Assessment of Load Bans for the City of Calgary using the TAC Guide to Load Management for Weak Pavement Structures

Abstract
Tetra Tech was retained by the City of Calgary (The City) to complete pavement data collection and analysis of the roadway segments subjected to spring load bans and year-round load bans imposed by The City. The load ban assessment effort comprised of pavement structure determination (using Ground Penetrating Road Radar testing and asphalt pavement coring), pavement strength testing using a Falling Weight Deflectometer (FWD), and analysis of the collected data to determine required load bans and structural adequacy of the existing pavement structures. A total of 49 roadway segments were included in this study. FWD data was collected in three rounds to evaluate seasonal variations in subgrade strength. Mean Benkelman Beam Deflections (MBD) were estimated from the FWD data, and the Maximum Tolerable Deflections (MTD) were calculated for the calculated design traffic. The proposed load bans or weight restrictions (spring and year-round) were determined based on the relationship between the MBD and MTD using the Transportation Association of Canada Guide to Load Management for Weak Pavement Structures.

Structural asphalt overlay required to convert the roads subjected to load bans to all season roads (roads with no load ban restrictions) were also determined using Asphalt Institute (AI) and American Association of State Highway and Transportation Officials (AASHTO) design standards. This paper provides a summary of the load ban estimation and structural overlay determination effort.