Discussion On Some Problems Of Design And Construction Course For Prestressted Concrete Transfer Girder Structure

Girder transfer floor structure has been used in housing building and bridge engineering which can solve the problem of vertical interruption of a whole structure. However, the practice case of supporting a column with cross transfer girder is quite few.Transfer girder, whose section is quite large, belongs to large volume concrete, in which crack is easy to develop before exacting prestress on the girder because of concrete shrinkage and hydration heat as well as load.In high-rise building, transfer girder co-works with the above structure, which will form a drag bar arc system after crack appears on the bottom.Associated with the design and in-site test of Nanjing railway station viaduct crossed transfer girder and transfer girder of Zhongyinhuilong Building in Suzhou Industrial Park, study on the reason of crack as well as the effect on the above structure is carried out in this paper. In concluding, the characteristics of transfer girder structure as well as itself are as follows:1. Crack with limited width is permitted under large accidental load, by which the internal force is controlled. Meanwhile, the transfer girder should be designed as full prestressed under long-term load. In elastic stage, the load allocation between girders could be adjusted by the number of steel wires.2. The steel framed reinforced concrete column partially penetrates into the transfer girder, whose build-in effect to the column enhances with the increase of the penetrating length.3. After the large volume concrete is poured, the stress caused by temperature difference of hydration heat and drying shrinkage is quite large if the concrete is not properly maintained. The stress is one of the key reasons that caused the crack.4. Transfer girder co-works with the structures above and below. The selected number of floors below takes great effect on the results when analyzing the local stress of the transfer girder. Crack is easy to appear at the unloading stage when the girder rigidity is large, on the contrast, the supporting negative moment will become small and the mid-span positive moment will become large when the girder rigidity is small, also the bending of near columns will become large. Througt system of drag bar arc composed by super-constucture and transfer girder, load of super-constucture will deliver the steel framed reinforced concrete columns which support transfer girder.5. For a partial prestressed concrete transfer short girder, a drag bar arc system is formed between the girder and supporting point after crack appears on the bottom of the girder, which is different with the common beam in essence. In this system, the steel wires and steel bars are the main parts that bear the tensile force, the stress in the district above the dragging bar is low. The maximum shear stress locates in the foot of the arc, the effect of the steel wires'resisting shear ability is quite limited.6. Based on on-site monitoring of practical engineering, the mechanical characteristics of transfer girder and all kinds of effects on it are properly reflected. It is concluded that the method of on-site monitoring is feasible, the testing data is believable and the conclusion is correct.7. As the analytical model is matching with practical situation, the experimental data and theoretical analysis is anastomotic. By contrasting with the result of ANSYS, the standpoint in this thesis is proved.8. In the end of this paper, according to on-site testing results and theoretical calculation, some rational suggestions on design and construction are presented.