The dimensions of the bars are:

-          Horizontal bars: Length 10m

-          Vertical bars:

o   External lateral bars: Length 5m

o   Internal lateral bars: Length 8m

o   Central bar: Length 9m

The boundary condition (restrictions) applied to the bridge truss (structure) are:

-    Node A: Fixed node

-    Node B: horizontal roller (Node that can move horizontally)

The loads applied to the structure are located in the following nodes:

-    N1, N5:               10 N

-    N2, N4:               10 N

-    N3:                      16 N

Once the problem to solve is defined, the DynamFluid proyect is created to model the simulation and its calculation.

Creating the Project in DynamFluid

To create the project in DynamFluid choose the Archive > New option menu. As Project Name BridgeTrussWithBars is used. The dialog box Project properties is shown.

Defining the nodes

The first step when creating the model for this structural problem is defining the points to locate the nodes used by the bars. These points are defined by the following coordinates:

When selecting the option menu Geometry > Point, the List of Points dialog box is shown:

Creating a point is done selecting the New button, which shows the dialog box Point.

After having introduced the coordinates in the dialog box, press Ok button. Repeat this process for each of the points where to place a node. Once all the points have been defined, press Ok button in the List of Points dialog box, which creates all the new points (Bear in mind that if the Cancel button is press all the introduced data is discarded).

Having defined the points, next step is defining the nodes, selecting the menu option Model > Structure > Node, which shows the List of Nodes dialog box.

Creating a node is done selecting the New button, which shows the dialog box Node.

Once the material properties have been defined, press Ok button. Next, press Ok button in the List of Material dialog box, which creates the material and saves the material properties in the model (bear in mind that if the Cancel button is pressed, all the introduced data are discarded).

The link between the material and the bars is the behaviour model object, which is defined choosing the Model > Behaviour menu option, showing the List of Behaviours dialog box.

Four behaviours are defined for the four type of used bars in the bridge truss (four different bar areas). Pressing the New button a new behaviour is created, for which a distinct Identifier is used (different than any already defined behaviour in the model).

The Type chosen for each behaviour is Rod, and in the Rod sheet the material properties are specified:

-          Rod Material Id: Identifier of the material

-          Area: Transversal area value of the bar. In this bar the following areas have been used:

o   Id Material 1:    1 m2

o   Id Material 2:    2 m2

o   Id Material 3:    3 m2

o   Id Material 10: 10 m2

After having introduced the values for the properties of the behaviour, press the Ok button, which adds the behaviour to the list of behaviours in the model. Then, press Ok button in the List of Behaviours dialog box, which saves the behaviours in the model (bear in mind that if the Cancel button is pressed, all the introduced data are discarded).

Defining the bars

After having defined the nodes, the next step in the process is defining the bars that link the nodes of the bridge truss. This process is done choosing the Model > Structure > Rod menu option, which shows the dialog box List of Rods.

A new rod is created selecting the New button, which shows the Rod dialog box. As identifier of the rod, a value not previously used is introduced. In the Properties tab sheet select the behaviour previously defined, and leave the default value of the rank of the element, 1 (linear element).

The behaviour to choose depends on the rod:

-          Horizontal rods:                           Behaviour with Identifier 2 (and transversal area 2 m2).

-          Vertical rods:                                Behaviours with Identifier 3 (and transversal area 3 m2).

-          Upper rods:                                   Behaviours with Identifier 10 (and transversal area 10 m2).

-          Diagonal rods:                              Behaviours with Identifier 1 (and transversal area 1 m2).

Insert two nodes defining the rod in the List of Nodes tab sheet (since the element is linear, with rank equal to 1).

Next, press Ok button. This action inserts a Rod element in the List of Rods dialog box. When all the Rods have been defined, press Ok in the List of Rods dialog box, which saves the list of defined rods in the model (bear in mind that if the Cancel button is pressed, all the introduced data are discarded).

Defining the constraints

The constrains (boundary conditions) are defined in the model selecting the Model > Constraints > Generic Constraint, which shows the List of Constraints dialog box.

