Transfer and Development Length of 0.6-inch Strand in High Strength Lightweight Concrete

Abstract

A research project conducted at Georgia Tech tested six pretensioned AASHTO Type II girders that were constructed using expanded slate lightweight concrete with design strengths of 8,000 and 10,000 psi, with actual strengths ranging from 8,790 to 11,010 psi. Each girder was prestressed using 0.6-inch diameter low relaxation strands tensioned to 75% of strand ultimate stress. In order to determine development length characteristics, three-point bending tests were conducted on each beam. The distance from the beam end to the load point varied from between 70 and 100 percent of the AASHTO specified development length. Development lengths of 91 inches and 67 inches were obtained for the 8,000 and 10,000 psi concretes which were 95 percent and 70 percent of the design development lengths allowed in AASHTO 16th Edition.