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一、问题的提出在我国现行钢筋混凝土结构设计规范中,列受弯构件抗裂度计算,采用了如图1所示的应力图形。图中引用了平截面假定,并近似地取压应力图形延线与拉区边缘交线制距为2R_f。用这种应力图形进行抗裂度计算的结果,对一般高度的梁式构件(h≤40厘米)还比较靠近,但对截面高度较大的构件,则多估了靠近中和轴处混凝土所承担的拉力,致使所采用的截面抵抗矩塑性系数γ值偏大。相反,对高度较小的板式构件,所采用的γ值又偏小。因此,对截面高度变化这个因素的影响,应给予恰当的考虑。
First, the problem proposed in China’s current design code for reinforced concrete structures, listed by the bending member anti-crack calculation, using the stress pattern shown in Figure 1. In the figure, the flat section hypothesis is quoted, and the distance between the extension line of the compression stress pattern and the edge of the drawing zone is approximately 2R_f. The results of the crack resistance calculation using this stress pattern are relatively close to the general height beam member (h ≤ 40 cm), but for the member with the larger section height, the concrete near the neutral axis is estimated more. Due to the tensile forces, the plastic coefficient γ of the cross-section resistance moment is large. On the contrary, the gamma value used is smaller for small height plate components. Therefore, proper consideration should be given to the influence of the change in the height of the section.