In 1986, reported research results indicated that current design provisions that govern the anchorage of steel prestressing strands were inadequate. The Federal Highway Administration (FHWA) responded by issuing a moratorium in October of 1988 that increased the development length requirements for pretensioned strands until additional research was available to restructure or verify the current code provisions. That moratorium remains in effect today. Subsequently, several research projects were undertaken to measure experimentally the transfer lengths and development lengths of pretensioned prestressing strands. However, the results from various research projects indicate widely disparate results, with measured transfer lengths varying more than 100% between different research projects. In fact, the defining characteristic of transfer length measurements appear to be their wide degree of scatter, despite researchers' best efforts to control variables. Collectively, the widely disparate transfer length and development length results indicate that all of the relevant variables have not been sufficiently identified nor quantified. This research will investigate the fundamental bond mechanisms to develop behavioral and analytical models that can become the foundation for design.
