mechanistic – empirical design guide...june 19 – 22, 2005 mechanistic – empirical design...
TRANSCRIPT
June 19 – 22, 2005
Mechanistic – Empirical Design Guide:
Rehabilitation Design2005 Southeastern Pavement
Management & Design Conference
Chris Wagner, P.E.FHWA – Resource CenterAtlanta, GA
Overview
• General Rehab Theory• Characterizing Existing Pavement
• Asphalt• Concrete
• Contrast with 1993 AASHTO
www.fhwa.dot.gov/pavement/dgit.htm
Pavement Layer Properties
Bound Layers
• MR, E (PCC, CSB)• E* (AC)• Rutting (AC)• Damage
Un-Bound Layers
• Mr • Rutting (AC)
Section 1.1.8.1
June 19-22, 2005
Damage and Existing Modulus
ε
εt
δ• Existing Modulus• Stress, Strain,
Deflection
• Damage
Design life
Dam
age Rehab
Bound Layers
E Max
Modulus
jdexisting eEEEE
+−
+=1
)( minmaxmin
Equation 3.6.1
E existing
dj @ overlay
E Minimum
Assumed Value
Measured Property
Calculated
DamageFigure 3.6.4
Existing Modulus
Photo courtesy NCAT
• Level 1: Use of FWD• Not Specific on Backcalculation Method• Level 2 & 3: Based on Pavement Condition
Maximum Modulus
• PCC Cores and Beams for testing E, MR • AC Uses Witczak Equation for E*
max
Witczak Equation for Computing E*f (Gradation, Volumetric, and Binder Properties)
))log(393.0)log(313.0603.0(34
238384
42
200200
10055.0)(00002.0004.0002.0872.3
8022.0058.0
0028.0)(0018.0029.075.3*log
η
ρρρρ
ρρρ
−−−++−+−
+
⎟⎟⎠
⎞⎜⎜⎝
⎛
+−
−−−+=
f
abeff
beffa
e
VVV
V
E
Will be on Exam
Maximum Modulus, EMaximum Modulus, E**
Several Different MixesTreated as a Single Layer1.5” - SMA
2” - 12.5 mm
4” - 19 mm
How do you combineinto 1 Modulus Value ?
Existing Pavement Rutting
Existing Pavement Rutting
% Rutting in Pavement Layers
HMA ThicknessLayer
< 4 in 4 in - 8 in > 8 in
Asphalt 70 80 100
Granular Base 15 10 0
Subbase 10 5 0
Subgrade 5 5 0
Modulus Back-calculated from FWD
Correction Factor converts FWD to lab Mr
Unbound Material Characterization
Table 3.6.8
AC Rehab Options
Overlay Overlay ChoiceChoice
PCC Rehabilitation Options
• JPCP Restoration• Bonded Overlay
• Monolithic section• Unbonded Overlay
• New PCC over strong base• PCC Over AC
• New PCC over damaged AC base
Concrete Slab(JPCP, CRCP)
Base Course(Unbound, Asphalt, Cement)
Ebase
E
Effective k
Ec
E
Ebase
EEbase
E
value
Ec
EEc
EConcrete Slab(JPCP, CRCP)
Base Course(Unbound, Asphalt, Cement)(Unbound, Asphalt, Cement)(Unbound, Asphalt, Cement)
, MRConcrete Slab(JPCP, CRCP)
Base Course
Concrete Slab(JPCP, CRCP)
Base Course(Unbound, Asphalt, Cement)
PCC Rehabilitation Options
Not included in DG• CRCP Restoration• JRCP• Ultra-thin whitetopping
Asphalt Calibration Sites
73
46
Appendix EE-2: Figure 1
PCC Calibration Sites
TYPE OF REHAB SECTIONS
Unbonded JPCP 16
Unbonded CRCP 8
Restored JPCP 15
Bonded PCC 3
TOTAL 42
CA(7)
AZ(3)
OK (1)
SD (4)
CO (2)KS (1)
NE (2)
MN(3)
IN(1)
IA (3)
WI(2)
MS(1)
AL(5)
GA(5)
TN (3)
TX (4)
PQ (1)
LA(2)
IL(3)
PA (2)
(1)(FL)
CA(7)
AZ(3)
OK (1)
SD (4)
CO (2)KS (1)
NE (2)
MN(3)
IN(1)
IA (3)
WI(2)
MS(1)
AL(5)
GA(5)
TN (3)
TX (4)
PQ (1)
LA(2)
IL(3)
PA (2)
(1)(FL)
Advantages Rehabilitation Design• Consistent with New Design• Considers Continued Damage to the Existing
Pavement
Limitations of Rehabilitation Design• Limited Data for Calibration
• Rubbilized Pavements• Bonded PCC Overlays
Summary
www.fhwa.dot.gov/pavement/dgit.htm
• Two Parts to MEPDG• NCHRP 1-37a Report• Software
• Full presentation available
http://www.trb.org/mepdg
Chris Wagner, P.E.FHWA – Resource [email protected]