ОЦІНКА НАДІЙНОСТІ МОСТІВ В УКРАЇНІ

Abstract

Introduction. The strength of the structure can be ensured in the case when the acting forces are less than the resistance of the element. In order to exclude the possibility of destruction, the resistance of the elements was artificially reduced, forming certain reserves. This method is called the allowable stress method. This method was used all over the world, and until recently the USA and Japan. Such reduction of stresses was performed more on experience than on the basis of mathematical calculations. Problem statement. The article provides a brief description of the principles of evaluation of structures reliability. It had been described as calculated characteristic and design loadings. It is shown that there is now a balance between the loadings in EN 1991-2 and in DBN B.1.2-15:2009. Purpose. The article is devoted to the problem of evaluation of the reliability of Ukrainian bridges, which are designed according to national standards. Materials and methods. The comparing of temporary loadings in DBN B.1.2-15:2009 with loadings according to Eurocodes and US norms has been given. Reliability coefficients for loadings had been evaluated. It is shown how the characteristic resistance values were obtained. Conclusions are made regarding the state of calculations according to DBN in comparing with Eurocodes. Expressed wishes for further corrections of DBN. Results. It is shown that the requirements for DBN B.1.2-14:2018 regarding the additional reliability coefficient for 1.25 liability for bridges are unacceptable, as they will change the existing balance between bridge calculations according to DBN and EN and may cause unjustified material overruns of up to 20 %. Conclusions. Today, it can be noted that there is a certain balance in the calculations of the strength, stability and endurance of bridges (except for railway bridges) according to EN and DBN standards. For reference: Actually in DBN, the railway design loading C14 exceeds the heaviest model, which is provided by EN 1991. The requirements put forward in DBN B.1.2-14:2018 regarding the assignment of bridges to class СС3 and the introduction of an additional reliability coefficient of 1.25 will make the loading on Ukrainian bridges are bigger, for the loading according to all world standards. Estimated material overruns will be up to 20 %. To correct the error, the easiest way in this situation is to make amendments to DSTU 8855:2019, in which all bridges should be assigned to SS2 class.