Pontis Modeling Approach Overview

presented by Cambridge Systematics, Inc.
May 2004

Outline

• What is Pontis?
• Developing a preservation
• policy in Pontis
• Simulating bridge conditions
• New modeling features in Pontis
  • Improved deterioration model updating
  • Performance targeting for the long-term preservation model
  • Other improvements
• Information resources

What is Pontis?

• Windows-based bridge management system (BMS) with functionality for:
  • Recording bridge inventory and inspection data
  • Developing an optimal preservation policy
  • Simulating conditions and generating work candidates
  • Developing a bridge program
• Used by over 45 agencies throughout the U.S. and abroad
• Originally developed for the FHWA, now owned by AASHTO with Cambridge Systematics as AASHTO's contractor
• One component of AASHTO's BRIDGEWare Suite

What is Pontis?

Key Features of Pontis

• Representation of a bridge as a set of structural elements
• Recommendation of an optimal preservation policy
• Extensive functionality for program simulation
  • Recommends preservation and improvements
  • Considers agency and user costs
  • Predicts a broad range of performance measures, with support from the FHWA NBI Translator
• Support for an Oracle, Sybase or SQL Server Sybase
• Extensive functionality for customization

What is Pontis?

Bridge Management Process Supported by Pontis

Developing a Preservation Policy in Pontis

Use of Elements in Pontis

• A bridge in Pontis is represented as a set of structural elements
  • AASHTO defines a set of Commonly Recognized (CoRe) elements, including descriptions of the element and condition states for each
  • Agencies may use the CoRe elements or define their own
• For each element the user specifies
  • Feasible preservation actions for each state
  • Action costs and deterioration rates (expressed using transition probabilities) for each state
• Bridges are inspected at the element level

Development of a Preservation Policy in Pontis

Element-Level Representation of a Bridge

Developing a Preservation Policy in Pontis

Modeling Approach

• Pontis recommends the optimal maintenance policy, or set of recommended actions for each state, for each element-environment combination
• Preservation models are built based on expert opinion (elicitations) and inspection history
• Each element is modeled independently
• The preservation models optimize based on discounted long-term agency costs using a Markovian decision model

Simulating Bridge Conditions

Purpose of a Program Simulation

• Pontis performs program simulations to
  • Determine current and future needs
  • Predict future performance
  • Develop work recommendations
• Pontis can be used to determine
  • Conditions predicted based on a given budget
  • Budget needed to achieve a target
• Given inspector and Pontis recommendations, an agency can use the system to develop its bridge plan

Simulating Bridge Conditions

Inputs to a Program Simulation

• Bridge inspection data
• Preservation policy (generated by Pontis)
• Functional improvement policy and costs
• Budget
• Agency business process rules
• Planned projects
• Additional simulation parameters

Simulating Bridge Conditions

Simulation Results

• Predicted conditions (network and bridge-level)
  • Needs and predicted work
  • Benefits of meeting needs and performing predicted work
  • Element conditions
  • Health index
  • NBI condition ratings
  • Sufficiency Rating
  • SD/FO status
• Bridge-level work recommendations

New Modeling Features

Improved Deterioration Model Updating

• Deterioration models can be build based on expert opinion (elicitations) and inspection history
• Recent improvements to the model updating process
  • Better algorithm for using inspection history in the update process
  • Option to specify what bridges' history to use for model updating
  • Ability to rebuild history or use prior history when performing successive model updates

New Modeling Features

Performance Targeting in the Preservation Model

• The long-term preservation model is used to specify optimal steady-state conditions
  • Steady-state conditions would result from following a specified policy over a period of many years
  • Pontis solves the long-term optimization model to determine what the annual cost would be to remain in the optimal steady-state condition
• With Pontis 4.4 a user can add performance targets to the long-term optimization
  • Targets are specified in terms of Health Index
  • Provides long-term steady state funding requirements to achieve a specified performance target

New Modeling Features

Performance Targeting Applications

• Determining the cost of meeting agency-defined performance targets
• Quantifying the costs of sub-optimal bridge conditions
• Determining long-term minimum preservation funding requirements
• Improved understanding of the Pontis-generated preservation policy

New Modeling Features

Other Improvements

• Ability to specify bridges exempted from the agency's functional improvement policy (e.g., historic bridges)
• Program simulation horizon of up to 99 years
• Flexibility for entering program simulation inputs in English or metric units
• Capability for specifying when a bridge should be removed from the inventory at some future point

Information Resources

• Web resources
  • FHWA: http://www.fhwa.dot.gov/infrastructure/asstmgmt/manag.htm
  • AASHTO: http://www.transportation.org/aashto/home.nsf/FrontPage
  • Pontis software support: http://aashtoware.camsys.com
• Documentation
  • Pontis User's Manual
  • Pontis Technical Manual
  • Referentia for Pontis Training CD