Strains and stresses in the end zone of pre-tensioned concrete beams

The purpose of the research described in the paper is to demonstrate the potential of optical strain measurement methods to determine the stress distribution in the end zone of prestressed concrete beams. The preliminary research covered beam randomly selected from the Consolis Poland production cycle. It was possible due to the non-destructive nature of optical technique of measurements. The test was carried out on a casting bed at the moment of tendons release. The imaged zone approximately corresponds to the transmission length of the prestressing force. Obtained deformations were compared with results of FEM analyses. The purpose of the comparison was to verify the applicability of FEM analysis in the design of reinforcement of support zones and to optimize the technique of modelling the increase of prestressing force. Provided research confirmed the possibility of using optical methods to assess the behaviour of end zones of pre-tensioned beams. Satisfactory agreement between the measurements and numerical analysis results was obtained, for both applied, the elastic and elastic plastic model of concrete Further studies of broader series of repeatable elements are planned, allowing to propose analytical methods for designing the reinforcement of these zones, considering the impact of disturbances such as dappedend and openings.