考虑徐变恢复的混凝土徐变效应分析

为了解决混凝土在复杂变化应力下的徐变计算问题,首先采用双函数法对叠加法的徐变计算公式进行修正;然后将修正叠加法应用到简单应力、阶梯变化应力、连续变化应力历史中,形成统一的徐变计算模式;最后设置3组阶梯变化应力历史、2组连续变化应力历史,分析叠加法与修正叠加法的差异性。结果表明:对于递增应力历史,2种方法徐变计算值相同;对于递减应力历史,2种方法徐变计算值的差异随龄期增大而增大,700 d的相对误差最大为47%;2种方法的差异与应力历史类型有关,其差异由小到大分别为递增应力、波动应力、递减应力历史。修正叠加法考虑了应力递减下的真实徐变恢复效应,适用不同类型的徐变模型与不同状态的应力历史,是一种较为准确的徐变计算方法。

Analysis of Concrete Creep Effect Considering Creep Recovery

In order to solve the creep calculation problem of concrete under complex varying stress,firstly,the twofunctions method was used to modify the creep calculation formula of superposition method.Secondly,the modified superposition method was applied to simple stress history,stepwise varying history and continuously varying stress history,and a unified creep calculation model was formed.Finally,3 groups of stepwise varying stress history and 2 groups of continuously varying stress history were set up to analyze the differences between the superposition method and the modified superposition method.The results indicate that the creep calculation value of two methods are same for the increasing stress history.For the decreasing stress history,the difference of creep calculation value between two methods increases with age,and the maximum relative error is 47%in 700 days.The difference between the two methods is related to the types of stress history,and the difference is from small to large,which is increasing stress history,fluctuating stress history,decreasing stress history.The modified superposition method considers the true creep recovery effect under decreasing stress.It is a more accurate creep calculation method that is suitable for different types of creep models and different states of stress history.