9. DETERMINATION OF THE CARRYING CAPACITY OF CULVERTS OF RAILWAYS

Abstract

Abstract: A method for determining the carrying capacity of culverts on the railway network is proposed. The methodology is based on the principle of classification by load capacity, adopted in the current regulatory documents for metal and reinforced concrete superstructures, railway bridge supports. The method is based on the principle of expressing the permissible time load in units of the reference load according to scheme C1. The permissible load is understood as the maximum intensity of the temporary vertical linear load, which does not cause a limit state. Rolling stock is classified by the expression of the equivalent load from the rolling stock in units of the same reference load, the number of units of which is the class of rolling stock. The possibility of skipping the load is determined by comparing the classes of elements of the structure with the load class. With the help of the methodology, it is possible to clarify the boundaries of the use of pipe structures according to current standard projects, as well as taking into account the actual working conditions of the pipes in operation.

Keywords: culverts; the principle of classification by load capacity; permissible temporary load; reference load according to scheme C1; expression of the equivalent load from the rolling stock in units of reference load; class of rolling stock; comparison of classes of elements of the structure with the load class; clarification of the boundaries of the use of pipe structures according to current standard projects; consideration of the actual operating conditions of the operated pipes.

OПРЕДЕЛЕНИЯ ГРУЗОПОДЪЕМНОСТИ ВОДОПРОПУСКНЫХ ТРУБ ЖЕЛЕЗНЫХ ДОРОГ

Ембергенов Авезмурат Бекмуратович

Ташкентский государственный университет транспорта, ассистент.

Мирханова Мавжуда Михайиловна

Ташкентский государственный университет транспорта, старший преподаватель.

Умаралиев Шохжахон Мухаммадрузи угли

Ташкентский государственный университет транспорта, ассистент.

Абдуалиев Элёрбек Бегалиевич

Ташкентский государственный университет транспорта, доктарант.

Аннотация: Предлагается методика определения грузоподъемности водопропускных труб на сети железных дорог. В основу методики положен принцип классификации по грузоподъемности, принятый в действующих нормативных документах для металлических и железобетонных пролетных строений, опор железнодорожных мостов. В основу метода заложен принцип выражения допускаемой временной нагрузки в единицах эталонной нагрузки по схеме C1. Под допускаемой нагрузкой понимается максимальная интенсивность временной вертикальной погонной нагрузки, которая не вызывает предельного состояния. Подвижной состав классифицируется выражением эквивалентной нагрузки от подвижного состава в единицах той же эталонной нагрузки, число единиц которой - класс подвижного состава. Возможность же пропуска нагрузки определяется сравнением классов элементов сооружения с классом нагрузки. С помощью методики возможно уточнение границ применения конструкций труб по действующим типовым проектам, а также учет фактических условий работы эксплуатируемых труб.

Ключевые слова: водопропускные трубы; принцип классификации по грузоподъемности; допускаемая временная нагрузка; эталонная нагрузка по схеме C1; выражение эквивалентной нагрузки от подвижного состава в единицах эталонной нагрузки; класс подвижного состава; сравнение классов элементов сооружения с классом нагрузки; уточнение границ применения конструкций труб по действующим типовым проектам; учет фактических условий работы эксплуатируемых труб.

Introduction. In accordance with paragraph 1.9 of the Instruction CP-628 on the maintenance of artificial structures [1] all railway bridges should be classified by load capacity, while the question of the carrying capacity of culverts is not specified in any way, and culverts make up up to 70% of all artificial structures on railways. The classification method was developed in the 60s of the twentieth century and is reflected in the Guidelines for determining the load capacity of reinforced concrete and metal superstructures, bridge supports, as well as in the Manual for the passage of rolling stock on railway bridges [2, 3, 4, 5, 6]. The method is based on the principle of expression The permissible time load in units of the reference load according to the scheme H1. The permissible load is understood as the maximum intensity of the temporary vertical linear load, which does not cause a limit state. Rolling stock is classified by the expression of the equivalent load from the rolling stock in units the same reference load, the number of units of which is the class of rolling stock. The possibility of skipping the load is determined by comparing the classes of elements of the structure with the load class. This method has passed the test of time, and despite the development of numerical modeling methods, it is currently successfully used to determine the conditions for passing train loads over railway bridges. From all of the above, it can be concluded that it is advisable to extend the classification principle adopted to determine the load-bearing capacity reinforced concrete and metal superstructures of railway bridges, on culverts.

