Research On Prestressed Loss Of Long Span Prestressed Concrete Continuous Beam Bridges

With the rapid development of highways in our country, bridge construction has come in the upsurge period hitherto unknown, the long span prestressed concrete bridge is used widely for its advantage. Because the span of the bridge becomes longer and longer, the request of designing, construction, material and equipments should be elevated. At present, crack phenomenon always appears in long span prestressed concrete continuous beam bridges used, the reason of which is that the structure prestressed loss is estimated lower. The security and dependability of the extra long bridge structure have become the general concern question of the society in these days.Because of the influence of the prestressed loss, the real stress doesn't coincide with the designed stress, that is to say, the calculated stress doesn't display the condition of the real structure stress properly, and thereby the undiscovered danger leads to the quality of the engineering construction. Compared with the prestressed loss in the short steel rope, the prestressed loss in the long steel rope nonlinearly increases with length of the steel rope. It is apparent that the error of piecing and locating the corrugated pipe and the error of level and upright and leaking in the part lead to increase of friction loss. So in the process of designing the long span concrete bridge, the estimation to prestressed loss should be proper. Only to do mis, the value of prestressed force is designed suitable, the capability that the prestressed concrete structure bears weight, security, and dependability, economy and service life of the structure can be convinced. How to give out the friction factor and the regular pattern is the importance of researching the prestressed loss in the long steel rope.In this article the prestessed loss in the prestressed concrete structure will completely be analyzed in the theory. Combining with the fourth-Hanjiang bridge of Xiang-Shi Freeway in Hubei Province, the prestressed friction loss of the prestressed steel rope is analyzed ideally and researched experimentally. At first, the soft of bridge structure, GQJS, is used to calculate the structure of prestressed concrete continuous beam bridge and the deformation and stress of the concrete box beam are given out; then by measuring and analyzing the datum of the stress in the prestressed steel rope and the stress of section in the concrete box beam, this article presents two ways to identify the reasonable friction deviation factor k between longitudinal prestressed tendons and the wall of duct (indirectly and directly), and discover the regular pattern of prestressed friction loss. The conclusion may provide reliable datum for structure construction controlling and guarantee the quality of construction. At the same time, the conclusion has guide significance for designing and constructing long span prestressed concrete bridges.