Welcome to the getting started with GeoStudio video series.
This tutorial introduces how to use the SIGMA/W product of GeoStudio 2012.
This tutorial video has been designed to help walk new users through the basics of setting up a simple stress and deformation analysis in SIGMA/W.
So, if you are new to SIGMA/W
and are not sure where to start, you have come to the right place.
The main topics that will be covered in the tutorial
will be how to create an analysis in SIGMA/W by using the define view to set up the analysis,
the solve manager to solve the numerical analysis,
and the options available in results view to gain a deeper understanding of the analysis.
So, let's get started...
Here are some results of the stress and deformation analysis completed and SIGMA/W.
The objective of the analysis was to determine the settlement of a circular water-filled tank.
The upper 5m of soil have different properties than the underlying 20 m.
The tank is 10 m in diameter with an applied pressure on the ground when the tank is full of 40 kilopascals.
Since the problem is symmetrical about the vertical center line of the tank, the problem will only include half of the tank
and we will conduct an axisymmetric analysis.
An axisymmetric formulation
considers the stresses in the X to Y plane as well as the circumferential stresses, and the profile you create is rotated
around the axis of symmetry.
We will start on the GeoStudio start page,
where you can create a new project,
open an existing project, or click on the appropriate links to view examples,
tutorial videos, or engineering books for each GeoStudio product on our web site.
We will create a new project and choose to create the project using the default International System of units.
If preferred, a blank document can be created with imperial units at this point.
Once our new project is created,
the KeyIn analyses window is opened,
where we can add a title to our analyses tree,
add an author or add comments for future users.
Now we are ready to add the SIGMA/W analysis to our analysis tree.
We will add a load/deformation analysis.
Here, we can change the name of our analysis,
as well as change our analysis type if desired,
but we will keep the load/deformation analysis type.
We can also add a description about the analysis to help future users.
The drop down boxes are available if there are previous analyses or results for the
initial stress or pore-water pressure conditions for the start of the analysis.
For this analysis, we will simply leave these drop down menus to none.
The convergence tab can be used to change the convergence settings for the analysis.
We will keep the default settings, but more information on these values can be seen in the engineering book for SIGMA/W
The time tab can be changed if desired including increasing the number of time steps or duration,
but will be left with the default settings of one time step that is one second to simulate the addition of a load in one step.
The advanced tab also has the option to include a body force in all steps
or to adjust the fill elevation with foundation settlement,
but these are not required for the purpose of this tutorial.
You can use the zoom options along the bottom bar of your screen,
or under set zoom,
to change the view of your analysis, either to the extents of your domain
or to the extents of the work area page or simply zoom in or zoom out.
We will simply zoom in to our drawing page, as we don't have our domain defined yet, and then take a look at the drawing scale of our analysis.
We will go to set, units and scale
and here we can see the units that are being used in our current analysis.
Here is where we can change our units if desired,
but I will keep the default of seconds and kilonewtons.
The problem extents boxes can be used to help modify the scale of the analysis.
Changing these values can change the view of your analysis so that the entire domain remains on a single page.
We will toggle off the calculate Max extents option
and change our minimum x coordinate to -8 m and our y coordinate to -6 m and our maximum x coordinate to 40 m
and maximum y coordinate to 30 m.
This automatically adjusts our scale values to accommodate these extents.
We will toggle on the calculate Max extents again
and fine tune our horizontal and vertical scale values to ensure a 1 to 1 aspect ratio.
Since we are conducting and axisymmetric analysis
we will toggle on the axisymmetric option.
Here a value of 360° indicates that all results will be calculated relating to the full circle around the axis of symmetry.
In this case, we will simply simulate the results of one of the sections by changing this value to 360° divided by 2 times PI
or 57.29578°.
As you can see in the background of the page of my screen, there is a grid already activated. You can go to set,
grid, to turn this grid off or on,
activate snap to grid,
or change the grid spacing.
Now we are ready to create our domain.
We will start by adding axes to our working area to help visualize the drawing extents of our domain.
This is completed by going to sketch,
axes. Here you can also change the names of the axis titles,
as well as the X and Y axis extents.
We will set the X axis extent to be from -5 m to 40 m
and the Y axis extents to be from -2 m to 15m.
You can also change the increment size of the axes labels by toggling off the auto
increment size button and changing the increment size for each axis.
The approach to use when developing a numerical model is to determine the geometry,
assign materials, assign boundary conditions,
and fine tune the finite element mesh.
Let's start by creating a domain.
Here, we have a sketch already completed of the water filled tank on the two soil layers.
To create our modeling domain, I will go to draw regions
and draw my two soil regions following the sketch of my problem.
Here, points will automatically be made wherever I use a left mouse button
to click on the working area.
Once the region is created, I can draw the next region
or I can use my right mouse button or the escape button on my keyboard to stop the draw regions command.
Next, we will add the materials to our analysis.
I will go to draw materials
and click on the KeyIn button to open the materials define window.
I will add a new material,
give my material a name,
and enter my soil properties for the linear
elastic, total stress model.
In this case, only the stiffness modulus and Poisson's ratio are required.
Next, we will add a second material for the lower soil layer.
There are two options that can be used when adding the second material. The first is to simply use the add button again to create a new material
or the clone button can be used to clone the first material.
