Visual inspection based approach for security assessment of concrete bridges

The article outlines a possible approach to estimating the vulnerability of normal reinforced and prestressed concrete bridges, developing a survey methodology based solely on its visual inspection. The visual result is a subjective assessment of structural safety. Our study addresses the extent of security using the fuzzy set theory. The fuzzy logic was created to quantitatively treat the uncertainty of reality and inaccuracy of natural language. For these unique properties, together with the conceptual simplicity and adaptability to different types of behaviour, it provides a strong support to the visual inspection. The observer doesn’t argue by means of mathematical calculations and rules, but with logical thoughts, language and expressions and often faces not probabilistic uncertainty (intrinsic to the phenomenon itself, not to its occurrence). The manipulation of the data obtained by visual inspection, achieves a measure of the failure probability of a bridge, through mathematical procedures which allow to transform the linguistic judgments, affected by subjectivity, in an objective quantitative assessment. This study is applied to a prestressed concrete bridge in an aggressive marine environment, affected by a severe state of damage involving the main beams and the abutments.