NTC 2018 Seism loads family

The NTC 2018 Seism family is created when the NTC 2018 - Italy standard is selected for the current project.

NTC 2018 Seism family properties

NTC 2018 Seism loads family - Properties

Name: the default name of the family.
No.: displays the ID number of the family.
Spectrum: allows the selection of the spectrum type: Elastic, Design or User defined.

Note

To edit the spectrum parameters, select User defined from the Spectrum drop-down list.

Ground acceleration agr m/s2: maximum horizontal ground acceleration (according to NTC 2018, chapter 3.2), agr/g (IMR = 100 years)
Amplification factor F0: maximum value of the amplification factor of the spectrum in horizontal acceleration (according to NTC 2018, chapter 3.2)
Period Tc*: upper limit of the period at spectrum's constant speed in horizontal acceleration (according to NTC 2018, chapter 3.2)
Topographic category: set the topographic category in order to set the ST amplification coefficient. Values are according to Table 3.2.V from NTC 2018 norm.
Soil type: allows the definition of the soil type according to table 3.2.V from NTC 2018 norm.
Ss - soil parameter: allows the definition of the soil parameter.
Imposed value Tb: lower limit of the period of the constant spectral acceleration branch (according to NTC 2018, art. 3.2.3.2.1).
Imposed value Tc: upper limit of the period of the constant spectral acceleration branch (according to NTC 2018, art. 3.2.3.2.1).
Imposed value Td: value defining the beginning of the constant displacement response range of the spectrum (according to NTC 2018, art. 3.2.3.2.1).

γI - Importance coefficient: coefficient relative to the consequences of a structure failure.
Horizontal q (x and y): behavior coefficient in the x and y directions.
Vertical q: behavior coefficient in the z direction.
Damping correction: by default, the program calculates the damping correction of the NTC 2018 spectrum. When disabled, the damping correction is not applied. According to NTC 2018, art. 3.2.3.2.1, the damping correction formula (3.2.4) is:

β: coefficient corresponding to the lower limit of the horizontal calculation spectrum.
Ductility class: select the ductility class, DCM (medium) or DCH (high).

Horizontal spectrum (x and y): the button provides access to the Function editor dialog box, where the horizontal spectrum parameters (on x and y directions) can be viewed or defined.
Vertical spectrum: the button provides access to the Function editor dialog box, where the vertical spectrum parameters can be viewed or defined.

Method: allows the selection of the mode superposition method (i.e., CQC or SRSS).
Residual mode: enables / disables the residual mode.

Define properties that are taken into account when generating concomitance combinations. See Configuring load cases combinations.

Group loads: when enabled, each load case inherits "combinations" properties from the corresponding load case family and will be grouped as a generic load case in the concomitance matrix.
Effect: sets the load case as "Leading", "Accompanying" or both.
Coefficient γ EQU: partial factor for seismic action considered in the EQU ultimate limit state (see chapter 2.6.1 from NTC 2018)
Coefficient γ STR: partial factor for seismic action considered in the STR ultimate limit state (see chapter 2.6.1 from NTC 2018)
Coefficient γ GEO: partial factor for seismic action considered in the GEO ultimate limit state (see chapter 2.6.1 from NTC 2018)
Ψ0 coefficient: factor that defines the combination value of a variable action (see chapter 2.5.2 from NTC 2018)
Ψ1 coefficient: factor that defines the frequent value of a variable action (see chapter 2.5.2 from NTC 2018)
Ψ2 coefficient: factor that defines the quasi-permanent value of a variable action (see chapter 2.5.2 from NTC 2018)

Tip

Click a section of the properties window. Notice the bottom area of the window; it displays a short description of the active cell's content.

After creating a seism family: in the Project Browser, expand the Loading group and select Earthquake NTC-2018.