About LTBP

This research was conducted 

as part of the Federal Highway 

Administration’s Long-Term 

Bridge Performance (LTBP) 

Program. The LTBP Program is 

a minimum 20-year research 

effort to collect scientific performance field data, from 

a representative sample of 

bridges nationwide, that will 

help the bridge community 

better understand bridge 

deterioration and performance. 

The products from this program will be a collection of 

data-driven tools including 

predictive and forecasting 

models that will enhance the 

abilities of bridge owners to 

optimize their management 

of bridges.

FHWA LTBP Workshop to Identify 

Bridge Substructure Performance Issues

TECHBRIEF

Objective

This TechBrief provides an overview of the proceedings 

and findings of the “FHWA Workshop to Identify Bridge 

Substructure Performance Issues” held in Orlando, FL, 

from March  4  to  6, 2010. The purpose of the workshop 

was to consider overall bridge performance and identify 

geotechnical performance metrics that may correspond to 

good and poor performance. The issues identified and the 

recommendations made at the workshop are being used 

in the design and implementation of the Long-Term Bridge 

Performance (LTBP) program. 

Introduction

FHWA launched the LTBP program to improve understanding of bridge performance. The program’s mission is to foster

improved bridge performance, health, stewardship, and 

management through the analysis of data collected over a 

20-year period on representative samples of highway bridges 

in the United States. To achieve this mission, the program 

is designed to produce or support improved deterioration 

models, reliable life-cycle cost and forecasting models, 

design procedures, and decisionmaking tools. One of the 

earliest steps in the implementation of the LTBP program was 

determining which aspects of bridge performance to study.

FHWA Publication No.: FHWA-HRT-13-049

FHWA Contact: Dr. Hamid Ghasemi, HRDI-60, (202) 493-3042, hamid.ghasemi@dot.gov

This document is a technical summary of the Federal Highway Administration (FHWA) report FHWA 

LTBP Workshop to Identify Bridge Substructure Performance Issues: March 4–6, 2010, in Orlando, FL

(FHWA-HRT-11-037). Copies are available through the National Technical Information Service (NTIS).

NTIS Accession No. of the report covered in this TechBrief: PB2013-107742

Research, Development, and Technology | Turner-Fairbank Highway Research Center | 6300 Georgetown Pike, McLean, VA 22101-2296

http://www.fhwa.dot.gov/research/
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After the LTBP program was initiated in 

April  2008, FHWA conducted a series of focus 

group meetings with bridge experts from State 

transportation departments in different regions 

of the country. The conclusions from those meetings are the subject of future TechBriefs. Among 

the general bridge performance issues identified, the following issues related to structural 

foundation elements or geotechnical factors 

were documented:

• Methods to measure scour that are direct, 

reliable, and timely.

• Performance of scour countermeasures.

• Performance of structure foundation types.

• Identification and performance of unknown 

foundation types.

• Performance of integral and semi-integral 

abutment bridges.

In order to further evaluate, prioritize, and refine 

these geotechnical issues, FHWA sponsored a 

workshop in Orlando, FL, from March 4 to 6, 2010. 

FHWA invited participants with different backgrounds and perspectives to ensure diversity 

of input. The 43 workshop attendees included 

bridge/geotechnical experts from State transportation departments, FHWA, academia, and 

industry groups. 

The workshop served as an opportunity to define 

how geotechnical issues could be incorporated 

in the LTBP program, what geotechnical data 

should be collected under the LTBP program, 

and what tools and technologies would be 

needed for collection of that data. The workshop 

consisted of a plenary session followed by three 

breakout sessions with the following objectives:

• Breakout session I: Identify key performance issues related to substructures and 

foundations.

• Breakout session II: Identify data needs 

and gaps related to the key geotechnical 

performance issues.

• Breakout session III: Identify tools, technologies, and monitoring necessary to collect 

critical geotechnical performance data.

The Plenary Session

The workshop began with a plenary session at 

which a series of speakers provided an overview 

of the LTBP program, summarized the findings 

from the focus group meetings, described the 

general LTBP research approach, discussed the 

pilot bridge phase, and gave an overview of geotechnical factors related to bridge performance. 

This session was intended to provide context for 

the subsequent breakout session discussions.

