The Beam-Slab-Combined Design Method For Prestressed Concrete Frame Structures

Along with boosting up of national economic ability, continuous extending of the architectural scale, prestressed structures are applied more and more in building because they are applicable to multi-function, large-span, heavy-loading structure. On the other hand, since the appearance of the FEM in 60's, the CAD technology has more and more important function in structure design along with the technical renewal of calculator. Therefore, making the best of the FEM to imitate the mechanics characteristic of the structures actually will be researcher and design personnel's target. Because it can make calculation more accurate ,design more reasonable, fast and structure more safe, economy.The calculating model recommended in present code has some suppose. These simplification is essential under the condition of adopting manual calculating means, that the FEM is not very mature and the hardware resources lack tightly. But it will bring to the error margin inevitably, even the mistake especially to the prestressed cast-in-site frame structures. Therefore, it is necessary to use the FEM stablishing actual structure mechanics model, and carrying on structure analysis and design.Making use of a procedure of ANSYS, internal force calculating value in models having different kinds of sections is compared with theoretic value firstly so that the correct establishing method of the beam-slab structure and the right infliction method of loading can be put forward.On the foundation of the actual establishing model, the calculation procedure about relationship of the crack width and nominal tensile stress is built up and some factors'influence on nominal tensile stress is analyzed. Using above analysing result, the crack-control criterion can be uniform. After that, the nominal tensile stress method and the ANN method of prestressed rebar area's estimating is educed. Making use of this method, we can estimate prestressed rebar area quickly and design the structure availably.At the same time, some parameter between the beam-slab frame and the T frame is analyzed, including: the prestressed rebar area contrast in two models and the reason; the lateral restraint's influence on the prestress establishment; flange width and juncture stress between beam and slab in the beam-slab frame; prestress value transferred to beam and slab in two kinds of model, and so on.On the other hand, different element is used to simulate beam and slab, thus the beam and slab's internal force result is outputted independently. After analyzing the unfeasibility of the whole internal force output, a new method about load-carrying capacity design is brought forward and the feasibility of this new method is analyzed.