Engineering Programs

Engineering Analysis & Design

Analysis of GFRC in Ansys APDL

April 27, 2012

Following is link contain APDL code for GFRC. It will be modified for better post processing result and topology optimization.

Download Ansys APDL file for Analysis of GFRC

The preview of above inp file is show below.

This APDL code is available for mentoring. Comment for your suggestions and improvements.

Analysis of GFRC in Ansys APDL

!Ansys APDL for GFRC
!
!!
!=======================================================
!Start of Solution
!=======================================================
!
!***** Author: Engr. Faisal ur Rehman *****
!*** enggprog.com – Engineering Programs ***
!
!
!27-04-12
!
!License under GNU/GPL V3 – gnu.org/licenses/gpl.html
!
!——-
!Goals:
!——-
!What’s Achieved: Demo for APDL modeling to analysis to Postprocessing.
!What’s Next to be added: Stress Distribution on Cross-section, P Delta plot.
!
!
!=============================================================
!Note: Ignore Warnings. Analysis is non linear. Approx Analysis time is 3 minutes.
!=============================================================
!
!=============================================================
!Start of File
!=============================================================
!

/Title, GFRC – By FR
/PREP7

Length=3048
D=152.4 !152.4panel depth= 6inch
n=7 ! number of triangular openings (Type A in Report) at the bottom of the panel
Tt=12.7 ! 0.5 inch thick top leaf
Tb=12.7 ! 0.5 inch thick bot leaf
Tl=12.7 ! 0.5 inch thick truss leaf
Ll=142.875! 5-5/8 inch truss member length

Lc=25.4/4 ! chamfer length= 0.25 inch

Wt=2*sqrt(Ll**2-(D-Tt-Tb)**2)
theta=abs(atan((D-Tt-Tb)/(0.5*Wt)))
W=(n*Wt)+(2*Tt)+(2*(n-1)*Tl/sin(theta))

! FLAT BASE Isoceles triangle hole
p1x=0.5*Lc/sin(theta/2)
p1y=0
p2x=2*(D-Tt-Tb)/tan(theta)-Lc/2/sin(theta/2)
p2y=0
p3x=2*(D-Tt-Tb)/tan(theta)-Lc*cos(theta)/2/sin(theta/2)
p3y=Lc*sin(theta)/2/sin(theta/2)
p4x=(D-Tt-Tb)/tan(theta)+Lc/2
p4y=(D-Tt-Tb)-Lc*tan(theta)/2
p5x=(D-Tt-Tb)/tan(theta)-Lc/2
p5y=(D-Tt-Tb)-0.5*Lc*tan(theta)
p6x=Lc*cos(theta)/2/sin(theta/2)
p6y=Lc*sin(theta)/2/sin(theta/2)

! First egde triangle hole
p7x=0
p7y=Tl/cos(theta)+0.5*Lc/sin((45*3.141592654/180)-(theta/2))
p8x=0.5*Lc*sin(90*3.141592654/180+theta)/sin(45*3.141592654/180-theta/2)
p8y=Tl/cos(theta)+0.5*Lc*sin(theta)/sin(45*3.141592654/180-theta/2)
p9x=(D-Tt-Tb)/tan(theta)-Tl/sin(theta)-0.5*Lc*cos(theta)/sin(theta/2)
p9y=(D-Tt-Tb)-Lc*sin(theta)/2/sin(theta/2)
p10x=(0.5*Wt)-(Tl/sin(theta))-(0.5*Lc/sin(theta/2))
p10y=(D-Tt-Tb)
p11x=Lc*cos(45*3.141592654/180)
p11y=(D-Tt-Tb)
p12x=0
p12y=(D-Tt-Tb)-Lc*sin(45*3.141592654/180)

! Pointed Isoceles triangle hole
p13x=(D-Tt-Tb)/tan(theta)-Lc/2
p13y=Lc*tan(theta)/2
p14x=(D-Tt-Tb)/tan(theta)+Lc/2
p14y=Lc*tan(theta)/2
p15x=2*(D-Tt-Tb)/tan(theta)-Lc*cos(theta)/2/sin(theta/2)
p15y=(D-Tt-Tb)-Lc*sin(theta)/2/sin(theta/2)
p16x=2*(D-Tt-Tb)/tan(theta)-Lc/2/sin(theta/2)
p16y=(D-Tt-Tb)
p17x=0.5*Lc/sin(theta/2)
p17y=(D-Tt-Tb)
p18x=Lc*cos(theta)/2/sin(theta/2)
p18y=(D-Tt-Tb)-Lc*sin(theta)/2/sin(theta/2)

