Question
How to create a composite filler beam section (steel girder encased in concrete) for correct analysis and design? In the Section database of CIVIL NX this type of section is apparently not available.
Answer
A composite filler beam section can be defined as composite general section from the Composite tab of the Section Data located in Section Properties (see picture below). Using such method will also unlock special features like Composite Section for Construction Stage and the automated Composite Steel Girder Design.
Before doing that, the composite general section shall be created in the built-in tool named SPC (Section Property Calculator) according to the following steps.
- Step 1) Open SPC
Apps > Section Property Calculator > Set Unit System > OK
- Step 2) Define Materials for Composite Section
Model > Material > Add > Define material property
Please, note that the material properties shown above have been defined according to Units : kN, m
- Step 3) Create geometry of the section.
This can be done in two ways:
Drafting manually directly in SPC: Model > Curve > Create > Line
Importing AutoCAD dxf file (recommended) : File > Import > AutoCAD DXF
For both methods, change the width of the girder elements to the real thicknesses:
Model > Curve > Change Width > Input width of the elements one by one > Apply
- Step 4) Generate Composite Section
- Model > Section > Composite Section > Generate
- Input Name, No. of parts ("2"), Base Material ("Steel") > Apply
- Step 5) Add the two Parts to the Composite Section:
Model > Section > Composite Section > Add Part
-
- For Steel: Select the steel elements as shown below;
Input > Part Name > Part Type ("Line") > Part Material > Apply
-
- For Concrete: Select all the area of the concrete slab excluding the steel parts as shown below;
Input > Part Name > Part Type ("Plate") > Part Material > Apply
- Step 6) Calculate Composite Section Property:
Property > Calculate Composite Property
Input Mesh Size > Select only one part of the Composite > Apply
>>> Change the mesh size if error about improper mesh is shown
- Step 7) Generate Steel Design Group :
Model > Section > Steel Design Group > Generate > Input Number of groups > Apply
- Step 8) Add Elements to Steel Design Group :
Model > Section > Steel Design Group > Add > Select each design group separately > Select the corresponding element > Apply
Repeat this step for every steel element
- Step 9) Export Composite Section:
Model > Section > Composite Section > Export
Click on 3 dots > Input File Name & Save > Select only one part of Composite > Apply
- Step 10) Import Section in Midas CIVIL NX:
Properties > Section Properties > Add > Composite > Input Name > Section type:
Composite General > Import the SEC File previously created > Select File > Open > OK
Once the section has been imported in CIVIL NX and the model and analysis have been completed, the Composite Design of the filler section is possible after having defined Flange and Web of the steel section.
This step is necessary to design every composite section defined as general, as also explained in the CIVIL NX manual (see screenshot below):
Follow the below steps to define Flange and Web:
The definitition of Flange & Web is the mandatory step to be done before being able to perform the composite section (general) design.