AASHTO Guide for Design of Pavement Structures, 1993 Book

PreFace

When construction, maintenance, and rehabilita-
tion costs are considered, the single most costly
ment Of our nation’s highway system is the pavement
Structure. In an effort to reduce this cost, the state
highway and transportation departments the Fed-
eral Government have sponsored a continuous pro-
gram Of research On pavements. One output of that
research effort was the Interim Guide for the Design Of
pavement Structures published in 1972 and revised in

It was based largely the findings at the
AASHO Road Test.
Because this is such an important topic, the Joint
lhsk Force On Pavements—composed of members
from the Subcommittee on Design, one each
fmrn the Materials, Construction, and Maintenance
Sutrommittees, and one from the Planning CMIWit
tee of AASHTO—was assigned the task of rewriting
the Interim Guide incorporating new developments
and specifically addressing pavement rehabilitation.
Because many states were found to be using at least
portions of the Interim Guide because no other
generally accepted procedures could be identified, it
was decided that this Guide uould retain the basic
algorithms developed from the AASHO Road Test as
used in the Interim Guide. Because the Road Test was
very limited in scope, i.e. a materials, One sub-
grade, non-mixed traffic, one environment, etc., the
Original Interim Guide contained many additional
models to expand the framework so designers could
consider Other conditions. The new Guide has
further expanded with the &’llowing 14 major new
con siderations:

TOC
Reliability
Resilient Modulus for Soil Support
Resilient Modulus for Flexible hvement
Layer Coefficients
Drainage
Improved Environment Considerations
Concrete Shoulders or Widened Lanes
Subbase Erosion Rigid Hvements
Life Cycle Cost Considerations
Rehabilitation
hvement Management

Extension Of Values
Improved Traffic Data
Design Of Hvements for Low
State of the knowledge on Mechanistic-
Empirical Design Concepts

The nsk Force recognizes that a considerable body
of itfirmation exists to design pavements utilizing
rnechanistic It further believes that
significant improvements in pavement design will
cxcur as these mechanistic models are calibrated to
in-service performance, and are incorporated in
weryday design usage. Part IV of this document sum-
marizes the mechanistic/empirical status.

In order to provide State-of-the—art
without lengthy research, values and concepts are
shown that have limited support in research or experi-
ence. Each user should consider this to be a reference
document and carefully evaluate his Or her need of
each concept and what initial values to use. TO most
effectively use the Guide it is suggested that the user
adopt a similar to the

Conduct a sensitivity study to determine which
inputs have a significant effect on pavement
design answers for its range of conditions.
For inputs that are insignificant or inap—
propriate, no additional effort is required.
those that are significant and the state has
sufficient data or methods to estimate design
values with adequate accuracy, no additional
effort is required.
Finally, for those sensitive inputs for which the
state has no data of methodology to develop the
inputs, research will be necessary. Because of
the complexity of pavement design and the
large expansion of this Guide, it is anticipated
that some additional research will be cost-
effective for each and every user agency in or-
der to optimally utilize the Guide.

Design related project level pavement management – Economic evaluation of alternative pavement design strategies – Reliability / – Pavement design procedures for new construction or reconstruction : Design requirements – Highway pavement structural design – Low-volume road design / – Pavement design procedures for rehabilitation of existing pavements : Rehabilitation concepts – Guides for field data collection – Rehabilitation methods other than overlay – Rehabilitation methods with overlays / – Mechanistic-empirical design procedures.