! Outer boundary of DPC panel
K,1,0,0
K,2,W,0
K,3,W,D
K,4,0,D
! Create Area for that
A,1,2,3,4

! Inner first corner hole of DPC panel
Tx=Tt
Ty=Tt
K,5,Tx+p7x,Ty+p7y
K,6,Tx+p8x,Ty+p8y
K,7,Tx+p9x,Ty+p9y
K,8,Tx+p10x,Ty+p10y
K,9,Tx+p11x,Ty+p11y
K,10,Tx+p12x,Ty+p12y

! Create Area for that
A,5,6,7,8,9,10

!Inner first flat base isosceles hole of DPC panel

Tx=Tt
Ty=Tt
K,11,Tx+p1x,Ty+p1y
K,12,Tx+p2x,Ty+p2y
K,13,Tx+p3x,Ty+p3y
K,14,Tx+p4x,Ty+p4y
K,15,Tx+p5x,Ty+p5y
K,16,Tx+p6x,Ty+p6y

! Create Area for that
A,11,12,13,14,15,16

! looping for n number of triangular areas

m=n-1
j=17
*do,i,1,m
Tx=Tt+Wt/2+Tl/sin(theta)+(i-1)*(Wt+2*Tl/sin(theta))
Ty=Tt
K,j,Tx+p13x,Ty+p13y

j1=j+1
K,j1,Tx+p14x,Ty+p14y

j2=j+2
K,j2,Tx+p15x, Ty+p15y

j3=j+3
K,j3,Tx+p16x,Ty+p16y

j4=j+4
K,j4,Tx+p17x,Ty+p17y

j5=j+5
K,j5,Tx+p18x,Ty+p18y

! Create Area, ID # i+3 th for that
A,j,j1,j2,j3,j4,j5

Tx=Tt+2*(Wt/2+Tl/sin(theta))+(i-1)*(Wt+2*Tl/sin(theta))
Ty=Tt

j6=j+6
K,j6,Tx+p1x,Ty+p1y

j7=j+7
K,j7,Tx+p2x,Ty+p2y

j8=j+8
K,j8,Tx+p3x,Ty+p3y

j9=j+9
K,j9,Tx+p4x,Ty+p4y

j10=j+10
K,j10,Tx+p5x,Ty+p5y

j11=j+11
K,j11,Tx+p6x,Ty+p6y

! Create Area, ID # i+4 th for that
A,j6,j7,j8,j9,j10,j11

!for next loop
j=j11+1
*enddo

! Inner last corner hole of DPC panel
Tx=W-Tt
Ty=Tt

j13=j
K,j13,Tx-p7x,Ty+p7y

j14=j+1
K,j14,Tx-p8x,Ty+p8y

j15=j+2
K,j15,Tx-p9x, Ty+p9y

j16=j+3
K,j16,Tx-p10x,Ty+p10y

j17=j+4
K,j17,Tx-p11x,Ty+p11y

j18=j+5
K,j18,Tx-p12x,Ty+p12y

! Create Area, ID # i+1 th for that
A,j13,j14,j15,j16,j17,j18

!
!================================================================
!End of Dimension Data Calc.
!================================================================
!

!
!================================================================
!Preprocessing
!================================================================
!