Several examples of geotechnical issues affecting bridge performance were described, including mechanically stabilized earth (MSE) walls, 

foundations on rock, abutment issues (in particular, settlement at the bridge-abutment interface 

and its effects on the superstructure), and scour.

The Breakout Sessions

The purpose of the breakout sessions was to 

consider overall bridge performance and identify 

geotechnical performance indicators that may 

correspond to good and poor performance. The 

information generated was to be provided to the 

LTBP program as recommendations to accommodate collection of additional data as well as to 

identify methods to collect and evaluate the data.

The focus group meetings held by the LTBP 

program had identified a few general topics 

related to substructures and foundations. The 

participant groups were asked to consider these 

and other geotechnical issues related to bridges 

that could merit consideration and to identify 

and define the key bridge performance issues 

related to substructures and foundations, data 

needs and gaps related to these key issues, and 

tools, technology development, and monitoring necessary to collect critical geotechnical 

performance data for the LTBP program. 

Breakout Session I: Bridge Performance Issues 

The first breakout session focused on identifying 

the most important bridge performance issues 

related to foundations, substructures, and geotechnical features. This breakout session developed and prioritized the key geotechnical issues 

that affect critical aspects of bridge performance 

as well as performance of the bridge as a whole. 
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Table 2. Breakout session II: Data needs and gaps related to priority geotechnical performance issues 

for bridges.

Performance Issue

Data Needs

Construction Records

Inspection and 

Maintenance History

Characterization of 

Service Environment

Post-Construction 

Monitoring

Approachbridge interface 

• As-built plans

• Foundation report

• Inspection reports

• Photos

• Voids under slabs

• Winter maintenance 

practices

• Climate data

• Traffic

• Loads

• Settlement 

• Rideability

• Deformations

• Vibrations

Material degradation

• As-built plans • Inspection reports

• Winter maintenance 

practices

• Climate data

• Groundwater info

• Soil characteristics

• Corrosion detection

• Condition of 

foundation elements

MSE walls

• As-built plans • Visual indications of 

corrosion

• Climate data

• Indications of salt 

intrusion from poor 

surface drainage

• Soil pH

• Water pH

Hydraulics

• As-built plans

• Abutment/pier type

• Channel capacity

• Type of scour 

countermeasures 

employed

• Predicted scour

• Historical flow data

• Channel stability 

and migration

• Flood data/records

• Climate data

• Ice data

• Stream velocity

• Scour depth

• Actual scour versus 

predicted scour

Table 1. Breakout session I: Summary of priority geotechnical performance issues identified by each group.

Group 1 Group 2 Group 3

• Abutments: Bump at end of bridge, 

integral abutments, piles

• Foundations: Measured loads, 

widening, unknown foundations, 

tolerable movements

• Hydraulics: Scour, drainage

• Materials: Corrosion

• Construction: Quality control

• Approaches: Settlement, global stability

• Piers: Scour, total differential 

settlement, horizontal movement

• Abutments: Vertical and horizontal 

joint movement, differential 

settlement, scour, pile performance

• Abutment walls: Corrosion, drainage 

failure, scour, soil restraint

• Corrosion/deterioration (MSE walls, 

steel in piles, embankment material)

• Bump at end of bridge (significant)

• Fatigue/integral abutment/lateral 

stress

• Drainage, runoff, erosion

• Remaining service life—long-term 

performance

Following brainstorming on bridge performance 

issues in the three breakout groups, the lists 

and priorities from each group were collected 

and presented. Despite different approaches 

to identifying and rating the importance of the 

issues, the groups generally identified the same 

issues and priorities. A summary of the priorities 

identified by each group is presented in table 1. 

Common issues identified by multiple groups 

were the bump at end of the bridge, integral 

abutments, settlement of abutments and piers, 

material corrosion, and scour.

Breakout Session II: Data Needs and Gaps Related 

to Geotechnical Performance Issues for Bridges

The second breakout session focused on 

discussing the data needs and gaps related to 

the key performance issues identified in the 

first breakout session. Each breakout group 

developed a list of data that can currently be 

collected, data that need to be collected during 

the course of the 20-year research program, and 

data that cannot currently be collected but would 

be important to the objectives of the program. 

