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本文对钢筋混凝土梁开裂后,在长期使用荷载下挠度的增长情况,即长期刚度问题进行了研究,并且短期刚度的计算问题也得到解决。文中引用了美国的、苏联的、我国的及我们自己的许多试验资料,对理论分析进行了比较,结果是良好的。短期刚度可按 vE=(0.77E bh_0~3[3-1.3k]k~2(0))/6进行计算,长期刚度按 vE(1+(a+1/2)φut)/a~2进行计算。并且在实际工程当中,可采用表四直接查到(1+(a+1/2)φt)/a~2值。同时文中对混凝土受压区相对高度的计算公式也进行了验证,并且发现在矩形单筋梁中使用的含钢率范围内相对高度与含钢率存在线性关系。对受压钢筋的影响也有表六或图五加以考虑。
In this paper, after the cracking of reinforced concrete beams, the increase of deflection under long-term load, that is, the problem of long-term stiffness is studied, and the calculation of short-term stiffness is also solved. The paper cites many experimental data from the United States, the Soviet Union, China, and our own, and compares the theoretical analysis. The results are good. The short-term stiffness can be calculated by vE=(0.77E bh_0~3[3-1.3k]k~2(0))/6. The long-term stiffness is according to vE(1+(a+1/2)φut)/a~2 Calculation. And in the actual project, you can use Table 4 directly to find (1 + (a + 1/2) φt) / a ~ 2 values. At the same time, the calculation formula of the relative height of the compression zone of the concrete is also verified, and it is found that there is a linear relationship between the relative height of the steel containing rate used in the rectangular single reinforcement beam and the steel containing rate. The impact on the pressed steel bar is also considered in Table 6 or Figure 5.