Unknown Bridge Foundations Finding a Solution : Unknown Bridge Foundations Finding a Solution
ggautrea@dotd.state.la.us and www.fdh-inc.com Louisiana DOTD and FDH, Inc.
Baton Rouge, LA and Raleigh, NC
For Louisiana DOTD : For Louisiana DOTD Gill M. Gautreau, P.E., Bridge Maintenance Engineer
Jack Manno, P.E., Hydraulics Engineer
FOR FDH, Inc. Senior Principals : FOR FDH, Inc. Senior Principals
John S. Fisher, Ph. D., P. E., Chairman
NCSU Civil Engineering Faculty
John D. Hunter, President
Ex-IBM Executive
J. Darrin Holt, Ph. D., P. E., Vice-Pres.
NCSU, NCDOT
Unknown Bridge Foundations How widespread is the problem? : Unknown Bridge Foundations How widespread is the problem? 5,000+ of 10,000 bridges over water in Louisiana alone have unknown foundations.
~ 90,000 of 500,000 bridges nationwide.
Bridges in Louisiana : Bridges in Louisiana
Scour Critical Bridges : Scour Critical Bridges
Unknown Foundation Bridges : Unknown Foundation Bridges
Why are unknown foundations a problem? : Why are unknown foundations a problem? Many Bridges with known foundations are scour critical.
Many with unknown foundations may be scour critical.
Records non-existent (lost, destroyed, etc.).
Records incomplete or even wrong.
Original contractors may no longer be around.
I-90 over Schoharie Creek : I-90 over Schoharie Creek
HEC 18 and HEC 20 : HEC 18 and HEC 20 FHWA Hydraulic Engineering Circulars
HEC 18 addresses bridge related scour.
HEC 20 addresses general stream changes.
Both must be combined to present clear prediction of scour problem.
HEC 18 Scour Predictions : HEC 18 Scour Predictions
HEC 20 Scour Predictions : HEC 20 Scour Predictions
Possible Steps for Tackling the Problem : Possible Steps for Tackling the Problem Gather all existing information.
Bridge Maintenance Records?
State Archives?
Persons that may have worked on a project?
Collect soils information.
Determine likely foundation type.
Formulate a plan for testing/investigation.
Design solution.
Possible Tools for Unknown Foundation Investigations : Possible Tools for Unknown Foundation Investigations Probing (rod & hammer - what’s under ground?)
Pulse-Echo (large width to thickness = spreads)
Ground Penetrating Radar (GPR) (site dependent)
Borehole methods (site dependent)
Dispersive Wave (slender members)
Rod and Hammer : Rod and Hammer Labor Intensive
Depth, soil dependent
May find spreads, pile lengths?
Slide16 : Computer Strike The Pulse-Echo Methods Strike Transducer Transducer Caisson / Auger cast (Be Careful ! - Dispersion occurs) Concrete Concrete
Slide17 : FDH’s technology is nondestructive, easy to apply, and does not require the site to be taken out of service. FDH does not utilize conventional pile testing technologies. The mathematics were developed by the FDH Principals.
Slide18 : Ground Penetrating Radar (GPR)
Uses electromagnetic waves to determine approximate distance to targets. Highly soil/ site dependent, good for finding metals. Finding concrete ?
Slide19 : Oscilloscope Strike Idea: Measures transit time from foundation to transducer
(Hydrophone/
Geophone) Borehole Borehole Methods
Dispersive Wave Methods : Dispersive Wave Methods Researched by FDH’s principals at NCSU
NCDOT/FHWA Funded Research
Verified Technology over Past 12 Years
Many DOT “blind tests” to Validate
Broad Applications (timber, steel H, concrete)
Previously used/adopted by NCDOT
Background : Background Douglas’ 1983 research
The timber pile length project - 1990
Fisher, Douglas, Holt (grad student)
Applications in steel, concrete driven piles
Tower applications lead to other foundation types and geometry beyond piles.
Projects: Wharves, buildings, bridges, towers, dams, etc.
Research Approach : Research Approach
Laboratory models and software development.
Field trials with known & unknown foundations.
Slide23 : Where it all began.. Timber pile bridges
NCDOT & FHWA’s interest
Slide24 : Strike a pile on its side to
create Dispersive wave motion.
(bending, flexural waves)
Record the wave motion.
Analyze data for length/condition
Dispersive Wave Propagation : Dispersive Wave Propagation Most difficult of all wave motions to handle.
Waves continually change their shape and appearance.
No mathematical solution to their motion existed.
Required ~10 years of experimental work. Began in 1983.
Slide31 : Data Acquisition
Portable
Slide32 : Steel pile testing.
Same principles apply.
Slide33 : Concrete is more difficult,
but can be tested for length
and condition (breaks).
Slide34 : Pile testing at a
wharf in NC
Slide36 : Sometimes conditions require a bigger hammer.
Slide37 : Testing can even be done underwater.
Foundation Types FDH has Tested : Foundation Types FDH has Tested Driven, Cast-in-Place piles
Spread footings
Caissons (drilled piers)
Auger cast piles
Buried concrete blocks
Tie-back rods
Sheet Piles
“Blind tests” of Dispersive Wave Technology : “Blind tests” of Dispersive Wave Technology
Slide43 : State of Mississippi
Extracting piles to directly verify technology. October 1998
Slide44 : A full day to
pull 10 piles.
Slide46 : Pile was broken probably during original installation
Slide47 : Another broken pile.
Slide48 : Unknown, deteriorated pile.
Dispersive wave data identified this damage.
Key Features of DWT... Nondestructive Robust Structure remains in service Can be used underwater (have used in 60 ft of water) Has been verified with existing records and pile extractions. : Key Features of DWT... Nondestructive Robust Structure remains in service Can be used underwater (have used in 60 ft of water) Has been verified with existing records and pile extractions.
DOT Bridge Foundation Testing : DOT Bridge Foundation Testing NC, SC, GA, FL, AL, MS, LA, TN, KY, MN, ID
Managed a $1 Mil.+ unknown bridge foundation contract in MS. FDH Has Extensive National Experience All states except: MT, ND, AK Prime contractor for : 170 telecom sites, 1000 + unknown foundations in 4 months.
The FDH Team : The FDH Team Registered PE’s with advanced degrees in Civil Engineering
Mathematician
Physicist
Experienced Field Technicians trained in NDT technologies
Project Managers
Publications... : Publications... Transportation Research Board
Various ASCE Seminars and Meetings
Various State DOT Engineers’ meetings.
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