Study On Prestress Loss Of Long Curved Steel Strand For Post-Tensioned Continuous Beam Bridges During The Process Of Tension

Prestressed technology has been widely used in the modern bridge engineering field asits unique advantage. According to the statistics of existing bridges in our country and abroad,the prestressed concrete (referred to as PC) bridges account for the largest proportion,especially the long span bridges. The main part of prestress loss of long and curvedprestressed steel strand in PC bridge occurred in the tensioning process. Therefore thecalculation of the prestress loss in the tensioning process is one of the most important issuesin bridge engineering field. In some practical engineering, the theoretical value of prestressloss and elongation are discordance to the measured value, sometimes the difference is serious.This paper mainly analysis and research on this phenomenon.First of all, this paper introduces the theory and calculation method of prestress loss andelongation of the steel strand during the tensioning stage.Secondly, the influence of the way concrete contacts with steel strand to the calculationresult of prestress loss has been studied. The result of test and theoretical analysis suggeststhat the distribution of pressure between long curved steel strand and prestressed duct hasinfluence to calculation of prestress loss. And if the pressure is considered aseven-distribution, the calculation of the pressure loss would not be short-calculated.Thirdly, the calculation methods of pressure loss and strand elongation have been studied.The regularity of pressure loss about the long curved strand is studied through analysis of thedata on the stress, strain and elongation collected in construction. Based on the existingcalculation formula of prestress loss, the correction formula is deduced through the regressionanalysis of the test data. Meanwhile, the precise calculation method is given out which hasalso been checked.Finally, sensitivity analysis about parameters affecting the calculation of prestress losshas been done. The sensitivity of parameters like μ、k、θ、L has been analyzed by researchingthe prestress loss and elongation in strand about different test point.The correction calculation method of prestress loss and elongation of long curved steelstrand in post-tensioned PC continuous girder is given in this paper. This paper has significantdirection to the double control which has a certain theoretical and practical value.