| dc.description.abstract | Many road performance models have been developed and used as important inputs for
design and evaluation of pavements especially in the Post-AASHO Road Test era. The
Highway Development and Management model (HDM-4), a computer model originally
developed by the World Bank, is particularly useful because it integrates pavement
performance models to the initial construction, maintenance and road user cost models
thereby enabling economic and financial evaluation of a project or alternative projects.
This research focused on a level two calibration of the road deterioration sub-model of
HDM-4, specifically the models of asphalt concrete (AC) on granular base pavements
to the conditions in Ethiopia, taking Addis-Modjo-Awasa Road as a case study.
To meet the objectives of the study, a thorough evaluation of historical data of the road
was conducted and suitable calibration pavement sections identified. A methodology
for field data collection was crafted. The field data collection includes measurement of
pavement deflection using a Benkelman Beam and the measurement of pavement
conditions of roughness, rutting and cracking using automated survey vehicle.
The calibration process includes prediction of pavement deterioration taking the
calibration factor as unity and scaling to match the observed level of deterioration. The
procedure of calibration is based on the provisions of the HDM-4 calibration manual
prepared by Bennett and Paterson in the year 2000.
The results showed that the calibration factors are well within the typical values of
factors included in the calibration manual of HDM-4 (Paterson and Bennett 2000)
indicating that the road deterioration models are generally applicable to the asphalt
concrete pavements to the Ethiopian conditions. The prediction of cracking initiation
and progression and the collected data generally show wider dispersion, resulting in
higher calibration factors especially for cracking initiation. The predictions of rutting and
roughness progression are more stable, and the calibration factors are close to unity.
The study also showed that local condition of material quality, workmanship and the
environmental effects of drainage affect deterioration rates more than traffic loading. | en_US |
