A semi-destructive test method was used to determine the remaining tendon force in a 17-rn-long (55.8 ft), 38-year-old bridge beam. An investigation of the test method is reported in this paper and it verifies that the test method is feasible. Recommendations for the use of the test method are presented. Measurements of the prestressing force losses are compared with calculation methods based on fib guidelines and Swiss code; calculated and measured prestressing force losses were generally in good agreement. A long-term prestressing force loss of about 20% was obtained. Results of material tests performed on the pretensioning steel and the concrete are also presented, and their strength development over time is assessed. The investigation described herein is the first part of an extensive test program on five similar test beams.
