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收缩徐变微差应力为均匀微差和梯度微差分别所产生的应力之和,不能无视梯度微差应力的存在。本文推导了用以计算梯度微差应力的公式,既适用于预制部分在预应力作用下,其曲率滑梁长方向为常量时;又适用于预制部分承受自重以及施工荷钱后,其曲率为变量时。试验表明,有支撑施工的非预应力混凝土迭合梁的收缩徐变微差应力随龄期而增长,达到最大值后又随龄期而减少,以至到达可以忽略不计的程度;在短龄期的应力,其计算值尚须乘以0.5左右的折减系数。无支撑施工、一次加载的预应力混凝土迭合梁,除预制部分高度为10厘米的梁外,收缩徐变微差应力的计算值与试验值基本一致。无支撑施工、二次加载的预应力混凝土迭合梁,预制部分底缘的收缩徐变微差的拉应力很小,在设计中可以忽略不计。为验证以上认识,进一步试验研究尚有必要。
The shrinkage and creep micro-stress is the sum of the stress generated by the uniform and the micro-gradient respectively, and can not neglect the existence of the gradient micro-stress. In this paper, the formula for calculating the gradient microdifferential stress is deduced. It is not only suitable for the prefabricated part under the prestress, but also when the curvature of the prefabricated part is under constant weight. Variable The tests show that the shrinkage and creep differential stress of non-prestressed concrete composite beams with supporting construction increases with age, reaches the maximum value and then decreases with the age, and reaches a negligible level. In the short-term stress , The calculated value still need to be multiplied by 0.5 or so reduction factor. Without support construction, once loaded prestressed concrete composite beams, in addition to the prefabricated part of the height of 10 cm beam, the calculated value of shrinkage and creep micro-difference basically consistent with the experimental value. In the prestressed concrete composite beam with no support and secondary loading, the shrinkage and creep differential stress at the bottom edge of the prefabricated part is very small and can be neglected in the design. To verify the above understanding, further experimental research is still necessary.