16h00silasnichols19-06.pdf

7/30/2019 16h00SilasNichols19-06.pdf

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Maintenance of Bridge Foundations:

Transportation Asset Management

Silas Nichols

Principal Bridge Engineer-Geotechnical

U.S. Federal Highway Administration

Office of Infrastructure

Washington, DC


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Some Context on NationalHighway System

Aging Infrastructure

Growing Congestion Funding Shortfall

Focus on System Performance

Asset Management is Imperative


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Transportation Asset Management

Transportation Asset Management is a strategic

and systematic process of operating,

maintaining, upgrading and expandingphysical assets effectively throughout their

lifecycle. It focuses on business and

engineering practices for resource allocation

and utilization, with the objective of better

decision making based upon quality

information and well defined objectives.

AASHTO Subcommittee on Asset Management


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Improved decision-making supported by policies,performance-based goals, performance measures, and

appropriate service levels Decisions are based on accurate data, and sound

engineering and economic analysis

Long-term view of assets More robust management and monitoring systems

How Does Transportation AssetManagement Work?


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Challenges in Measuring BridgePerformance

Dependent on multiple and often interrelated factors, Original design parameters and specifications

Initial quality of materials and of the as-builtconstruction

Varying environmental conditions

Type, timing and effectiveness of

preventive maintenance, minor and major rehabilitation actions

replacement actions


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UncertainAction Effectiveness

1. different actions at a given

application time (t1)2. same action at different

application time (t1 vs. t2)

Time

Action A2 at

time t1

Action A1 at

time t1

Action A2at time t2

Uncertain

Time of Applying/Delaying Actions

Uncertain

Costsassociated with

applied actions

Uncertain

Deterioration Ratesassociated with

different actions

Condition

Bridge Condition vs. Age

t1t2

Uncertainty in Data


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Geotechnical Assets and LiabilitiesGeotechnical Features are often overlooked when

considering assets and liabilities with regard tomanagement, maintenance and data collection protocols

Soil and Rock Fills and Cuts Soil and Rock Instabilities and Hazards Shallow and Deep Foundations Earth Retaining Structures Ground Improvement Installation Geotechnical Databases/Material Information


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Why and when should Transportation ownersbe interested in evaluating Geotechnical

Features?

During installation as part of quality control and assurance As part of periodic evaluations and inspections When some distress is visually observed When rehabilitation or reconstruction, load rating, and

widening is being considered

After the feature has experienced an extreme event


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Differential Settlement


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Bridge Abutment MovementsBridge Span

Soft Layer

AbutmentFill

Foundation Layer


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BACKGROUND: Little if any thought hastraditionally given to the short and long-term

condition of Geofeatures.

This situation is largely based on ignorance, a false

sense of security that Transportation Assets aregrossly over designed, will last FOREVER and a

frustration regarding the means and methods of such

evaluation (reliable, accurate, rapid and cost

effective).


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Historical Perspective

Small design loads, very conservative designs Geotechnical Designers had little knowledge of loads and

performance requirements.

Primitive specifications and construction control methods No real consideration of long-term behavior No discussion of design life and life cycle cost modeling


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Historical Perspective Lack of practical, reliable and cost effective tools to evaluate

existing geofeatures

Minimal consideration of deterioration models Relatively small effort devoted to determining long term

behavior

Perhaps most complex and difficult component to evaluate Rehabilitation and reconstruction a huge expense for

transportation owners


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CURRENT PRACTICE AND FUTURETRENDS Load magnitude and general demand per element is greatly

increasing

Many more choices

Nominal dimensions are greatly increasing (length and cross-section). Smaller number of elements per support

Demand on geotechnical and structural materials increasing (in

general, lower safety factors)

Better appreciation and concern of geofeatures by the structural

community Designs become more deformation based sensitive and complex

Much better Site Investigation and Construction Monitoring tools


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EVALUATING STRUCTURAL FOUNDATIONS:What aspects of the foundation are needed for an

analysis?

Foundation Types: shallow and deep (driven, drilled shafts,micropiles, auger cast)

Foundation Dimensions (length, geometry) Foundation material Integrity (short/long) Load Carrying Capability Load Displacement Behavior (vertical and lateral) Knowledge of loads and desired performance


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TESTING CHALLENGES


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Resources and GapsFHWA OPPORTUNITIES

National Bridge Inventory

Long Term Bridge Performance Program

Geotechnical Asset Management Initiatives

Unknown Foundations Program

RESEARCH DEVELOPMENT

Ever shrinking number of sources and level of resources.

Ever increasing number of dedicated projects and programs.

Increasing need for interdisciplinary teams and solutions to problems.

Need to better combine basic and applied research tools and

accelerate mainstream implementation approaches


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Thank You!

Silas Nichols, P.E.Principal Bridge Engineer Geotechnical

FHWA Office of Bridge Technology

1-202-366-1554

[email protected]

16h00silasnichols19-06.pdf

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