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Informacje o czasopiśmie
Format
Czasopismo
eISSN
1338-3973
ISSN
1210-3896
Pierwsze wydanie
23 May 2011
Częstotliwość wydawania
4 razy w roku
Języki
Angielski

Wyszukiwanie

Tom 26 (2018): Zeszyt 1 (March 2018)

Informacje o czasopiśmie
Format
Czasopismo
eISSN
1338-3973
ISSN
1210-3896
Pierwsze wydanie
23 May 2011
Częstotliwość wydawania
4 razy w roku
Języki
Angielski

Wyszukiwanie

6 Artykułów
Otwarty dostęp

A Strut Finite Element for Exact Incompressible Isotropic Hyperelastic Analysis

Data publikacji: 28 Mar 2018
Zakres stron: 1 - 9

Abstrakt

Abstract

This text describes a mathematical model of a strut finite element for isotropic incompressible hyperelastic materials. The invariants of the Right Cauchy-Green deformation tensor are written in terms of nodal displacements. The equilibrium problem is formulated as an unconstrained nonlinear programming problem, where the objective function is the total potential energy of the structure and the nodal displacements are the unknowns. The constraint for incompressibility is satisfied exactly, thereby eliminating the need for a penalty function. The results of the examples calculated by the proposed mathematical model show five significant digits in agreement when compared with commercial finite element analysis software.

Słowa kluczowe

  • Hyperelasticity
  • Incompressibility
  • Minimization
  • Nonlinear
  • Finite element.
Otwarty dostęp

Secondary Moments due to Prestressing with Different Bond at the Ultimate Limit State

Data publikacji: 28 Mar 2018
Zakres stron: 10 - 18

Abstrakt

Abstract

Secondary effects of prestressing develop in statically indeterminate structures (e.g., continuous beams) due to the restraint of deformations imposed by hyperstatic restraints. These effects may significantly influence internal forces and stresses in prestressed structures. Secondary effects are influenced by the redundancy of a structural system, which raises the question of whether they will remain constant after a change in the structural system, e.g., due to the development of plastic hinge(s) in a critical cross-section(s) or after the development of a kinematic mechanism, or if they will disappear when the structure changes into a sequence of simply supported beams. The paper deals with an investigation of the behavior of continuous post-tensioned beams subjected to an ultimate load with significant secondary effects from prestressing. A total of 6 two-span beams prestressed by tendons with different bonds were tested in a laboratory with a load that changed their structural system into a kinematic mechanism. The internal forces and secondary effects of the prestressing were controlled through measurements of the reactions in all the supports. The results revealed that the secondary effects remained as a permanent part of the action on the experimental beams, even after the development of the kinematic mechanism. The results obtained confirmed that secondary effects should be included in all combinations of actions for verifications of ultimate limit states (ULS).

Słowa kluczowe

  • Prestressed concrete
  • Secondary moments
  • Plastic hinges
  • Kinematic mechanism
Otwarty dostęp

Use of Adhesion Promoters in Asphalt Mixtures

Data publikacji: 28 Mar 2018
Zakres stron: 19 - 24

Abstrakt

Abstract

The purpose of asphalt binder as a significant binder in road constructions is to permanently bind aggregates of different compositions and grain sizes. The asphalt binder itself does not have suitable adhesiveness, so after a period of time, bare grains can appear. This results in a gradual separation of the grains from an asphalt layer and the presence of potholes in a pavement. Adhesion promoters or adhesive agents are important and proven promoters in practice. They are substances mainly based on the fatty acids of polyamides which should increase the reliability of the asphalt’s binder adhesion to the aggregates, thus increasing the lifetime period of the asphalt mixture as well as its resistance to mechanical strain. The amount of a promoter or agent added to the asphalt mixture is negligible and constitutes about 0.3% of the asphalt’s binder weight. Nevertheless, even this quantity significantly increases the adhesive qualities of an asphalt binder. The article was created in cooperatation with the Slovak University of Technology, in Bratislava, Slovakia, and focuses on proving the new AD2 adhesive additive and comparing it with the Addibit and Wetfix BE promoters used on aggregates from the Skuteč - Litická and Bystřec quarries.

Słowa kluczowe

  • Asphalt binders
  • Additives
  • Adhesion promoters
  • Adhesion assessment
Otwarty dostęp

Extending the Service Life of Pavements

Data publikacji: 28 Mar 2018
Zakres stron: 25 - 32

Abstrakt

Abstract

The cost of road construction and expenditures on the maintenance of pavements, i.e., their whole life cost, represents a lot of money. The paper describes a procedure for a pavement management system with degradation models and estimates the length of time for the rehabilitation of an asphalt pavement. Using a theory of pavement mechanics, we calculated the stresses and strains on the layers of two pavement models. High modulus asphalt concrete, an asphalt mix with a high binder content, and an asphalt mix with binder modifications are new road building materials. Prolonging the time for the rehabilitation of pavements is possible.

