Averageforcealongunbondedtendons:afieldstudyatnuclearreactorcontainmentsinSwedenOriginalResearchArticle

ThetightnessandintegrityofallSwedishreactorcontainmentsdependdirectlyandindirectlyonthefunctionofthepost-tensionedsystem.Thetendonforceincontainmentswithunbondedtendonsisfollowedupatregularin-serviceinspections(ISI)toensurethattheremainingforceissufficient.Attheinspections,thetendonforceismeasuredwithso-calledlift-offtechnique,whereajackisusedtolifttheendanchor.Theinterpretationofthemeasuringresultsisnotobvious.Onedifficulty,whichaffectsalltendonstodifferentextents,istheinfluenceoffrictionbetweenthetendonandduct.Thisinfluencecancausearedistributionofforcealongthetendonsaftertheoriginaltensioning.Theordinarylift-offmethodonlymeasurestheforceattheendofthetendon,whichnotalwaysrepresentsthechangeofforceintherestofthetendon.Amethodformeasuringaverageforcealongatendonispresentedinthisarticle.Inthismethod,theelongationofthetendonismeasuredwhenthejackforceisincreasedtoareferencelevelwithknownforcedistribution.MeasuringresultsfromthelatestISIinSwedenshowthattheendforcehasdecreasedmorethantheaverageforce,especiallyforlongtendonswithhighinfluenceoffriction.