Property modifiers for 1D and 2D members
Certain properties of both 1D and 2D members can be modified for the calculation using special attribute called Property modifier.
Properties that can be altered include:
- stiffness
- self weight,
Types of modifiers
Two types of Property modifiers available:
- for 1D members,
- for 2D members.
Practical application of the modifiers
Stiffness
In the dynamic analysis it is allowed to model cracked concrete using a simplified model whereby the cracked 1D members are taken as a % from the un-cracked ones. (EC8, IBC).
Stiffness
In tall buildings, the correct behaviour of the structure can be modelled by recalibrating the stiffness of specific 2D member which creates a more realistic model.
Mass
In the dynamic analysis, it corrects the mass of 1D members.
Weight
It represents an easy way to take account of the weight of coating on 1D members.
Property modifier factors
There are three property modifier factors:
Stiffness factors:
Refers to a record in the library of Stiffness factorswhich defines how the stiffness is modified.
Self weight factor:
Factor to modify the self weight of the member.
Mass factor:
Factor to modify the mass of the regarded member without affecting the self weight.
The value of the factors can be from interval 0 to 10.
Property modifiers for 1D members
Function Property modifiers 1D is available under Structure > Model data. It defines member data Property modifier 1D and assigns them to selected 1D members.
The function is available only if:
- functionality Property modifiers is selected in the Project Data dialogue,
- project type is one of following: Frame xz / Frame xyz / General xyz,
- at least one 1D member is available in the project file.
The display of the modifier and its labels are managed with the view parameters in the group Model:
- Other model data: displays the modifier,
- Labels of other model data: displays the labels.
Property modifiers for 2D members
Function Property modifiers 2D is available under Structure > Model data. It defines member data Property modifier 2D and assigns them to selected 2D members.
The function is available only if:
- functionality Property modifiers is selected in the Project Data dialogue,
- project type is General xyz,
- at least one 2D member is available in the project file.
The display of the modifier and its labels are managed with the view parameters in the group Model:
- Other model data: displays the modifier,
- Labels of other model data: displays the labels.
Transfer to FEM solver
The property modifiers are intended for linear analysis and affect linear, nonlinear and linear staged (including TDA) analysis, but they do not affect calculation of code dependent deformations (CDD).
Following physical properties are affected by the property modifiers:
Stiffness modifiers:
The program computes the stiffness’s of 1D and 2D members and then assigns them to the stiffness matrix for the linear solution of equations.
Weight modifiers:
The program computes the self weight (or line and surface load of type self weight). This weight is affected by the coefficient for modifying the self weight.
Mass modifiers:
The program computes the mass from the unit mass (material property) which is used in the eigenmode calculation. This mass is affected by the coefficient for mass modifiers
Remarks on property modifiers:
- A property modifier on a 1D member which has arbitrary beams defined affects all spans of the regarded members in the same way.
- A property modifier on a 2D member which has sub regions defined affects all sub regions of the regarded members in the same way.
- The direction of orthotropy follows the local member axis.
- Regarding the stiffness used in PGNL in case of 2D members and stiffness of 1D members, which are without PNL data or with linear behaviour, only one stiffness modifiers are applied for all analysis. The PGNL uses the linear solution for the calculation of the adapted stiffness’s. This linear solution can be affected by stiffness modifiers. Then PGNL runs without modifiers.
- Regarding the dynamic analysis, the stiffness affects all linear load cases in the same way.
Transfer to staged (including TDA) solver
Same logic is used as for the transfer to the FEM solver.