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Response spectrum generator according to CSN (Czech standard)

Procedure to input a new CSN seismic spectrum

1. Expand branch Libraries of the main tree menu.
2. Expand sub-branch Loads.
3. Start function Seismic spectrum to open the Seismic Spectrum Manager.
4. Click button New.
5. In combo box Input type select option CSN - Czech standard.
6. Review and, if required, adjust the spectrum parameters.
7. Click button Code parameter to review or modify the code-defined parameters of the spectrum.
8. Confirm the code parameters with OK.
9. Click OK to confirm the spectrum.
10. Close the Seismic Spectrum Manager.

Spectrum definition and code parameters

A response spectrum can be defined according to CSN by selecting CSN - Czech standard as Input type.

Max frequency & Step

The values of the spectrum are generated between a maximum period of 4 seconds (=0.25 Hz) and the input maximum frequency, using the input Step value.

Code parameters

This button opens the dialogue defining the code-dependent parameters.

coeff. accel. ag

Value of the design acceleration expressed as a multiple of the acceleration of gravity g

Ag - nominal acceleration

Nominal ground acceleration

n - Eta (damping coefficient)

Damping correction coefficient

E - Xi (relative damping coefficient)

Relative damping coefficient, given in % (typical value is 5%)

Tb, Tc, Td, S, Beta, k1, k2 manually?

When this setting is No, the values Tb, Tc, Td, beta0, k1, k2, S are calculated

When this setting is Yes, the values Tb, Tc, Td, beta0, k1, k2, S are input manually

Subsoil type

Ground type (A, B, C)

Tb

Lower limit of the period of the constant spectral acceleration branch

Tc

Upper limit of the period of the constant spectral acceleration branch

Td

Value defining the beginning of the constant displacement response range of the spectrum

k1

Exponent for the T_C-T_D branch

k2

Exponent for the long period branch (T>T_D)

S - soil factor

Soil factor

beta0

Amplification factor for type A subsoil

Theoretical background

The seismic spectrum is defined as

The damping correction factor is calculated as

The values S, Tb, Tc, Td are defined according to the subsoil type (unless defined manually)

The values k1, k2 and beta0 are set by default (unless defined manually)

Although the formulation slightly differs, with the default values of k1, k2 and beta0, the definition of the spectrum is exactly the same as the elastic response spectrum of the EN1998-1:2004

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