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本文首先给出部分预应力单筋矩形截面混凝土梁开裂后中和轴位置的计算图表。对于单筋T形截面的中和轴位置,本文提出了有关计算参数,利用上述图表,通过简单迭代,亦可很快求出。对于矩形和T形截面的双筋梁,均可换算成T形单筋粱,从而求出其中和轴的位置。当T形截面的翼板尺寸较大,其配筋率和预应力又都较小时,可直接用近似的线性方程求得能够满足设计精度的中和轴位置。本文还对线性方程的误差进行了分析,并给出了近似公式的适用范围。本文所述计算方法可供设计应用。
This paper first gives a calculation chart of the neutral axis position after cracking of partially prestressed single-reinforced rectangular section concrete beams. For the position of the neutral axis of the single-rib T-section, the calculation parameters are presented in this paper. Using the above diagram, it can be quickly determined by simple iteration. For double-reinforced beams with rectangular and T-shaped cross-sections, they can be converted into T-shaped single tendons to determine the position of the neutral axis. When the wing plate size of the T-shaped section is large and its reinforcement ratio and prestress are both small, the neutral axis position that can meet the design accuracy can be obtained directly by using an approximate linear equation. This paper also analyzes the error of the linear equation and gives the applicability of the approximate formula. The calculation methods described in this article are available for design applications.