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Stadium Display Truss – TroubleshootingStadium Display Truss – Troubleshooting

Estimated time required: 35 min

Experience level: Higher

MD Patran 2005 r2

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What You Will Learn…What You Will Learn…

• The process of troubleshooting a database file so that the errors can be fixed and analyzed by MD Nastran

• Identifying key locations where mistakes could be found and fixing them.

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Problem DescriptionProblem Description

Your engineering team was given the task to design a stadium truss system to support a large stadium display. A FEA model has already been built by one of your co-workers but Patran will not create a bdf file and Nastran can not process the model. Clearly there are crucial errors in the development of the model. Open the database of the model and fix the mistakes of your co-worker.

• Truss is made from steel:

• Modulus of Elasticity = 30 x106 psi

• Poisson’s ratio = 0.3

• Yield Strength = 36 ksi

• Cross-sectional Area = 4.516in2

• Torsional Constant = 37.398 in4

• A 500 lb point load is applied at coordinate (60, 168, 0)

• The truss is bolted down at the Y=0 boundary in all translational and rotational directions

• Model the truss with rod elements

• Detail of the geometry is displayed in the next slide

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Problem Description – Geometry Details of the TrussProblem Description – Geometry Details of the Truss

500lbs

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Objectives of the AnalysisObjectives of the Analysis

• Find all 4 errors present in the original database

• Determine stress levels in the truss members under loading. The maximum stress must be below the yield point of the truss material

• Determine the maximum vertical displacement of the structure. The architect has specified that the maximum vertical movement of the scoreboard should not exceed 0.25 inch.

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Loading the Database FileLoading the Database File

a. Copy stadium_truss_wrong.db file to the default Patran folder (usually C:\windows\temp)

b. Start MSC.Patran

c. Under File menu click on Open

d. Double click o stadium_truss_wrong.db to open the database

e. Use the given information to find where the errors are.

c

a

d

b

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Showing/Modifying Node CoordinatesShowing/Modifying Node Coordinates

a

a. Click on Elements icon

b. Select Show / Node / Location from the drop down menus

c. In the Node List text field select all the truss structure

d. A new window will appear with the node locations information displayed on a table

To modify the node coordinate:

e. Select Modify / Node / Move from the drop down menu.

f. In the Node List text field select the node to be moved

g. In the New Node Location text field the new coordinate points should be entered (remember [ _ _ _ ] format)

b

c

d

e

fg

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Expected Results - StressExpected Results - Stress

To provide a way to verify that all the right corrections are made, verify your results by creating a x-direction stress fringe plot. If the values match the results shown below you will know that all the mistakes have been fixed.

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HintsHints

Things that you might want to check:

• Node coordinate locations

• Material properties

• Element properties

• Force being applied

• Boundary conditions

• Overlapping nodes/elements/curves