Ferrebee Guest Lectures at Washington State University
In support of ACPA’s technical service and outreach activities, Eric Ferrebee presented a guest lecture at Washington State University last week.
The presentation was for WSU Professor Somayeh Nassiri’s Pavement Design Course (CE 473). (Somayeh is a Board member of ISCP.)
Eric said Professor Nassiri had previously covered the main AASHTO design methodologies including AASHTOWare Pavement ME and the AASHTO 93 design guide, so he focused on pavement design for streets and local roads.
He covered a brief history of pavement design dating back to the first concrete pavement in Bellefontaine, noting “this was a time when we weren’t really designing pavements, but just creating concrete slabs with as much concrete as we could produce.”
He also covered the evolution of concrete pavement jointing, the first major road tests (Bates and Pittsburg), and Westergaard’s stress equations. “This is the pre-history that sets the foundation for the modern highway concrete pavements,” he said.
He also covered the history of the AASHO Road Test and the subsequent AASHTO Design Guides that were based on it (including AASHTO 93, 86, 72, etc.) that inherently have limitations built in from the limited inference space of the road test. He noted that this works reasonably well for asphalt pavements, but significantly over designs concrete pavements.
He also spoke about the development of the PCA method, which started shortly after the AASHO road test, but took a mechanistic approach (vs. the empirical approach at the road test). “This led to the developments of the PCA method, the update in 1984 to include erosion and edge support, ACPA’s purchase of the design methodology in 2005, and the introduction of StreetPave, as well as the major updates in 2012.” The discussion segued to a presentation on PavementDesigner.org.
Eric also covered the history of Pavement ME and how it is made for Interstate and state highways and is a great tool, albeit expensive and complex, and likely beyond the reach of many cities, counties, towns, and local municipalities.
The 25 to 30 students had an opportunity to do real-world demo runs of PavementDesigner, including one that compared AASHTO 93, PD, and Pavement ME. Eric also mentioned opportunities in the concrete pavement industry.