Nauki Techniczne

Archives of Civil Engineering

Zawartość

Archives of Civil Engineering | 2014 | No 3 |

Abstrakt

The process of railway track adjustment is a task which includes bringing, in geometrical terms, the actual track axis to the position ensuring safe and efficient traffic of rail vehicles. The initial calculation stage of this process is to determine approximately the limits of sections of different geometry, i.e. straight lines, arcs and transition curves. This allows to draw up a draft alignment design, which is subject to control the position relative to the current state. In practice, this type of a project rarely meets the requirements associated with the values of corrective alignments. Therefore, it becomes necessary to apply iterated correction of a solution in order to determine the final project, allowing to introduce minor corrections while maintaining the assumed parameters of the route. The degree of complexity of this process is defined by the quality of determining a preliminary draft alignment design. Delimitation of the sections for creation of creating such a design, is usually done by using the curvature diagram (InRail v8.7 Reference Guide [1], Jamka et al [2], Strach [3]), which is, however, sensitive to the misalignment of the track and measurement errors. In their paper Lenda and Strach [4] proposed a new method for creating curvature diagram, based on approximating spline function, theoretically allowing, inter alia, to reduce vulnerability to interference factors. In this study, the method to determine a preliminary draft alignment design for the track with severe overexploitation was used, and thus in the conditions adversely affecting the accuracy of the conducted readings. The results were compared to the ones obtained using classical curvature diagram. The obtained results indicate that the method allows to increase the readability of a curvature graph, which at considerable deregulation of a track takes an irregular shape, difficult to interpret. The method also favourably affects the accuracy of determining the initial parameters of the project, reducing the entire process of calculation.

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Autorzy i Afiliacje

G. Lenda

Abstrakt

In the paper, the method of a numerical simulation concerning diagonal crack propagation in con-crete beams was presented. Two beams reinforced longitudinally but without shear reinforcement were considered during the Finite Element Method analysis. In particular, a nonlinear method was used to simulate the crack evaluation in the beams. The analysis was performed using the commercial program ANSYS. In the numerical simulation, the limit surface for concrete described by Willam and Warnke was applied to model the failure of concrete. To solve the FEM-system of equations, the Newton-Raphson method was used. As the results of FEM calculations, the trajectories of total stains and numerical images of smeared cracks were obtained for two analyzed beams: the slender beam S5 of leff = 1.8 m and the short beam S3k of leff = 1.1 m. The applied method allowed to generate both flexural vertical cracks and diagonal cracks in the shear regions. Some differences in the evaluation of crack patterns in the beams were observed. The greater number of flexural vertical cracks which penetrated deeper in the beam S5 caused the lower stiffness and the greater deformation in the beam S5 compared to the short beam S3k. Numerical results were compared with the experimental data from the early tests performed by Słowik [3]. The numerical simulation yielded very similar results as the experiments and it confirmed that the character of failure process altered according to the effective length of the member. The proposed numerical procedure was successfully verified and it can be suitable for numerical analyses of diagonal crack propagation in concrete beams.

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Autorzy i Afiliacje

M. Słowik
P. Smarzewski

Abstrakt

The paper presents a numerical study of an aircraft wheel impacting on a flexible landing surface. The proposed 3D model simulates the behaviour of flexible runway pavement during the landing phase. This model was implemented in a finite element code in order to investigate the impact of repeated cycles of loads on pavement response.

In the model, a multi-layer pavement structure was considered. In addition, the asphalt layer (HMA) was assumed to follow a viscoelastoplastic behaviour.

The results demonstrate the capability of the model in predicting the permanent deformation distribution in the asphalt layer.

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Autorzy i Afiliacje

G. Leonardi

Abstrakt

The energy saving tendencies, in reference to residential buildings, can be recently seen in Europe and in the world. Therefore, there are a lot of studies being conducted aiming to find technical solutions in order to improve the energy efficiency of existing, modernized, and also new buildings. However, there are obligatory solutions and requirements, which must be implemented during designing stage of the building envelope and its heating/cooling system. They are gathered in the national regulations.

