ANSYS - Structural Analysis/FEA
2D truss with inclined support and support settlement
Problem: Analyze the 2D truss as shown below. All the members have cross-sectional
area of 5000 mm2 and are made of steel with Young’s modulus 210000 MPa. The
settlement at support B is 10 mm. The roller at C is on a floor 45° from horizontal
direction.
(a)
If the applied force P is 200 kN, determine the member forces and stresses.
(b)
Determine the maximum value of P in which the maximum member force does
not exceed 600 kN.
2P
P
P
F
E
D
P/2
C
B
A
L = 3000 mm
H
G
45°
δ = 10 mm
L
L
1
Step 1: Start up & Initial Set up
Start ANSYS
Set Working Directory
Specify Initial job name: 2DTruss
Set Preferences: Structural
Set the unit system to SI by typing in “/units, SI” in the command line.
Check the output window for the units in SI system.
Step 2: Element Type and Real Constants
Specify element type: Main Menu > Preprocessor> Element Type > Add/Edit/Delete > Add
Pick Link in the left field and 2D Spar 1 in the right field. Click OK.
Click Close.
Main Menu > Preprocessor > Real Constants > Add/ Edit/ Delete, and click ADD
Enter the cross-sectional area as 5000E-6 m2
Click OK. Click Close.
Step 3: Material Properties
Main Menu > Preprocessor > Material Props > Material Models > Structural > Linear >
Elastic > Isotropic
Enter the Elastic modulus as 210Ee9 (Pa).
Save your work
File > Save as Jobname.db
Step 4: Modeling
Create Keypoints
Main Menu > Preprocessor > Modeling > Create > Keypoints > In Active CS
Enter the keypoint number and coordinates of each keypoint. Click Apply after each input.
Click OK when finish.
Note that: If the keypoint number is not blank, the program will automatically use the
smallest available number (that has not yet been specified)
Create Lines from Keypoints
Main Menu > Preprocessor > Modeling > Create > Lines > Lines >Straight Line
2
Select the two keypoints to be joined by the line.
Continue the same to construct lines.
Step 5: Meshing
Main Menu > Preprocessor > Meshing > Mesh Tool
There will be a Mesh Tool window pop up. In the third section Size Controls >Lines
Click Set.
Select Pick All.
Another window pops up. Enter the number of element divisions (NDIV) as 1. Click OK.
In the Mesh Tool pop up (fourth section), Mesh: Lines. Click Mesh.
Select Pick All
Then close the Mesh Tool window.
To see node and element numbering, use: Plot Ctrls >Numbering>Node Numbers and Plot
Ctrls >Numbering >Element/Attr Numbering
Choose Plot > Elements to see the elements and the nodes
Step 6: Specify Boundary Conditions & Loading
Main Menu > Preprocessor > Loads > Define Loads > Apply > Structural > Displacement >
On Nodes
Now select point A.
Select “ALL DOF” in the box showing DOF to be constrained.
Set Value as 0
Click Apply
Select point B. Constrain “UY” and set displacement value to -10e-3 m. Click OK.
Since the roller at point C is 45° from global x axis. We cannot apply the support directly.
We need to create a local coordinate system at point C in the orientation of the support.
Work Plane > Local Coordinate Systems > Create Local CS > By 3 Nodes
Read the instruction at the bottom of ANSYS window. It says Pick or enter 3 nodes: origin,
X axis and XY plane.
Choose the nodes in that order by clicking node 3, 5and 2, respectively (See figure below).
Note that node 5 defines the direction of the x-axis and node 2 defines the xy plane. The
direction of y-axis is perpendicular to the x-axis toward node 2.
3
2
3
1
After you clicked the 3 nodes, there will be a pop up window asking for Reference number of
new CS and its type. The Reference number starts at 11 by default. Choose Cartesian CS.
Click OK.
Select List > Other > Local Coord Sys. You can see that the Active CS is now CS no. 11
(which is the local CS we just created). CS number 0 to 6 are global CS. Check the origin and
orientation of CS 11.
4
Now we have to rotate the orientation of node 3 from global CS to the local CS
Main Menu > Preprocessor > Modeling > Move/Modify > Rotate Node CS > To Active CS
Pick node 3. Click OK
Next, constrain “UX” at node 3. Check the orientation of the triangle at node 3 (Plot > MultiPlots).
Apply Loading:
Main Menu > Preprocessor > Loads > Define Loads > Apply > Structural > Force/Moment >
On Nodes
Now select Node 4 and 6
In the menu that appears, select FY for Direction of force.
Enter -200e3 for Force/ moment value.
Click Apply.
Similarly, you can apply other forces.
You can check your applied loads by from the graphic window or
List > Load > Forces > On All Nodes
Step 7: Solve
Main Menu > Solution > Solve > Current LS
Click OK
Step 8: Post Processing
Plot Deformed Shape
Main Menu > General Postproc > Plot Results > Deformed Shape
Select Deformed+Undeformed
Click OK
5
Animate the Deformation
PlotCtrls > Animate > Deformed Shape
List Member Forces & Stresses
Main Menu > General Postproc > Element Table > Define Element Table > Add >
Select By Sequence number in the left list box, and SMISC in the right list box. Type “1”
after the comma in the box at the bottom of the window.
Click Apply
For member stresses, choose By Sequence num> LS, 1
Main Menu > General Postproc > Element Table > List Element Table >
Select SMIS1 and LS1
Click OK
Now you can see the element forces and the stresses .
List the Deflections and Reaction Forces
Main Menu > General Postproc > List Results > Nodal Solution
Click DOF Solution and in the sub-list select Displacement vector sum
Click OK
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Main Menu > General Postproc > List Results > Reaction Solution
Select All Items or All Structural Forces
Click OK
(b)
From (a), the maximum member force (consider both from compression and tension) for P
equal to 200 kN is 1146.4 kN. Since this is an elastic problem, you can find the maximum P
that the member forces do not exceed 600 kN simply by
Pmax = 200 × 600 = 104.7 kN
1146.4
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