Following brainstorming on data needs 

and gaps in the three breakout groups, the 

lists and priorities from each group were 

presented to the larger group. The complete 

list of data needs and gaps identified by the 

three groups is available in the full report, 

FHWA LTBP Workshop to Identify Bridge 

Substructure Performance Issues: March  4–6, 

2010, in Orlando, FL. Table 2 provides some of 
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Table 3. Breakout Session III: Needed tools, technology development, and monitoring.

Geotechnical 

Performance Issue Tools Currently Available

Short-Term Technology 

Development

Long-Term Technology 

Development and Monitoring

Bump at the end 

of the bridge

• Ground-penetrating radar 

• Survey

• Inclinometer

• TDR moisture sensors

• Settlement points at depth

• Road profiler

• Airborne LIDAR

• User feedback (phone calls)

• Accident data

• Maintenance records

• Peak particle vibration 

monitoring

• Quality geotechnical data

• In situ geotechnical testing

• Tiltmeters

• High-speed pavement 

profilers

• Smart pavement to capture 

loading

• Earth pressure cells

• Smart soils with MEMS 

embedded

Foundations

• Strain gauges

• Load cells

• Survey

• Inclinometer

• Settlement points at depth

• Laser scanning

• Maintenance records

• Quality geotechnical data

• In situ geotechnical testing

• Tiltmeters

• Bridge response WIM

• Crack meters

• TDR cables embedded in 

foundation

• Settlement of foundation

• Load test data

• Embedded GPS reference 

points in foundations

• Smart foundation elements

• Technique to measure 

existing load on foundation

• Laser/radar interferometry 

monitoring of deflection

• Earth pressure cells

• Energy piles/geothermal 

heating for heating of decks

See notes at end of table.

the data needs identified by the groups for the 

performance issues identified at the workshop. 

It was recommended that a follow-up task 

group formulate research needs related to data 

needs and gaps for the LTBP program.

Breakout Session III: Tools, Technology 

Development, and Monitoring Needed 

for Geotechnical Performance Data

The third breakout session focused on how 

geotechnical performance data can be collected. 

The breakout groups identified tools and technologies that are currently available and 

should be used in the LTBP program as well as 

technology development and monitoring that 

are needed to address identified data gaps. 

Following brainstorming on tools, technology 

development, and monitoring in the three 

breakout groups, the lists and assessments 

from each group were presented to the larger 

group. The benefit of this session was that the 

breakout groups identified a comprehensive 

list of tools and technologies for data collection and, in some measure, mapped the tools/

technologies to specific data needs as well as 

future and long-term needs. Table 3 provides 

some of the ideas developed on tools, technology development, and monitoring; the 

complete list is provided in the full report, 

FHWA LTBP Workshop to Identify Bridge 

Substructure Performance Issues: March 4–6, 

2010, in Orlando, FL. It was recommended that 

a follow-up task group better define the tools, 

technology development, and monitoring 

of geotechnical-related bridge assets for the 

LTBP program.
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Table 3. Breakout session III: Needed tools, technology development, and monitoring—Continued.

Geotechnical 

Performance Issue Tools Currently Available

Short-Term Technology 

Development

Long-Term Technology 

Development and Monitoring

Deterioration

• Half cell potential

• Resistivity

• Sacrificial steel and inspection

• Concrete coring

• Concentrations of chloride 

and sulfate in concrete

• Concrete cover 

measurements

• Ultrasonics

• Optical TDR

• Laser/radar interfereometry 

monitoring of deflection

• Shear/p-wave velocity (for 

elemental stiffness)

• Smart paint/coating (to 

measure stress, corrosion)

• Self-healing steel 

• Self-healing concrete

• Maintaining compatibility of 

strains in repair materials

• Embedded biosensors (i.e., 

effervescent bacteria)

Earth-retaining 

structures

• Strain gauges

• Load cells

• Survey

• Inclinometer

• TDR moisture sensors

• Settlement points at depth

• Laser scanning

• Airborne LIDAR

• Maintenance records

• Quality geotechnical data

• In situ geotechnical testing

• Tiltmeters

• Crack meters

• Piezometers

• Inspect drains

• TDR cables

• Smart concrete/structure 

members to capture loading

• Electro-conductivity of wall

• Earth pressure cells

• New technique to measure 

water height behind wall face

• Smart soils

• Harnessing movement on 

bridge to capture energy to 

power sensors

Hydraulics (scour)