Słowa kluczowe

  • Pavement management system
  • Degradation model
  • Long life pavement
Otwarty dostęp

Experience with The Use of Warm Mix Asphalt Additives in Bitumen Binders

Data publikacji: 28 Mar 2018
Zakres stron: 33 - 39

Abstrakt

Abstract

In most European countries, Hot Mix Asphalt (HMA) technology is still being used as the standard for the production and processing of bituminous mixtures. However, from the perspective of environmental acceptability, global warming and greenhouse gas production, Slovakia is making an effort to put into practice modern technology, which is characterized by lower energy consumption and reducing negative impacts on the environment. Warm mix asphalt technologies (WMA), which have been verified at the Department of Transportation Engineering laboratory, Faculty of Civil Engineering, Slovak University of Technology (FCE, SUT) can provide the required mixture properties and can be used not only for the construction of new roads, but also for their renovation and reconstruction. The paper was created in cooperation with the Technical University of Ostrava, Czech Republic, which also deals with the addition of additives to asphalt mixtures and binders. It describes a comparison of the impact of some organic and chemical additives on the properties of commonly used bitumen binders in accordance with valid standards and technical regulations.

Słowa kluczowe

  • Environmentally acceptable technologies
  • Bitumen binders
  • Warm mix asphalt
  • Additives
  • Penetration
  • Softening point
Otwarty dostęp

The Impact of Global Warming on Precipitation Patterns in Ilorin and the Hydrological Balance of the Awun Basin

Data publikacji: 28 Mar 2018
Zakres stron: 40 - 46

Abstrakt

Abstract

This study presents the impact of global warming on precipitation patterns in Ilorin, Nigeria, and its implications on the hydrological balance of the Awun basin under the prevailing climate conditions. The study analyzes 39 years of rainfall and temperature data of relevant stations within the study areas. Simulated data from the Coupled Global Climate model for historical and future datasets were investigated under the A2 emission scenario. Statistical regression and a Mann-Kendall analysis were performed to determine the nature of the trends in the hydrological variables and their significance levels, while a Soil and Water Assessment Tool (SWAT) was used to estimate the water balance and derive the stream flow and yield of the Awun basin. The study revealed that while minimum and maximum temperatures in Ilorin are increasing, rainfall is generally decreasing. The assessment of the trends in the water balance parameters in the basin indicates that there is no improvement in the water yield as the population increases. This may result in major stresses to the water supply in the near future.

Słowa kluczowe

  • Global warming
  • Coupled global climate model
  • Soil and water assessment tool (SWAT)
  • Hydrological balance
  • Awun basin
6 Artykułów
Otwarty dostęp

A Strut Finite Element for Exact Incompressible Isotropic Hyperelastic Analysis

Data publikacji: 28 Mar 2018
Zakres stron: 1 - 9

Abstrakt

Abstract

This text describes a mathematical model of a strut finite element for isotropic incompressible hyperelastic materials. The invariants of the Right Cauchy-Green deformation tensor are written in terms of nodal displacements. The equilibrium problem is formulated as an unconstrained nonlinear programming problem, where the objective function is the total potential energy of the structure and the nodal displacements are the unknowns. The constraint for incompressibility is satisfied exactly, thereby eliminating the need for a penalty function. The results of the examples calculated by the proposed mathematical model show five significant digits in agreement when compared with commercial finite element analysis software.

Słowa kluczowe

  • Hyperelasticity
  • Incompressibility
  • Minimization
  • Nonlinear
  • Finite element.
Otwarty dostęp

Secondary Moments due to Prestressing with Different Bond at the Ultimate Limit State

Data publikacji: 28 Mar 2018
Zakres stron: 10 - 18

Abstrakt

Abstract

Secondary effects of prestressing develop in statically indeterminate structures (e.g., continuous beams) due to the restraint of deformations imposed by hyperstatic restraints. These effects may significantly influence internal forces and stresses in prestressed structures. Secondary effects are influenced by the redundancy of a structural system, which raises the question of whether they will remain constant after a change in the structural system, e.g., due to the development of plastic hinge(s) in a critical cross-section(s) or after the development of a kinematic mechanism, or if they will disappear when the structure changes into a sequence of simply supported beams. The paper deals with an investigation of the behavior of continuous post-tensioned beams subjected to an ultimate load with significant secondary effects from prestressing. A total of 6 two-span beams prestressed by tendons with different bonds were tested in a laboratory with a load that changed their structural system into a kinematic mechanism. The internal forces and secondary effects of the prestressing were controlled through measurements of the reactions in all the supports. The results revealed that the secondary effects remained as a permanent part of the action on the experimental beams, even after the development of the kinematic mechanism. The results obtained confirmed that secondary effects should be included in all combinations of actions for verifications of ultimate limit states (ULS).

