Experimental Study On Full-scale Model Of Prestressed Concrete Box Girders

Because of the size effect of concrete structure,the mechanical behavior of concrete scale model and full-scale model is not the same.At present,because the full-scale model test is difficult,the studies on full-scale model are less.Beside,the losses of prestressing is a complicated problem,which has not been resolved completely,and need be resolved urgently in bridge engineering.Combined with the facts of bridges,the investigations are carried out to obtain the structural behaviors of concrete box girder of full-scale model,and the real losses of prestressing would bring practical values,and the study on structural behaviors of prestressed concrete of actual bridge is theoretical meanings.The main investigations are summarized as follows:1.The whole course tests were carried out on the 20m-span prestressed concrete of simply supported hollow-slab and the 30m-span prestressed concrete simply supported box girder.The paper assesses the applicability of the related calculation formulaes in domestic and international norms by the test values.The simplified formula of residual deformation for the prestressed concrete box girders was put forward,the values calculated by the simplified formula compared with the test values show that this simplified formula is feasible.A program and an analytical model were developed for the analysis of the prestressed concrete box girders and the parametric study was conducted using the program.2.The test on the longitudinal prestressing loss of 20m-span prestressed concrete simply supported hollow-slab was carried out. The results show that the friction loss and anchoring loss by testing are close to the calculation results by the JTG D62-2004.By the analysis of measured strain,we can match k and u,which are close to the values specified by the JTG D62-2004.For the short prestress tightwire,the prestressing loss will be reduced by tensed at on end.3.The results shows that the anchoring loss is about 58.5 percent-62.7 percent of the total prestressing loss in vertical tendons and 73.0 percent in transverse tendons.The paper discusses the effect on vertical tendons due to the tension modes.It shows that the anchoring loss is more than 32.4MPa by single tension,which is about 9.5 percent of the total loss.Three kinds of prestress loss except for loss of creeping are basically close to the values,which are calculated by concrete standard.Test results show that prestressing loss caused by temperature can not be ignored.The actual provision about road bridge criterion at home and abroad do not make provision for this loss, it is worth further studying.