The user interface is divided into three main parts:
- Drawing Canvas: where geometry is defined and results are drawn
- Toolbar: where the main tools can be selected and the structure view switched
- Footer Bar: where extra information and view options (such as zoom) can be found
You can configure the units the app uses, choosing to format quantities in the International or US unit systems. You are given a lot of flexibility in the selection of which units use for what magnitudes.
To edit the default units used by the app:
- From the menu: InkStructure > Preferences...
The analysis of a structure can be subdivided in three stages:
- Definition of geometry
- Addition of loads
- Analysis of results
InkStructure has three different views that correspond to the above mentioned stages. When a view is selected, only relevant options and tools are available.
The views also prevent the structure from being edited in undesired ways. For instance, if you are defining the loads on structural elements you wouldn't want to edit the dimensions or remove external constraints. Therefore, when the Loading View is selected, only operations related to loading the structure are presented to you.
Zoom & pan
There are three ways of zooming in and out the drawing:
- Use the mouse wheel (or trackpad in the MacBook)
- From the menu View > Zoom In
- Clicking the icons in the footer bar
Zoom in increases the size of the drawing, whereas zoom out makes it smaller. Zoom all will try to fit all the drawing inside the canvas.
To pan the canvas: Hold the space bar + left mouse click + drag. Release the the mouse button to stop panning the canvas.
To draw a new structural element:
- Make sure Geometry View is active. Select the Geometry tool from the toolbar or from the menu, Geometry > New Geometry
- Click in the canvas to set the position of the initial node. Hold the mouse button
- Drag the mouse to define the length of the geometry
- Release the mouse button to set the position of the final node
guide lines & direction detection
Every node adds both a horizontal and vertical guide lines to the drawing. A orthogonal grid of guides is generated automatically as you draw new geometries, as can be seen above, figure A. These guides are not always visible, but rather appear as you need them.
Guide lines assist you in drawing new geometry and are displayed in the canvas when the cursor is close enough to them. In these cases, the cursor point will be forced to fall exactly on the guide line (see figure B). This is commonly referred as "snapping". Guide intersections also try to snap the cursor to that point (see figure C).
When drawing, geometries forming angles that are close to multiples of 15º are forced to follow those directions. You can think of it as an invisible guide line forming that particular angle that appear as you draw.
Directions defined by these angles may intersect with existing guide lines in the drawing. Intersection points of this nature are also used to force the cursor point.
DIMENSIONS & Smart Dimensions
Once your structure is defined in terms of shape, you can dimension each of the geometric elements. You can alternatively dimension elements right after drawing them (which involves switching tools), but the recommended workflow is the former.
You can edit the length, angle with horizontal, width and height of every linear geometry. When one of these values is changed and "Smart Dimensions" option is checked, the rest get recalculated. Unchecking the "Smart dimensions" option resizes the selected element, but does not try to keep the overall structure geometry similar to how it was before the edition, as explained later in this section.
To dimension a geometry element:
- Make sure Geometry View is active. Select the Dimension tool from the toolbar or from the menu, Geometry > Dimensions
- Select an element. A popover window with the dimensions of the element appears.
- Edit any of the dimensions and click TAB or ENTER
Note that only one element can be selected at a time.
Dimension edition is a process that may alter the geometry of the rest of the structure. InkStructure includes a smart dimension engine which adapts the parts of the structure that haven't been edited so that the overall structure makes sense.
This concept is illustrated in the two figures above. The left column of a portal is resized, which causes the beam to come down a bit, which causes the right column to be resized as well. After the column resize, the shape of the structure resembles the original shape.
The "Smart Dimensions" engine follows two simple rules:
- Elements that where horizontal before the edition should remain horizontal (as long as this doesn't generate conflicts)
- Elements that where vertical before the edition should remain vertical (as long as this doesn't generate conflicts)
Alternatively, the "Smart Dimensions" option can be unchecked, in which case, the edition of the dimension is as illustrated in the two figures below:
The nodes in the structure can be moved to adapt the geometry further in ways that would be complicated by just editing the dimensions of the structural elements.