Słowa kluczowe

  • Prestressed concrete
  • Secondary moments
  • Plastic hinges
  • Kinematic mechanism
Otwarty dostęp

Use of Adhesion Promoters in Asphalt Mixtures

Data publikacji: 28 Mar 2018
Zakres stron: 19 - 24

Abstrakt

Abstract

The purpose of asphalt binder as a significant binder in road constructions is to permanently bind aggregates of different compositions and grain sizes. The asphalt binder itself does not have suitable adhesiveness, so after a period of time, bare grains can appear. This results in a gradual separation of the grains from an asphalt layer and the presence of potholes in a pavement. Adhesion promoters or adhesive agents are important and proven promoters in practice. They are substances mainly based on the fatty acids of polyamides which should increase the reliability of the asphalt’s binder adhesion to the aggregates, thus increasing the lifetime period of the asphalt mixture as well as its resistance to mechanical strain. The amount of a promoter or agent added to the asphalt mixture is negligible and constitutes about 0.3% of the asphalt’s binder weight. Nevertheless, even this quantity significantly increases the adhesive qualities of an asphalt binder. The article was created in cooperatation with the Slovak University of Technology, in Bratislava, Slovakia, and focuses on proving the new AD2 adhesive additive and comparing it with the Addibit and Wetfix BE promoters used on aggregates from the Skuteč - Litická and Bystřec quarries.

Słowa kluczowe

  • Asphalt binders
  • Additives
  • Adhesion promoters
  • Adhesion assessment
Otwarty dostęp

Extending the Service Life of Pavements

Data publikacji: 28 Mar 2018
Zakres stron: 25 - 32

Abstrakt

Abstract

The cost of road construction and expenditures on the maintenance of pavements, i.e., their whole life cost, represents a lot of money. The paper describes a procedure for a pavement management system with degradation models and estimates the length of time for the rehabilitation of an asphalt pavement. Using a theory of pavement mechanics, we calculated the stresses and strains on the layers of two pavement models. High modulus asphalt concrete, an asphalt mix with a high binder content, and an asphalt mix with binder modifications are new road building materials. Prolonging the time for the rehabilitation of pavements is possible.

Słowa kluczowe

  • Pavement management system
  • Degradation model
  • Long life pavement
Otwarty dostęp

Experience with The Use of Warm Mix Asphalt Additives in Bitumen Binders

Data publikacji: 28 Mar 2018
Zakres stron: 33 - 39

Abstrakt

Abstract

In most European countries, Hot Mix Asphalt (HMA) technology is still being used as the standard for the production and processing of bituminous mixtures. However, from the perspective of environmental acceptability, global warming and greenhouse gas production, Slovakia is making an effort to put into practice modern technology, which is characterized by lower energy consumption and reducing negative impacts on the environment. Warm mix asphalt technologies (WMA), which have been verified at the Department of Transportation Engineering laboratory, Faculty of Civil Engineering, Slovak University of Technology (FCE, SUT) can provide the required mixture properties and can be used not only for the construction of new roads, but also for their renovation and reconstruction. The paper was created in cooperation with the Technical University of Ostrava, Czech Republic, which also deals with the addition of additives to asphalt mixtures and binders. It describes a comparison of the impact of some organic and chemical additives on the properties of commonly used bitumen binders in accordance with valid standards and technical regulations.

Słowa kluczowe

  • Environmentally acceptable technologies
  • Bitumen binders
  • Warm mix asphalt
  • Additives
  • Penetration
  • Softening point
Otwarty dostęp

The Impact of Global Warming on Precipitation Patterns in Ilorin and the Hydrological Balance of the Awun Basin

Data publikacji: 28 Mar 2018
Zakres stron: 40 - 46

Abstrakt

Abstract

This study presents the impact of global warming on precipitation patterns in Ilorin, Nigeria, and its implications on the hydrological balance of the Awun basin under the prevailing climate conditions. The study analyzes 39 years of rainfall and temperature data of relevant stations within the study areas. Simulated data from the Coupled Global Climate model for historical and future datasets were investigated under the A2 emission scenario. Statistical regression and a Mann-Kendall analysis were performed to determine the nature of the trends in the hydrological variables and their significance levels, while a Soil and Water Assessment Tool (SWAT) was used to estimate the water balance and derive the stream flow and yield of the Awun basin. The study revealed that while minimum and maximum temperatures in Ilorin are increasing, rainfall is generally decreasing. The assessment of the trends in the water balance parameters in the basin indicates that there is no improvement in the water yield as the population increases. This may result in major stresses to the water supply in the near future.

Słowa kluczowe

  • Global warming
  • Coupled global climate model
  • Soil and water assessment tool (SWAT)
  • Hydrological balance
  • Awun basin

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