Relaxation of Prestressing Steel – Comparison between Virgin Strands and Strands Exposed to Long-term Loading
2005 (English)In: Nordic Concrete Research, ISSN 0800-6377, no 2/2004, 55-68 p.Article in journal (Refereed) Published
The prestressing force in concrete structures is successivelyreduced by steel relaxation, concrete shrinkage, and concretecreep. A temperature increase from 20 to 40°C may double therelaxation. In nuclear reactor containments, the temperature isoften considerably above 25°C. However long term measuringseries indicate, that the losses are less dramatic than anticipated.In order to investigate how long-term exposure to real conditionsinfluence strength and relaxation properties, 7 thirty years oldwires from Forsmark nuclear power plant were tested in thelaboratory and compared with 7 virgin wires of similar type. Thetest results indicate that the strength is slightly reduced due to thelong term exposure. For new wires, a relaxation of 2 % wasdetermined after 5 days at 22°C and 4 % at 55°C. The old wireswere, however, resistant to renewed loading and did not show anynoticeable relaxation. This means that it is likely that theprestressing forces at Forsmark will not be reduced further if thetemperature during a limited time would be increased to 55°C.
Place, publisher, year, edition, pages
2005. no 2/2004, 55-68 p.
concrete structures, prestressing steel, reactor containment, tensile force loss
IdentifiersURN: urn:nbn:se:kth:diva-68310OAI: oai:DiVA.org:kth-68310DiVA: diva2:485107
QC 201201302012-01-272012-01-272012-01-30Bibliographically approved