LTBP Tools and Products
- Bridge Deterioration Models
- Bridge Performance Transition Forecast
- Bridge Condition Transition History Tool
- Asset Valuation Tool
- Historical Bridge Specification Changes
- LTBP Program Protocols
Bridge Deterioration Models
Bridge condition forecast models are an essential component for implementing a data-driven bridge asset management program by optimizing the funding allocation that is associated with bridge replacement, rehabilitation, repairs, maintenance, or preservation.
The LTBP Program developed three bridge components (deck, superstructure, and substructure) condition forecast models (Base Models, Survival Models, and Machine Learning Models) and implemented them in the January 2020 LTBP InfoBridge release. The models are updated annually to account for annual submittals of the National Bridge Inventory (NBI).
The three models represent three levels of modeling complexities. Base Models are statistically deterministic and compute the average time-in-condition for each bridge type from historical National Bridge Inventory (NBI) data and apply those to each bridge component condition forecasting. Survival models derive condition rating transition probabilities from survival-analysis curves and use Markov chain probabilistic methods to forecast future condition ratings. Machine-learning models are developed by mining the historical NBI and climate data using a deep learning approach.
Figure 1. InfoBridge showing the Bridge Deck (Component) Condition Forecast Modeling Tool (Source: FHWA)
The Bridge Performance Transition Forecast tool in InfoBridge™ produces a list of bridges that may transition from one condition state to another over a user-specified time period. Under Performance Forecast, select the Bridge Condition Transition Forecast tab to access the tool. The tool can also be accessed from the Tools menu.
The starting year for the forecast is set to the latest year for which the National Bridge Inventory (NBI) data are available. For selected bridges, users can specify the condition in the start year and the desired condition in a later year. Users may also input the minimum probability of occurrence for the forecast. Users select one of two deterioration models—the proportional hazards deterioration model or the machine learning model—to perform the calculations.
The resulting list of bridges, and a few pertinent NBI items, are displayed on screen and can also be exported into an Excel® spreadsheet.
Figure 2. InfoBridge showing the Bridge Performance Transition Forecast Tool (Source: FHWA)
The Bridge Condition Transition History tool in InfoBridge™ produces a list of bridges that has transitioned from one condition state to another over a user-specified period. Under Performance History, select the Bridge Condition Transition History tab to access the tool. The tool can also be accessed under the Tools menu.
The starting year selection is limited to the year from which InfoBridge maintains condition data for all bridges; in most cases this year is 1985. The ending year must occur later than the starting year, and both the starting and ending years cannot occur later than the current NBI data year.
The tool generates a list of bridges meeting the user-specified requirements. The list includes a few pertinent NBI items. The bridge condition in terms of Good, Fair, and Poor is displayed for each year of the specified duration. The list can be exported into an Excel© spreadsheet.
Figure 3. InfoBridge showing the Bridge Condition Transition History Tool (Source: FHWA)
The asset valuation tool in InfoBridge provides an estimate of the replacement value, existing value (EV), and remaining value of user-selected bridges.
The tool also provides a State-wise summary of the replacement value, EV, and remaining value of bridges in each State.
Details of the calculations are available under the InfoBridge Library menu.
Figure 4. InfoBridge showing the Bridge Asset Valuation Tool (Source: FHWA)
For more information visit https://infobridge.fhwa.dot.gov/.
This tool documents the historical changes in bridge materials and design specifications in chronological order. It also provides an easy to use search feature.
Figure 5. InfoBridge showing the Historical Bridge Specification Tool (Source: FHWA)
To ensure that LTBP Program data are collected in a consistent manner over the duration of the program, FHWA is developing data collection protocols for use by practitioners, LTBP Program researchers, and decisionmakers involved with the research, design, construction, inspection, maintenance, and management of bridges. The LTBP Program protocols are for research purposes and intended primarily for use within the LTBP Program.
The LTBP Program protocols are organized into a hierarchy based on the following chronology of a data collection effort for a single bridge: Previsit (PRE), Field Visit (FLD), and Postvisit (PST). This simple chronology was selected to make finding the required protocols intuitive for users. The first three levels of the proposed hierarchy are shown in figure 1.
Figure 6. Illustration. LTBP Program Protocol Hierarchy.
The PRE protocols focus on preparation and actions that occur prior to collecting data at the bridge. This group includes the following activities:
- Sampling and Selection (SS): The process involved with bridge selection.
- Existing Documentation (ED): The obtaining of existing bridge documentation from bridge owners and detailing legacy data mining for specific performance issues.
- Equipment (EQ): Equipment related to structural testing, including sensors and data acquisition systems along with specific protocols related to each type of truck testing.
- Planning and Logistics (PL): Preparation for a field data collection effort, from personnel safety to the processes for maintenance and protection of traffic and site-specific requirements.
The FLD protocols focus on collecting research-quality data in a consistent manner to facilitate comparative analysis across structures and with time. This group contains the following activities:
- Onsite Pretest Activities (OP): Segmentation, identification, and labeling of the various elements of a bridge so recorded findings of the field assessment and testing activities may be tied to specific elements and locations on the bridge.
- Field Data Collection (DC): Data collection at the bridge, including photography, material sampling, NDE, visual inspection, instrumentation logistics, and various types of testing. (Note: this makes up the main portion of the protocols.)
- Data Storage (DS): Proper storage of raw data immediately after collection to ensure no repeat field efforts are required and that no data are lost.
The PST protocols focus on actions taken after the data are collected at the bridge and how the collected data are used to draw conclusions and include the following activities:
- Data Reduction and Processing (DR): Data interpretation methods and steps to evaluate and interpret the data and metadata.
- Archiving and Reporting (AR): Consistency in reporting results as well as formatting data and metadata for inclusion in the LTBP InfoBridge™ Portal.
Released in January 2016, Report FHWA-HRT-16-007, Long-Term Bridge Performance (LTBP) Program Protocols, Version 1, presents the first 51 protocols (selected PRE and FLD protocols) that will be used throughout the LTBP Program for data collection, mining of bridge legacy data, visual inspection, sampling and testing of concrete materials, and NDE of bridges, as well as data management and storage. Future versions of the protocols will be published and include additional protocols that will be implemented in the LTBP Program studies as well as any modifications deemed necessary to the protocols already published.