MIT Scan-2 Using MIT Scan-2 for Evaluating Designed specificall - PDF document

MIT Scan-2 Using MIT Scan-2 for Evaluating  Designed specificall yfor measuring Dowel Bar Placeme nt dowel bar position and alignment  Offers pr actical means of evaluating Prepared By: dowel placement accuracy Geoffrey J. Kurgan and H. Thomas Yu Prepared For: ND A CPA Workshop Bismarck, ND 12 March 2008 Example Output Three Easy Steps to Testing (R) MIT Gmb H Gost ritz er Str. 61- 63 D-01 217 Dre sden , GE RMAN Y web : www .mit -dre sden .de Signal intens ity emai l : mit @mit .tz- dd.d e Contour plot Fede ral Hig hway Adm inis trat ion Offi ce o f P avem ent Tech nolo gy sam. tyso n@f hwa. dot. gov tel. : web : www .fhw a.do t.go v ---- ---- --- ---- ---- ---- ---- ---- --- ---- ---- Date + T ime : 26 /08/ 2004 1 0:09 File g:\ 04_ 08_2 6\26 0810 09.h df ---- ---- --- ---- ---- ---- ---- ---- --- ---- ---- High way : US 90 Dire ctio n : E Stat ion No. : 1 + 00 Lane : La ne 1 Join t : 1 Bar type : 45 4 x 38m m Bar spac ing : 30 0 mm Conc rete th ickn ess : 28 0 mm ---- ---- --- ---- ---- ---- ---- ---- --- ---- ---- Bar x- Loc a De pth Sid e M isal ign m. B ar No. ti on Shi ft h or. ver t. S pace m m mm m m mm mm mm ---- ---- --- ---- ---- ---- ---- ---- --- ---- ---- 1 12 9 138 5 4 -19 8 129 2 45 5 146 2 5 -7 -6 326 3 76 6 148 - 2 -3 - 10 311 Horizontal 4 107 1 143 2 7 0 -2 305 Vertical 5 137 9 151 -1 3 8 12 308 alignment 6 169 0 151 -3 2 -1 4 311 alignment 7 199 6 148 -1 9 -3 6 307 8 230 2 137 1 0 2 2 305 9 260 1 140 9 -2 - 10 300 10 290 8 137 - 9 -3 0 307 11 321 1 141 -1 7 8 -7 304 12 351 6 144 -2 6 2 -2 304

Dowel Alignment Key Acceptance Items Plan Plan Plan  Concrete strength  Slab thickness  Air content Horizontal Longit udinal Horizontal translation translation skew  Initial smoothness Section Section  Dowel bar alignment Vertical Vertical translation tilt State Specifications So what if dowels are misaligned? 10 9  Pav ement damage may result  Spalling 8 Numberof states 7  Cracking 6  The eff ectiveness of dowel bars may be 5 compromised 4  Loss of load transfer efficiency(LTE) 3  Premature development of faulting 2  How bad is bad? – we don’t know 1  Existi ng specifications maybe too tight 0 5 mm (3/16 in) 6 mm (1 /4 in) 10 mm (3/8 i n ) 13 mm (1/2 in)  Comprehensive study under way (NCHRP 10-69) Tolerance on Horizontal or Vertical Misalignement

IN1 – 5 years old Joint Score for IN1 (Basket) 5 0 4 5 4 0 3 5 Joint Score 3 0 2 5 2 0 1 5 1 0 5 0 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 J oint KS4, NB I-35 – 6 years ol d Joint Score for KS4 (DBI) 5 0 4 5 4 0 3 5 Joint S core 3 0 2 5 2 0 1 5 1 0 5 0 1 3 5 7 9 1 1 1 3 1 5 1 7 1 9 2 1 2 3 2 5 2 7 2 9 3 1 3 3 3 5 3 7 3 9 4 1 4 3 4 5 4 7 4 9 Join t

30- yr old GA section with extremel y poor dowel alignment Joint Score for the GA Section (DBI) 50 45 40 35 Joint Score 30 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 6 2 7 2 8 3 0 3 2 3 3 3 5 3 6 3 7 3 8 3 9 4 0 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 5 0 Joint Joint Score for the WA Section (Retrofit) 5 0 4 5 4 0 3 5 Joint S core 3 0 2 5 2 0 1 5 1 0 5 0 1 3 5 7 9 1 1 1 3 1 5 1 7 1 9 2 1 2 3 2 5 2 7 2 9 3 1 3 3 3 5 3 7 3 9 4 1 4 3 4 5 4 7 4 9 Join t

WA section – 35 yr old pavement; 8 yr old retrofit Effects of Embedment Length ( Burnham 1999 ) Effects of Dowel Misalignment Comparison of DBI and Basket (Prabhu et al. 2006) 10 0% Bas ket 9 0% DBI 78.8% 8 0% 72.7% 7 0% ent of bars 6 0% 5 0% Perc 4 0% More critical ranges of misalignment 3 0% 1 9.2% 2 0% 14. 2% 1 0% 5.7% 3.6% 1.7% 1.8% 1. 6% 0.6% 0% d ≤ 10 10 <d ≤ 15 15<d ≤ 2 0 20 <d ≤ 25 d >2 5 Range of misalignment,mm

ProblemJoints Typical Joint

Use of MIT Scan-2 data in optimizing Dowel Placement Specifications PCC mix for dowel-bar inserter (CPTP Techbrief FHWA-HIF-07- 021) 12%  Ideally , dowel bars should be placed without any Aug 7 placement error Aug 10 10% Aug 12  There are tolerable lev els of placement errors 8% % of Bars  Stringent (but constructible) requirements should 6% be specif ied, but allowance should be made f or tolerable errors 4% 2% 0% 10<d ≤ 15 15<d ≤ 20 20<d ≤ 25 d > 25 Range of misalign ment, mm

Possible Options for Correcting Misaligned Bars  Cut misaligned bars  Retrof it additional dowel bars  Remov e and replace slab  Full-depth repair

Best approach: don’t create problems Some misalignments are harmless 5 0 5 0 4 5 4 5 4 0 4 0 3 5 3 5 Joint Score 3 0 Joint Score 3 0 2 5 2 5 2 0 2 0 1 5 1 5 1 0 1 0 5 5 0 0 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 3 5 7 9 1 2 3 4 5 6 7 8 9 10 1 1 2 1 13 14 1 5 6 1 17 18 9 1 2 0 21 22 23 4 2 25 26 27 8 2 29 30 31 3 2 33 34 35 3 6 37 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 Joint J oint

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