This module requires the license “Seismic analysis“.
Click on 
to define the seismic standard and the seismic spectrum. The following dialogue appears:
Specify the standard according to which you want to generate the seismic spectrum. A full list of available standards in Diamonds can be found here.
A seismic spectrum consists of:
- a horizontal spectrum in the u direction
- a horizontal spectrum in the v direction.
- And optionally, a vertical spectrum in the w direction.
The response acceleration in function of the modal period is given for each spectrum (u, v and w direction) in the graph.
- Enter the angle between the direction of the spectrum and the global axes. The image shows how the spectrum is rotated with respect to the global axes.
If the angle is 0°, the u and v-direction coincide respectively with the global X and Z direction. - Select whether or not you want to take into account the vertical component.
- If the eigen modes are independent of each other, it is allowed to calculate the total response with the ‘sum of the squares’ method. If the eigen modes are dependent of each other, you need to use Complete Quadric Combination-method (CQC- method).
- By checking the option ‘Apply quasi static correction’ the lack of effective modal mass is compensated (see further in this topic).
- Choose the spectrum type. You have the choice between type I or II.
- Choose the soil type. You have the choice between types A → E .
- Choose the building’s important class. You have the choice between I until IV. Depending on the important class, Diamonds will fill out a importance factor γl for you.
- If you choose ‘—‘, you will need to enter yourself a value for the importance factor γl.
- Enter the behaviour factors per direction qu, qv, qw.
- Ground acceleration
- Displacement factor
More information about these parameters can be found in the standard.
You can export and import a defined spectrum using 
and 
. Read here how to create a user defined spectrum.
Remarks:
- A seismic action is considered to act on all supports simultaneous.
- A seismic action can be removed with the button
. - If you have not obtained sufficient effective modal mass, you can
- Either try to recalculate the model but ask a larger number of eigen modes.
- Either select the option ‘Apply quasi static correction’.
All the results for the relevant directions with modal mass <90% will be divided by the mass obtained.
For example: 40% => results divided by 0,4.
- A seismic load is represented by the symbol below
. This symbol is always displayed in the XZ plane. With this symbol you’ll also find the following information: - The total mass [kg] taken into account when performing a seismic analysis. The total mass consists of:
- for Eurocode: the vertical components of the loads in load group x Ψ2 x φ-factor
The Ψ2 and φ-factor are defined in the window for the load groups
. - for CTE: the vertical components of the loads in load group x φ-factor
- for Eurocode: the vertical components of the loads in load group x Ψ2 x φ-factor
- A number of points
- A black point: centre of gravity of the total mass
- A blue point: centre of gravity of the mass due to the self-weight
- A red point: centre of gravity of the added mass
- You can show the distribution of the ‘self mass’ and the ‘added’ mass by selecting the options ‘Show self-weight’ and ‘Show mass’ in the window with the settings for the loads configuration
.
