| In order to overcome the huge vertical prestress loss in prestressed concrete box girder bridges,of which the main purpose is to improve the stress condition of webs,the OHM system which uses two-times tensioned steel strands has been applied in our country by recent years to gradually replace the YGM system which uses finished deformed bars.However,since that a complete computing method has never been came up with,the comparison between these two kinds of vertical pretress systems’ pretress losses has always been staying in a perceptual cognition stage.Aiming at the problem mentioned above,the vertical prestress losses of two support-project bridges have been tested on site and the testing results have been used to discuss the computing method of vertical prestress loss.Plenty of testing results from former researchers have also been collected to support the analysis.The main research works of this paper are as follows:Firstly,the main causes of vertical prestress loss have been discussed,after which the differences between each type of vertical pretress loss in the two systems have also been discussed,based on the two systems’ different structural characteristics and construction processes.Secondly,the on-site testing process of vertical prestress loss has been introduced.Based on the testing results,the difference between the compositions of vertical prestress loss in the two different systems and the causes of such difference have been discussed.Finally,according to the different vertical prestress systems’ distinctive structural characteristics,the computing methods of vertical prestress losses under two different systems have been came up with respectively.According to the testing results tested on-site and collected,Least Square Method has been applied to calculate the parameters of the equations.The finite element method software ANSYS has been applied to vertify the accuracy of the computing methods mentioned above. |
PDF Full Text Request