Parameters of a structure seismic analysis depend on a seismic code used during calculations of a structure influenced by seismic impact.
- Access
- Select seismic code EC 8 (EN 1998-1:2004) in the
New Case Definition dialog or click
Parameters in the
Analysis Types
dialog.
To complete the seismic analysis according to the rules given in a code, define the following parameters.
- ag
- Specifies the design ground acceleration on type A ground as specified by Local Authorities. The design ground acceleration is defined in terms of the reference peak ground acceleration on type A ground agR and importance factor γ derived from the building class:
ag
= γ × agR
- Beta
- Specify the value of the lower bound factor for the horizontal design spectrum.
- Ground type
- Select the type of ground (A, B, C, D or E), as specified in the Table 3.1.
- The parameters of the ground type influence describe the response spectrum (S, Tb, Tc and Td) according to the tables 3.2, 3.3 and 3.4.
Note: Select
Envelope to enable the Parameters button which allows you to open theSpectrum Envelope
dialog.
- Spectrum
- Select a
Design or
Elastic Spectrum, as specified in point 3.2.2.
- Direction
- Specify if the direction is Horizontal or Vertical.
- Spectrum type
- Select a Spectrum type as specified in point 3.2.2.
- Behavior factor
- Specify the value of the
Behavior factor according to point 3.2.2.5.
- The Behavior factor is a reduction factor of the design response spectrum in relation to the elastic response spectrum. You can edit its value after selecting the Design spectrum option.
Note: The behavior factor q reduces the design spectrum; this way it also decreases seismic loads and the resulting internal forces. However, as specified in point 3.2.2.5, the displacement based on the design response spectrum is multiplied by the behavior factor q. Thus, usually such displacement is not reduced in relation to the elastic response spectrum.
- Eccentricity Definition
- Opens the
Definition of mass eccentricities dialog which allows you to specify how to account for the eccentricity of a mass in the seismic analysis.
- Direction definition
- Opens the Direction dialog which allows you to define the direction of the spectral or seismic excitation.
- Filters
- Opens the Filters dialog which allows you to determine the number of modes to be taken into account during dynamic analysis of structures.
- Residual Mode
- Allows you to calculate pseudostatic forces for a residual mode.
The details concerning this structure analysis method can be found in the mentioned code.