scholarly journals Features of the bridge span performance when shifting the axis of the rail-sleeper grid

2020 ◽  
Vol 79 (3) ◽  
pp. 127-138
Author(s):  
V. V. Korolev ◽  
A. A. Loktev ◽  
I. V. Shishkina ◽  
E. A. Gridasova
Keyword(s):  
Concrete Strength ◽  
Analytical Calculation ◽  
Free Vibrations ◽  
Railway Track ◽  
Normal Operation ◽  
Cement Stone ◽  
Joint Work ◽  
Principal Stresses ◽  
Engineering Structures ◽  
Beam Design

Engineering structures form an integral part of the railways, both already operated and yet designed. The joint work of the upper structure of the railway track and the supporting structures of the bridge crossing is an important condition for the normal operation of the railway section without various restrictions and additional work on the current maintenance and diagnostics of structural elements. Presented study is devoted to the investigation of the stress-strain state of a small railway bridge with a beam design, when the axis of the rail-sleeper grid relative to the axis of the bridge is shifted by an amount exceeding the limit value determined by regulatory documents. In the analytical calculation of the behavior parameters and the state of the span under the action of the load, a differential equation is used that describes the vertical vibrations of the beam and allows considering them as a combination of forced and free vibrations. In numerical modeling, the finite element method is used as the solution method, the deter mining equations of which contain linear and angular displacements of nodes of the calculation scheme as unknowns. As a result of the calculations, graphical dependences for normal and horizontal displacements, internal forces, principal and equivalent stresses at various points of the span are obtained. Presented values show an increase in bending and torsional forces, as well as principal stresses when the axis of the railway track is displaced relative to the axis of the bridge. It is noted that although the increase in stresses (by about 6 %) can generally be considered insignificant, the presence of defects in the span beams (concrete chips, cracks in the stretched zone, exposure and corrosion of working reinforcement, decrease in the calculated cross section, leaching of cement stone from concrete, decrease in concrete strength over time) can make it a significant enough factor limiting the operational capabilities of bridge crossings.

scholarly journals Span operational aspects under offsetting the axis of the track panel

2020 ◽  
Vol 164 ◽  
pp. 03037
Author(s):  
Alexey Loktev ◽  
Vadim Korolev ◽  
Irina Shishkina ◽  
Olga Lokteva ◽  
Ekaterina Gridasova
Keyword(s):  
Analytical Calculation ◽  
Solution Procedure ◽  
Free Vibrations ◽  
Railway Track ◽  
The Finite Element Method ◽  
Principal Stresses ◽  
Beam Design ◽  
Internal Forces ◽  
Vertical Vibrations ◽  
Angular Displacements

The stress-strain state of a small railway bridge with a beam design is considered in the article for the case of offsetting the track panel axis relative to the bridge axis by the value exceeding the limit determined by regulatory documents. The differential equation is considered in the analytical calculation of the behavior parameters and the state of the span under the action of the load. This equation describes the vertical vibrations of the beam and allows considering them as a combination of forced and free vibrations. In numerical modeling, the finite element method is used as the solution procedure. Determining equations of the method contain linear and angular displacements of nodes in the model as unknowns. As a result of the calculations, graphical dependences for normal and horizontal displacements, internal forces, principal and equivalent stresses at various points of the span are obtained. Values are presented that show an increase in bending and torsional forces, as well as in principal stresses when the axis of the railway track is displaced relative to the bridge axis.

Research Status of Concrete Strength Theory Based on Stress and Strain

2014 ◽  
Vol 670-671 ◽  
pp. 445-448
Author(s):  
Guo Jun Liu
Keyword(s):  
Failure Criterion ◽  
Concrete Strength ◽  
Failure Criteria ◽  
Practical Significance ◽  
Engineering Structures ◽  
Research Status ◽  
Advantages And Disadvantages ◽  
Strength Failure ◽  
Micro Cracks ◽  
Strain Space

In the civil engineering structures, when concrete structure withstand external loads, internal defects such as micro-cracks gradually developed, eventually will lead to the destruction of the concrete. Currently, there are two types of strength failure criterion of concrete, strength failure criterion based on stress-space and strength failure criterion based on strain-space, both of which have advantages and disadvantages, this paper introduces the research status of the two strength failure criteria of concrete, and the problems need further study in the future. It plays a strong practical significance in scientific research.