! subtract triangles from rectangle
ASBA, 1, ALL

!Copy areas to 3
!AGEN, ITIME, NA1, NA2, NINC, DX, DY, DZ, KINC, NOELEM, IMOVE
AGEN, 3, ALL,,,,,Length/3

!extrude to volume
!VEXT, NA1, NA2, NINC, DX, DY, DZ, RX, RY, RZ
VEXT,17,,,,,Length/3
VEXT,1,,,,,Length/3
VEXT,2,,,,,Length/3

!glue together all vols
VGLUE,1,2,3

! Define Element Type
ET,1,SOLID65 !concrete solid 65

! Define Material Properties
MP,EX,1,2.37e9 ! mp,Young’s modulus,material number,value
MP,PRXY,1,0.24 ! mp,Poisson’s ratio,materialnumber,value
MP,DENS,1,2.3e3 ! mp,mass density,material number,value

TB,CONCR,1 !non linear properties

!TBDATA,startlocation,ft,fc,fu(tensile),,fu(compressive)
!(startloc = 3 means first data = 3rd row i.e ft)
TBDATA,3,7.8e6,2.2e7,2.64e7,3.81e7,3.19e7,3.795e7

!meshing
ESIZE,100 !global size of mesh
MSHKEY,0
MSHAPE,1,3D
VMESH,ALL !create Volume mesh of vol

FINISH ! Finish pre-processing

!
!============================================================
!Finished Pre-processing
!============================================================
!

!
!============================================================
!Start of Solution
!============================================================
!

/SOLU ! Enter the solution processor
ANTYPE,0 ! Analysis type,static
! Define Displacement Constraints on Lines (dl command)

!Supports
DL,1,,ALL,0 !Fixed
DL,659,,UX,0 !UX and UY for 659 is for hinge
DL,659,,UY,0

!Applied Displacement Load
DL,285,,UY,-30
DL,473,,UY,-30

!NSUB,10,50,5
SOLVE ! Solve the problem
FINISH ! Finish the solution processor
SAVE ! Save your work to the database

!
!=========================================================
!End of Solution.
!=========================================================
!

!
!==========================================================
!Start of Postprocessing.
!==========================================================
!

/post1 ! Enter the general post processor

!/WIND,ALL,OFF
!/WIND,1,LTOP
!/WIND,2,RTOP
!/WIND,3,LBOT
!/WIND,4,RBOT
!GPLOT
!/GCMD,1, PLDISP,2 ! Plot the deformed and undeformed edge
!/GCMD,2, PLNSOL,U,SUM,0,1 ! Plot the deflection USUM
!/GCMD,3, PLNSOL,S,EQV,0,1 ! Plot the equivalent stress
!/GCMD,4, PLNSOL,EPTO,EQV,0,1 ! Plot the equivalent strain
!/CONT,2,10,0,,0.0036 ! Set contour ranges
!/CONT,3,10,0,,8
!/CONT,4,10,0,,0.05e-3
!/FOC,ALL,-0.340000,,,1 ! Focus point

!my post process plot
/WIND,ALL,OFF
/WIND,1,FULL
GPLOT
/GCMD,1, PLDISP,2 ! Plot the deformed and undeformed edge

/replot
PRNSOL,DOF, ! Prints the nodal solutions

!
!==========================================================
!End of Post Processing.
!==========================================================
!

!
!==========================================================
!EOF
!==========================================================
!

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Classificaiton of Load with respect to Time

April 23, 2012

Static:

A static load is time independent. It’s value is constant w.r.t time.

Dynamic:

A dynamic load is time dependent and for which inertial effects cannot be ignored.

Quasi-Static/Pseudo-Static:

A quasi-static/pseudo-static load is time dependent but is “slow” enough such that inertial effects can be ignored. Note that a load quasi-static for a given structure (made of some material) may not be quasi-static for another structure (made of a different material).

Quasi-Dynamic/Pseudo-Dynamic:

In pseudo-dynamic loading, inertia and damping properties are simulated while stiffness properties are acquired from the structure.

Reference:

IMECHANICA

ASCE

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Debian4Engr Series: 05 Document writing using LaTeX

April 5, 2012

LaTeX is a high-quality typesetting system; it includes features designed for the production of technical and scientific documentation. LaTeX is the de facto standard for the communication and publication of scientific documents. One of great benefit of LaTeX is that it can be converted easily to postscript, pdf or html. There is excellent collection documentation and books on LaTeX website which can be helpful to get started with LaTeX.

Following packages are required to work with LaTeX in Debian:

texlive – the base TEX/LATEX setup.

emacs (with auctex) – a Linux editor that integrates tightly with LATEX through the add-on AucTeX package.

ghostscript – a PostScript preview program.

xpdf and acrobat – a PDF preview program.

imagemagick – a free program for converting bitmap images.

gimp – a free photoshop look-a-like.

inkscape – a free illustrator/corel draw look-a-like.

