VisualAnalysis Tutorials: Basic Modeling Techniques
This tutorial introduces you to basic structural modeling in VisualAnalysis. You will see how to model "member elements' (beams and columns). The tutorial demonstrates a variety of methods for creating members and assigning their cross section and material properties.
Generating Structural Models
Sketching & the Edit Grid (Highly Recommended)
VisualAnalysis allows you to sketch a structural model directly on the screen which is a fantastic way to generate 2D models. Start a new project and make sure the Default Grid box is checked "Shown" (Grids tab of the Project Manager under the "Visibility" heading). Under the "Grids" tab, you may edit spacing values appropriate to your structure dimensions (the default is a 2ft by 2ft rectangular grid centered at the global origin.) For example, if you wish to draw a 2D bent frame with a 12ft story height and a 20ft beam span, you could set the edit grid to use 20ft spacing in X and 12 ft spacing in Y. You can then simply draw members by dragging the mouse between grid points in the Model View. Once you are finished generating the model, it is a good idea to turn off the edit grid to avoid accidentally creating additional members by un-checking the "Default Grid" box.
The sketch method also works great for creating 3D models. One quick technique for creating a 3D model is to sketch a 2D frame, select all of the members using Shift + Click, and then use the Model | Generate Copies command to repeat the frame in the out-of-plane (Z) direction. Once you have two or more frames created, you can rotate the view (Ctrl + Right Arrow, Ctrl + Down Arrow) to see both frames. New members in the Z direction between the existing frame nodes can then be sketched. In order to model in 3D, the structure type must either be a Space Frame (the default structure type) or a Space Truss. The model type can be edited in the "Modify" tab when nothing in the model is selected.
Other Methods of Generating Models
VisualAnalysis supports a number of other approaches for creating structural models, which may be more convenient for certain projects:
- Importing from a DXF file (File | Import DXF)
- Using Generate Standard (Create Tab)
These techniques are described in the help file and other tutorials.
Defining Member Shape Properties
VisualAnalysis supports three easy ways to assign member shape properties:
- Database Shapes (e.g., SS2x4, W8x10)
- Standard Parametric Shapes (e.g. Square, Rectangle)
- Custom Blobs (e.g. Raw Properties: A, I)
To specify that a member is a commonly available manufactured shape, you can use the Modify tab of Project Manager. Select the member or a group of members by holding Ctrl + Click (by default, the Shape Source should be "Database Shape"). Now double-click the ellipses button next to the Shape Type to select the member from the extensive library of steel, wood, aluminum, and cold-formed steel shapes. Database shapes may be added by using the Right Click context menu. Consult the User's guide for more information on editing the shape database.
Standard Parametric Shapes
An easy way to get a general shape into VisualAnalysis is to use a parametric shape with user specified dimensions. VisualAnalysis supports eleven types of "Standard Parametric' shapes: Square, Rectangle, Round, Pipe, Single Angle, Channel, Tee, I-Beam, Rectangular Tube, Spandrel and Zee. Next, Double-Click the ellipses button to bring up the Parametric Shape Dimensions Dialog, make your selection from the drop down menu, and enter in the desired dimensions.
If you are trying to achieve a specific Area or Moment of Inertia for a shape, enter in a dimension in one field and Click in another field. The shape properties shown at the bottom of the dialog will be updated for your use.
Custom Blobs (Raw Properties)
If you have custom shapes, the best approach is to create them in ShapeBuilder. This is a separate product from IES and is not included with VisualAnalysis. The "Custom Blob" is quick way of creating an undefined shape with a basic set of section properties. In the Project Manager under the Modify tab, specify the Shape Source as <Add Custom Blob>, which presents the following dialog:
A: Cross sectional area.
Iz, Iy: Strong and weak moment of inertia, respectively.
J: Torsion constant.
Sz(+y), Sz(-y), Sy(+z), Sy(-z): Section modulus for the four "edges".
SAz, SAy: Optional, shear areas for shear
deformation effects, may be zero.
In a Plane Frame or Plane Truss, the critical values are A, and Iz. For a 3D model (Space Frame or Space Truss) VisualAnalysis needs: A, Iz, Iy, and J. The section modulus values must be "reasonable' (e.g. greater than zero), they are used to calculate member stresses. The shear areas are there if you are solving "deep beam" problems where shear deformation effects are important, they can be safely ignored (left at zero) for most projects!
Assigning Material Properties
Assigning material properties to members is easy and flexible in VisualAnalysis. If you select a database shape for a member, the material is automatically assigned based on the default material specified for shape categories. For some shape types you encounter, you will need to explicitly set the material.
VisualAnalysis ships with an extensive database of typical construction materials: steel, concrete, wood, aluminum, and much more. We have also included some special materials like "weightless steel" for when you don't want to automatically model the effects of self-weight in some members. Chances are the material you need is already in the database!
Add New a Material
If you do need a non-standard material, it is very easy to create a new material. With a member selected, find the Modify tab in the Project Manager, and Double-Click the ellipses button next to the Material Name to open the "Choose Material" dialog box. It the bottom right corner, Click the "Add New Material" button and you will be presented with a dialog box to define the material properties:
You should name your material, specify a color (for when Picture View filter is displayed) and pick the category of materials in the database in which the material will belong. Next define values for all these properties:
E: Modulus of elasticity (> 0)
nu: Poisson's ratio, (>0, <0.5), 0.2 is a typical value
alpha: Thermal coefficient (>0), 1.0e-6 is a typical value
gamma: Density (>0).
Please note that it is important to input values that are reasonable with how the desired material will behave. For example in the basic structural analysis, Modulus of Elasticity and Poisson's ratio should be reasonable as they are used internally to calculate other properties such as Shear Modulus. The material you create is added to the material database for use on future projects. Each material category has an associated .dbm file that may be distributed to colleagues who need to use your custom materials. Please refer to the User's Guide for details on file locations and operations.