Technique for Construction of the Cap Beam of the Door-Shape Piers of an Overpass Transversal to the Contact Wire of an Existing Railway

2012 ◽  
Vol 178-181 ◽  
pp. 1596-1600
Author(s):  
Xin Min Xie
Keyword(s):  
Intellectual Property ◽  
Construction Method ◽  
The State ◽  
Railway Track ◽  
Normal Operation ◽  
Steel Beams ◽  
Steel Beam ◽  
Contact Wire ◽  
Type Steel ◽  
Electric Railway

In the construction of an overpass transversal to an existing electric railway, when the overpass pier is door-shaped, and, when the clearance height from the bottom of the door-shaped pier cap beam to the contact wire electrified body is too small to use steel beam or I-beam for holding the formwork and meet the safety need prescribed by the Ministry of Railways, an innovative construction method was employed, in which D-type steel beams, originally used for railway track reinforcement, was lifted to get across the contact wire and the catenary from above with a gap more than 33.8cm, resting on the top surface of temporary buttress, and letting stocky horizontal beams hold the formwork of cap beam, so as not to affect the normal operation of the existing electric railway. This innovative technique has been granted patent for invention by the State Intellectual Property Office.

An Impact of Carbon Nanostructured Additives on the Kinetics of Cement Hydration

2015 ◽  
Vol 725-726 ◽  
pp. 425-430 ◽  
Author(s):  
Artem Frolov ◽  
Artemiy Cherkashin ◽  
Luka Akimov ◽  
Nikolai Vatin ◽  
Tatiana Koltsova ◽  
...  
Keyword(s):  
Carbon Material ◽  
Cement Hydration ◽  
Concrete Strength ◽  
Kinetic Method ◽  
Cement Stone ◽  
Exothermic Effect ◽  
Kinetics Of

There are supplements that could accelerate or slow down the process of setting and formation of the cement stone structure. After examining the effect of these particles, we can predict how they could influence on the growth of concrete strength. It is possible to assess the effect of supplementation activity using the thermo-kinetic method by exothermic effect, which is obtained by wetting and hydration of cement. A calorimetric research of the effect of cement-carbon material was held in this article.

scholarly journals Study of modern software capabilities for complex shell analysis

2020 ◽  
Vol 16 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Marina I. Rynkovskaya ◽  
Timur Elberdov ◽  
Enes Sert ◽  
Andreas Öchsner
Keyword(s):  
Fourier Series ◽  
Series Expansion ◽  
Complex Geometry ◽  
Analytical Calculation ◽  
Shell Structures ◽  
Fourier Series Expansion ◽  
Median Surface ◽  
Stress Strain ◽  
Engineering Structures ◽  
Software Packages

Relevance. In design and calculation of civil engineering structures, several standard commercial software packages, which are successfully applied to solve everyday engineering problems, are traditionally used. However, when it is necessary to design the models of complex shape shell structures with defining surfaces based on parametric equations, such programs often have certain drawbacks. The aim of the work - analysis of existing types of commercial computational software packages in order to check which allow to design finite element models for shell structures with median surfaces of complex geometry given by parametric equations. Methods. The analysis of commercial computational software packages is carried out by studying the software manuals, and by building and calculating a model in the shape of a right helicoid as a test example. To evaluate the results of the stress-strain state of a shell with a middle surface in the form of a right helicoid, an analytical calculation method based on the Reissner’s equations and Fourier series expansion is used. Results. A review of modern commercial computational software packages as applied to models defined by parametric equations is carried out. A model for a shell structure with a median surface in the form of right helicoid is built. The numerical results of stress-strain behavior of the right helicoid are obtained and analyzed in comparison with the analytical solutions obtained using the Reissner’s equations with Fourier series expansion. The pros and cons of several popular means of software are presented.

