PAVEMENT THICKNESS DESIGN CTC 440 OBJECTIVES Know how
PAVEMENT THICKNESS DESIGN CTC 440
OBJECTIVES Know how to determine thickness of flexible/rigid pavements
COMPREHENSIVE PAVEMENT DESIGN MANUAL (PDM) NYS PDM can be found at https: //www. dot. ny. gov/divisions/engineering/de sign/dqab/cpdm Chapter 4 (New Construction/Reconstruction) is what we’ll cover https: //www. dot. ny. gov/divisions/engineering/de sign/dqab/cpdm/repository/chapter 4. pdf
CPDM-OTHER AREAS 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
INTRODUCTION: 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
RIGID PAVT. (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 Dis. Advantages May lose original nonskid surface Must have even subgrade/uniform settling Joints Reinforced Contraction joints (50 -100 ft) Epoxy-coated steel to prevent corrosion Unreinforced Contraction joints (15 -30 x pavt thickness)
FLEXIBLE PAVT. (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” top course 1 -1/2” binder course Remaining thickness is base course
MATERIAL DESIGN-ASPHALT Superpave http: //www. youtube. com/watch? v=GPw. WNKYr. Qw 8 Marshal Mix (old)
PERPETUAL PAVEMENT 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: http: //asphaltroads. org/images/documents/ghg-carbon_footprint_of_various_pavement_types. pdf
CARBON FOOTPRINT OF HMA AND PCC PAVEMENTS http: //asphaltroads. org/images/documents/carbon_footprint_web. pdf
WHY THE DIFFERENCE Carbon is sequestered in the HMA pavement CO 2 is released when producing portland cement via kiln; limestone disassociation produces CO 2 Ref: http: //asphaltroads. org/images/documents/ghg-carbon_footprint_of_various_pavement_types. pdf
OTHER “GREENER” PAVEMENTS 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: http: //www. asphaltpavement. org/index. php? option=com_content&view=article &id=872&Itemid=61
BASIS FOR THICKNESS DESIGN Axle loading from truck traffic An 80 k. N axle load (18 -kip axle load in English units) is standard loading. All traffic is converted into the number of 80 -k. N passes that would cause the same structural damage The converted # is referred to as the 80 k. N 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
RIGID PAVEMENTS-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
FLEXIBLE PAVEMENT-ESAL AASHTO equation is used Other methods CALTRANS Asphalt Institute
DETERMINING ESAL-SIMPLE METHOD (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
ESAL METHOD-STEPS Determine ESAL Determine HMA thickness by using table 4 -5 Mr-subgrade resilient modulus (load carrying capabilities of the materials below the pavt. ) Mr=28 (clay); Mr=62 (gravel) Determine PCC thickness by using Table 4 -4
ESAL-EXAMPLE-BOTH PCC AND HMA (ASSUME MR=48 MPA) AADT % HV DDHV 2006 3165 6 325 195 2011 -ETC 3494 6 359 215 2021 4260 6 437 262 2031 5192 6 533 329 2041 6330 6 650 390
EXAMPLE: STEPS 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
EXAMPLE-ANSWERS 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. 42 E 6 PCC – 8. 80 E 6 Determine pavt. thickness HMA 165 mm (7”) PCC 225 mm (9”)
ESAL-BASED METHOD Projects over 1. 5 km in length
CONVENTIONAL METHOD 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 160 mm (6. 5”) PCC not applicable
Other Pavement Software • http: //www. pavexpressdesign. com/ Simplified pavement design. Version 2. 0 has anew module for asphalt overlay designs. • http: //iriexplorer. com/home/ Developed to analyze roughness data from the FHWA’s Long Term Pavement performance program, the tool allows for data to be analyzed by climatic region, traffic conditions, or network segment. IRI Explorer can also estimate the maintenance and use-phase greenhouse gas emissions for different pavement options.
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