Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: AASHTO LCG:2010
• Năm ban hành / Publication date: 2010
• Tình trạng / Status: A - Còn hiệu lực
• Tên tiếng Anh / Title in English: Guide for the Local Calibration of the Mechanistic-Empirical Pavement Design Guide
• Số trang / Page: 202

Phạm vi áp dụng / Scope of standard

Introduction

The overall objective of the Mechanistic-Empirical Pavement
Design Guide (MEPDG) is to provide the highway community with
a state-of-the-practice tool for the design of new and
rehabilitated pavement structures, based on mechanistic-empirical
(M-E) principles. This means that the design procedure calculates
pavement responses (stresses, strains, and deflections) and uses
those responses to compute incremental damage over time. The
procedure empirically relates the cumulative damage to observed
pavement distresses. This M-E based procedure is shown in flowchart
form in Figure 1-1. "MEPDG," as used in this guide, refers to the
documentation and software package (NCHRP 2007).

Pavement distress prediction models, or transfer functions, are
the key components of any M-E design and analysis procedure. The
accuracy of performance prediction models depends on an effective
process of calibration and subsequent validation with independent
data sets. Pavement engineers gain confidence in the procedure by
seeing an acceptable correlation between observed levels of
distress in the field and those levels predicted with the
performance model or transfer function. The validation of the
performance prediction model is a mandatory step in their
development to establish confidence in the design and analysis
procedure and facilitate its acceptance and use. It is also
necessary to establish the design reliability procedure. It is
essential that distress prediction models be properly calibrated
prior to adopting and using them for design purposes.

The term calibration refers to the mathematical process through
which the total error (often termed residual) or difference between
observed and predicted values of distress is minimized. The term
validation refers to the process to confirm that the calibrated
model can produce robust and accurate predictions for cases other
than those used for model calibration. A successful validation
process requires that the bias and precision statistics of the
model for the validation data set be similar to those obtained
during calibration. This calibration-validation process is critical
for potential users to have confidence in the design procedure.

All performance models in the MEPDG were calibrated on a global
level to observed field performance over a representative sample of
pavement test sites throughout North America. The Long Term
Pavement Performance ( LTPP) test sections were used extensively in
the calibration process, because of the consistency in the
monitored data over time and the diversity of test sections spread
throughout North America. Other experimental test sections were
also included such as MnRoad and Vandalia. However, policies on
pavement preservation and maintenance, construction and material
specifications, and materials vary across the United States and are
not considered directly in the MEDPG. These factors can be
considered indirectly through the local calibration parameters
included in the MEPDG. The purpose of this guide is to provide
guidance in calibrating the MEPDG to local conditions and materials
that may not have been included in the global calibration
process.