Optimum Sampling for Structural Strength Evaluation

An assessment of the strength of an existing structural component or system is commonly made by determining the strength at selected sample points in the space of the structure. Samples may be obtained as cores or nondestructive test measurements. The number of sample points and their layout affect both the cost and the accuracy of testing. The objective of this paper is to demonstrate the use of semivariogram analysis and kriging estimation in evaluating the strength of structural components. These methods provide the basis for establishing guidelines for developing a sampling program that balances the cost of data collection and accuracy requirements. Examples on the strength evaluation of columns and slabs are presented. The calculation of the relative error variances of both point and mean value estimates for the strength of columns and slabs is demonstrated. Guidelines for establishing testing programs are presented.