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NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-1
BRIDGE TRUSS
WORKSHOP 5
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-2
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-3
● Workshop Objectives● Mesh curve geometry to generate CBAR elements ● Set up CBAR orientation vector and section properties● Set up multiple load cases● View CBAR stress components in Patran
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-4
● Problem Description● The preliminary design of a steel truss bridge has been completed.
You are asked to evaluate the structural integrity of this bridge.● The truss is made from steel with E = 30 x 106 psi and n = 0.3● The truss members are I-beams with H = 18 in, W = 12 in, Tf = 0.5
in, and Tw = 0.5 in ● The bridge needs to be able to support a 23,000 lb truck traveling
over it. The truck weight is supported by two planar trusses. Model one planar truss with half the truck weight applied to it.
● One end of the truss is pinned while the other end is free to slide horizontally.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-5
11,500 lb
(Subcase 1)
x
y
11,500 lb
(Subcase 2)
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-6
● Suggested Exercise Steps1. Create a new database named bridge_truss.db 2. Create the geometry of the truss using the table on the previous page3. Set Picking preference.4. Create a mesh seed of 6 elements per curve along the bottom of
truss (Y = 0) and of 2 elements per curve for the rest of the truss (Y > 0)
5. Create a finite element mesh of 2-noded bars and equivalence the model
6. Create a material property for steel: elastic modulus = 30e6 and Poisson’s ratio = 0.3
7. Create a 1D beam physical property● Apply the isotropic material to the model● Create an I-beam with dimensions as shown on page WS5-4 ● Orient the bars so the strong axis is vertical
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-7
● Suggested Exercise Steps (Cont.)8. Create boundary conditions
● Constrain all degrees of freedom except rotation about the z-axis at the left end of the truss
● Constrain all degrees of freedom except translation along the x-axis and rotation about the z-axis at the right end of the truss.
9. Create loads.● Create 11500 lb force in the negative Y direction on the node: X = 840, Y
= 0● Create another 11500 lb force in the negative Y direction, apply this load
to the midpoint of the truss. 10. Create two load cases.
● For first load case, select the displacement constraints and the load at X = 840.
● For the second load case, select the displacement constraints and the load at the mid-span.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-8
● Suggested Exercise Steps (Cont.)11. Run a linear static analysis with two subcases using the load cases
created in the previous step.12. Create fringe and deformation plots for both subcases. Record
maximum and minimum axial stresses, combined stresses, and deformations.
13. Examine the .f06 file. Verify that the displacement and stress results agree with the graphical results shown in Patran.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-9
Step 1. Create New Database
a
Create a new database called bridge_truss.db:
a. Under the Home tab click the New icon in the Defaults group.
b. Enter bridge_truss as the File name.
c. Click OK.d. Select Default for Tolerance.e. Select MD Nastran as the
Analysis Code.f. Select Structural as the
Analysis Type. g. Click OK.
d
f
g
e
b c
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-10
Step 2. Create Geometry
a
b
c
Create the first point:a. Under the Geometry Tab click
XYZ in the Points group.b. Enter [0 0 0] for the Point
Coordinate List.c. Click Apply.d. Under the Home tab, click the
Point Size icon in the Misc. group.
d
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-11
Finish creating all 12 points with the data from the table below
Step 2. Create Geometry (Cont.)
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-12
b
c
Step 2. Create Geometry (Cont.)
Create curves to represent the truss members:
a. Under the Geometry Tab click Point in the Curves group.
b. Screen pick the bottom left point as shown.
c. Screen pick the top left point. A curve will automatically be created, if Auto Execute is checked; else click Apply.
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-13
Step 2. Create Geometry (Cont.)
a. Finish creating all 21 curves.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-14
b
Step 3. Set Picking Preferences
Set Picking Preference:a. Preferences / Pickingb. Select Enclose entire entity
under Rectangle/Polygon Picking.
c. Click Close.
a
c
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-15
Step 4. Create Mesh Seeds
Create mesh seeds:a. Under the Meshing Tab click
Uniform in the Mesh Seeds group.
b. Enter 6 for the Number of Elements.
c. Click in the Curve List box.d. Click and drag mouse to
rectangular select the bottom of the truss.
e. Click Apply, if Auto Execute is not selected.
c
e
d
a
b
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-16
c
e
d
f
Step 4. Create Mesh Seeds
Create another mesh seed:a. Reverse the setting made in
Step 3. Select Enclose any portion of entity under Rectangle/Polygon Picking, then click Close.
b. Under the Meshing Tab click Uniform in the Mesh Seeds group.
c. Enter 2 for the Number of Elements.
d. Click in the Curve List box. e. Rectangular pick the rest of
the truss, as shown. f. Click Apply
b
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-17
b
c
d
e
Step 5. Create Mesh
Create a finite element mesh:a. Under the Meshing Tab click
Curve in the Meshers group.b. Set Topology to Bar2.c. Click in the Curve List box.d. Rectangular pick all of the
curves, as shown.e. Click Apply.
