Page - 704 - in Book of Full Papers - Symposium Hydro Engineering

ASPECT 1974 1980 1986 1996 2004 2014 Applications 16 18 0 0 0 0 Recordkeeping 0 1 1 1 ½ 1 ½ 2 Specifications, Responsibilities and Submittals 0 1 1 ½ 2 2 2 Epoxy-Coated Strand 0 0 0 No separate section 10 10 TOTAL PAGES 32 57 41 70 98 109 In this regard, it may be noted that, in the earlier days of practice in the U.S., anchoring was a technique pioneered by the post-tensioning suppliers themselves, subcontracting out to specialty geotechnical contractors the “dirty bits,” i.e., the actual drilling, water testing, tendon placement and grouting processes. This tendency was reversed by the early 1980’s: in the U.S. the geotechnical contractors win the projects, buy the steel and frequently rent the prestressing equipment. Again it is reiterated that industry operates under a set of “Recommendations” provided by an ad hoc committee of a Trade Association, i.e., the Post-Tensioning Institute. However, for liability reasons, industry treats the Recommendations virtually as a standard, and it is very rare for any significant deviation to be found in Specifications or associated Method Statements. In the authors’ experience, the “Recommendations” constitute excellent, comprehensive and practical guidance, and stand in very favorable comparison with more rigorous European standards and guidelines. The Recommendations do not provide guidance on the analysis or overall design of an anchored structure (e.g., selection of number and capacity of anchors, their length, spacing and inclination), for that is the responsibility of the Engineer-of-Record, using well established methods of rock mechanics and structural engineering. The Recommendations address the design, construction, testing and performance of individual anchors. 2.2 EVOLUTION OF PRACTICE This is covered in detail in the papers contained in the References, and only a very brief summary is provided hereunder, insofar as the points have relevance to the assessment of aging anchors. 2.2.1 Design Excluding, for the moment, the critical issue of corrosion protection, it may be concluded that most key elements of design have been little changed over the years, and so remain as described in Littlejohn and Bruce’s State of the Art Study [5]. It is tacitly assumed that load transfer mechanisms in and around the bond 704