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FHWA Unknown Foundations Summit
Unknown Foundations and Their Impact on Retrofitting Bridges
Ian Friedland, FHWA R&D
IF: Been involved with UF since 1988 as staff engineer at NCHRP. 15 years later. I'm concerned or disappointed that we haven't resolved this. We still have 86,000 bridges, that's a large number of structures. Historically, parallel to collapse of bridge in late 60s in Ohio. Killed 40 people. FHWA had no inventory or standards.
To get handle and start getting info, comparison with JFK's challenge to get man to moon. 1988 should not have been a surprise. In 15 years have some solutions but not enough, not cost-effective, etc.
One reason why not made enough progress. Summit needs to set course. Not due to money, lack of leadership or innovative thinking?
My points have already been made. Need to keep re-emphasizing some key points.
What is UF? Dictionary: unknown is not have value/quality; foundation: act of founding; basis of support; underlying natural prepared base of support;
FHWA HEC-18 Definition
Type, material, dimensions, rein Doesn't talk about quality, but almost as important. Need technology to help define these things
not just a hydraulic problem, not just a scour issue
it is with earthquake engineering, see what bridge can handle. Find our bridges are inadequate in foundations
Need to know what's in the foundations. Can't make assumptions. Need know bridges will withstand any impact, top to bottom.
Terrorism. Need to identify foundations, etc. can handle blast pressure waves?
Every day events
Capacity improvements, i.e., widening.
Repair/restoration. If patching columns need info on foundation
Bridge inspection/load capacity rating—is foundation adequate to support loads?
Discuss state of the art techniques to manage bridges
Determine capability reliability and probable cost of tools (hard side and soft side)
Provide guidance and management strategies to owners
Not just scour problem, geotech and engineering problem
Why are new bridges be coded unknown?
Foundation integrity is as important as size/type/length
Can we make certain assumptions and use this in our decisionmaking?
How essential to have high quality data on low volume, low risk structures?
Will we ever be able to assess foundations covered in rip-rap or other difficult geometries, do we need to?
Q: Compared going to moon, budget not comparable. How much is this worth to us?
IF: Lots of answers, put in as much as we have, but don't know what we have yet. This question needs to go to bridge owners. Having inadequate info not good. I think worth large investment. NCHRP also thinks good thing. Do we need 10 or 100 fold increase? Don't know.
Q: Average bridge is $500,000. need think in terms of investment and what to put into it.
IF: Value of national bridge inventory at about $2 or $3 trillion.
Q: Risk based assessments. Lots of variances between States and what affect RBAs. Differences in piles.
Q: Ratings. We have to lower rating cuz we don't know what foundation is. Also, what causes this problem? Some of info out there needs to be explored.
IF: Good point, older bridges all built the same, even though we don't' have plans for them. That's what needs go out.
Q: Budget issues. In Florida, bridges built privately, then turned over to public sector, no standards. Will be adding lots of uf due to development.
IF: Need as-builts. May not know what final product looks like.
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