Investigation of Pavement Temperatures for Asphalt Pavements in WA - - PowerPoint PPT Presentation

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Investigation of Pavement Temperatures for Asphalt Pavements in WA - - PowerPoint PPT Presentation

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Investigation of Pavement Temperatures for Asphalt Pavements in WA MRWA Meeting and WAPG February 2018 42 C Introduction 40 C Predicted pavement temperature is a major component in our 40 C current design methodology through

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SLIDE 1

Investigation of Pavement Temperatures for Asphalt Pavements in WA

MRWA Meeting and WAPG February 2018

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SLIDE 2

Introduction

40 °C 31 °C 24 °C 42 °C 34 °C 29 °C 26 °C 30 °C

  • Predicted pavement temperature

is a major component in our current design methodology through the WMAPT value

  • WMAPT does not consider:
  • asphalt thickness
  • underlying material properties
  • localised weather
  • climate trends

40 °C

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SLIDE 3

Previous projects

  • Curtin University instrumented two pavements on the Great Eastern Hwy
  • Two sites at EME2 trials
  • Sites cover high proportion of

climate zones in Australia

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SLIDE 4

What did we do?

  • Installed on Kwinana Freeway near Berrigan

Drive overpass in Jandakot in Sept 2016

  • Six temperature probes at depths of 45mm

down to 320mm

  • Linked to weather station with sensors for

ambient temperature, solar radiation, rainfall, humidity, wind speed

  • Data provided over 4G modem to live web

portal, downloaded monthly and analysed before being sent to MRWA

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SLIDE 5

Observations

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SLIDE 6

Observations

5 10 15 20 25 30 35 40 45 12 AM 2 AM 4 AM 6 AM 8 AM 10 AM 12 PM 2 PM 4 PM 6 PM 8 PM 10 PM 12 AM Pavement Temperature (ºC) Brisbane 50mm Brisbane 200mm Perth 45mm Perth 200mm South Gippsland 55mm South Gippsland 185mm

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SLIDE 7

Observations

  • 5

5 10 15 20 25 30 5 10 15 20 25 30 Daily solar exposure (MJ/m2) Perth

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SLIDE 8

Observations

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SLIDE 9

Observations

  • Surface temperatures vary by location across road

Breakdown lane Left Lane Middle lane Highest temp. 5-8°C lower 8+°C lower Edgeline 1-4°C lower

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SLIDE 10

Implications for design

  • Climate change has led to growth in temperatures over last 70 years
  • WMAPT have not been adjusted upwards
  • ‘Average’ WMAPT in Perth over 40-year design life should be 31°C
  • Equivalent to reduction in design life of 17% (7 years of design traffic)
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SLIDE 11

Implications for design

  • WMAPT was adopted from the Shell Pavement Design Guide (1978)
  • How does this compare to temperatures at the instrumented site?
  • Average annual pavement temperature (similar for all depths) is 25.3°C

Methodologies for calculating WMAPT – Perth 2016/17 Average annual pavement temperature at 100 mm (°C)

25.3

Austroads WMAPT (2017) WMAPT (°C)

29

Offset to actual (°C)

3.7

Calculate WMAPT from 2016/17 weather station data WMAPT (°C)

28.2

Offset to actual (°C)

2.9

Shell PDM Chart RT (correcting for depth) WMAPT (°C)

26.8

Offset to actual (°C)

1.5

Shell PDM Chart RT (2016/17 weather station data) WMAPT (°C)

26.0

Offset to actual (°C)

0.7

  • Closest methodology is to adjust

for recent climate data, then use the Shell PDM chart but interpolate for the correct depth

  • Same holds true for data from

South Gippsland and Brisbane

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SLIDE 12

Implications for design - Examples

Thick pavement = 300mm Thin pavement = 100mm

0.0E+00 5.0E+05 1.0E+06 1.5E+06 2.0E+06 2.5E+06 3.0E+06 3.5E+06 0.0E+00 5.0E+07 1.0E+08 1.5E+08 2.0E+08 2.5E+08 3.0E+08 3.5E+08

18 20 22 24 26 28 30 32 34

Thin pavement fatigue life (ESA) Thick pavement fatigue life (ESA)

WMAPT (oC)

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SLIDE 13

Implications for design - Examples

  • Generic thick pavement at various temperatures

Asphalt 350mm

Wearing course 30mm

Granular 250mm @ 250MPa

Asphalt 364mm

Wearing course 30mm

Granular 250mm @ 250MPa

Asphalt 336mm

Wearing course 30mm

Granular 250mm @ 250MPa

28°C 30°C 32°C

Subgrade CBR 10 Subgrade CBR 10 Subgrade CBR 10

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SLIDE 14

Implications for design - Examples

  • Generic thin pavement at various temperatures

28°C 30°C 32°C

Asphalt 75mm

Wearing course 30mm

Granular 500mm @ 500MPa

Subgrade CBR 10

Asphalt 70mm

Wearing course 30mm

Granular 500mm @ 500MPa

Subgrade CBR 10

Asphalt 61mm

Wearing course 30mm

Granular 500mm @ 500MPa

Subgrade CBR 10

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SLIDE 15

Modelling

  • Several models have been proposed previously
  • A model with relatively simple inputs and outputs can improve accuracy of
  • ur fatigue life predictions

𝑈𝑞 𝑛𝑏𝑦 𝑏𝑢 𝑒𝑓𝑞𝑢ℎ 𝐸 = 𝛽 + 𝛾 ∗ (𝑈

𝑏 max) + 𝛿 ∗ 𝑇𝑆

1000 + 𝜀 ∗ 𝐸 𝑈𝑞 𝑛𝑗𝑜 𝑏𝑢 𝑒𝑓𝑞𝑢ℎ 𝐸 = 𝛽 + 𝛾 ∗ (𝑈

𝑏 min) + 𝛿 ∗ 𝑇𝑆

1000 + 𝜀 ∗ 𝐸 INPUTS OUTPUTS

Daily maximum air temp. (BoM) Maximum pavement temp. at any depth Daily minimum air temp. (BoM) Minimum pavement temp. at any depth Daily total solar exposure (BoM) Four constants (α, β, γ, δ) Pavement depth Sunrise/sunset times (day/night mode)

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SLIDE 16

Modelling

  • Use max & min daily pavement temp. and two part function to

calculate hourly pavement temperature

  • Sine curve during daylight hours, proportionate drop-off during night
  • Merge with traffic distribution from WiM site or counter
  • Calculate fatigue life estimate based on 8760 (=24*365) data points
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SLIDE 17

Benefits of this approach

  • We have a more localised and accurate

understanding of the pavement response to climate and traffic

  • Compatible with mix-specific fatigue

relationships and changes to Austroads methodology

  • May not be suitable to all projects but

relevant when looking at major projects

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SLIDE 18

Summary

  • Project due for finalisation in June 2018
  • Second instrumented site planned for later in 2018 or early 2019
  • Continuous monitoring until at least end of 2nd full year at each site