The paper describes the process of raising the energy standard of buildings between 1974–2021 in Poland. Therefore, the objective of this study is to show energy savings, which can be generated by modernization of thermal insulation of partitions of existing buildings and by the use of different ways of heat supply. The calculations are made on the selected multi-family buildings located in Poland, with the assumption of a 15 years payback time.

It is shown that it is not possible to cover the costs of the modernization works by the projected savings with the compliance to the assumption of 15 years payback time.

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Autorzy i Afiliacje

A. Życzyńska
T. Cholewa

Abstrakt

In the paper, a choice criterion between flower roundabouts and double-lane roundabouts is proposed, focusing on operational benefits that can derive from one scheme over the other, and outlining a general framework for benefit-cost analysis. In order to assess operational benefits of innovative roundabouts over modern roundabouts, a comparative analysis was made. Capacity was estimated using gap-acceptance models. In detail, assuming the dichotomic shifted negative exponential distribution to model headways in circulating streams, the Hagring formula was adjusted to obtain entry capacity estimations at roundabout approaches where entering vehicles face one or two conflicting flows. Based on the control delay, the suitability domains and indifference areas were constructed. Thus, a sensitivity analysis to changes in traffic demand for operational benefits of flower roundabouts over double-lane roundabouts was carried out and discussed. At last, evidence for new installations and conversion of existing roundabouts can be found.

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Autorzy i Afiliacje

O. Giuffrè
A. Granà
T. Giuffrè
R. Marino
S. Marino

Abstrakt

The present paper is dedicated to presentation and energy verification of the methods of stabilization the strain energy by penalty coefficients. Verification of the methods is based on the consistency and ellipticity conditions to be satisfied by the finite elements. Three methods of stabilization are discussed. The first does not satisfy the above requirements. The second is consistent but cannot eliminate parasitic energy terms. The third method, proposed by the author, is based on the decomposition of the element stiffness matrix. The method can help to eliminate locking of the finite elements. For two-noded beam element with linear shape functions and exact integration a stabilized free of locking (and elliptical) element is received (equivalent to reduced integration element). Two plate finite elements are analyzed: four-noded rectangular element and DSG triangle. A new method of stabilization with the use of four independent parameters is proposed. The finite elements with this kind of stabilization satisfy the consistency condition. In the rectangular element it was not possible to eliminate one parasitic term of energy which appears during the procedure. For DSG triangle all parasitic terms of energy are eliminated. The penalty coefficients depends on the geometry of the triangle.

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Autorzy i Afiliacje

W. Gilewski

Redakcja

Editor-in-Chief
Henryk Zobel


Scientific Advisory Committee
:
Andrzej M. Brandt
Werner Brilon (Germany)
Jacek Chróścielewski
Luc Courard (Belgium)
Andrzej Garbacz
Andrzej Garstecki
Wojciech Gilewski
Marian Giżejowski
Oleg Kapliński
Piotr Konderla
Aleksander Kozłowski
Marian Kwietniewski
Zbigniew Młynarek
Andrzej S. Nowak (USA)
Anna Siemińska-Lewandowska
Jan Szwabowski
Waldemar Świdziński
Andrew P. Tarko (USA)
Marian Tracz
Edmundas K. Zavadskas (Lithuania)
Jerzy Ziółko

Secretary
Dorota Walesiak

,

Editor-in-Chief
Henryk Zobel


Scientific Advisory Committee
:
Andrzej M. Brandt
Werner Brilon (Germany)
Jacek Chróścielewski
Luc Courard (Belgium)
Andrzej Garbacz
Andrzej Garstecki
Wojciech Gilewski
Marian Giżejowski
Oleg Kapliński
Piotr Konderla
Aleksander Kozłowski
Marian Kwietniewski
Zbigniew Młynarek
Andrzej S. Nowak (USA)
Anna Siemińska-Lewandowska
Jan Szwabowski
Waldemar Świdziński
Andrew P. Tarko (USA)
Marian Tracz
Edmundas K. Zavadskas (Lithuania)
Jerzy Ziółko

Secretary

Dorota Walesiak

Kontakt

 

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Wydział Inżynierii Lądowej

Al. Armii Ludowej 16, 00-637 Warszawa, Polska Pokój 618; Telefon 22 234 62 84

e-mail: ace@il.pw.edu.pl;

website: http://ace.il.pw.edu.pl

 

 

 

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