In 1968 T.Y. Lin endowed the ASCE Prestressed Concrete Award in order to "encourage the preparation of meaningful papers in the designated field of endeavor." Tanya Luthi, Jeffrey R. Diephuis, Juan Jose Icaza, John E. Breen, and Michael E. Kreger received the 2009 T.Y. Lin Award from the American Society of Civil Engineers at the Structures Congress in Austin on 30 April for their paper Effects of Duct Types and Emulsifiable Oils on Bond and Friction Losses in Posttensioned Concrete
which appeared in the January/February 2008 issue of the Journal of Bridge Engineering. This is Dr. Breen's fouth time to recieve this honor.
Abstract
Effects of Duct Types and Emulsifiable Oils on Bond and Friction Losses in Posttensioned Concrete
Emulsifiable oils are often used in posttensioned construction to reduce friction losses and provide temporary corrosion protection for tendons prior to grouting. This paper addresses the effects of two emulsifiable oils and three duct types on bond and friction losses. Bond test results indicate that corrugated galvanized steel ducts provide better anchorage than corrugated HDPE ducts. Rigid steel pipes performed poorly because of failure at the duct-concrete or grout-duct interface. Bond test results also indicate that the ultimate strength of posttensioned specimens with oiled tendons is similar to or better than the ultimate strength of specimens with unoiled tendons. However, specimens with oiled tendons experienced greater slip at a given load than specimens with unoiled tendons. Friction test results indicate that current recommended design values for the coefficient of friction for steel pipes and galvanized ducts are accurate. However, the measured coefficient for HDPE ducts is significantly less than the AASHTO-recommended value. Friction tests also indicate that lubrication of the tendon reduces the friction coefficient by 15% in rigid steel pipes and HDPE ducts if stressing occurs while the oil is fresh.
The full paper can be read by clicking here.