This tutorial was created using ANSYS 7.0 to solve a simple 2D Truss problem. This is the first of four introductory ANSYS tutorials.

Determine the nodal deflections, reaction forces, and stress for the truss system shown below. Note that Young's Modulus, E, is 200GPa while the crass sectional area, A, is 3250mm2 for all of the elements.

Truss Bridge Geometry

(Modified from Chandrupatla & Belegunda, Introduction to Finite Elements in Engineering, p.123)


! ANSYS command file to perform 2D Truss Tutorial (Chandrupatla p.123)
!
/title, Bridge Truss Tutorial
/PREP7                  ! preprocessor phase
!
! define parameters (mm)
height = 3118
width = 3600
!
! define keypoints 
!
K,1,    0,   0               ! keypoint, #, x, y
K,2,   width/2,height 
K,3,     width,  0
K,4, 3*width/2,  height
K,5,   2*width,   0 
K,6, 5*width/2,  height
K,7,   3*width,  0
!
! define lines
!
L,1,2                   ! line connecting kpoint 1 and 2
L,1,3
L,2,3
L,2,4
L,3,4
L,3,5
L,4,5
L,4,6
L,5,6
L,5,7
L,6,7
 
!
! element definition
!
ET,1,LINK1              ! element type      #1; spring element
R,1,3250                ! real constant     #1; Xsect area: 3200 mm^2
MP,EX,1,200e3          ! material property #1; Young's modulus: 200 GPa

LESIZE,ALL, , ,1,1,1    ! specify divisions on unmeshed lines
LMESH,all               ! mesh all lines
!
FINISH                  ! finish pre-processor
!
/SOLU                   ! enter solution phase
!
! apply some constraints
DK,1,ALL,0        ! define a DOF constraint at a keypoint
DK,7,UY,0 
!
! apply loads
!
FK,1,FY,-280e3          ! define a force load to a keypoint
FK,3,FY,-210e3          
FK,5,FY,-280e3          
FK,7,FY,-360e3          
!
SOLVE                   ! solve the resulting system of equations
FINISH                  ! finish solution

/POST1
PRRSOL,F                ! List Reaction Forces
PLDISP,2                ! Plot Deformed shape
PLNSOL,U,SUM,0,1        ! Contour Plot of deflection

ETABLE,SAXL,LS, 1         ! Axial Stress
PRETAB,SAXL               ! List Element Table
PLETAB,SAXL,NOAV          ! Plot Axial Stress