Defining a Fault Tree Analysis

You can structure a fault tree with events and operators to organize the failure scenario.

This task shows you how to:

Display a Top Event

You can display the top event of a fault tree element.

Create a root failure mode at the root of the system to be analyzed.
For more information, see Creating a Failure Mode.
To display the fault tree element (event) pointing to a failure mode, click the failure mode associated with the root node of the architecture tree.

Tip: The navigation bar displays the breadcrumb tail in the model. For more information, see User Interface Description.

This event is considered as the top event. You can now create intermediate events or gates to describe the failure scenario by defining the current fault tree element.

You can develop a fault tree by instantiating failure modes or by creating gates.

From the fault tree, select an event.
To instantiate a failure mode, drag a failure mode from the architecture tree onto an event in the fault tree.

Note: Each failure mode is associated with a fault tree element. Dragging the failure mode onto a gate extends the tree with the contents of its child tree.

Tip: When a failure mode is instantiated more than once, a triangle appears, with a figure that indicates the number of instances.
To create a gate, do one of the following:
- From the Edit section of the action bar, click Create Fault Tree Gate .
- On the fault tree element, click Create Fault Tree Gate .
If no event is associated with the gate, the intermediate event is considered as an undeveloped event.

Defining a fault tree, you can change the default operator of the events and gates.

Even if no operator is displayed, hover over the current operator at the bottom of the event.

The change icon named Change Fault Tree Gate appears.
Click this icon until the right operator replaces the previous operator.

For more information about the available operators, see Operators.

A basic event is a leaf of a fault tree pointing to a failure mode, which has a reliability formula associated with it.

From the Reliability Source widget, drag a formula onto a failure mode in the architecture tree.

If no formula is associated with the pointed failure mode, the event is still considered as an undeveloped event.