The system is capable of tracking the deteriorating structural elements so that each element can get deteriorated individually and at more granular level compared to component deterioration. User can setup performance models for each element. Performance model utilizes Wei-Bull distribution model for the element condition states.
Set Performance Class
Since the deterioration model for a given element may differ based on some factors such as traffic, location, protective system, etc. users can define the parameters in the Element Performance Class so that they will be able to define separate model for any combination of those factors. Users can insert an Element Performance Tree in the left pane and in the right pane they can use the Tree structure to define parameters and their corresponding thresholds. Example: A user can define a performance class for AADT (Traffic) in the left pane and can add three leaves to the tree for AADT<4000, 4000<ADDT<10000, and AADT>10000.
Element Performance Model
For each element in the left pane, users can pick a tree and in the Element Probability Models define the model parameters. As mentioned above, the system can use multiple models for an element based on the bridge attributes. In order to add the models, users can right-click and select Add the Models from any performance class defined in the previous section. Then the user needs to define the model parameters which include the year count each Condition State takes to fall into the immediate worse condition state and Shape factor. For example for the default model for the Deck element it takes 19 years that 100% of the CS1 (Excellent condition) falls into CS2 (Fair condition), and 14 year that 100% of CS2 falls into CS3 (Poor condition) and 10 year that 100% of the element goes into CS4 (worst condition). The shape factor defines how fast the deterioration occurs. The higher the shape factor, the faster the element deteriorates.
Element Health Index
The Element Health Index is a single number (0-100) representing the overall condition of the element forecast by the model. The system uses weight factors (top pane) to convert the condition states into a single number, health index. The calculation is:
Element Health Index in a given year = (CS1 weight factor x (foretasted CS1 in that year)) + (CS2 weight factor x (foretasted CS2 in that year)) + (CS3 weight factor x (foretasted CS3 in that year)) + (CS4 weight factor x (foretasted CS4 in that year))
The weight factors can be defined by the user and the forecast Condition States are calculated based the model parameters. The graph in the lower left pane displays the element health index for each model selected in the Element Probability model. If the user is willing to see the predicted model for a longer time frame they can change the Number of Years and the system calculates the displays the model results for the defined period.
The lower right pane shows the distribution of element condition states for the selected model.
Users can also see the condition states values in the Matrix tab in the bottom pane. The system shows how much of the element degrades from its original condition state for each year.