Effect Of Tensioning Method On Internal Forces In Multi-story Prestressed Concrete Framed

Prestressed concert with unbonded tendons(BUPC) is a newly arisen technique in the concrete structure realm. Compared with prestressed concrete with bonded tendons, it abridges preformed hole, drifting steel, grouting craft etc, the method of laying steels is more agile: Compared with reinforced concrete, it strengthens the applicability of the building function, economizes a great deal of steel material and improves the structure to be subjected to the dint function clearly. Therefore, be close to more than ten in the last hearses to construct the application in the structure to get the fast fierce development in our country.However, when implementing the prestressed techniques for large span frame structure, some issues still remain to be unsolved and unclear in the design and construction process. For example, the construction of prestressed concrete structures is different from that of reinforcement concrete structures. It not only asks for higher requirements in technology, but also has more close relationships to design and construction, as different assumptions in design and construction method may cause different internal forces.The design of prestressed concrete frame based on the current method does not consider that the structural types and bearing load vary with the construction process. The designed internal forces value deviate from the real value resulting from that analytical model is different from practical construction method. On this point, some researches were undertaken by comparing the so called "Cast-in-place and Prestressed Story-by-Story" construction method adopted in multi-storied prestressed concrete frame structure with the popular method of "Prestressed after Completion of Construction".Based on theories of structural mechanics and analysis of analytical results, discussion was made to effect of different tensioning construction methods on the comprehensive and designed bending moment in the frame columns. Analytical and computational results show that the effect is much significant. The discrepancy between the comprehensive moments derived from the measured value is relevant wilt such factors as the number of spans, location of sections, and linear stiffness ratio of beam to column.