ANALYSIS ANAL YSIS OF HYDRA HYDRAULIC ULIC STUCTURES IN ANSYS ®
Muhammad Adil Javed WAREM Generation Gene ration 2011
WHAT IS FINITE ELEMENT ANALYSIS For many engineering problems analytical solutions are not suitable because of the complexity of the material properties, the boundary conditions and the structure itself.
The basis of the finite element method is the representation of a body or a structure by an assemblage assemblage of subdivisions su bdivisions called finite elements.
The Finite Element Method translates partial differential equation problems into a set of linear algebraic equations.
Stiffness matrix
Nodal Displacement Vector
Nodal Vector Force
INTRODUCTION TO ANSYS ®
ANSY ANSYS S is a gener eneral al purp purpos ose e fini finite te elem elemen entt mo mode deli ling ng pa pack ckag age e for nume numeri rica callly solv solvin ing g a wide variety of mecha chanical problems. These problems include: static/dynamic stru strucctural analysis sis (both linea near and non-l n-linear), r), heat tra transfe sfer and flu fluid problems, as wellll as ac we acou oust stic ic and elec electr trom omag agne neti ticc prob proble lems ms.. This tutorial will walk you through the static analysis of a simple concrete gravity dam. This will show you how you can create geometry, define element types, assign physical properties, mesh the model, conduct static analysis and perfor m postprocessing.
ANALYSIS ANAL YSIS IN ANSYS ANSY S Like in any numerical simulator, Performing Performing Analysis in Ansys can also be divided in three major stages i.e.
PreProcessing
Analysis
PostProcessing
PROCEDURE SUMMARY Pre-processing
Start Ansys
Specify Title
Define Element Types
Define material Properties and Real Constants
Generate Model Geometry
Mesh Geometry
Apply Loads and Boundary Conditions
Analysis
Set Analysis Type (i.e. Static, Modal, Harmonic, Frequency Responce...)
Set Analysis Preferences accordingly
Start Analysis
Post-processing
View and Process Results
Contour Plots Vector Plots Plot Graphs
Etc...
ANALYSIS ANAL YSIS IN ANSYS Free or structured ?
Solid or Shell ?
Geometry
Element Type
Material Properties
Mesh Definition
Isotropic or anisotropic ?
Static, Modal, Harmonic… ??
Boundary Conditions
Analysis
Fixed, roller or free ? Loads.
Post Processing
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 negligible compare to its length and width.
Nevertheless, a plate modeled with solid element would provide similar results. The disadvantage lies in computation time.
Ansys provides a large choices of elements. In In fact ANSYS element library consists of more than 100 different element formulations or types.
DAM CROSS-SECTION
SCHEMATIC PARAMETERS a = 55 mb = 41 m (Width) (Width) c = 4 m (Service (Ser vice Road) x = 0.70 (chosen from 0.7 – 0.8) y=1 L = 400 m
Geometry
There are two way in which you can command ANSYS, one way is to use GUI and the other way is by using APDL code.
Bottom to Top strategy
Key points
Lines
Areas
Volumes
MAIN GUI Main Menu [Controls in which phase of Analysis you are]
Geometry
Creating KP by commands K, NPT , X , Y , Z Defines a keypoint.
k,1,0,0,0 k,2,41,0,0 k,3,4,51,0 k,4,4,55,0 k,5,0,55,0
Creating KP by GUI
Geometry
In the same way, lines, areas and volumes can be generated
L, P1, P2, Defines a line between two kp.
VOFFST, NAREA, DIST, Generates a volume, offset from a given area.
L,1,2 L,2,3 L,3,4 L,4,5 L,5,1
VOFFST,1,-1,
AL, L1, L2, L3, Generates an area bounded by previously defined lines. …
AL,1,2,3,4,5
Element Type
Or by just using command ET, ITYPE, Ename, Defines a local element type from the element library. library.
1
ET,1,SOLID185 ET,2,SOLID185 3
2
Material Properties
Creating Variables in APDL
Density_conc = 2250 EX_conc = 15e9 Poiss_conc=0.2
!Density of Concrete in [kg/m^3] !Modulus of Elasticity for concrete [N/m^2] !Poisson's Ratio for concrete (0.1 - 0.2)
Density_rock = 2640 EX_rock = 15e9 Poiss_rock=0.15
!Density of of Bo Bottom ro rock in in [k [kg/m^3] !Modulus of Elasticity for concrete [N/m^2] !Poisson's Ratio for concrete (0.1 - 0.2)
desn desnit ity_ y_wa wate ter r = 1000 1000
!
[kg/ [kg/m^ m^3] 3]
Element Type
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_conc MP,NUXY,1,Poiss_conc
MP,EX,2,EX_rock MP,DENS,2,Density_rock MP,NUXY,2,Poiss_rock
1
2
3
Mesh Definition
Two Types of Meshing
Mesh Definition
Free Meshing
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,,,50 LESIZE,10,,,50 LESIZE,3,,,10 LESIZE,8,,,10 LESIZE,4,,,10 LESIZE,9,,,10 LESIZE,11,,,2 LESIZE,12,,,2 LESIZE,13,,,2
Unstructured Meshing on Dam slice
Mesh Definition
Structured Meshing
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 on Dam slice
Boundary Conditions
Hydrostatic Pressure Uplift Pressure
max_hydrostati max_hydrostatic c =desnity_water* =desnity_water*9.81*A 9.81*A max_hydrostati max_hydrostaticBottom cBottom =desnity_water*9 =desnity_water*9.81*B* .81*B*0.7 0.7 SFGRAD,PRES,0,Y,0,-1*(max_hydrostatic/A) nsel,s,loc,x,0 SF,ALL,PRES,max_hydrostatic nsel,s,loc,y,0 SFGRAD,PRES,0,x,0,-1*(max_hydrostaticBottom/B) SF,ALL,PRES,max_hydrostaticBottom
! Select nodes for pressure application ! Apply Pressure at all selected nodes: ! Select nodes for pressure application ! Apply Pressure at all selected nodes:
Boundary Conditions
Hydrostatic Pressure
Uplift Pressure
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,
Analysis
Starting a Static Analysis
/SOL ANTYPE,0 SOLVE
1 2
3
PostProcessing
1
3 2
Deformed Shape
Contour Plots
Deformation in X dir
Von Mises Stress Stress
Vector Plots
Displacement Vectors
Graphical Plots
Download APDL File http://goo.gl/LTSZLj
Thanks ! !