Then I will adjust the soil properties to represent the second layer.
Now that my two materials are defined, I will go to draw materials
and add the materials to each region representing the soil layers.
The next step will be to define the boundary conditions.
I will go to KeyIn,
boundary conditions.
Here, we can see by default there are three boundary conditions already defined for stress strain scenarios.
You can also create your own boundary condition to represent the pressure of the water filled tank on the ground surface. So we will add a new boundary
condition and apply the vertical stress of 40 kilopascals onto the ground surface.
Here, the negative sign indicates that the pressure is going down onto the soil surface.
You can also change the color of the boundary condition
by going to color, set...
To apply the boundary conditions to the domain,
we will go to draw boundary conditions and choose the fixed X boundary condition to apply
to the left boundary representing the vertical axis of symmetry in this analysis.
This is the only boundary that we want to allow vertical movement or settlement, but we still want to restrict any lateral or horizontal movement.
For the bottom and right boundaries, we will assume that the movement can be fixed in both the x and y directions.
Now we are ready to apply the tank pressure boundary condition to the line under the location of the tank.
Here, we require a point to be added to the domain to ensure that the boundary condition does not extend past the actual location of the tank.
So we will click on draw point.
Now this point has become a part of the domain and we can add the tank pressure boundary condition to
the line representing the contact between a soil surface
and the bottom of the tank.
Now that the geometry has been drawn and the material properties and boundary conditions have
been applied, we are ready to review a finite element mesh and make any necessary adjustments.
We will click on the draw mesh properties button
and see that the meshing algorithm has a global element size of 2 m with a meshing pattern of an unstructured mesh of quadrilaterals and triangles.
We will keep the 2 m element size, but we will change all regions to include a meshign pattern of the structured quadrilateral elements only.
You can also hold down the control button on your keyboard and click on multiple regions to apply
changes in the meshing properties of multiple regions.
We will decrease the size of a mesh for the two soil layers directly below the tank
as these layers are expected to be affected the most by the pressure applied by the tank.
We will choose to change the element size to half of the global mesh element size or 1 m.
We will also apply secondary nodes to these regions so that the eight noded elements are used,
while the remaining elements will be kept with the default four noded elements.
The number of nodes in your finite element mesh will affect both the size of the file and the amount of time required to solve the problem, so it is important
to only use secondary nodes when necessary to obtain a better solution.
Now we will make sure that the analysis is activated in the solve manager window
and solve the analysis by clicking on the start button.
Once solved, the window will automatically change to the results view instead of the define view.
By default, Y total stress contours will be shown.
Contour options can be changed by going to the draw contours window.
Here, you can change the coloring scheme of your contours,
add or remove a legend,
change the increments of your contours,
or add new contours to the contour drop down menu, such as material properties or other results information.
The draw contours labels button can be used to add or remove contour labels by simply clicking on the contour where you want a label painted.
Labels can also be removed by clicking the label again.
The main objective of the simulation was to determine the vertical settlement of the water filled tank.
We can go to draw vectors and choose to view the displacement as either a deformed mesh or with
vectors and the magnification of the displacement on the profile can be adjusted here.
The maximum displacement is also summarized in this dialog box.
You can turn on or off this displacement visualization, along with other visualization tools
om the view preferences toolbar, either along the right side of your screen
or under view preferences.
Another way to view results is to create a Mohr Circle. We can use the draw Mohr Circle button and choose a node or gauss
region below the tank where we would like to know more information about stress results.
A Mohr Circle window will appear showing the stresses for that node or element gauss region.
This information can be copied and pasted into another program or printed from this window.
We can also draw a graph of the lateral displacements under the tank.
I will go to draw graph and add a new graph to the window.
I will select the displacement,
X displacement vs. elevation,
and choose a vertical profile below the edge of the tank.
Here you can either drag and drop a box around the desired nodes or
hold the shift button on your keyboard while drawing a line through the desired nodes.
Now we can see the X displacement along the vertical path we chose.
I can use the more button to copy the graph image so that it can be pasted as a picture into another program,
the graph data as tab-delimited columns which can be pasted into another software like Microsoft Excel,
or exported as a separate comma-delimited file.
I can change the visualization of my graph by clicking on more options.
Here I can customize the labels on my graph,
change the scale of my axes,
rotate my graph so that the elevation is on the Y axis,
add or remove a legend,
change the style of my lines,
or change the font of the text on my graph.
There are also other options that can be used to view result information within the results window.
For example, you can view result information,
which outlines the result information for each geometry item, such as the total stress applied to a node below the tank.
The view report button can be used to develop a report of the input data
and will open the report in an HTML format.
This gives you all of the information regarding the input data,
geometry and other information from the analysis.
Note, if at any time you are unsure in your understanding of the dialog boxes,
you can simply click on the question mark in the top right corner of the dialog boxes,
use the help tab or use F1 on your keyboard
to access the online help.
If at any time you would like to view the engineering book for the product you are using and do not want to return to the
GeoStudio start page, you can simply click on the home button of the online help.
We have now reached the end of this introductory tutorial.
Note that not all of the powerful features of SIGMA/W 2012
have been used or discussed here.
Further information on each command can be found in the online help,
supporting documentation for SIGMA/W,
as well as another tutorial videos of the Getting Started with GeoStudio video series.
Thank you for watching.