scholarly journals QUALITATIVE PROPERTIES OF VIBRATIONS OF ELASTICALLY SUPPORTED RIGID BODY

2020 ◽  
Vol 2 (2) ◽  
pp. 85-94
Author(s):  
S Bekshaev ◽  
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Natural Vibrations ◽  
Qualitative Properties ◽  
Engineering Structures ◽  
Natural Oscillations ◽  
Geometric Characteristics ◽  
Operating Modes

The paper investigates free vibrations of an absolutely rigid body, supported by a set of linearly elastic springs and performing a plane-parallel motion. The proposed system has two degrees of freedom, which makes it elementary to determine the frequencies and modes of its natural oscillations by using exact analytical expressions. However, these expressions are rather cumbersome, which makes it difficult to study the behavior of frequencies and modes when the characteristics of the model change. Therefore, the aim of the work was to find out the qualitative properties of the modes of free vibrations depending on the elastic, inertial and geometric characteristics of the system, as well as to study the effect of changing the position of elastic supports on its natural frequencies. The main qualitative characteristic of the mode of natural vibrations of the system in consideration is the position of its node – a point that remains stationary during natural vibrations. For the practically important case of a system with two supports, it has been established in the work that, in the general case, of two modes corresponding to two different natural frequencies, one has a node located inside the gap between the supports, and the other – outside this gap. Analytical conditions are found that must be satisfied by the inertial and geometric characteristics of the system, which make it possible to determine which of the two modes corresponds to the internal position of the node. It is noted that these conditions do not depend on the stiffness of the supports. Analytical results were also obtained, allowing to determine a more accurate qualitative localization of the node. To clarify the behavior of natural frequencies when the position of the supports changes, an explicit expression is obtained for the derivative of the square of the natural frequency of the system with respect to the coordinate defining the position of the support. This expression can be used to solve a variety of problems related to the control and optimization of the operating modes of engineering structures subjected to dynamic, in particular periodic, effects. The results of the work were obtained using qualitative methods of the mathematical theory of oscillations. In particular, the theorem on the effect of imposing constraints on the natural frequencies of an elastic system is systematically used.

scholarly journals UV activation building sand with the dehydration factor

2020 ◽  
Vol 8 (4) ◽  
pp. 37-42
Author(s):  
Andrei Pavlov ◽  
Yurii Gol'tsov ◽  
Levon Mailyan ◽  
Sergey Stel'makh ◽  
Evgeniy Shcherban' ◽  
...  
Keyword(s):  
Ultraviolet Irradiation ◽  
Cement Hydration ◽  
Concrete Strength ◽  
Free Water ◽  
Concrete Mixture ◽  
Cement Stone ◽  
Concrete Mix ◽  
Sand Particles ◽  
Additional Reason

The analysis of the influence of ultraviolet irradiation of building sand, which is a filler in a concrete mixture, on the dependence of the strength of concrete on the content of filler is carried out. With an increase in the content of sand due to the hydrophilicity of the surface of its particles in the mixture, the amount of free water required for the hydration of cement and the formation of cement stone decreases. Along with a decrease in the content of binder cement, this factor is an additional reason for a decrease in the strength of concrete with an increase in the content of sand. Ultraviolet irradiation leads to dehydration of the surface of the sand particles and the appearance of hydrophobic centers. As the hydrophobicity of the sand in the concrete mix increases, the content of free water available for cement hydration increases, and the strength of the cement stone increases. The change in the hydrophobicity of the surface of sand particles depending on the time of irradiation is non-monotonic. Therefore, there is an optimal UV activation mode that provides the greatest increase in concrete strength.

scholarly journals Shear Strengthening of Deep T-Section RC Beams with CFRP Bars

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6103
Author(s):  
Zheng-Nan Jing ◽  
Rong-Gui Liu ◽  
Gui-Hua Xie ◽  
Dan Liu
Keyword(s):  
Design Theory ◽  
Experimental Tests ◽  
Economic Benefits ◽  
Shear Capacity ◽  
Shear Strengthening ◽  
Engineering Structures ◽  
Near Surface ◽  
Strut And Tie ◽  
Beam Design ◽  
Strut And Tie Model

