On determination protocols of characteristic in-situ compressive strength of concrete for existing structure: Case study with core samples from actual bridges

Abstract

A case study was conducted to explore a more rational and robust process for determining the characteristic in-situ compressive strength of concrete structures from core samples. Slabs and girders were obtained from a total of seven bridges, earmarked for demolition due to social and performance considerations. Approximately 600 concrete core samples were extracted from various locations on these bridges. Statistical simulations were carried out using both conventional protocols and a newly proposed method to ascertain the characteristic strength from the cores. This led to a comprehensive discussion on the appropriate sample size, as well as the probabilistic robustness and reliability of the protocols. The proposed method demonstrated the ability to minimize over- or under-estimation of the characteristic strength, providing stable values less affected by fluctuations in core strengths.

Keywords

• Concrete strength assessment
• Characteristic strength
• Existing bridges
• Probabilistic analysis
• Code and standard
• Core sampling