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-18
b
Step 5. Create Mesh (Cont.)
Equivalence the model:a. Under the Meshing Tab click
Equivalence in the FEM Actions group.
b. Click Apply.
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-19
Step 6. Create Material Properties
Create an isotropic material:a. Under the Properties tab click
Isotropic in the Isotropic group.
b. Enter steel as the Material Name.
c. Click on Input Properties.d. Enter 30e6 for Elastic
Modulus and 0.3 for Poisson Ratio.
e. Click OK. f. Click Apply.
d
e
b
c
f
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-20
b
f
c
d
Create element properties:a. Click Beam in the 1D
Properties group.b. Enter i_beam as the Property
Set Name.c. Click on Input Properties.d. Click on the Select Material
icon.e. Select steel as the material.f. Click on the Beam Library
button.
Step 7. Create Physical Properties
d
a
e
f
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-21
a
c
d
Step 7. Create Physical Properties (Cont.)
Define the beam section: a. Enter i_section for the New
Section Name.b. Enter the appropriate values
as shown to define the beam’s dimensions.
c. Click Calculate/Display to view the beam section and its section properties.
d. After verifying that the section is correct, click OK.
b
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-22
Note: Any vector in the XY plane that is not parallel to any truss member would work as well.
a
b
Step 7. Create Physical Properties (Cont.)
Define the bar orientation: a. Enter <1 2 0> for the Bar
Orientation.b. Click OK.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-23
a
b
d
e
c
f
Select application region:a. Click on Select Application
Region.b. Click in the Select Members
box.c. Rectangular pick the entire
truss, as shown.d. Click Add.e. Click OK.f. Click Apply.
Step 7. Create Physical Properties (Cont.)
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-24
b
e
g
ch
Step 7. Create Physical Properties (Cont.)
Verify the beam section:a. Display : Load/BC/Element
Props….b. Set Beam Display to 3D:Full-
Span.c. Click Apply.d. Right-click in the viewport
and select Viewport Display > Smooth Shaded from the context menu.
e. Rotate the model and zoom in to verify that the I-beams are oriented correctly.
f. Right-click in the viewport and select Model Orientation > Orthographic > Front View from the context menu.
g. Set Beam Display back to 1D:Line.
h. Click Apply again.
a
f
d
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-25
b
d
ec
Step 8. Create Boundary Conditions
Create a boundary condition:a. Under the Loads/BCs Tab
click Displacement Constraint in the Nodal group.
b. Enter left_side as the New Set Name.
c. Click on Input Data.d. Enter <0, 0, 0> for
Translations and <0, 0, > for Rotations.
e. Click OK.
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-26
e
c
d
Apply the boundary condition:a. Click on Select Application
Region….b. Select the bottom left point
as the application region.c. Click Add.d. Click OK. e. Click Apply.
Step 8. Create Boundary Conditions (Cont.)
a
b
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-27
b
c
d
e
Step 8. Create Boundary Conditions (Cont.)
a
Create another boundary condition:
a. Click Displacement Constraint in the Nodal group again.
b. Enter right_side as the New Set Name.
c. Click on Input Data.d. Enter < ,0,0> for Translations
and <0,0, > for Rotations. e. Click OK.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-28
a
b
c
Apply the boundary condition:a. Click on Select Application
Region.b. Select the bottom right point
as the application region.c. Click Add.d. Click OK. e. Click Apply.
Step 8. Create Boundary Conditions (Cont.)
d
e
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-29
c
b
d
e
Step 9. Create Loads
Create the mid span load:a. Click Force in the Nodal
group.b. Enter mid_span_load as the
New Set Name.c. Click on Input Data.d. Enter <0 -11500 0> for Force. e. Click OK.
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-30
a
d
e
f
b
Step 9. Create Loads (Cont.)
Apply the mid span load:a. Click on Select Application
Region.b. Set the geometry filter to
FEM.c. For the Application Region,
select the node in the middle of the span to the right of the center, as shown.
d. Click Add.e. Click OK.f. Click Apply.
c
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-31
b
c
Step 9. Create Loads (Cont.)
a
d
e
Create the truss joint load:a. Click Force in the Nodal
group again. b. Enter truss_joint_load as
the New Set Name.c. Click on Input Data.d. Enter <0 -11500 0> for Force. e. Click OK.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-32
a
b
d
e
f
Apply the load:a. Click on Select Application
Region.b. Set the geometry filter to
Geometry.c. For Application Region,
select the point at the center of the bridge, as shown.
d. Click Add.e. Click OK.f. Click Apply.
Step 9. Create Loads (Cont.)
c
c
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-33
b
c
d
e
f
Step 10. Set up Load Cases
Create a load case:a. Click Create Load Case
under Load Cases.b. Enter mid_span as the Load
Case Name.c. Click on Input Data.d. Click on Displ_left_side,
Displ_right_side, and Force_mid_span_load to add them to the Load Case.
e. Click OK. f. Click Apply.
