Design and Behavior of Anchorage Zones in Post-Tensioned Concrete Members

The major emphais of this research was the development of a generalized approach for the design and proper reinforcement of anchorage zones in post-tensioned concrete members. The approach addresses the serviceability limit state with a plasticity based solution called the strut-and-tie model (STM).

Experimental tests were conducted to verify the ultimate strength analytical and design models developed. A total of 36 experimental specimens were tested. The specific types of anchorage zones that were tested include: concentric tendon, multiple tendons, and inclined tendons with curvature. The basic STM which assumes an elastic stress distriubtion at the end of the general zone was developed in detail. The model was found to be a very conservative estimate of the anchorage zones. Examples are given and procedures developed for determining the dimensions and capacities of the nodes and compression struts within the STM. A modified STM was also developed which more accurately represents the ultimate behavior and capacity of the anchorage zone. The model allows a more plastic stress distribution at the end of the anchorage zone than in the basic STM. The serviceability limit state was addressing with the development of methods for predicting the first cracking load. The first cracking load was found to be difficult to predict but conservative design models were determined.

The document has an extensive state-of-the-art review that examines exisiting technical literature, product literature, codes, and handbooks. New terminology was introduced which helps to define the anchorage zone. This terminology was also used to propose divisions of responsibilities within the anchorage zone between the engineer-of-record, the anchorage device supplier and the constructor. A proposed revision to the AASHTO Bridge Specifications is presented that incorporate the division of responsibilites, the results from this document, and companion research at The University of Texas at Austin conducted by Burder and Roberts.