In 2005, the DVGUPS developed a textbook on the definition of the carrying capacity of railway culverts according to the method of permissible technical conditions [7]. The manual discusses the issues of the load capacity of operated pipes with various damages and deformations. In this article, an attempt is made to determine the carrying capacity of culverts by the strength of the structures used, using traditional principles of classification of elements of railway bridges.

Culverts on railways are represented by the following main types in terms of material and cross section:

• stone arched, vaulted or ovoidal cross sections;
• concrete or stone (according to the material of the walls) rectangular cross

-section with reinforced concrete floors;

• reinforced concrete of round and rectangular cross sections;
• round metal cross-section smooth and corrugated.

Let's consider the application of the classification method on the example of reinforced concrete pipes circular cross-section (standard inv. No. 101/2 is one of the most common on the railway network) [8]. Standard design of unified prefabricated culverts for railways and highways of the general network and industrial enterprises, inv. No. 101/2, developed by the Lengiprotransmost Institute in 1962 and operated until 2002 (replaced by the standard project cipher 1484, Transmostproekt, 2002). Pipes are designed according to the specifications of CH 200-62 for a temporary vertical load of C14. Pipe links are divided into three types according to bearing capacity:

• Type I corresponds to the height of the embankment - up to 3.0 m;
• Type II corresponds to the height of the embankment - from 3.1 to 6.0-8.0 m;
• Type III corresponds to the height of the embankment - from 7.1-8.1 to 19.0 m.

The scope of application of pipes for this standard project is limited by the height of the embankment of 19 m. Round pipes, in accordance with the requirements of SP 35.13330.2011 (SNiP 2.05.03-84*) [9], calculated from the limiting states of the first group on the effect of ground pressure from the weight of the embankment and ground pressure from the time load. The design scheme of the pipe link is a ring to which a vertical evenly distributed load and a horizontal load of variable intensity are applied along the height of the pipe. The forces arising in the cross-sections of the link are determined by the joint the action of vertical and horizontal loads. The link is calculated for the action of the bending moment without taking into account the normal and transverse forces [10, 11,12]. The maximum values of positive and negative bending moments occur respectively in the vertical and horizontal diametrical sections of the link. The design scheme and the type of the moment plot is shown in Figure 1. According to the condition of pipe strength, the actual values of bending moments from force influences at the stage of operation should not exceed the limit value bending moment, which is determined by calculation based on the formwork and reinforcement drawings of the link.

Fig. 1. Design model of a circular pipe and type of a bending-moment curve

Conclusion. Analyzing the obtained graphs, we can draw the following conclusions:

• The outlines of the graphs of the link classes by load capacity reflect the working conditions of the pipes in the body of the embankment. The ascending section of the graph indicates the predominance of ground pressure from the time load, and the descending section the graph is due to the predominance of pressure from the weight of the embankment soil over the pressure from the temporary load, the intensity of which is steadily decreasing with the growth of the filling thickness. • The actual load capacity of the considered types of reinforced concrete pipe links mainly corresponds to the boundaries of the fields of application of these types, specified in the standard project. However, as follows from the graphs and 3, it is necessary to adjust (in a smaller direction) the upper boundaries of the declared areas of application of the types of pipe links (type 2 pipes with a diameter of 1.0 m, types 2 and 3 pipes with a diameter of 1.25 m).

Literatura

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