Two restrictions have been defined:

-    A fixed node, with Identifier 1:

In this boundary condition, both directions are restricted (setting 0 as displacement value) and having ticked the Restricted check box for the component. This is the constraint that is applied to node A with Identifier equal to 1. To assign this boundary condition to Node A, choose menu option Model > Structure > Node, which shows the dialog box List of Nodes. Then select the row with Identifier equal to 1, and press Edit button. In the Node dialog box, select the Constraint tab sheet to assign the boundary condition just created to the Variable Index list box control equal to 1 (displacement) as Dirichlet Displacement.

Then press Ok button twice: in the Node dialog box and in the List of Constraints dialog box.

-    A roller restriction allowing the horizontal movement of the node, with Identifier equal to 2:

In this boundary condition, only the vertical displacement related to the Ref. Coord. System is restricted, setting as zero the vertical displacement. This is the boundary condition to apply to node B, with Identifier 7. To assign this boundary condition to Node B, choose menu option Model > Structure > Node, which shows the dialog box List of Nodes. Then select the row with Identifier equal to 7, and press Edit button. In the Node dialog box, select the Constraint tab sheet to assign the boundary condition just created to the Variable Index list box control equal to 1 (displacement) as Dirichlet Displacement.

Then press Ok button twice: in the Node dialog box and in the List of Constraints dialog box.

Defining the loads

For this problem, two types of loads are defined:

-          One load of 10 Newton in vertical direction downwards, applied to nodes N1, N2, N4 and N5.

-          One load of 16 Newton in vertical direction downwards, applied to the node N3.

These two loads are defined choosing the menu option Model > Source > Point source, which show the following dialog box List of Sources. The loads are created pushing the New button which shows the Source dialog box, where the components of the loads are defined. The following figures show the introduced values for the components of each defined source.

Left default value for the Scale factor (1). Pushing the Ok button, and afterwards the Ok button in the List of Sources dialog box, the loads are defined in the model.

Configuration of the simulation

After having followed the previous steps, the Project contains all the needed elements to perform the simulation (calculation). Navigating to the menu option Calculation > Configuration, the Simulation Configuration dialog box is shown, where the following options are used in for the static simulation:

Results

The results are obtained selecting the menu option Calculation > Solving, which:

-          Shows a dialog box with the progress of the simulation.

-          Inserts the logs associated to the executed action (The resolution of the problem starts / The resolution of the problem has finished).

In this problema two types of results are obtained: (a) The displacement in the nodes and (b) the reactions of the nodes.

The displacementes in the nodes can be shown graphically using the post-processing module integrated into the DynamFluid application. Just follow the following steps:

1. Configure the post-processing: Navigate through the Post-processing > Configuration menu. In the 'Post-processing Configuration' dialog select 'Displacement / Velocity' in the Variable drop-down list box, and configure the 'Identity' function as post-processing function. Press 'Ok' button.

2. Run the post-processing phase: Navigate through the Post-processing > Post-process menu. This runs the build-in post-processing module that applies the defined post-processing function.

The displacements are displayed in the model view. The colour indicates the magnitude of the displacement. A colour-scale is located in the side of the model view.

The size of the results can be changed navigating to the Edit > Properties menu option, and selecting the Scales tab sheet in the Properties dialog box, which specifies the scale for the results in the edit control Vector (in this case 5 has been used as scale).

The displacements can be exported into a clear-text file, for deeper analysis if required: Navigate to Archive > Export, which will show a dialog box to specify the file name for the file where the data is going to be exported. There are two types of text files the data can be exported into: .res type file format or .vtk type file format (Which can be imported in Paraview, i.e.).

Full contents of both files can be found at: (a)  BridgeTrussDisplacements.res, for the cleartext file, and (b)  BridgeTrussDisplacements00001.vtk, for the Paraview.vtk file.

Reactions in the restricted nodes also can be displayed in the model view. The following steps must be followed: 

1.  Configure the post-processing function: Navigate through the Post-processing > Configuration menu. In the 'Post-processing Configuration' dialog select 'Node Reactions / Pressure' in the Variable drop-down list box, and configure the 'Identity' function as post-processing function. Press 'Ok' button.

2.   Run the post-processing phase: Navigate through the Post-processing > Post-process menu. This runs the build-in post-processing module that applies the defined post-processing function.

The Reactions are displayed in the model view. The colour indicates the magnitude of the reaction. A colour-scale is located in the side of the model view.