Stiffness factors library
Libraries for stiffness modification definitions
Two libraries: Stiffness factors 1D and Stiffness factors 2D are available under Libraries > Structural analysis.
The library item contains a set of coefficients which define how the modified stiffness properties are to be computed.
Four different logics are available to define the values of the properties, depending on the definition type: Standard; Bending; Axial; Percentage
- Standard : All properties are displayed.
- Bending : Only the bending properties are displayed. The "not-displayed" properties are not affected.
- Axial : Only the properties for axial stiffness are displayed. The "not-displayed" properties are not affected.
- Percentage : Reduction percentages for “Axial” and “Bending” are displayed.
Stiffness factors 1D
With a Stiffness factor 1D library item, the user defines how the stiffness is modified for a 1D member. For each definition set, the user can set a description to recognize easily the considered data set.
In case of 1D members, the program requires coefficients for all the properties of a cross section:
Ax ,Ay, Az, Ix, Iy and Iz. Then, the modified properties are computed as:
Property_(solver) = Coefficient x Property_(1D member)
Case “Type” is “standard”:
The user defines the stiffness modification by entering values for coefficients {Ax ,Ay, Az, Ix, Iy, Iz} as a real number between 0 and 10. The program multiplies the cross section properties with the inputted coefficients.
Case “Type” is “Bending”:
Only the bending properties modifier coefficients Iy and Iz are displayed. For these the user is allowed to define the stiffness modification by inputting a real value between 0 and 10. The other properties get a coefficient 1.
Case “Type” is “Axial”:
Only the axial property modifier coefficient, Ax, is displayed. For this the user is allowed to define the stiffness modification by inputting a real value between 0 and 10. Other properties get a coefficient 1.
Case “Type” is “Percentage of stiffness”:
The user defines the corrections of “axial” and “bending” stiffness as percentages (of the values computed from the defined cross section properties).
Therefore:
- Two fields are displayed “Axial stiffness” and “Bending stiffness”
- Both fields expects a percentage (as a value between 0 and 1000)
- By default 100% is used (which means “no correction”)
- The fields Ax, Ay, Az, Ix, Iy, Iz (which are read only) displays the coefficients which are computed from “Axial” and “Bending” as bellow:
Ax =PA/100
Ay =1
Az =1
Ix =1
Iy =PB /100
Iz =PB/100
Axial stiffness[%] = PA
Bending stiffness[%] = PB
Stiffness factors 2D
With a Stiffness factor 2D library item, the user defines how the stiffness is modified for a 2D member. For each definition set, the user can set a description to recognize easily the considered data set.
In case of 2D members, the program requires coefficients for all the properties of orthotropy:
D11 ,D12, D22, D33, D44, D55, d11, d12, d22 ad d33. Then, the modified properties are computed as:
Property_(solver) = Coefficient x Property_(2d member)
Four different logics are available to define the values of the properties, depending form the definition type: Standard; Bending; Axial; Percentage
Case “Type” is “standard”:
The user defines the corrections of the stiffness as a coefficient. This coefficient multiplies the isotropic stiffness properties as computed from 2D member geometry and assigned material.
The user defines the stiffness modification by entering values for coefficients {D11 ,D12, D22, D33, D44, D55, d11, d12, d22, d33} as a real number between 0 and 10. The program multiplies the isotropic properties with the inputted coefficients.
Case “Type” is “Bending”:
Only the bending properties modifier coefficients, D11, D12, D22 and D33 are displayed. For these the user is allowed to define the stiffness modification by inputting a real value between 0 and 10. Other properties get a coefficient 1.
Case “Type” is “Axial”:
Only the axial property modifier coefficients, d11, d12, d22 and d33, are displayed. For these the user is allowed to define the stiffness modification by inputting a real value between 0 and 10. The other properties get a coefficient 1.
Case “Type” is “Percentage of stiffness”:
The user defines the corrections of “axial” and “bending” stiffness as percentages of the isotropic stiffness properties computed from 2d member geometry and installed material.
Therefore:
- Two fields are displayed “Axial stiffness” and “Bending stiffness”
- Both fields expects a percentage (as a value between 0 and 1000)
- By default is installed 100% (which means “no correction”)
- The fields D11, D12, D22, D33, D44, D55, d11, d12, d22, d33 (which are read only) displays the coefficients which are computed from “Axial” and “Bending” as bellow:
D11 =PB/100
D12 =PB/100
D22 =PB/100
D33 =PB/100
D44 =1
D55 =1
d11 =PA/100
d12 =PA/100
d22 =PA/100
d33 =PA/100
Axial stiffness[%] = PA
Bending stiffness[%] = PB