Pavement design

Pavement design ppt

The tools necessary to analyze pavement failures, such as coring, boring, trenching, and deflection measurements, are well known, and need to be employed more often. The nest step is the foundation design. Weight information should be obtained using weigh-in-motion WIM equipment, for this data is more representative than data obtained using static enforcement scales, which are plagued with avoidance problems. It provides bonding between two layers. Equivalent design implies that each alternative will be designed to perform equally, and provide the same level of service, over the same performance period and have similar life-cycle costs. When performing LCCA for pavement design, the variability of input parameters needs to be considered. The SHAs are encouraged to use paved shoulders where conditions warrant. In such situations, sub-base course may not be provided. Interim Technical Bulletin. Normally a design is carried out for each of the alternatives and then the most economical chosen.

The SHAs should consider a new distress survey if the original condition survey was sample based or if the survey is not current in terms of the time the project is scheduled to go to contract. Accurate cumulative load normally expressed as 18 kip equivalent single axle loads or ESALs estimates are extremely important to pavement structural design.

Toole and Eller's memorandum dated November 12,summarizes FHWA's existing guidelines on surface related characteristics, including safety. In a design-bid-build DBB or design-build DB project delivery environment, it is assumed that the design methodology will adequately predict the ability of the constructed pavement to meet the performance objectives.

However, the resulting numbers themselves are less important than the logical analysis framework fostered by LCCA in which the consequences of competing alternatives are evaluated.

Failure of flexible pavements The major flexible pavement failures are fatigue cracking, rutting, and thermal cracking.

flexible pavement design

Two design methods have been used to control rutting: one to limit the vertical compressive strain on the top of subgrade and other to limit rutting to a tolerable amount 12 mm normally. These are as follows: Foundation Design - That is the design of the Subgrade and sub-base Thickness Design - That is the design of the actual road surface Unfortunately to include both of the areas on this page would cripple your browser so they have been split up and this page contains only the introduction and links to the different areas.

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The failure criterion relates allowable number of load repetitions to tensile strain and this relation can be determined in the laboratory fatigue test on asphaltic concrete specimens. Load estimates should be based on representative current vehicle classification and truck weight data and anticipated growth in heavy truck volumes and weights.

The lack of good as-constructed data on pavement rehabilitation and preventive maintenance techniques is one of the weaker points in the pavement management process.

Pavement design

Normally a design is carried out for each of the alternatives and then the most economical chosen. Rutting occurs only on flexible pavements as indicated by permanent deformation or rut depth along wheel load path. This section requires the use of alternate bid items "When The results of LCCA should be evaluated to determine whether differences in costs between competing alternatives are statistically significant. It is this aspect of the design which is treated first. Weight information should be obtained using weigh-in-motion WIM equipment, for this data is more representative than data obtained using static enforcement scales, which are plagued with avoidance problems. A traffic data collection and forecasting program that identifies the most important truck types and the changes in numbers and weights of these truck types during the design period should provide realistic load estimates. In addition, maintain adequate communication between the design, construction, and maintenance engineers. The failure criterion relates allowable number of load repetitions to tensile strain and this relation can be determined in the laboratory fatigue test on asphaltic concrete specimens. Figure 1.

Figure 1.

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Introduction to pavement design