Following is a simple getting started tex file that should be save with name of hello.tex using emacs or gedit.

\documentclass{article}
\begin{document}
A \textbf{bold \textit{Hello \LaTeX}} to start!
\end{document}

Above file can be compile either directly from emacs or from terminal by following command:

$ pdflatex hello.tex

The result will be a pdf file with following writing:

A bold Hello LaTeX to start!

Creating CV, Technical Reports and Presentation:

You can write your entire technical report, thesis or CV in LaTeX. You can also use Beamer class (latet-beamer) to create Powerpoint like presentation in LaTeX.

Converting odt to LaTeX:

Libre documents can be converted to LaTeX using w2l command from terminal. This feature will requires installation of libreoffice-writer2latex and writer2latex.

$ apt-get install openoffice.org-writer2latex writer2latex

Then executing w2l will convert odt to LaTeX file.

$ w2l your-document.odt

Converting LaTeX to odt:

tex4ht package is required for this conversion:

$ apt-get install tex4ht

To convert document, use oolatex command:

$ /usr/share/tex4ht/oolatex your-file.tex

Another package for LaTeX to odt is pandoc. To install use:

$ apt-get install pandoc

To convert, LaTeX to odt, use:

$ pandoc your-file.tex -o your-file.odt

pandoc can be used to convert tex to other formats.

Both conversion are not giving ditto copy of original tex file. But they are helpful to get required file which need further editing to make it same as original tex file.

Reference:

LaTeX Project

Sample Thesis and CV in LaTeX on tedpavlic.com

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Strong and Weak Form Solution – FEA

April 4, 2012

Partial Differential Equations – PDE is called “strong form” because the relationship MUST satisfy at every mathematical point in the domain.

A “weak form” means that the relationship (in integral form) is only satisfied in overall sense. In another word, “it is only satisfied in an integral (sum) sense, it is not a requirement that every point in the domain MUST obey”

The strong form of a differential equation is just that: the (partial) differential equation itself. Evaluating the PDE requires being able to get all the associated derivatives. It is satisfied pointwise at every point in a body, and is usually stated as D[u] = 0, where D is some partial differential operator. In this case, I am using u as the displacement. It may be more appropriate to look at, say, Cauchy stress (s) instead of displacement. Then the strong form might be something like D[s,u] = div[s] – ru,tt= 0.

The weak form is obtained by multiplying the PDE by an arbitrary weighting function of (in most cases) the spatial variables, then integrating the result over the domain. One then requires that the result is zero for all choices of such functions. An integration by parts is performed, leading to differentiability requirements on the weighting function, but relaxing, or “weakening” the requirements on the field described by the PDE. Once we start setting requirements on these functions, we “weaken” the form even more, but often provide a basis for expressing the approximate solution.

Questions:

Q1. Why do we multiply the PDE by the weighting function?

Q2. How do we choose the weighting function?

Answers:

The “why” is to reduce differentiability requirements on our approximate solution.
The “how” is whatever works. If you know of a particular set of functions that work well in your geometry (say Bessel functions for axisymmetric problems), you can use these. We often use arbitrary combinations of nodal basis functions (compact support, C1, finite domains). If we use the same basis for our weighting functions as we use to represent our primary variable field(s), e.g. displacement, we are using a Galerkin method.

By Matt Lewis
Los Alamos, New Mexico

This excerpt is taken from IMECHANICA Forum.

Reference:

Weak Derivative – Wikipedia

Weak Formulation – Wikipedia

Weak Solution – Wikipedia

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Understanding Retrofitting, Repair, and Strengthening

March 16, 2012

In Structural Engineering, retrofitting, repair and strengthening of structure are most commonly used words. It is important to distinguish them and defined them for better understanding.

Retrofitting: Retrofitting is the bringing the structure back to its original strength after damage + further increase in its strength to make it more strong than before.

Repair: Repair is bringing back the structure to its original strength after damage.

Strengthening: Strengthening is increase in strength of structure which is not damaged.

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