP pairs of damping values if IDMP > 1:

DAMPGEO1 DISP1 ... DAMPGEOidmp DISPidmp

  • DMPGEO1: real: Damping coefficient corresponding to DISPL1

  • DISPL1: real: Displacement corresponding to damping coefficient DMPGEO1. \([\mathrm {L}]\)

  • DMPGEOi: real: Damping coefficient corresponding to DISPLi

  • DISPLi: real: Displacement corresponding to damping coefficient DMPGEOi. \([\mathrm {L}]\)

um ii fig49
Figure 1. Spring degradation model

The figure shows the initial stiffness \(\mathrm {K_i}\) and updated secant stiffness \(\mathrm {K_s}\) after displacement \(\mathrm {d_u}\) in Geotechnical spring.