Slide 1

FWD BackCalculation of Existing Pavement Structure

Slide 2

Pavement Structure

Slide 3

Critical Responses

Slide 4

Overlay Thickness Design (Critical Responses) RuttingVertical strain on top of the subgrade, within the unbound/bound base and AC layers Fatigue crackingHorizontal strain at the bottom of AC layers Thermal crackingTensile stress at the surface of the AC layer

Slide 5

Structural Responses for AC/AC Overlays Critical structural responses are: Tensile strain at the bottom of AC overlay Tensile strain at the bottom of original AC layer Vertical stress at the top of the subgrade

Slide 6

Structural Responses for AC/AC Overlays AC Overlay Existing AC Pavement r Base Subgrade v r Bond Milling and Tack Coat

Slide 7

Structural Responses for AC/AC Overlays Other considerations: Not all design procedures consider both strains at the bottom of the overlay and existing layer Both strains should be examined as a minimum If the existing layer is extensively cracked it may be modeled as a granular layer, thus consider only strains at the bottom of overlay

Slide 8

EverStress Input

Slide 9

EverStress Load & Evaluation Locations

Slide 10

EverStress Output

Slide 11

Pavement Deflection 012244872 60

Slide 12

EVERCALC General File

Slide 13

EVERCALC Deflection File Mil = 1/1000 inch

Slide 14

EVERCALC Output File

Slide 15

EVERCALC Summary File

Slide 16

EVERCALC General File

Slide 17

EVERCALC Output File