An approach to assignment of dynamic coefficients determining the totality of the phenomena of interaction of the "bridge-train" system, presented in most modern standards for design of bridge structures, is controversial from the point of view of the methodology and physical nature and does not have a due theoretical basis. The long-term practice of registration of dynamic effects in bridge design, built on an empirical approach, has a very limited field of application and cannot be used in the bridge structures design for train speeds more than 200 km / h [1]. Attempts to introduce new recommendations for determination of the dynamic coefficient while registering of high-speed load for the bridges calculation were made in [2].Dynamic processes accompanying the movement of the train across a bridge materially determine the construction, building material, cross-sectional dimensions, rigidity of individual elements and a structure in total [3,4,5,21]. Since absence of Russian experimental and experienced data, designing of bridge structures on high-speed railways is currently applied on the basis of calculations and numerical simulation [6,7]. It should be noted that the analysis of dynamic problems in software systems implementing the finite element method (FEM), requires considerable time spending and depends on a choice of a solution method. AbstractThe aim of the work is to improve the methodology for the dynamic computation of simple beam spans during the impact of high-speed trains. Mathematical simulation utilizing numerical and analytical methods of structural mechanics is used in the research. The article analyses parameters of the effect of high-speed trains on simple beam spanning bridge structures and suggests a technique of determining of the dynamic index to the live load. Reliability of the proposed methodology is confirmed by results of numerical simulation of high-speed train passage over spans with different speeds. The proposed algorithm of dynamic computation is based on a connection between maximum acceleration of the span in the resonance mode of vibrations and the main factors of stress-strain state. The methodology allows determining maximum and also minimum values of the main efforts in the construction that makes possible to perform endurance tests. It is noted that dynamic additions for the components of the stress-strain state (bending moments, transverse force and vertical deflections) are different. This condition determines the necessity for differentiated approach to evaluation of dynamic coefficients performing design verification of I and II groups of limiting state. The practical importance: the methodology of determining the dynamic coefficients allows making dynamic calculation and determining the main efforts in split beam spans without numerical simulation and direct dynamic analysis that significantly reduces the labour costs for design.
When designing bridges on high-speed railways, special attention should be paid to ensuring the safety of train traffic and the comfort of passengers. On high-speed railways, the proportion of the length of bridge structures in the composition of the entire route is much larger than on conventional railways, which makes the present study relevant. In this paper based on numerical simulation, the results of the study of the motion of a high-speed train along bridge structures in the resonance mode of vibrations are presented. In this formulation, special attention was paid to the control of dynamic phenomena at the level of the "wheel-rail" contact. The dynamics of loose parts of the train car determines the magnitude of the contact force, which in turn characterizes the possible detachable movement of the wheel, which is inadmissible for the safety of the train. Analysis of the obtained results, using the example of a 50 m long simple span structure developed for the Moscow-Kazan high-speed railway, allows us to conclude that the resonant nature of the vibrations of simple beam is not a critical phenomenon.
The aim of this work is to show how the concrete damage plasticity model developed by Lubliner et al. can be applied for calculation of a motorway bridge collapse occurred in the Amur region, Russia. The concrete structural behaviour is highly complex. Being a quasi-brittle material, concrete demonstrates softening behaviour that is numerically complex due to the loss of positive definiteness of the tangent rigidity matrix of the material, and hence the loss of the ellipticity of the equilibrium rate equation. This eventually leads to the loss of well-posedness of the rate boundary value problem. Besides that, concrete behaviour in compression differs from that in tension. There are a few different failure modes of concrete material: tension cracking, compression crushing, spalling of concrete, etc.
The purpose of this study is to determine the rational use areas of various computational models types while dynamic analysis. This topic is relevant because of the need to carry out precise dynamic calculations for structures at the high-speed rail, in order to ensure the design of a reliable structures. The object of the study is a single-span girder for the high-speed rail. Research methods are numerical analysis using various models; modal calculation of the oscillation shapes and frequencies; comparative analysis. The result of this study are recommendations on the areas of rational use of various types of models.
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