effect of water, speed, and grade on continuous friction ... · center for sustainable...

Center for Sustainable

Transportation Infrastructure

Effect of Water, Speed, and Grade

on Continuous Friction

Measurement Equipment (CFMEs)

Edgar de León Izeppi Center for Sustainable Transportation Infrastructure (CSTI),

Virginia Tech Transportation Institute

Co-Authors

Gerardo Flintsch, Director, CSTI

Virginia Tech Transportation Institute

Kevin McGhee, Associate Principal

Scientist, Virginia Center for

Transportation Innovation and

Research

Center for Sustainable Transportation Infrastructure (CSTI)

Overview of Presentation

Objectives

Background

Methods

Tests results

Conclusions

Center for Sustainable Transportation Infrastructure

Evaluate and compare CFMEs from the

Friction Loan Program

Data base for quick comparisons

between deployments

Perform tests with varying speed and

water film thicknesses

Assess the effect of the grade on the

measurements

Objectives



Objectives

Background

Methods

Tests results

Conclusions


Surface Properties Consortium: Project

through the Transportation Pooled Fund

Project # TPF5 (141), a joint effort of six

member states, the Federal Highway

Administration , VCTIR and VTTI.

Background


http://www.dot.state.pa.us/internet/web.nsf/PennDOTHomepage?OpenFrameSet

http://www.dot.state.sc.us/

Background

To establish a research program

focused on enhancing the level of

service provided by the roadway

transportation system through

optimized pavement surface texture

characteristics.

Evaluation of new

technologies


Demonstration Loan Program for

Continuous Friction

Measurement Equipment (CFME)

US norm:

Locked-wheel

skid trailers

(100% slip)

Measurements

every 300 to 500

feet

CFMEs:

Fixed (10-20%)

slip comparable

to ABS brake

Continuous

measurements

(1 to 3 feet)

Continuous Friction Fixed-slip


Equipment

GripTester


Equipment

Dynatest HFT


Smart Road

12

Virginia Smart Road PCC, HFS

and bridges

Sections

Loop-A-B-C-D

Sections

E-F-G-H-J-I-K-L

VTTI and labs

Asphalt Sections

PCC, HFS and bridge sections

CRCP section

RR Bridge

JCPC section

Smart Road Bridge

The Virginia Smart Road Layout

Section

A

Starting

Location

Section

B

Section

C

Section

DCRCP

Ending

Location

Railroad

Bridge

Cargill

EP5 CRCP

CRCP

CRCP

Cargill

EP 5

EP 5

Cargill

Asphalt

Sections

Asphalt

Sections

Smart Road

Cargill Application

0 ft. 60 ft. 100 ft. 200 ft.

Scale: 1" : 100'

CRCP CRCP

CRCP

100'-0"100'-0" 300'-0"

500'-0"

CRCP

CRCP

CRCP

Cargill

EP 5

EP 5

Cargill

Asphalt

Sections

Asphalt

Sections

Smart Road

Cargill Application

0 ft. 60 ft. 100 ft. 200 ft.

Scale: 1" : 100'

CRCP CRCP

CRCP

100'-0"100'-0" 300'-0"

500'-0"

SM 12.5 D

SUPERPAVE

OGFC

SMA

9.5 D

Tined

CRCP

JRCP

Ground

JRCP

Cargill

SafeLane™

VDOT EP5LV

Testing wheel path


Objectives

Background

Methods

Tests results

Conclusions



Equipment: Grip Tester


Deployment of Grip Tester

95%

confidence

interval

Methods

Limits of Agreement (Bland & Altman)

Combination of both devices variability

Three components: one for each device

and a third one of their interaction

Variances:

Combined effects:


ninteractiovar and device2,var device1,var 22

2

2

1 Dsss

2

22

2

11

2 sfsfss Dc

1

1

11

mf

2

2

11

mf

imnf

111

Methods

Both Grip Testers collect at 3 ft. interval

Dynatest HFT every ft.; averaged to 3 ft.

Then averaged all to 30 and 300 ft. too.

