Design Method And Calculation Scheme On Prestressed Concrete Structure By Prestressing Force

With the great development and application of prestressed concrete structure in our country, some defects still existed in theory field and couldn't be ignored. Traditional numerical theories and methods faced new challenge when confronted with complex modern structures. Several considered and difficult problem in the field were studied in the paper, which included the method of prestressed load for statically indeterminate prestressed concrete, the ultimate limit states analysis of normal section of prestressed concrete structures considering the effects of secondary moment and secondary axial force, methods for analyzing lateral restraint of prestressed concrete structures, a practical improvement method for the design of normal section of prestressed concrete structures.Based on the producing mechanism of prestressing equivalent loads, the prestressed force effect of statically indeterminate prestressed concrete structure was analyzed. Focus on the behavior characteristic of presrressed tendon, classify the contribution of prestressed tendon as two sides, design equation of the ultimate normal section load bearing capacity of prstressed beam is derived according to this concept, and the influence of the beam axial prestressing effect obstructed by column is discussed in detail also, the deficiency of prevailing plane rigid frame method is pointed out. This thesis analyzes the present design methods of statically indeterminate prestressed concrete on the base of previous research and presented an improving normal section design method of statically indeterminate prestressed concrete structure. The principle of this design method is to ensure all of the prestressed concrete structural components satisfy the two kinds of limit states simultaneously. It set up simultaneous equations to make the structure satisfy the service performance in general, and then ascertain the non-prestressed rebar using the carrying capacity calculational formulae for the normal section and the request for the structure. The method has avoided secondary internal force problem in the process of prestressed concrete framedesign and has considered the effect of lateral restraints and the construction consequence to the internal force of the structure. At the same time, an example has demonstrated that the lateral limitations can reduce the carrying capacity of prestressed beam. This method can satisfy the requests of anti-cracking performance and carrying capacity, simplify the design process, avoid trivial error-tests, thus it benefits the spread of concrete techonology.