PAVEMENT MATERIALS SELECTION: A DECISION THEORY APPROACH
PAVEMENT MATERIALS SELECTION: A DECISION THEORY APPROACH
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Date
1996-08
Authors
SARKI, UMARU PETER
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Abstract
In highway pavement design, the main factors considered
are the expected traffic, subgrade strength, and the
constituent materials for the pavement structure. Associated
with each of these factors, however, are elements of
uncertainty. Ignoring these uncertainties, means that either
high factors of safety are applied in design, with its cost
implications, or a high risk of failure must be accepted.
A model is developed, using the Bayesian approach to
statistical decision making, which accounts for the
uncertainties in the pavement materials selection process. The
main elements of the pavement materials selection model include
the alternative materials for a given pavement layer; the
states of nature associated with each alternative (material
strength states); an estimation of the likelihood associated
with each state of nature; an assessment (through utility
functions) of the consequences of each combination of
alternative material and state of nature; and a systematic
evaluation of all alternative materials to determine the
optimal material selection.
The model is illustrated by its application to a case
study involving the selection of a base course material from
among alternative materials for use in a flexible pavement
structure. With the uncertainties regarding the possible range
of material strength states being expressed as probabilities,
the materials selection process, proceeds by a prior analysis
with existing information, which, after the acquisition of
additional information, is updated by a posterior analysis. The
optimal material selection is made on the basis of maximum
expected utility.
The case study shows that, the magnitudes of the expected
utilities depend on the magnitudes of the prior, and, or
posterior probabilities associated with the respective strength
states; while any change in the magnitudes of these
probabilities, depend on the sample likelihoods estimated from
experimental results.
It is recommended, as improvements to the model,that the
utility functions be further refined, such that the effects of
costs on materials selection are explicitly reflected in the
decision analysis; and that, the possibility of incorporating
procedures for the selection of surfacing materials be
invest igated.
The design approach proposed, when fully developed,is
expected to bring about not only monetary savings, which
otherwise would not have been made due to less than optimal
selection of materials; but also result in more efficient use
of scarce resources, to be reflected through a satisfactory
return on the investment of highway funds.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL AHMADU BELLO
UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF SCIENCE (HIGHWAY AND TRANSPORTATION
ENGINEERING)
DEPARTMENT OF CIVIL ENGINEERING
AHMADU BELLO UNIVERSITY
ZARIA
AUGUST, 1996
Keywords
PAVEMENT,, MATERIALS,, SELECTION: