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混凝土的验收强度和配制强度关系工程安全和造价,应结合混凝土强度的实际,用数理统计方法加以确定。但是现行的方法,有的没有将强度都按正态分布计;有的强度标准差按未知计;有的抽样检验因素(试件组数和两类错误)没有考虑或没有全部考虑;还有的甚至不采用数理统计方法而采用经验法;……,致使所得验收强度和配制强度不正确,也不统一。本文针对存在的问题,提出以按正态分布计的设计强度为基础;强度标准差按已知计;考虑试件组数和允许较小的抽样检验的第Ⅱ类错误(将不合格的漏判为合格)确定试件强度平均值的验收强度;在此基础上,再允许较小的抽样检验的第Ⅰ类错误(将合格的错判为不合格),确定配制强度和预期强度正态分布;再在预期强度正态分布的基础上,考虑试件强度最小值随试件组数增多而降低的统计规律,确定试件强度最小值的验收强度。最后举例说明本文方法的合理性。
Acceptance of concrete strength and strength of the relationship between engineering safety and cost should be based on the actual strength of concrete, using mathematical statistics to determine. However, some of the current methods do not consider the intensity as a normal distribution. Some standard deviations of intensity are unknown. Some sample test factors (the number of test pieces and two types of errors) are not considered or not fully considered. Do not even adopt mathematical statistics and adopt the empirical method; ..., resulting in the strength of acceptance and preparation of the strength is not correct, nor uniform. In this paper, according to the existing problems, the design strength based on the normal distribution is proposed; the standard deviation of the strength is calculated by the known method; the error of the second kind considering the number of the test pieces and the smaller sample test The judgment is qualified) to determine the strength of the specimen strength of the acceptance of acceptance; on this basis, and then allow a smaller sample of the first class of errors (will be qualified as the wrong wrong decision), to determine the strength of the preparation and expected strength normal Based on the expected distribution of normal distribution, the statistical rule that the minimum value of specimen strength decreases with the number of specimens increases, and the acceptance strength of the minimum specimen strength is determined. The last example illustrates the rationality of this method.