Investigation of Unknown Bridge Foundations in Oregon

Transcription

1 Investigation of Unknown Bridge Foundations in Oregon 2013 Pacific NW Bridge Inspection Conference Portland, Oregon April 24, 2013 Jan Six, Sr. Geotechnical Engineer ODOT Bridge Engineering Section 1

2 Scour Problems 2

3 Bridge Inspection Reports (108) Wearing Surface 600 (109) Truck ADT 12 (110) Designated National Network 0 Unknown foundations are coded as U for Item 113 Scour, and are all categorized as scour critical bridges. (111) Pier Protection 1 (112) NBIS Bridge Length Y (113) Scour Critical Bridge U (114) Future ADT 7600 (115) Year of Future ADT 2030 (116) Vert-Lift Clearance ***State Information*** (117) Est M aint Cost (118) Culvert Length (119) Culvert Inside Height (120) Inspector Robert Burns (S0033) (125) Embankment Erosion 5 3

4 NBI Item Scour 4

5 Background Approximately 580,000 bridges in NBI, about 104,000 have unknown foundations in terms of type and/or depths. Generally two types: the foundation type and depth are unknown; the foundation type is known, but its depth is unknown Need foundation type and depth (along with dimensions) to perform scour evaluation at each bridge. With foundation type and depths known, and a scour analysis (scour depths), we can determine if remedial (mitigation) measures are necessary. 5

6 Background Table 1 - Number of Bridges over Waterways Coded U (Unknown Foundations) for Item 113 of the NBI Agency NHS Non-NHS Total Federal State 1,155* 12,864 14,019 Local ,577 52,901 Other Bridge Owners Total 1,481 65,759 67,240 * Includes 144 bridges with Interstate designation Data as of September 2007 Source: Federal Highway Administration, January 9, 2008 Memorandum ACTION: Technical Guidance for Bridges over Waterways with Unknown Foundations 6

7 Background January, 2008 FHWA issued a memorandum providing technical guidance for reducing the number of bridges with unknown foundations. Memorandim targeted November, 2010 as the date for eliminating all unknown foundations from the NBI. Later memo (October, 2009) recognized that some unknown foundations will remain and recommends development and implementation of Plans of Action for all U coded bridges. FHWA promotes a risk-based assessment of unknown foundation bridges. Website: 7

8 NCHRP Study Project Scour Risk Management Guidelines Probability of Failure Cost of Failure Risk of Failure Quantifying Risk for Scour Failure Mitigating Actions for Scour Scour Management Case Studies 8

9 Other NCHRP Reports Determination of Unknown Subsurface Bridge Foundations (NCHRP 21-5), Focused on the identification of potential Non-Destructive Methods (NDE) methods for determining depths of unknown bridge foundations at 7 bridges in Colorado, Texas and Alabama that had known foundations. Unknown Subsurface Bridge Foundation Testing (NCHRP 21-5(2), Draft), June, 2001 Focused on evaluating the validity and accuracy of the identified NDE methods for determining depths of 20 known bridge foundation sites. Phase II research also involved the development of hardware and software needed to perform the NDE testing. 9

10 ODOT Situation ODOT has 2714 NBI bridges, 1575 over waterways Starting in 2006, information was compiled on all U bridges for use to either recode the bridge or prioritize for field investigation work. Addition staff (1 temp) in 2006 to assist in office research. As of September 2007, ODOT had 175 Unknown Bridge Foundations listed in the NBI. Some preliminary non-destructive testing (NDT) was conducted on 2 ODOT bridges. 10

11 ODOT Approach Screen all U bridges to check that they are correctly coded and then prioritize them. Conduct office research for existing information Develop inferred foundations (if possible) Conduct field investigations Conduct a scour evaluation at each site, compare the results with the foundation depths obtained from the research and investigation work and recode Item 113 for the bridge accordingly. This may also involve an evaluation of the stability of the bridge under scour and flood water conditions. 11

12 Screening Screen all bridges coded U to ensure that they are correctly coded as having unknown foundations. Also screened out: culverts bridges to be replaced within 5 years recently constructed bridges Prioritize these bridges based on their functional classification and ADT. Principal Arterial - Interstate Principal Arterial - Other Freeways or Expressways Other Principal Arterial Minor Arterial Major Collector Minor Collector 12

13 Office Research Collect and document existing information for each bridge from the following resources: Bridge plan sheets, (as-constructed or not) Pile driving record books Bridge construction records Bridge archive records (design and construction information) Is there sufficient as-built information to perform a scour analysis? 13

