Comprehensive analysis of existing endurance testing methods of flexible dowel crutches of composite reinforced concrete road bridges according to the standards of a number of countries

In the article, the author considers the verification issue of the endurance of the venture elements of steel-reinforced concrete spans of bridges, in particular, flexible dowel crutches («Nelson’s anchors»). According to the existing domestic regulatory framework, the endurance test of the flexible dowel crutches for road bridges is not required; at the same time, the survey’s results of the operated superstructures indicate the presence of problems associated with the insufficient endurance of these elements. The article presents comprehensive (qualitative and quantitative) comparative analysis results of the world’s existing approaches to testing the endurance of the venture elements. At the stage of qualitative analysis, the author considered methods of checking the endurance of elements in general according to the norms of 8 countries and regions (Russia, the European Union, the USA, Ukraine, Australia, Canada, Japan, China) and highlighted a basic set of methods for checking the endurance of the venture elements (Russia, the European Union, USA, Ukraine). The models of the basic set were subjected to a detailed qualitative analysis according to the criteria of the models used and the parameters included in them. The quantitative analysis of the selected basic set techniques, carried out in relation to the existing bridge, included an analysis of the effects of moving loads on the venture elements, direct elements verification using the considered methods, as well as the design damage comparison of the elements obtained by the Palmgren-Miner linear summation hypothesis. Based on the obtained values of design damage, the values of the use of endurance reserves were determined and analyzed for each of the considered methods and the conditional load model. Based on the results of the qualitative and quantitative analysis, the author draws conclusions based on the comparison of various methods and highlights the rational directions for improving the existing domestic methodology.