International Concrete Abstracts Portal

Title: A study of Brazilian concrete strength (non-)compliance and its effects on reliability of short columns

Author(s): Wagner Carvalho Santiago, Andre Teofilo Beck

Publication: IBRACON

Volume: 4

Issue: 4

Appears on pages(s): 663 676

Keywords: non-compliance of concrete strength, concrete structures, structural safety, structural reliability, short columns, axial compression

DOI:

Date: 10/10/2011

Abstract:
This paper presents a study of the strength (non)compliance of structural concretes produced in Brazil, and a study of the detrimental effects of non-compliance in reliability of short columns subject to axial compression. The investigation is based on experimental results of over two thousand concrete samples from different parts of Brazil. Results show that a significant part of these concretes do not reach the characteristic strength specified in design. As a consequence, these concretes should be considered non-compliant, and mitigation measures should be adopted (design revision, further testing, structural reinforcement, load restrictions and demolition/reconstruction). The study also investigates the impact of concrete strength non-compliance on the reliability of short columns subject to axial compression, when mitigation measures are not adopted. In reinforced concrete, short columns are the structural elements whose resistance most directly deppends on the compressive strength of concrete. In order to reflect different design conditions, three classes of concrete strength, five load ratios and three reinforcement ratios are considered. One consequence of concrete strength non-compliance is that the theoretical relation between mean and characteristic values of concrete strength cannot be employed in the reliability analysis. Using an equivalent relation, derived from the experimental results, it is shown that concrete strength non-compliance significantly reduces the reliability of short columns. These results stress the necessity of a rigorous control of concrete deliveries, and the importance of a rigorous control of the mitigation actions, in case of concrete strength non-compliance.