中外标准中混凝土强度接收准则对比分析

Comparative Analysis of Concrete Strength Acceptance Criteria in Chinese and Foreign Standards

对中国、美国、英国标准中的混凝土强度接收准则进行对比分析,结果表明,我国标准规定的极限质量水平偏低,导致混凝土强度接收准则明显低于国外标准,既不利于保证工程质量、降低用户方风险,又不利于与国际标准接轨;中外多数标准的混凝土强度平均值接收准则不符合一次计数抽样检验理论,标准差未知统计方法、非统计方法与标准差已知统计方法的检验功效差异较大;多数情况下无须同时设置平均值接收准则和最小值接收准则。美国标准的接收准则较好地平衡了生产方风险和用户方风险,检验功效较好,统一了标准差已知统计方法和标准差未知统计方法,非统计方法与统计方法采用了较一致的数理统计原则,其混凝土强度接收准则总体较均衡、合理。根据中外标准的对比分析结果,提出我国混凝土强度接收准则的初步改进建议,包括根据合理的生产方风险、用户方风险和极限质量水平,确定标准差已知的抽样方案;以贝叶斯理论为依据,采用与标准差已知方案保持一致的分位值,确定标准差未知时的抽样方案;当样本容量较小时,改用非统计方法,或基于贝叶斯理论将前一检验批与本次检验批样本合并。

The acceptance criteria of concrete strength in standards of China,the United States and the United Kingdom are compared and analyzed.The results show that the limit quality level specified in Chinese standards is obviously lower than that in foreign standards,which is not conducive to ensuring the engineering quality,reducing the user’s risk,and connecting with international standards.The acceptance criteria of strength average value in most Chinese and foreign standards do not conform to the theory of one-time sampling inspection,and the inspection efficacy of statistical methods with unknown standard deviation,non statistical methods and statistical methods with known standard deviation are quite different.In most cases,it is not necessary to set minimum acceptance criteria at the same time.The acceptance criteria of American standard well balance the risks of the manufacturer and the user,and the inspection effect is better.It unifies the statistical method with known standard deviation and the statistical method with unknown standard deviation,and the non statistical method and the statistical method adopt more consistent mathematical statistical principles.The acceptance criteria of concrete strength are generally balanced and reasonable.Based on the comparative analysis of Chinese and foreign standards,some suggestions for improving the acceptance criteria of concrete strength in China are put forward.The sampling scheme with known standard deviation was determined reasonably based on of the risk of the producer,the risk of the user and the limit quality level.The sampling scheme with unknown standard deviation was determined using the quantile value consistent with the scheme with known standard deviation based on the Bayesian theory.When the sample size was small,the non-statistical method was used or the samples in the current inspection batch could be combined with the samples in the previous inspection period based on the Bayesian theory.