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预应力筋的优化布置是大内跨小边跨的多跨预应力混凝土框架结构合理设计计算的关键.为满足控制截面承载力最大的需要,以往常将大跨所需预应力筋布置为连续曲线,并按水平直线延伸通过其相邻的两小跨,按这种布置方式仅使大跨内产生竖向向上的预应力等效荷载,可较好平衡大跨的竖向外荷载;而若将大跨及相邻的两小跨统一考虑,预应力筋按连续曲线布置,张拉产生的预应力等效荷载不但可有效平衡大跨的竖向外荷载而且也可平衡小跨的竖向外荷载,可以使荷载平衡得到优化实现.以一典型工程为例,分析了在相同条件下两种预应力筋布置过程中张拉引起的综合弯矩、主弯矩和次弯矩的分布和量值上差异,比较了两类布筋形式对正截面承载力计算结果的影响,验证了对大内跨小边跨框架结构统一考虑后整体上按三段连续正反抛物线预应力筋布置的合理性.
The optimal arrangement of prestressed tendons is the key to the rational design and calculation of multi-span prestressed concrete frame structures with large span and small span.In order to meet the needs of the maximum bearing capacity of the control section, prestressing tendons Curve, and according to the horizontal straight line extends through the two adjacent small span, according to this arrangement only within the span to produce vertical upward prestressed equivalent load, can better balance the vertical external load of large span; and If we consider the large span and adjacent two small span uniformly, the prestressing tendons are arranged by continuous curve. The prestressed equivalent load produced by the tension can not only effectively balance the vertical external load of the large span but also balance the vertical direction of the small span The outward load can optimize the load balance.Using a typical project as an example, the distribution of the composite bending moment, main bending moment and secondary bending moment caused by the tension in two prestressed tendons under the same conditions are analyzed And the difference between the value of the two kinds of tendons form of the cross section bearing capacity of the calculation results are verified to verify the large internal span of the small span of the frame structure unified consideration of the whole by three consecutive positive and negative parabolic tendon layout The rationality.