Recommendations for the Development Length of Prestresssing Strands Including the Effects of High Strength Concrete

Abstract

Development length is a design requirement specified by the design codes for ensuring adequate anchorage of the prestressing strands. Current code provisions do not consider the effects of changing concrete strengths on the required development length. This research is focused on finding these effects and proposes a design equation, based on the experimental results, for calculating development length of prestressing strands. For this purpose, development length tests are carried out on multiple rectangular and I-shaped beams with various concrete strengths at Oklahoma State University. Experimental results clearly indicate that the bond between prestressing strands and concrete is improved as the concrete strength is increased. Appropriate changes to the current design code equations for development length are recommended. A minimum NASP Pull-Out value is suggested for safe use of the prestressing strands with respect to their anchorage requirements.