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Load Definition > Earthquake Load

Definition of seismic events. The upper table (table of earthquake events) contains the numbers of  the seismic events to be considered, and related general parameters. The parameters describing the intensity and direction of the currently selected event are shown in the lower table.

SettingDescription
Table of earthquake events
SettingDescription
Number Number of the earthquake event
Modal file Name of the file, where the considered modes (eigenforms) are stored.
Rule  Superposition rules for the individual modal contributions
  • ABS: the absolute values of the contributions are added
  • SRSS: the absolute values of the contributions are added
  • DSC: superposition with correlation factors according to Newmark/Rosenblueth
  • CQC: complete quadratic combination (with correlation factors, signs adjusted)
  • CQCX: complete quadratic combination (variant without sign adjustment)
Duration Duration of the relevant part of the seismic event (only for CQC rules)
Description Descriptive text for the seismic event
Intensity parameters of the selected earthquake event

The intensity of the earthquake event is described by the direction and the design value (mostly the maximum value) of the amplitudes of the ground displacement, velocity or acceleration occurring during the earthquake event.

SettingDescription
Vec-Vx x-component of the design value
Vec-Vy y-component of the design value
Vec-Vz z-component of the design value
Note: Vec-Vx, Vec-Vy and Vec-Vz are true components of the intensity,i.e. they are not internally normalized to a unit direction vector.
Damp-Fact Damping ratio (for calculating the correlation factors for the superposition rules DSC, CQC, and CQCX and for specifying, which damping ratio is assumed valid for  the specified response spectrum Var-Name.
Var-Name (Graph) Name of the variable (table) describing the considered  response spectrum
Type Type of the definition of the excitation
  • d: the excitation is given in terms of displacement amplitudes and the response spectrum is related to ground displacements respectively.
  • v: the excitation is given in terms of velocity amplitudes and the response spectrum is related to the ground velocity respectively.
  • a: the excitation is given in terms of acceleration amplitudes and the response spectrum is related to the ground acceleration respectively.
Note: The type of the definition of the intensity must already be known when defining the response spectrum. In the last years, working in terms of accelerations has become accepted as a standard nearly all over the world.
Note: Different response spectra dependent on the damping ratio can be assigned to the considered earthquake event. The input values for specifying the direction, intensity and type of the excitation are only relevant in the first line of the table. Any differing entries in the ensuing lines are ignored. The definition of damping-dependent response spectra allows for assigning in the calculation action RespS different response spectra to the individual modes. 
Seismic events > Definition/Modification
Mode Superposition Rules
Seismic > Response Spectrum
Parent topic: Load Definition
Related reference