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The material properties for use in an FE surface analysis are defined under the Material/Thickness tab within the FE Surfaces menu. There are four options for the material definitions. Isotropic materials have uniform properties in all directions, and as such the same Young's Modulus E and Shear Modulus G apply in all directions. Orthotropic materials have different material properties in three mutually perpendicular directions. In the case of the MasterFrame materials, the software requires the input of two Young's Moduli values along with three perpendicular Shear Moduli values. The layered material allows for the definition of different material properties within the cross section thickness of the section. The Ribbed material is for use when modelling composite floors with attached steel members. The deck dims are sued to modify the stiffness of the FE surface to account for the shape and direction of the profiled deck.
The Finite Elements are not material specific. While the most common use of FE surfaces in structural models is to model concrete elements, it is possible to model other materials, as long as the materials can be assumed to be adequately modelled using a 1st order linear elastic analysis.
The Material/Thickness area of the FE Surface menu can be accessed from MasterFrame by going to Properties>FE Surface Material Properties.
To enter the material properties for an isotropic material, select the Isotropic Materials tab. The materials properties can be input manually in each of the inputs. For an isotropic material the required inputs are:
E kN/mm² - the Young's Modulus or Elastic Modulus of the material. The required input units are
Poisson's ratio - the measure of lateral strain to longitudinal strain. Poisson's ratio is dimensionless
Density - the material density, input in units kg/m³. The density is used along with the FE surface thickness to calculate the self weight of the FE surface
G - the shear modulus or modulus of rigidity of the material. The input units are kN/mm². The shear modulus can be calculated from the Young's modulus G and the Poisson's ratio.
Fyc - the yield stress of the material under compression. The input units are N/mm²
Fyt - the yield stress of the material under tension. The input units are N/mm²
Of the above inputs, the Fyc and Fyt are optional. These values are used as part of the results, when looking at the Von Mises, Tresca, Drucker-Prager or Mohr-Columb stress results. The Fyc and Fyt values are not used as part of the analysis of the FE surface, where the analysis is based on the linear elastic value derived from the input Young's modulus.
An orthotropic material requires additional material properties to be input to define the material properties in two orthogonal directions. The local axes for the material definitions are shown below:
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The axis 1 (deg) defines the direction of axis 1 relative to the local x-axis. The z-axis is always coincident with the FE surface local z-axis. The material inputs are as follows:
E1 kN/mm² - the input for the Young's modulus E-value of the material to be taken in the direction of the 1-axis.
E2 kN/mm² - the input for the Young's modulus E-value of the material in the direction of the 2-axis.
Pois. ratio (21) - Poisson's ratio to apply for the horizontal plane stress and strain.
Density kg/m³ - the material density. The material density is used along with the Thickness to determine the self-weight of the FE surface.
G12 kN/mm² - The Shear modulus of the material in the 1-2 plane
G13 kN/mm² - The shear modulus of the material in the 1-3 plane
G23 kN/mm² - The shear modulus of the material in the 2-3 plane
Axis 1 (deg) - the angle theta of the orientation of the 1-axis relative to the local FE surface x-axis.
The layered material allows for the input of different materials in layer within a parent material. The parent material (within which the layers exist) and the layers are orthotropic. The layers form full layers within the depth of the parent material, so to model rebar in a concrete slab, the area of the reinforcement has to be modelled as a smeared plate, that is, the reinforcement is modelled as a thin plate of steel. It should be noted that this method accounts for the potential increased in stiffness of a layered material, but the analysis remains 1st order linear elastic with no account of creep or section cracking.
The Thickness of the main material layer is controlled by the the Thickness input. The main layer material inputs are the same as described above for an orthotropic material. The Main Mat. Name is simply a label to attach to the main material and is only used to assist checking the materials, it does not control the material properties.
The layer inputs are controlled by selecting the layer number from the material drop down. The software allows for the definition of up to 8 layers within a main material. For each layer selected, the additional material inputs Star z(mm) and End z(mm) control the position and depth of the layer. The depth z is measured from the bottom of the FE surface.
The overall depth of a layered material is controlled by the depth of the main layer, which is controlled by the Thickness (mm) input.
The ribbed material modifies the cross section properties to model a profiled cross section, such as occurs when using composite metal decks. The ribbed material is assumed to be isotropic, with the same material properties in all directions, with the section stiffness being based on the cross sectional area.
The dimensions of the ribbed profile can be input manually by typing in the required dimensions in the input area. These inputs are are
Rib depth (mm) - the height of the rib as measured form the bottom of the slab
Rib width (mm) - the width of the base of the rib
Rib spacing c/c (mm) - the spacing of the ribs
E kN/mm² - the Young's Modulus or Elastic Modulus of the material. The required input units are
Poisson's ratio - the measure of lateral strain to longitudinal strain. Poisson's ratio is dimensionless
Density - the material density, input in units kg/m³. The density is used along with the FE surface thickness to calculate the self weight of the FE surface
G - the shear modulus or modulus of rigidity of the material. The input units are kN/mm². The shear modulus can be calculated from the Young's modulus G and the Poisson's ratio.
Rib Axis to x (deg) - the orientation of the ribs, measured from the FE surface local x-axis.
The software contains a library of decks which can be used to automatically add the deck dimensions. The deck type is selected from the "Select Deck and Apply" drop down. Once the required deck is selected, clicking the .png){kind=small}
will automatically fill the required dimensions in the relevant material properties inputs.
The overall depth of a ribbed slab is controlled by the Thickness (mm) input.
To assist in selecting appropriate material values for use in the analysis, the software contains a number of pre-set material properties. These can be accessed by selecting the Material Library drop down. Once the required material is selected, clicking on the .png){kind=small}
icon will fill out the relevant parts of the materials inputs.
User defined materials can also be added to the materials library. To do this, select the material type using the Isotropic, Orthotropic, Layered or Ribbed material tabs, input the material name and material properties, and then click on the .png){kind=small}
icon. This will add the material to the library and, since the material library is saved on each PC, that material will be available in other models.
A material can also be deleted from the library by selecting the material from the drop down list and then clicking on the .png){kind=small}
icon.
When a material has been added to the model, whether or not the material is in the Material Library, that material is added to the Materials Used drop down. This allows for material definitions to be reused within a model quickly and easily. To apply a material from the Materials Used drop down, simply select the material required and then click on the button. This will the add the previously used material properties to the material property inputs for the currently selected FE surface.
The material factor inputs allows for a factor to be applied to the Young's modulus and Shear modulus for use with the serviceability load cases. This allows for an factor to the FE surface material properties to take account of cracking and/or creep in the serviceability load cases. This allows the deflections of the FE to be modified to take account of the long term effects of creep and cracking.
The Material factors can be be applied to all serviceability load cases, or, alternatively, the factors can be applied to specific load cases by setting the Material factor to be taken as on of the Load Groups N0-N9. The Material Factor is then included in a particular load case by including the appropriate Load Group with a factor of 1.0 in the Load Combinations.
The software includes the material factors:
1.0 - no adjustment to the material properties
0.5 - cracked section. The Section Elastic modulus is multiplied by 0.5 to account for cracking in the concrete cross section.
0.25 - cracked section and short term loading - modifies the elastic modulus by a factor of 0.25
0.167 - cracked section and long term creep - modifies the elastic section modulus by a factor of 0.167, to account for long term creep and cracking of the cross section.
A user defined value can also be input by clicking in the material factor input and then over typing with the required factor.
The global editing .png){kind=small}
icon allows the properties of multiple FE surfaces to be edited at once. The FE surfaces must match in material properties and thickness to the currently selected FE surface.