现场实测混凝土强度特征值推定的贝叶斯方法

Bayesian Method for Estimating the Characteristic Value of Concrete Strength Measured in Situ

回弹法、钻芯法和回弹-钻芯修正法是混凝土强度现场检测常用的非破损检测方法,但工程实践中经常发现,用回弹法检测的混凝土强度方差偏小而钻芯法检测的方差偏大。推定现场实测的混凝土强度特征值时,如何取用合理的方差,直接影响推定结果的准确性和合理性。通过120个既有结构实例的混凝土强度回弹-钻芯修正法检测结果的统计分析,获得了钻芯法、回弹法检测混凝土强度的均值、方差等统计参数及其分布规律。建议在工程质量符合性评定和既有结构安全性评定中,现场混凝土强度特征值均采用90%的等效保证率,并采用贝叶斯全概率公式计算得到了对应于0.1分位值的评定系数。根据校核区回弹-钻芯混合方差,并结合先验方差计算得到后验方差,建立了回弹-钻芯修正法的强度特征值推定贝叶斯方法,经简化后提出了回弹法和钻芯法的强度特征值推定贝叶斯方法。通过新建工程和既有结构实测数据的验证分析表明,建议的强度特征值推定贝叶斯方法结果合理、准确,克服了现行标准中方差取值误差大、抽样数量不足的缺陷,可在工程质量符合性评定和既有结构安全性评定中采用。

Rebound method,core drilling method and rebound-core drilling correction method are commonly used in-situ concrete strength non-destructive detection methods,but the variance of concrete strength detected by rebound method is smaller than that by core drilling method,which is a common phenomenon in engineering practice.How to use the reasonable variance in the estimation of the strength characteristic value of the measured concrete directly affects the accuracy and rationality of the estimation result.Based on the statistical analysis of 120 existing structural concrete strength rebound core drilling correction method,the statistical parameters and their distribution rules of core drilling method and rebound method are obtained.It is suggested that 90%equivalent assurance rate should be adopted for the characteristic value of concrete strength in situ,and the evaluation coefficient corresponding to 0.1 quantile value is obtained by using Bayesian total probability formula.According to the mixed variance of rebound and core drilling method in the check area,and the calculated posterior variance by combining with the prior variance,the Bayesian estimation method of strength characteristic value of rebound-core drilling correction method is established,and the Bayesian estimation method of strength characteristic value of rebound method and core drilling method is obtained after simplification.Through the verification and analysis of the measured data of new projects and existing structures,it is shown that the Bayesian estimation method of strength characteristic values proposed in this paper is reasonable and accurate,which overcomes the defects of large error in variance value and insufficient sampling quantity in the current standard,and can be used in engineering quality compliance assessment and safety assessment of existing structures.