To move a node:
- Make sure Geometry View is active. Select the Move tool from the toolbar
- Select a node (the move node popover appears)
- Specify the horizontal or vertical distance to move the node and click TAB or ENTER
Note that only one node can be selected at a time. Note as well that if you specify a negative distance, the icon on the left of the text field changes its direction, indicating in which direction will the node be displaced.
Every node in the structure has three degrees of freedom (possible ways the node can move):
- Displacement in X direction
- Displacement in Y direction
- Rotation about Z direction
External constraints describe the way degrees of freedom of nodes are attached to the "rest of the world". Constraints fix one or more of these degrees of freedom. In the figures above, blue arrows represent the degrees of freedom which are fixed in each of the three different types of external constraints.
To define external constraints on nodes:
- Make sure Geometry View is active. Select the Constraint tool from the toolbar, or from the menu Geometry > Define Constraint
- Select one or more nodes
- Click the mouse right button
- From the external constraint dialog, select an option
section & material
A geometrical shape, in order to be used as a structural member, needs to have resistant and inertia properties. These properties are defined by a section and a material, which are assigned to the geometry.
To assign section and material to a geometry:
- Make sure Geometry View is active. Select the Define tool from the toolbar, or from the menu Geometry > Define Geometry
- Select one or more geometries
- Click the mouse right button
- From the dialog, select a section and material
- Click OK
InkStructure comes with a section catalogue that can be opened from the menu Geometry > Section Catalogue. This catalogue includes European section families (IPE, IPN, HEA, HEB...).
A material catalogue can be found under Geometry > Material Catalogue, which includes Eurocode steels (further materials will be added to the catalogue in future versions).
A structural member is connected to the rest of the structure by its nodes. Connections can be of two types:
- Rigid (default): can pass axial forces, shear forces and bending moments to connected elements
- Pinned: can pass axial and shear forces to connected elements, but not bending moments
To define the connections of a structural element:
- Make sure Geometry View is active. Select the Connection tool from the toolbar, or from the menu Geometry > Define Connection
- Select a geometry
- From the dialog select the connection for the first and last nodes between rigid / pinned
Loads are external forces acting upon the structure. Loads can be applied to structural elements or structural nodes, can be distributed or punctual. InkStructure currently supports distributed loads on structural elements, but punctual loads, both on members and nodes, will be available on future versions.
In the Figure A below, different types of distributed loads are shown.
To apply a load on structural members:
- Make sure Loading View is active. Select the Load tool from the toolbar, or from the menu Load > New Load
- Select one or more geometries
- Click the mouse right button
- Select the type of load you want to apply, the direction in which is applied and its values
- Click OK to confirm or Cancel to discard the changes
To calculate the structure:
- Click in the Calculate icon, in the right-most part of the toolbar
- After the calculation process has finished, click OK
The view is automatically switched to Results View.
Before starting the calculation process, several checks take place. If any of the checks fails, the calculation is aborted and an error message explaining the problem appears (see Figure B above). These checks include that all structural elements have material and section assigned, that some external constraints exist or that loads have been applied to the structure.
The results are presented in diagrams which X axis is the structural member itself. Result values are plotted in the element's local reference system Y axis. To find the value in a given point of the structural member, mouse over the diagram.
Result diagrams include:
- Axial Stress (in Newtons)
- Shear Stress (in Newtons)
- Bending Moment (in Newtons centimeter)
- Displacement in X (in centimeters)
- Displacement in Y (in centimeters)
- Rotation about Z (in radians)
There is also a diagram that displays the geometry of the deformed structure. The original structure drawing can be hidden unchecking the "Original Geometry" option.
Diagram values may vary a lot between elements. A scale can be applied to the diagram plot. The values of the diagram are always the same, regardless of the drawing scale, which only alters the size of the drawing. The effect of changing the diagram scale can be better understood by looking at figures A and B above.