Approximated methods of estimation of the reliability of framed railway structures of railway bridges

Engineering and construction of roads, subways, airfields, bridges and transport tunnels

The development of methods for rapid assessment of the reliability of span structures of beam railroad bridges is relevant in connection with the trend towards increasing loads from the reversing freight rolling stock and the speeds of movement on the main transport with a mixed cargo-andpassenger turnover. This problem is especially urgent for the creation and implementation of special technical conditions (STC) for the design of bridges on high-speed lines (BCM), as in Europe and in America, the process of improving the regulatory framework is actively being implemented and innovative developments in this field. Normative documents of the STС take into account only two opposite tendencies. The first is the reduction of equivalent loads from specialized high-speed rolling stock, the second is the increase in dynamic coefficients with an increase in speeds of up to 350 ... 400 km/h. At the same time, the documents being developed require the provision of a relatively heavy load from a special technological rolling stock when planning work on the maintenance of the railway track, as well as during the elimination of the consequences of accidents and other emergencies. The class of this load corresponds to C11, which is 78.5 % of the load of class C14, which is calculated for bridges on public railways. The authors suggests a method for estimating the reliability of a limited pass on beam span structures of a railway transport, the load from which is 10–20 % higher than the design load. A solution describing the probability of failure-free operation in the absence of a sudden failure at the level of 0.97- 0.98 is described. Such a solution is relevant for railways with normal traffic conditions with the possibility of providing high-speed rail traffic. This technical method for rapid assessment of the reliability of span structures of beam railroad bridges be used as a basis for harmonizing National Standard and for the further evolution of the codes for HSR. Bridge authorities are therefore interested in agreed methods to assess the safety, reliability, durability of existing bridges.