Research On Prestressing Effects Of Prestressed Steel-concrete Composite Continuous Beams

With the development of economy and society, architectural styles and structural types are tending to be more and more diversified. Magnificent and novel buildings come forth continuously. New-type prestressed composite structure emerges as the time requires which breaks through the traditional design concept .It makes different kinds of materials and structural types combined and optimized. Prestressed steel-concrete composite beams are widely applied in the high buildings, wide-span structures, bridges and special type structures etc. which have a good prospects. Up to now, less systematic researches are processed in the prestressed steel-concrete beams at home and abroad, and there aren't specific regulations in the Chinese design specifications. In order to make the structural system more popularized, it is necessary to research the working behavior and advance reasonable design methods.Based on the preceding theory and experiment researches, prestressing effects of prestressed steel-concrete composite continuous beams are mostly analyzed and discussed in this paper. Parameter analysis ,3d Nonlinear finite element program and experimental study are carried out to discuss the prestressing effects in terms of ultimate flexural strength, deflection, cracking moment, the redistribution of internal force , the stress increment of prestressed tendons, and the slip at the interface of prestressed steel-concrete composite continuous beams. Reasonably good correlation between analytical and experimental results are obtained.Based on the experimental results and the analysis of the prestressed composite continuous beams, the following conclusions are drawn.1. Prestressing a composite girder enlarges the range of elastic behavior, adjusts the redistribution of internal force, reduces deflections, increases craking load and ultimate loading capacity.2. The displacement ductility coefficients of the prestressed composite continuous beams surpass 4, which means this type of structure has better ductility.3. Before the steel yields, the stress increment of prestressed tendons changes approximately linearly with the incremental load. After the yielding occurs, the stress increment increase evidently.4. The slip between the concrete slab and the steel girder of complete-shear-connection prestressed steel-concrete composite beams is small enough to justify the assumption of complete interaction between the interface under service load .