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Probabilistic reliability analysis of a prestressed concrete bridge – part 1 – Semi‐probabilistic reassessment and probabilistic modeling of a single‐span 6‐webbed t‐beam bridge Maintaining the existing transportation infrastructure is a major challenge as the structures continue to age, the traffic loads increase and comprehensive replacement is impossible given limited budgets and resources. On existing structures present material characteristics, geometries or loads can be recorded on an object‐specific basis. In Germany the reassessment of existing bridges is carried out in accordance with the reassessment guidelines at the stages 1 and 2 using the semi‐probabilistic partial safety concept. Only in exceptional cases will a measurement‐based assessment or a scientific analysis acc. to levels 3 and 4 be carried out. However the inclusion of additional information from condition assessment offers many advantages for a realistic reassessment. In probabilistic calculation methods, such information can be taken directly into account. The aim of this two‐part article is to present the potentials and advantages of directly including the results of non‐destructive testing methods when assessing the condition of bridge structures. The concept is presented on a prestressed concrete bridge. The first part deals with the possibilities for transferring the input values of the usual semi‐probabilistic calculation into stochastic models. Starting from the semi‐probabilistic reassessment acc. to current regulations, the probabilistic modeling of all relevant basic variables for the ultimate limit states of bending, shear and torsion is carried out. [ABSTRACT FROM AUTHOR]

Translation abstract Probabilistic reliability analysis of a prestressed concrete bridge – Part 2 – Mechanical modelling and probabilistic reassessment of a single‐span 6‐webbed t–beam bridgeIn the second part of this article the limit state functions in the ultimate limit state for bending with axial force, shear with shear reinforcement and torsion are presented. The input variables of the mechanical resistance models are accompanied by numerous illustrations. The probabilistic verifications are carried out on the basis of the probabilistic models from the first part of this article and the mechanical models from this second part. In the subsequently compiled reliability analysis, reference is made to the semiprobabilistic calculation results. With the parameter studies it is shown which input variable measurable by non‐destructive testing methods have the greatest influence on the calculated reliability. On this basis finally it is shown what opportunities arise for a reassessment from conducting non‐destructive testing in the inspection. [ABSTRACT FROM AUTHOR]

Background: Various vital dyes exist on the market for intraoperative internal limiting membrane (ILM) identification. The aim of this study was to verify the added value of these dyes for ILM identification and in the difficulty of ILM peeling during pars plana vitrectomy (ppV) by a single surgeon highly experienced in this operation., Material and Methods: In this study 400 ppV surgical reports involving ILM peeling were retrospectively analyzed. Intraoperative assessment of identification or difficulty of intraoperative ILM peeling had to be documented in the surgical report. The total group consisted of 2 cohorts each with 200 surgical reports (first cohort without selective vital dyes, period 2004-2006; second cohort with vital dyes in the majority of ppVs, period 2013-2020)., Results: The difference between both groups in terms of intraoperative identification of ILM was statistically significant (p < 0.001); however, no statistically significant difference (p = 0.951) was found between the two groups in terms of difficulty of ILM peeling. In logistic regression analysis neither patient gender, age, eye side, lens status nor posterior vitreous limiting membrane status were significantly associated with ILM identification., Conclusion: The introduction of intravital dyes represents a decisive advancement in retinal surgery. In the investigated sample this benefit was evident from two precisely defined surgical cohorts of a single highly experienced surgeon. This underlines the additional benefit of using selective vital dyes to identify ILM in macular surgery for less experienced surgeons., (© 2024. The Author(s).)