基于概率分析的普通混凝土抗压强度等级评定

通过正态分布保证率，建立普通混凝土抗压强度等级设计与评定之间的概率联系，并给出不同工况下的抗压强度等级评定方法及保证率。结果表明:普通混凝土配合比设计的抗压强度是通过混凝土抗压强度代表值的平均值,在95%的保证率条件下计算得到的；普通混凝土抗压强度评定统计方法基于普通混凝土的抗压强度服从正态分布，抗压强度的平均值和最小值的保证率不同。当混凝土样本数量≥10组，混凝土抗压强度标准差已知时，抗压强度的平均值大于等于设计强度的保证率是75%；抗压强度标准差未知时，根据试样组数，混凝土抗压强度的平均值大于等于设计强度的保证率分别是875%、853%和829%，低于混凝土配合比设计时的保证率，同时约束混凝土抗压强度的最小值；当混凝土样本数量<10组时，混凝土抗压强度评定采用非统计方法即安全系数方法来评定。

Probability based Evaluation of Grade of Compressive Strength of Ordinary Concrete

Probability relation between grade and its evaluation of the compressive strength of ordinary concrete is established with normal distribution of the probability,which includes the evaluation methods and probability of the compressive strength grade under different working conditions.The analysis results show that the designed compressive strength of ordinary concrete composition is calculated as the average value of the representative value of the concrete compressive strength with the probability of 0.95.The statistical method for the evaluation is based on the normal distribution of the compressive strength of ordinary concrete and the different probabilities of the average value and minimum value of the compressive strength of ordinary concrete.When the number of concrete samples is greater than or equal to 10 and the standard deviation of concrete compressive strength is known,the probability for the average value of concrete compressive strength to be greater than or equal to the designed strength is 0.75when the standard deviation of concrete compressive strength is unknown,the probability for the average value of concrete compressive strength to be greater than or equal to the designed strength is 0.875,0.853 and 0.829 respectively according to the number of concrete sample groups,lower than the requirements for the probability design while high enough to restrict the minimum value of the compressive strength of the concretewhen the number of concrete samples is less than 10 groups,the non statistical method—the safety factor method—is used for the evaluation of the concrete.compressive strength.