Agenda Packets - 2023/03/03 - Laserfiche WebLink

Home Browse Search

road vs. urban street) and the nature of the heavy traffic loading (very heavy loads concentrated in time and space vs. legal loads applied consistently over long periods of time, and often in perpetuity). Methods of Pavement Design and Analysis The Heavy Traffic Generators project utilized three methods of pavement design and analysis for estimating the damage and the related cost associated with heavy traffic loads. These are described below. • Incremental Design This method involves the design of two new pavements for future service — one without any of the heavy vehicles in question, and one with the additional heavy vehicle loads. The difference in the predicted construction cost of these two pavements is assumed to be the direct result of the additional loads. This additional cost must be considered over the entire life of the pavement, since it represents the additional pavement structure that must be built to accommodate the heavy vehicles over the life of the pavement. • Overlay Design This method uses the standard MnDOT overlay design method for bituminous pavements. After a period of time, defined by the user, the expected damage caused by additional heavy vehicles is computed, and an appropriate overlay thickness is determined to accommodate the additional loads. The cost of the overlay is assumed to be related directly to the additional damage caused by the heavy vehicles in question. Often, however, the computed overlay thickness needed is less than the minimum thickness that is appropriate for overlay construction. In this case, the owner has two options: consider the cost to be that of the minimum overlay thickness, or set aside the small cost and use it in a future overlay to be constructed at some later date. • Percent of Life Consumed Comparing the amount of additional "life" consumed by additional pavement loads each year with the annual or total loads for which the pavement was designed. This approach computes the proportion of the reconstruction cost based on the proportion of the original design life (in terms of ESALs) consumed by the additional loads. Pavement Damage Modeling There are many methods of modeling the damage produced by traffic, and by heavy vehicles in particular. Most of the research utilizes the standard AASHTO concept of serviceability (2) and equivalent single axle load (ESAL) or some variation of that method. The AASHTO method is a sound and viable way of conducting this type of analysis, however, and the references discussed below support this. Rutherford, South Dakota Department of Transportation, 1994 (3) The South Dakota Department of Transportation hired GeoEngineers in 1994 to conduct a study to develop a model for predicting the impact of heavy garbage trucks on city, county, and state roads. This is likely the most comprehensive study undertaken on the subject, and it has many of the components that are necessary to develop the impact analysis tool for the current project. These include considerations of the following parameters.