Deep T-section beams have been widely used in engineering structures due to their high bearing capacity, high construction efficiency and economic benefits, while the current beam design theory can hardly interpret reasonably the mechanical behaviors of deep beams. The performance features of the deep T-beam were investigated, involving in strain distribution and principal stress trace using experimental tests. Different near surface mounted (NSM) reinforcement schemes were proposed for deep T-beams aiming at improving the shear capacity. The results show that the behaviors of deep T-beams dissatisfy the assumption of plane cross-section, and the ‘strut-and-tie’ model is applicable in such structures. The reinforcement systems can significantly relieve the strain concentration, mid-span deflection and crack width in deep T-beams, consequently improving the shear capacity range from 45 to 65%. The scheme is preferential for the reinforcement of deep T-beams when the applied angles, positions and lengths of CFRP bars are optimized based on the ‘strut-and-tie’ model.

scholarly journals Study of the railway embankment operation that crossing faults upland movements at different angles

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Semyon Isaev
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Railway Track ◽  
Tectonic Activity ◽  
Engineering Structures ◽  
Main Site ◽  
Fault Block ◽  
Longitudinal Slope ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The article discusses the issues of the railway embankment operation crossing faults with upland movements at different angles. Examples of the engineering structures operation are given in this article: tunnels, bridges, roadbed, pipelines in conditions of tectonic activity. Existing regulatory documents recommend choosing a route with a bypass of the places where tectonic faults reach the ground’s surface. However, taking into account the existing fault-block structure of the ground’s crust, it is practically impossible to bypass the tectonic fault zones. The existing network of railways for the most part was laid without taking into account modern requirements norms. Therefore, it seems relevant to study the operation of both the operated and the projected railway track in the tectonic disturbances zones with upland movements. In this article, using the software and computing complex Midas GTS, designed for geotechnical calculations, a study of the railway embankment operation crossing at different angles in the horizontal plane faults with conditional upland movements of the fault block has been carried out. For this, a three-dimensional finite element model was created. The calculations used the Coulomb-Mohr elastoplastic soil work model. As a result, the deformations of the embankment’s main area were analyzed. The deformations components and their contribution to the overall value are considered in detail. Conclusions are made about the change in the longitudinal slope of the axis and the skew of the transverse profile of the main site. For the most deformed sections, normal and tangential stresses diagrams. The research results analysis made it possible to establish a number of characteristic regularities in the change in the embankment’s stress-strain state, depending on the angle between the track and the fault axes. The article is part of the author’s dissertation research

Design of Timber Single-Span Beam with Steel Reinforcement

2019 ◽  
Vol 972 ◽  
pp. 111-117
Author(s):  
Farid A. Boytemirov ◽  
Dmitry D. Koroteev ◽  
Makhmud Kharun
Keyword(s):  
Bearing Capacity ◽  
Research Work ◽  
Steel Reinforcement ◽  
Timber Beam ◽  
Joint Work ◽  
Inertia Moment ◽  
Limit Condition ◽  
Beam Design ◽  
Operation Process ◽  
Timber Beams

Vital problem, occurring in the operation process of structures such as timber beams, is the increase of their bearing capacity and span length with keeping their height. One of the possible ways to solve this problem is steel reinforcement of such structures. The aim of the research work is to show possibility of increasing bearing capacity of single-span reinforced timber beams and develop the main points of calculation and design of such structures. The beam is reinforced symmetrically by 2 rods d28 with both sides with Ar=24.63 cm2 (4d28 A300). The reinforcement is placed in compressed and stretched areas. Reinforced timber structures are designed on two groups of limit conditions. Design on the first limit condition (normal and tangential stress) is made using geometric characteristics of rectangular section of reinforced timber beam. Design on the second limit condition is made taking onto account the timber elastic nodule and inertia moment for reinforced timber beam. The main features of joint work of timber and reinforcement, which can increase operation reliability of bearing structures, are shown in the research work.

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