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P AVEMENT T HICKNESS D ESIGN CTC 440. O BJECTIVES Know how to determine the thickness of flexible/rigid pavements.

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Presentation on theme: "P AVEMENT T HICKNESS D ESIGN CTC 440. O BJECTIVES Know how to determine the thickness of flexible/rigid pavements."— Presentation transcript:

1 P AVEMENT T HICKNESS D ESIGN CTC 440

2 O BJECTIVES Know how to determine the thickness of flexible/rigid pavements

3 C OMPREHENSIVE P AVEMENT D ESIGN M ANUAL (PDM) NYS PDM can be found at https://www.dot.ny.gov/divisions/engineeri ng/design/dqab/cpdm https://www.dot.ny.gov/divisions/engineeri ng/design/dqab/cpdm Chapter 4 (New Construction/Reconstruction) is what we’ll cover https://www.dot.ny.gov/divisions/engineeri ng/design/dqab/cpdm/repository/chapter4. pdf https://www.dot.ny.gov/divisions/engineeri ng/design/dqab/cpdm/repository/chapter4. pdf

4 CPDM-O THER A REAS Ch 2 Evaluation of Existing Pavements Ch 3 Project Development Process Ch 5 Rehabilitation Ch 6 Materials Ch 7 Shoulders Ch 8 Pavement Joints Ch 9 Subsurface Pavement Drainage Ch 10 Preventative Maintenance

5 I NTRODUCTION : NYSDOT uses a modified version of the AASHTO’s 1993 Guide for the Design of Pavement Structure Features include Thickness design procedure for pavements 50-year design life Permeable base layer for drainage Edge drains or daylight Full-depth shoulders

6 R IGID P AVT. (PCC) Used for High volume traffic lanes Freeway-to-freeway connections Exit ramps Advantages Durability Long service life Withstands repeated flooding and subsurface water w/o deterioration DisAdvantages May lose original nonskid surface Must have even subgrade/uniform settling Joints Reinforced Contraction joints (50-100ft) Epoxy-coated steel to prevent corrosion Unreinforced Contraction joints (15-30x pavt thickness)

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8 F LEXIBLE P AVT. (HMA) Used for Traffic and auxiliary lanes Ramps, parking areas, frontage roads and shoulders Advantages Adjusts to limited amounts of differential settlement Easily repaired and overlaid Non-skid properties do not deteriorate Disadvantages Loses flexibility/cohesion over time Must be resurface sooner than concrete Not usually chosen where water is expected Minimum layer is usually 1-1/2” 1-1/2” top course 1-1/2” binder course Remaining thickness is base course

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10 M ATERIAL D ESIGN -A SPHALT Superpave Marshal Mix (old)

11 P ERPETUAL P AVEMENT Introduced in 2003 by the National Center for Asphalt Technology and the Asphalt Pavement Alliance HMA pavement designed to last 50 years or more without major structural rehabilitation or reconstruction Ref:

12 C ARBON F OOTPRINT OF HMA AND PCC P AVEMENTS

13 W HY THE D IFFERENCE Carbon is sequestered in the HMA pavement CO 2 is released when producing portland cement via kiln; limestone disassociation produces CO 2 Ref:

14 O THER “G REENER ” P AVEMENTS Warm-Mix Asphalt (WMA) 86.7 million tons in 2012 Reclaimed Asphalt Pavement (RAP) 68.3 million tons in 2012 Reclaimed Asphalt Shingles (RAS) Other: Ground tire rubber, steel and blast furnace slag, other waste materials (repurposed into pavement) Reference Report: ew=article&id=872&Itemid=61 ew=article&id=872&Itemid=61

15 B ASIS FOR T HICKNESS D ESIGN Axle loading from truck traffic An 80kN axle load (18-kip axle load in English units) is standard loading. All traffic is converted into the number of 80- kN passes that would cause the same structural damage The converted # is referred to as the 80kN ESAL (Equivalent Single Axle Loads) The effect of passenger cars, pickups, 2- axle trucks w/ single rear tires and buses (FHWA vehicle classes 1-4) are not even considered

16 R IGID P AVEMENTS -ESAL Modified AASHTO equation is used Modified because NYSDOT experience is that pavements in NYS last longer than would be predicted from the original equation Other method Fatigue Strength

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18 F LEXIBLE P AVEMENT -ESAL AASHTO equation is used Other methods CALTRANS Asphalt Institute

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20 D ETERMINING ESAL-S IMPLE M ETHOD ( WORKSHEET ON 4-9) Design life Initial 2-way AADT % HV (class 4 or greater) % of all trucks in the design direction % of all trucks in the design lane Truck equivalency factor Annual truck volume growth rate Annual truck weight growth rate

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22 ESAL M ETHOD -S TEPS Determine ESAL Determine HMA thickness by using table 4-5 M r -subgrade resilient modulus (load carrying capabilities of the materials below the pavt.) M r =28 (clay); M r =62 (gravel) Determine PCC thickness by using Table 4-4

23 ESAL- EXAMPLE - BOTH PCC AND HMA ( ASSUME M R =48 MP A ) AADT% HVDHVDDHV ETC

24 E XAMPLE : S TEPS Determine whether the traffic growth rate is simple or compound Determine the growth rate and % traffic in the design direction Determine the ESAL Determine the pavement thickness

25 E XAMPLE -A NSWERS Determine whether the traffic growth rate is simple or compound (compound) Determine the growth rate (2%) and % traffic in design direction (60%) Determine the ESAL (see next slide) HMA – 6.42E6 PCC – 8.80E6 Determine pavt. thickness HMA 165 mm (7”) PCC 225 mm (9”)

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27 ESAL-B ASED M ETHOD Projects over 1.5 km in length

28 C ONVENTIONAL M ETHOD Projects < 1.5 km in length Use Table 4-1 For Interstate Highway Conventional Pavement Requirements see page 4-2 For our previous example: HMA 160mm (6.5”) PCC not applicable

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