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1929年,Rausch根据空间桁架模型导出了一个预估钢筋混凝土构件抗扭强度的方程。然而,这个方程过高地估计了构件的实际抗扭强度。过去50年内,对这个方程,已提出了三种修正建议:(1)补充钢筋有效因子;(2)剪力流中线的定义;(3)略去混凝土保护层的作用。尽管这些方法满足设计的要求,但在理论上并不令人满意。因为作这种假定是为了使Rausch方程的结果能够人为地与试验结果一致. Rausch方程的不安全性来源于斜裂缝产生的混凝土软化。本文根据新的应力—应变关系提出了一种关于混凝土软化的新理论。用这个理论计算过文献中提供的108根试验梁的抗剪行为.它不仅可以预估构件的抗扭强度,而且还可以预估构件在整个加载过程中的扭转角,钢筋应变及混凝土应变。
In 1929, Rausch derived an equation for estimating the torsional strength of reinforced concrete members based on the spatial truss model. However, this equation overestimates the actual torsional strength of the component. Over the past 50 years, three proposed corrections have been made for this equation: (1) Reinforcing the effective factor of the bar; (2) Defining the midline of the shear flow; and (3) Removing the effect of the concrete cover. Although these methods to meet the design requirements, but in theory not satisfactory. Because this assumption is made so that the results of the Rausch equation can be artificially consistent with the experimental results, the unsafeness of the Rausch equation stems from softening of the concrete produced by oblique fractures. Based on the new stress-strain relationship, this paper presents a new theory about concrete softening. Using this theory, the shear behavior of 108 test beams provided in the literature is calculated, which not only can predict the torsional strength of the component, but also can predict the torsion angle, the strain of reinforcement and the strain of concrete during the whole loading process.