Optimized Post-Tensioning Anchorage in Prestressed Concrete I-Beams

Anchorage zones in prestressed concrete I-beams are designed to accommodate anchorage hardware and to provide adequate space for the reinforcement needed to distribute the highly concentrated post-fensioning force. Based on analytical and full-scale experimental studies, optimized anchorage zone details have been developed. The proposed standardized anchorage zone is suitable for use with a post-tensioning tendon size up to 15- 0.6 in. (15 mm) diameter strands. It has a width of 28.5 in. (725 mm), which tapers for a distance of 39.4 in. (1000 mm) to the standard I-beam web width. Standard welded wire reinforcement is proposed for post-tensioning of up to three 15 - 0.6 in. (15 mm) diameter strand tendons. The use of a reduced block size can result in a weight reduction of as much as 80 percent compared to the commonly used anchorage block. A detailed example is included to demonstrate application of the strut-and-tie model to the design of the anchorage zone.