14 Inferred Foundation Depths Collect information on the geologic subsurface conditions at each site and in the general area. If foundation type, design loading and subsurface materials are known to a sufficient extent, perform calculations to determine inferred foundation depths. Able to do this for 5 bridges 14

15 Current Status of Unknown Foundations Original Total 175 remove culverts and scheduled replacements - 16 Revised Total 159 Completed (or Inferred) with inhouse records 46 Revised Total 113 Already Recoded - 2 Revised Total 111 Completed under FDH WO#1 (2011) - 33 Revised Total 78 YR2000 Bridges left - 3 Waiting for as-built elevs. Revised Total for NDT 75 Postponed for scour review 20 Remaining Bridges for NDT Piles Supported; 8 Footing Supported; 14 Unknown 15

16 Field Investigation Methods Conventional Methods 16

17 Field Investigation Methods Conventional Methods Generally expensive, destructive, and limited in their application to the unknown foundation problem. Nondestructive testing methods are preferred at many locations to provide better data at a lower cost. 17

18 Non-Destructive Testing Methods Stress Wave Techniques NDT Stress Wave Methods from Substructure or Superstructure Sonic Echo/Impulse Response Dispersion of Bending Wave Energy Ultraseismic Dynamic Foundation Response Surface Seismic Methods Borehole Methods Electrical and Electromagnetic Techniques Magnetic Techniques Gravity Techniques 18

19 Non-Destructive Testing Methods Surface Techniques (requiring access to exposed parts of the bridge substructure) Sonic Echo (SE)/Impulse Response (IR), Bending Wave (BW) Ultraseismic (US) Spectral Analysis of Surface Waves (SASW) Surface Ground Penetrating Radar (GPR) Subsurface Techniques (requires access through a nearby borehole) Parallel Seismic (PS) Borehole Radar (BHR) Borehole Sonic (BHS) Induction Field (IF) 19

20 Non-Destructive Testing Methods Applicability of Each Method depends on: Foundation characteristics (materials, shallow or deep foundation, etc.) Access requirements Cost for equipment and testing Required expertise Limitations of method 20

21 Non-Destructive Testing Methods Bending Wave Test Method Timber, concrete or concrete filled pipe piles Must have good access to exposed piles Waves reflect off on splices or breaks in piles giving false lengths 21

22 Accelerometers 22

23 23

24 24

25 Data Acquisition System 25

26 26

27 Bending wave test on steel H-Piles (with pile splices) 27

28 28

29 Bending Wave Test Method Test Results using dispersive wave filtering techniques First part of signal Observed Reflection 29

30 Non-Destructive Testing Methods Sonic Echo/Impulse Response Test Method 30

31 Non-Destructive Testing Methods Ultraseismic Method Vertical Profiling 31

32 Non-Destructive Testing Methods Spectral Analysis of Surface Waves Method 32

33 Compression Wave Test Result (Sonic Echo) 33

34 Non-Destructive Testing Methods Parallel Seismic Test Method Ref: FHWA Engineering Notebook, GT-16 34

35 Non-Destructive Testing Methods Dispersive Side Sonic Test Method 35

36 Non-Destructive Testing Methods Sample of Dispersive Side Sonic Test Results 36

37 Validation Study Dispersive (bending) wave testing methods generally within 10-15% of the actual pile length. ODOT conducted NDT study in 2005 on 2 bridges. Octagonal concrete piles Timber piles 37

38 Validation Study Trask River Bridge (#07147), Hwy 9, M.P Pile ID(FDH #) Overall Length Computed by FDH Overall Length from ODOT records Accuracy in Percent B2P B2P B2P B9P B9P B10P B11P Kilchis River Bridge (#07424), Hwy 9, M.P Pile ID(FDH #) Overall Length Computed by FDH Overall Length from ODOT records Pile Length To 1 St Splice B2P B2P B3P ? B3P

39 Validation Study Performed under Work Order No. 1 (calibration) Contractor reviewed test data and recognized misinterpretation of data. Current work order will revisit WO #1 validation site and also test known pile foundation lengths at 2 additional sites. Dispersive Bending Wave Validation Testing Willamette River Overflow Bridge Bridge 8157 Bent 6 Timber Piles Pile ID Computed Length As-Built Length B6P B6P B6P B6P B6P B6P B6P Average Delta 13.0 feet % DIFF 23% 39

40 Future Work About 55 bridges remaining for NDT investigation Current work order issued for NDT testing 20 more bridges this spring Scoping out bridges for parallel seismic testing Remaining bridges on low volume roads, will screen to see if NDT is warranted About local agency unknown foundation bridges. 40

41 Thank You! 41