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-34
a
b
c
d
e
Step 10. Set up Load Cases (Cont.)
Create another load case:a. Enter truss_joint as the
Load Case Name.b. Click on Input Data.c. Click on Displ_left_side,
Displ_right_side, and Force_truss_joint_load to add them to the Load Case.(if mid_span_load is still an assigned load / BC, click, and remove selected row)
d. Click OK. e. Click Apply.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-35
b
Step 11. Run Linear Static Analysis
Analyze the model:a. Under the Analysis tab click
Entire Model in the Analyze group.
b. Click on Solution Type.c. Select Linear Static as the
Solution Type. d. Click OK.
a
c
d
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-36
a
c
b
d
e
Step 11. Run Linear Static Analysis (Cont.)
Analyze the model:a. Click on Subcase Select.b. Select Unselect All to
deselect any existing Subcase.
c. Click on mid_span and truss_joint to add them to the Subcases Selected list.
d. Click OK.e. Click Apply.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-37
Step 11. Run Linear Static Analysis (Cont.)
Review the Nastran input file.a. Open the file
bridge_truss.bdf b. Review the two subcases.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-38
b
c
e
d
Step 12. Plot Displacements and Stresses
a
Attach the results file:a. Click XDB in the Access
Results group.b. Click on Select Results File.c. Select the results file,
bridge_truss.xdb.d. Click OK. e. Click Apply.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-39
d
e
b
c
Step 12. Plot Displacements and Stresses (Cont.)
Create a deformation plot for the mid span result case:
a. Under the Results tab, click Deformation in the Result Plots group.
b. Select the mid_span Result Case.
c. Select Displacements, Translational as the Deformation Result.
d. Check Animate. e. Click Apply.f. Record the maximum
deformation.g. Click Pause Animation and
Refresh Results Tools.Max Deformation = ____________
a
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-40
b
c
d
f
g
Step 12. Plot Displacements and Stresses (Cont.)
Create a Fringe Plot of X Component Axial Stress:
a. Click Fringe in the Result Plots group.
b. Select the mid_span Result Case.
c. Select Bar Stresses, Axial as the Fringe Result.
d. Select X Component as the Fringe Result Quantity.
e. Click on the Plot Options icon.
f. Set the Averaging Definition Domain to None.
g. Click Apply.
a
e
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-41
Step 12. Plot Displacements and Stresses (Cont.)
View the results:a. Record the maximum and
minimum X component axial stress.
Max X Axial Stress = _________________Min X Axial Stress = __________________
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-42
b
c
d
Step 12. Plot Displacements and Stresses (Cont.)
a
Create Fringe Plots of maximum and minimum combined bar stresses:
a. Click on the Select Results Icon.
b. Select the mid_span Result Case.
c. Select Bar Stresses, Maximum Combined as the Fringe Result.
d. Click Apply.e. Record the Maximum
combined stress. Max Stress= _______
f. Repeat the procedure with Bar Stresses, Minimum Combined as the Fringe Result and record the Minimum Stress. Min Stress = _______
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-43
c
d
b
f
Step 12. Plot Displacements and Stresses (Cont.)
a
e
Create a deformation plot for the truss joint result case:
a. Click Deformation in the Result Plots group.
b. Select the truss_joint Result Case.
c. Select Displacements, Translational as the Deformation Result.
d. Check Animate.e. Right-click in the viewport
and select Reset Graphics from the context menu.
f. Click Apply.g. Record the maximum
deformation.h. Click Stop Animation and
Refresh Results Tools.Max Deformation = ____________
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-44
Step 12. Plot Displacements and Stresses (Cont.)
f
a
b
c
d
e
g
Create a Fringe Plot of X Component Axial Stress:
a. Click Fringe in the Result Plots group.
b. Select the truss_joint result case.
c. Select Bar Stresses, Axial as the Fringe Result.
d. Select X Component as the Fringe Result Quantity.
e. Click on the Plot Options icon.
f. Set the Averaging Definition Domain to None.
g. Click Apply.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-45
Step 12. Plot Displacements and Stresses (Cont.)
View the results:a. Record the maximum and
minimum X component axial stress.
Max X Axial Stress = _________________Min X Axial Stress = __________________
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-46
a
b
Step 12. Plot Displacements and Stresses (Cont.)
Create Fringe Plots of maximum and minimum combined bar stresses:
a. Select Bar Stresses, Maximum Combined as the Fringe Result.
b. Click Apply.c. Record the Maximum
combined stress.Max Stress= _______
d. Repeat the procedure with Bar Stresses, Minimum Combined as the Fringe Result and record the Minimum Stress. Min Stress = _______
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-47
Step 13. Examine the .f06 File
Examine the .f06 filea. Open the directory in which
your database is saved.b. Find the file titled
bridge_truss.f06.c. Open this file with any text
editor.d. Verify that the displacement
and stress results agree with the graphical results shown in Patran.
This completes the workshop.
NAS120v, Workshop 5, November 2010Copyright 2010 MSC.Software Corporation WS5-48