Browsing by Author "Botes, Lizbe"
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- ItemAssessment of usually encountered damage on concrete bridges and its influence on the load carrying capacity capacity and safety of users(Stellenbosch : Stellenbosch University, 2018-03) Botes, Lizbe; Lenner, Roman; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: The assessment of existing bridges is becoming increasingly important since it is necessary to ensure that all bridges maintain structural integrity in terms of the ultimate limit state for which they were designed. South Africa uses a Bridge Management System (BMS) to assess and manage existing structures. The assessment is based on visual inspection, and ratings form 0-4 are assigned to the extent of damage (DERU-rating system) which occurs on the bridge. Using the condition analysis, a prioritised list is compiled where ranking all inspected bridges from worst to least degraded. This list is then used to determine what resources should be allocated and which bridges need to be repaired first. A more accurate way of assessing existing bridges is however required to determine which bridge will fail first, if not repaired. This study developed a method for assessing existing bridges based on their reduction in structural integrity. It was done by relating compiled damage distributions to the DERU-ratings, then using the assigned DERU-ratings in accordance with a reliability-based model, to determine reductions in structural strength. The critical damages identified were reinforcement corrosion, cracking, and spalling of concrete. These damages were compared and it was assumed that a natural sequence will follow; the reinforcement will start to corrode, induce cracking and lead to concrete spalling. This natural sequence was divided into categories, each representing a state of degradation. Distribution functions were compiled to represent the critical damage and were related to the established categories. To determine the effect of these categories, a representative beam was used and degradation applied. The reduction in structural strength was determined according to a reliability assessment, and these results were compared to the results if the beam was analysed according to the BMS. It was concluded that the reliability assessment gave a better representation of structural degradation since, in this case, most of the degradation was not visible from the outside, and thus could not be correctly assessed by visual inspection.