Evaluation Impacts of Scuffing Forces Induced Due to Braking And Turning of Vehicles on The Flexible Pavement Performance Capacity Using Finite Element Modeling Approach
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Date
2020-02
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Addis Ababa University
Abstract
The induced scuffing force is one of the major factors that significantly affect the distress
resisting capacity of flexible pavement at vehicles stop or turn. Braking causes extra significant
longitudinal load on the flexible pavement surface whereas turning causes additional significant
lateral load on the pavement surface. These additional horizontal forces (scuffing) are controlled
by tire slip ratio, road adhesion coefficient and tire turning angle/angle of steering
Thus the objective of this study was identification and evaluation of the major possible causes
that responsible for the premature failure of flexible pavement mainly in vehicles’ stopping and
turning areas or stretches.
In this study, the flexible pavement responses to tire-pavement moving loads (vertical load,
longitudinal load, and lateral load) at various rolling conditions were examined with developed
(3-D) finite element model. The flexible pavement structure layers characterized as elastic
materials, and the transient dynamic tire loadings were simulated using trapezoidal moving load
for transient dynamic analysis. The analyses were mainly on the rolling conditions (braking
load, turning load and free rolling load); affectivity of asphalt concrete thickness with shear
stress-strain and influence of braking and cornering on pavement interface were investigated.
The study found that, top-down fatigue cracking and shoving are the main distress type observed
at tire braking and turning. The damage ratio of fatigue cracking due to tire braking is, 2.04
times compared to free rolling condition; the shoving potential of asphalt due to tire turning is
1.93 times compared to free rolling condition and the shoving potential of asphalt due to tire
braking is 2.85 times compared to free rolling condition.
The overall impacts of scuffing load due to braking and turning of vehicles is estimated. The
combined relative damage ratio convenes that, braking of tire reduces the pavement distress
resisting capacity approximately by 1.77 times, and turning reduces the capacity by 1.33 times
compared to free rolling conditions.
Thickness optimization for shear stress-strain for typical flexible pavement structure (150mm,
170mm, 190mm, 210mm, and 240mm asphalt thickness) showed that the thickness barely
increase carrying capacity of scuffing force unless it increased more; that is uneconomical. The
effect of scuffing force is also significant at the interface of asphalt and base course that reduce
the performance of flexible pavements.
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Keywords
Finite element model, moving load, scuffing force, relative damage, flexible pavement