Therefore for these three cases:

For 3 ft., m= 1550, f1=f2=

For 30 ft., m=155, f1=f2=

For 300 ft., m=15, f1=f2=


999.01550

11

11

m

994.0155

11

11

m

933.015

11

11

m

Methods

For 95% confidence, z = 1.96 (≈2)

Repeatability

r1 and r2, for each device, respectively

Limits of Agreement (LOA) between the

two devices

Proposed instead of reproducibility (R)


277.2296.1 iii ssr

csLOA 96.1


Objectives

Background

Methods

Tests results

Conclusions


Effect of the grade (diff. speeds)


Effects of grade (same unit)

Varying the speed 25mph 40 mph 55 mph 25mph 40 mph 55 mph 25mph 40 mph 55 mph

Mean down 0.93 0.84 0.74 0.89 0.82 0.73 0.80 0.75 0.66

Mean up 0.85 0.79 0.64 0.82 0.74 0.66 0.81 0.75 0.65

Bias 0.08 0.06 0.10 0.07 0.08 0.08 0.00 0.00 0.00

Every 3 feet

Repeatability factor r1: down 0.10 0.10 0.19 0.14 0.09 0.14 0.12 0.11 0.15

Repeatability factor r2: up 0.09 0.14 0.15 0.11 0.14 0.14 0.14 0.10 0.15

Limits of Agreement 0.14 0.19 0.24 0.17 0.16 0.20 0.19 0.15 0.19

Every 30 feet




Every 300 feet




GripTester 1 GripTester 2 Dynatest HFT

Effect of speed between units


Effects of speed change between units

DOWNHILL GT1-GT2 GT1-HFT GT2-HFT GT1-GT2 GT1-HFT GT2-HFT GT1-GT2 GT1-HFT GT2-HFT

Limits of Agreement: 3 feet 0.15 0.18 0.20 0.14 0.17 0.16 0.21 0.23 0.22



UPHILL




25ph 40 mph 55 mph

Supports the recommended operating

speed of 65 km/h (40mph)




DOWNHILL GT1-GT2 GT1-HFT GT2-HFT

Limits of Agreement: 3 feet 0.14 0.17 0.16



UPHILL




40 mph



DOWNHILL GT1-GT2 GT1-HFT GT2-HFT

Repeatability factor r1: 0.04 0.04 0.04



UPHILL




40 mph



Effect of water film thickness

Effects of grade (same unit)

Varying the water film thickness 0.25mm 0.50mm 1.00mm 0.25mm 0.50mm 1.00mm 0.25mm 0.50mm 1.00mm

Mean down 0.83 0.79 0.76 0.84 0.79 0.75 0.76 0.74

Mean up 0.76 0.74 0.69 0.77 0.71 0.67 0.78 0.73

Bias 0.07 0.06 0.07 0.07 0.08 0.08 -0.01 0.01

Every 3 feet

Repeatability factor r1: down 0.13 0.14 0.15 0.15 0.11 0.13 0.13 0.13

Repeatability factor r2: up 0.15 0.18 0.16 0.14 0.13 0.14 0.12 0.12

Limits of Agreement 0.25 0.27 0.27 0.25 0.27 0.25 0.23 0.21

Every 30 feet




Every 300 feet




GripTester 1 GripTester 2 Dynatest HFT

More water film, less friction.


Effects of water change between units

DOWNHILL GT1-GT2 GT1-HFT GT2-HFT GT1-GT2 GT1-HFT GT2-HFT GT1-GT2 GT1-HFT GT2-HFT

Limits of Agreement: 3 feet 0.17 0.17 0.19 0.17 0.17 0.20 0.18



UPHILL




0.25mm 0.50mm 1.00mm

Effect of water film thickness

Speed tests: air temperature 74°F

Water film thickness tests: air temperature 82°F


Objectives

Background

Methods

Tests results

Conclusions



Effects of the grade between

units

Limits of Agreement Method

Proposed new method to compare the

repeatability and a new alternative for

the reproducibility factors known as the

Limits of Agreement

More research is proposed to

understand the effect of the factors that

introduce variability to measurements

As expected, both water and speed

decreased the friction measurements


QUESTIONS?


effect of water, speed, and grade on continuous friction ... · center for sustainable...

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