Saturday, 18 August 2018

# Truss Analysis-Static Analysis of Structural Truss System in ANSYS APDL

Truss Analysis-Static Analysis of Structural Truss System in ANSYS APDL:The main aim of  Static Analysis of Structural Truss System is to determine the Nodal Deflections,Reaction forces,Stresses induced in the Truss system etc.under the application of external forces.In order to do Truss Analysis under the Application of External forces in ANSYS Software,we require 4 steps.
I.Preferences
II.Preprocessor
III.Solution
IV.General Post Processor.

## Numerical for Truss Analysis:

Determine the Nodal Deflections,Reaction forces and stresses of a Truss system whose Area = 3250mm2,Youngs Modulus(E)=2X105 and Poisson’s Ratio(µ)=0.3.

## Truss Analysis-Procedure to perform Static Analysis of Truss System:

The step by step procedure of Truss Analysis is to perform Static Analysis of Structural Truss System in APDL is as follows.

This can be analyzed in ANSYS Mechanical APDL 15.0 under four stages and are follows.
I.Preferences
II.Preprocessor
1. Element Type
2. Real Constants
3. Material Properties
4. Modeling
5. Sections
6. Meshing
III.Solution
1. Analysis Type
2. Solve
IV.General Post Processor.
1. Plot Results
2. List Results
3. Element Table
The detailed explanation of Truss Analysis under these four stages are as follows:
I.PreferencesStructural-ok.

### II.Preprocessor:

The Element Type,Real constants,Properties of materials,Creating a model,meshing,application of loads etc.was given to the material in Pre-Processor.

ELEMENT TYPE:

REAL CONSTANTS:

MATERIAL PROPERTIES:

Material Models–>Structural–>Linear–>Elastic–>Isotropic –>Provide the Young’s Modulus (E= 2X105) and Poisson’s Ratio (µ) =0.3–>OK.

MODELLING:

Create–>Keypoints –> In Active CS–>Provide the Keypoints 1,2,3,4,5,6 & 7 and give their respective values in X,Y&Z Direction as shown below.

 Keypoints X Y Z 1 0 0 0 2 1800 3118 0 3 3600 0 0 4 5400 3118 0 5 7200 0 0 6 9000 3118 0 7 10800 0 0

Lines:

Lines–>Lines–>Straight Lines–>Now Select the keypoints 1&2,2&3 etc. such that the construction of Truss must be completed with Lines.

MESHING:

Now,you need to mesh the whole Truss system so that the load applied on the Truss can be distributed Uniformly on all elements and For Meshing any Component,you need to provide the “Element edge length” or “No.of Element divisons” depending upon the component imported or drawn into the ANSYS Software.Under Meshing Option,You need to use both Size Ctrls and Mesh option for meshing.

• Size Cntrls–>Manual Size–>Lines–>All Lines–>No.of Element divisons=1(Only for Truss)–>OK.

As you had given the “No.of Element divisons =1” which means that the total Truss system will divide into 1mm equally so that the load can be distributed uniformly on the whole structure.

• Mesh–>Lines–>Click on ‘Pick All’ in the Dialogue box.By Clicking on Pick All button,the software can mesh the body completely.

Constraining the Truss and Application of Loads:

• Define Loads–>Apply–>Structural–>Displacement–>On Keypoints–>Pick the 1st Keypoint–>Apply–>Click on All DOF(Constrained in all Directions)–>OK.

Now,Constrain the structure at Keypoint 7,For that

• Define Loads–>Apply–>Structural–>Displacement–>On Keypoints–>Pick the 7th Keypoint–>Apply–>Click on UY & UZ and Don’t constrain in Ux direction(slider support).

Forces:

Now Apply the forces on the Truss so as to see how much amount of stress is induced in the truss system and was as follows.

• Define Loads–>Apply–>Structural–>Force/Moment–> On Keypoints–>Now select the Preferred Keypoint for the Application of Force.

In this Truss System,the Force is applied at 1,3,5,7 Keypoints of 280KN,210KN,280KN and 360KN respectively in the vertical direction(Downward)as shown in the below figure.So,Take the units of Force interms of Newtons i.e.

(FY) = -280000N,(FY) = -210000N,(FY) = -280000N and (FY) = -360000N

As every parameter was given to the Truss system,its the time to solve it.

III.SOLUTION

• Analysis Type–>New Analysis–>Static Analysis–>OK.
• Solve–>Current LS File–>OK–>Solution is done.

To Check the Results,go to General Post Processor,where you can get the results on Deformation of the structure.

GENERAL POST PROCESSOR:

• Plot Results–>Deformed Shape-->Def+Undeformed Model–>Ok.
• Plot Results–>Contour Plot–>Nodal Solution–>DOF Solution–>Check the Displacement of the structure in X,Y,Z Components and Displacement Vector Sum to get the overall Displacement in all the directions.
• Plot Results–>Contour Plot–>Nodal Solution–>Stress-->Check the stress induced in the structure at X,Y,Z Components along with Von Mises stress.As you had observed,that the truss is not at all showing the values of Stresses.Therefore we need to create the Element Table.

ELEMENT TABLE:

Finding Stress:

In this Table,we need to add the Keyword and Value for the Structural Analysis of Truss to check the stress induced and was shown below.

General Post Processor–>Element Table–>Define Table–>Add–>Now,provide these Details..

• User Label for Item   –  Stress
• Results Data Item      – By Sequence No.
• Keyword -LS & Value – 1

Now Close this Tab and check the results in

Plot Results–>Contour Plot–>Line Element Results–>

• Element Table Item at Node i    –   Select Stress
• Element Table Item at Node j    –   Select Stress
• Items to be plotted on                –   Deformed Shape   –>OK.

List Results:

Reaction Forces:

General Post Processor–>List Results–>Reaction solutions–>All structural Forces–>OK.Now you can get the Reaction forces at Keypoint 1 and 7.