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ANALYSIS OF HYDRAULIC STUCTURES
IN ANSYSMuhammad
WAREM Ge
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WHAT IS FINITE ELEMENT ANALYSIS
For many engineering problems analytical solutions are not suitable becausecomplexity of the material properties, the boundary conditions and the structuitself.
The basis of the finite element method is the representation of a body or a stby an assemblage of subdivisions called finite elements.
The Finite Element Method translates partial differential equation problems in
of linear algebraic equations.
Stiffness matrix Nodal Displacement
Vector
Nodal Vector Force
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INTRODUCTION TO ANSYS
ANSYS is a general purpose finite element modeling package for numericalla wide variety of mechanical problems. These problems include: static/structural analysis (both linear and non-linear), heat transfer and fluid prob
well as acoustic and electromagnetic problems.
This tutorial will walk you through the static analysis of a simple concrete
dam. This will show you how you can create geometry, define element type
physical properties, mesh the model, conduct static analysis and
postprocessing.
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ANALYSIS IN ANSYS
Like in any numerical simulator, Performing Analysis in Ansys can also be dividthree major stages i.e.
Pre-Processing Analysis
Post-Processing
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PROCEDURE SUMMARY
Start Ansys
Specify Title
Define Element Types
Define material Properties
and Real Constants Generate Model Geometry
Mesh Geometry
Apply Loads and BoundaryConditions
Set Analysis Type (i.e. Static,Modal, Harmonic, FrequencyResponce...)
Set Analysis Preferencesaccordingly
Start Analysis
View and PContour Plots
Vector Plots
Plot Graphs
Etc...
Pre-processing Analysis Post-
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ANALYSIS IN ANSYS
AnalysisBoundaryConditions
MeshDefinition
MaterialProperties
ElementType
Geometry
Solid or Shell ?
Isotropic or anisotropic ?
Free or structured ?
Fixed, roller or free ? Loads.
Static, Modal, H
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GEOMETRY AND ELEMENT TYPE
The Geometry and element type have to be considered together.
Shell element are typically used for structure where the thickness is negligiblcompare to its length and width.
Nevertheless, a plate modeled with solid element would provide similar resudisadvantage lies in computation time.
Ansys provides a large choices of elements. In fact ANSYS element library co
of more than 100 different element formulations or types.
SOLID185SHELL281SHELL181
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DAM CROSS-SECTION
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SCHEMATIC
PARAMETERS
a = 55 mb = 41 m (Width)
c = 4 m (Service Road)
x = 0.70 (chosen from 0.7
y = 1
L = 400 m
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Geometry
Bottom to Top strategy
Keypoints
Lines Areas Volume
There are two way in which you can command ANSYS, one way is to us
and the other way is by using APDL code.
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MAIN GUI
Main Menu [Controls in which phase of Analysis you are]
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Geometry
Creating KP by GUI Creating KP by commands
K, NPT, X, Y, Z
Defines a keypoint.
k,1,0,0,0
k,2,41,0,0
k,3,4,51,0k,4,4,55,0
k,5,0,55,0
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Geometry In the same way, lines, areas and volumes can be gene
L, P1, P2,
Defines a line between
two kp.
L,1,2
L,2,3
L,3,4
L,4,5
L,5,1
AL, L1, L2, L3,
Generates an area
bounded by previously
defined lines.
AL,1,2,3,4,5
VOFFST, NAREA, DIST,
Generates a volume,
offset from a given area.
VOFFST,1,-1,
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1
2
ElementType
ET, ITYPE, Ename,
Defines a local element type from
the element library.
ET,1,SOLID185
ET,2,SOLID185
Or by just using command
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Material
Properties
Density_conc = 2250 !Density of Concrete in [kg/m^3]
EX_conc = 15e9 !Modulus of Elasticity for concrete [N
Poiss_conc=0.2 !Poisson's Ratio for concrete (0.1 - 0
Density_rock = 2640 !Density of Bottom rock in [kg/m^3]
EX_rock = 15e9 !Modulus of Elasticity for concrete [N
Poiss_rock=0.15 !Poisson's Ratio for concrete (0.1 - 0
desnity_water = 1000 ! [kg/m^3]
Creating Variables in APDL
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ElementType
MP, Lab, MAT, C0, C1, C2, C3, C4
Defines a linear material
property as a constant or a
function of temperature.
MP,EX,1,EX_conc
MP,DENS,1,Density_concMP,NUXY,1,Poiss_conc
MP,EX,2,EX_rockMP,DENS,2,Density_rock
MP,NUXY,2,Poiss_rock
1
3
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MeshDefinition
Structured Meshing Unstructured/Free Meshin
Two Types of Meshing
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MeshDefinition Unstructured Meshing on Dam sl
LESIZE, NL1, SIZE, ANGSIZ, NDIV, SPACE,
Specifies the divisions and spacing ratio on
unmeshed lines.
LESIZE,1,,,50
LESIZE,6,,,50
LESIZE,2,,,50
LESIZE,7,,,50
LESIZE,5,,,50LESIZE,10,,,50
LESIZE,3,,,10
LESIZE,8,,,10
LESIZE,4,,,10
LESIZE,9,,,10
LESIZE,11,,,2
LESIZE,12,,,2
LESIZE,13,,,2
LESIZE,14,,,2VMESH,ALL
Free Meshing
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MeshDefinition Structured Meshing on Dam slice
LESIZE, NL1, SIZE, ANGSIZ, NDIV, SPACE,
Specifies the divisions and spacing ratio on
unmeshed lines.
LESIZE,1,,,20
LESIZE,2,,,20
LESIZE,3,,,3
LESIZE,3,,,3
LESIZE,4,,,3
LESIZE,5,,,26
VOFFST,1,1, ,
VSWEEP,1,1,2
Structured Meshing
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Boundary
Conditions
Hydrostatic Pressure
Uplift Pressure
max_hydrostatic =desnity_water*9.81*A
max_hydrostaticBottom =desnity_water*9.81*B*0.7
SFGRAD,PRES,0,Y,0,-1*(max_hydrostatic/A)
nsel,s,loc,x,0 ! Select nodes for pressure
SF,ALL,PRES,max_hydrostatic ! Apply Pressure at all sel
nsel,s,loc,y,0 ! Select nodes for pressure
SFGRAD,PRES,0,x,0,-1*(max_hydrostaticBottom/B)
SF,ALL,PRES,max_hydrostaticBottom ! Apply Pressure at all sel
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Boundary
Conditions
Uplift Pressure Hydrostatic Pressure
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Boundary
Conditions
Fixed BC on bottom of Dam Slice
NSEL
NSEL, Type, Item, Comp, VMIN, VMAX, VINC
Selects a subset of nodes.
nsel,s,loc,y,0
D
D, NODE, Lab, VALUE, VALUE2, NEND, NINC,
Defines degree-of-freedom constraints at nodes.
D,all,,0,
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Analysis
Starting a Static Analysis
/SOL
ANTYPE,0
SOLVE1
3
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Post-
Processing
1
2
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Deformed Shape
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Deformation in X dir Von Mises St
Contour Plots
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Displacement Vectors
Vector Plots
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Vertical Distance vs Displacement
Graphical Plots
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http://goo.gl/LTSZLj
Download APDL File
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