Externally Prestressed Simply Supported Beam Time-varying Effect Analysis

The technology of external prestress has been widely used in old bridge strengthening and new bridge around the world. At present, there are large amount of researchs on the limit stress of external prestressed beam have been complished,while little research on long-term deformation and concrete stress and steel stress due to shrinkage and creep of concrete ,and the relaxation of prestressed steel.The main works completed in paper include following parts: Firstly,based on up-to-date research on external prestressed concrete beams ,the advantages,appliation and mechnical performance of external prestressed concrete beams are analysised,and some proble ms needed to solve are presental which should be mentioned in des ign and calculation.Secondly,a novel approach to compute the deflection of girder,stresses of concrete and steel is established according to the relationship between the deformation of girder and the deflection and angular in anchor regions and deviators under the action of loads,and a set of formula are deduced.Thirdly,the redistribution of stresseds of concrete and steel in a section is analysied based on internal force eguilibrium and copatibility of deformation while adopting the Age-adjusted Effective Modulus Method,also,the formulae on computing the prestress loss and deflection of beam..Finally,analysis on examples are accomplished by MIDAS and presented method,respectively,and some important conclusions have been oblained by comparing the theonetical results.