Title: Spatial Variation of Concrete Strength in Safety Evaluation of Existing Structures

Author(s): Ming Liu

Publication: Symposium Paper

Volume: 340

Issue:

Appears on pages(s): 197-209

Keywords: spatial variation; concrete strength; safety evaluation; existing structures; statistical

DOI: 10.14359/51725813

Date: 4/1/2020

Abstract:
The root causes of uncertainties in new concrete structures have been evidenced to be substantially different from those in safety evaluation of existing structures. Therefore, the design methodology in ACI 318 shall be re-calibrated to better reflect the effects of these significant differences, particularly for the spatial variation of concrete strength in existing structures. The degree of uncertainties that whether the testing data can reliably represent the concrete strength at the critical locations of interesting has been identified to play a vital role in developing an effective structural safety evaluation methodology. This paper presents a novel statistical procedure, where the semi-variogram modeling is used to establish the spatial variation of concrete strength so that the degree of uncertainty mentioned above can be quantified as a function of the spacing intervals of the testing points. Kriging is used to estimate the expected concrete strength with the desired confidence levels for the locations between the measurement locations to ensure the critical locations are covered. The actual concrete coring data were analyzed to illustrate how to estimate the spatial variation. The proposed methodology can also be applied to any testing data that can characterize the stochastic properties of concrete strength in existing structures.