NTC-2018 Wind loads family

 

The NTC-2018 Wind loads family is created when the Italian climatic standard NTC-2018 is selected for the current project.

NTC 2018 Wind loads family - Properties

Family

• Name: the default name of the family.

• No.: displays the ID number of the family.

Automatic generation

Allows enabling / disabling the automatic wind generation components (i.e., loading areas exposure, split loading areas, loads generation, automatic Cpe and Cpi calculation).

Wind direction: Select the wind direction (WindX+, WindX-,WindY+, WindY-)

• Cpe type: Lets the user impose the type of the external pressure coefficients (cpe) are extracted from the tables. Values for cpe,1 are intended for the design of small elements and fixings with an area per element of 1 m2 or less such as cladding elements and roofing elements. Values for cpe10 may be used for the design of the overall load bearing structure of buildings.

- Default cpe calculation. By using this option, the cpe is chosen based on the area of the load area (and the coplanar ones).

* If the area A <= 1 m2 then cpe = cpe1

* If the area A >= 10 m2 then cpe = cpe10

* else the Figure 7.2 is used:

- cpe10. Only the cpe10 values are extracted from the tables.

- cpe1. Only the cpe1 values are extracted from the tables.

• Wind definition: Lets the user define the wind properties differently per wind direction.

- per direction:: The user can define parameters for each wind direction.

- all directions: The fields are defined the same for all directions.

• Current wind direction: This represents the direction for which the user defines or views parameters.

Dynamic base pressure

• Wind speed regions: defines the wind region. Each region has its own wind pressure and speed coefficients. The button displays the wind regions map and allows the selection of the corresponding region.

Regions for NTC 2018 wind loads family

• Wind speed: displays the wind speed (in m/s) according to the selected region. A custom value can be set by selecting Other from the Wind speed regions category.

• Pressure: the wind pressure value, automatically calculated according to the wind speed value.

• Altitude: defines the altitude of the building location.

• Dynamic factor Cd: dynamic factor for wind according to 3.3.9 from NTC 2018. It can be conservatively assumed to be equal to 1 in recurring constructions, such as regular buildings not exceeding 80 m in height and industrial buildings, or it can be determined by specific analyses or by referring to data of proven reliability.

• Building height: allows the definition of the height of the building. If it is set to 0 m (the default value) then after the automatic generation of the loads it is filled with the automatic detected value. If the imposed value is higher than the building qpz determined in the calculation is influenced by this value.

• Tr (years): return period TR.

• Site exposure category: site exposure category according to 3.3.7 from NTC 2018.

• Roughness length z0: the specific value, according to the terrain category.

• kr: terrain factor according to table 3.3.II from NTC 2018.

Site effect

• Topographical factor: the increase of wind speed in special topographic conditions.

Dynamic effect

• Exposure factor ce(z) (informative for the imposed building height above): according to chapter 3.3.7 from NTC 2018, it depends on the height z on the ground of the considered point, the terrain topography and the exposure category of the site where the building is located.

• Peak velocity pressure qp(z) (informative for the imposed building height above): includes mean and short-term velocity fluctuations.

Combinations

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/GEO: partial factor for seismic action considered in the STR/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)

Color

• View / change the representative color for the family.

 

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.

Accessing the properties

After creating a wind load case family: in the Project Browser, expand the Loading group and select Wind NTC-2018.