• Sonar

• Plumb bobs

• Float out device

• TDR vertical and horizontal

• Sub-bottom profiler

• Ground-penetrating radar 

• Flow monitoring

• Visual inspection/diver

• Embedded GPS reference 

points in countermeasures

• In-place sonar

• Float out device attached to 

structure

• Vibrations of pier structure

• Smart particles

• Satellite/airborne imagery to 

detect scour holes

GPS = Global Positioning System. MEMS = Microelectromechanical systems. WIM = Weigh in motion.

LIDAR = Light detection and ranging. TDR = Time domain reflectometry. 

Conclusions

A number of short-term geotechnical bridge 

performance priorities emerged from the workshop. These priorities can be summarized in four 

categories. For each of the performance issues, 

assessments of the cause and effect of the 

issue, the quality control and quality assurance 

aspects, the detection and monitoring aspects, 

and the remedial actions to overcome the issues 

need to be completed.

Approach/bridge interface issues included the 

following: 

• Settlement, including foundation and fill

settlements, erosion of toe fills, poor 

material quality, and substandard construction practices.

• Integral abutments, temperature loads, and 

ratcheting effects.

Material degradation/corrosion/long-term deterioration issues included the following: 

• Effects of salt water on both concrete and 

steel piles.

• Metallic inclusions (e.g., soil nails, anchors).

• Aggressive soils.
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Researchers—This study was performed by Rutgers, the State University of New Jersey, 

Highway R&D Services; the Virginia Center for Transportation Innovation and Research; Iowa State 

University; and Parsons Brinckerhoff. For additional information, contact Dr. Hamid Ghasemi in 

the FHWA Office of Infrastructure Research and Development, located at 6300 Georgetown Pike, 

McLean, VA 22101-2296. 

Distribution—This TechBrief is being distributed according to a standard distribution. Direct 

distribution is being made to the Divisions and Resource Center.

Availability—Report No. FHWA-HRT-11-037, FHWA LTBP Workshop to Identify Bridge Substructure 

Performance Issues: March 4–6, 2010, in Orlando, FL, is available. It can be obtained from the 

National Technical Information Service, www.ntis.gov.

Key Words—LTBP program, Bridge performance, Bridge substructure, Substructure 

performance, Long-term bridge performance.

Notice—This document is disseminated under the sponsorship of the U.S. Department of 

Transportation in the interest of information exchange. The U.S. Government assumes no liability 

for the use of the information contained in this document. The U.S. Government does not endorse 

products or manufacturers. Trademarks or manufacturers’ names appear in this TechBrief only 

because they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration provides high-quality 

information to serve Government, industry, and the public in a manner that promotes public 

understanding. Standards and policies are used to ensure and maximize the quality, objectivity, 

utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its 

programs and processes to ensure continuous quality improvement.

June 2013 FHWA-HRT-13-049

HRDI-60/06-13(750)E

MSE wall issues (material degradation and assessment of wall integrity) included the following:

• Condition of reinforcement, including possible corrosion, deterioration, and creep.

• Deformation of MSE walls.

• Quality of backfill.

• Leakage of backfill.

Hydraulic issues included the following:

• Direct, reliable, and timely methods to 

measure scour.

• Performance of scour countermeasures.

• Drainage, joint infiltration, weep holes, and 

underdrains.

• Erosion of approach embankments and of 

soil supporting and behind cast-in-place 

concrete walls.

From the results of this workshop and other 

available information, these issues can be 

considered for inclusion on the LTBP list of study 

topics. Each issue will have to be further studied 

for the state of practice, related research, and 

identification of key questions that might be 

addressed under the LTBP program. 

A number of data needs were identified for 

the short-term bridge performance issues 

identified. Some data needs, such as as-built 

plans and climate data, cut across all the 

performance issues. 

The workshop participants did an outstanding 

job of identifying the data needs. The identification of needed tools, technology development, 

and monitoring was helpful to FHWA.