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Zeitschriftendaten
Format
Zeitschrift
eISSN
1338-3973
ISSN
1210-3896
Erstveröffentlichung
23 May 2011
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 22 (2014): Heft 3 (September 2014)

Zeitschriftendaten
Format
Zeitschrift
eISSN
1338-3973
ISSN
1210-3896
Erstveröffentlichung
23 May 2011
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

5 Artikel
access type Uneingeschränkter Zugang

Study of Post-Cracking Torsional Behaviour of High-Strength Reinforced Concrete Beams with a Ferrocement Wrap

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 1 - 12

Zusammenfassung

Abstract

The post-cracking behaviour of structures subjected to torsion can be well predicted by Hsu’s softened truss model. The softened truss model is applicable to structures having symmetry in their material properties on all four sides. Wrapping on three faces is a common phenomenon when the top face is provided with a flange or slab. Such a wrapping on three faces of a beam is referred to as a “U” wrap. “U” wraps are better wrapping strategies for distressed structures, as their top face is not accessible for many structures. The material property of an unwrapped face differs from the rest of wrapped faces. For the effective use of wrapping, the unwrapped face needs to be provided with a material having a higher resistance to tension and shear. For this, high-strength concrete in the core is a better option. Here, an attempt is made to predict the torsional capacity of “U” wrapped high-strength concrete beams having an asymmetry in the material using a softened truss model with suitable modifications of the material properties. Efficient algorithms are proposed for the solution of simultaneous equations. The predictions are found to be in good agreement with the experimental test results

Schlüsselwörter

  • High-strength concrete
  • torsional strength
  • twist
  • toughness
  • stiffness.
access type Uneingeschränkter Zugang

Analysis of the Skpos® users Initialisation Times

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 13 - 20

Zusammenfassung

Abstract

From the establishment of the Slovak real time positioning service (SKPOS®), the reference stations’ observations, network solutions and outputs from the user communications with the service control software were set for archiving. Today we know that all those archived data have the potential to give us valuable information about the service’s character and quality and about the conditions during the performance of Real time Kinematic (RTK) measurements. After conducting some analyses, we are able to easily understand how important factors such as the number of satellites used, the state of the ionosphere, network solutions in the border zone, densification of the network, etc., can affect those measurements. For those purposes the users’ initialisation times derived from the archived National Marine Electronics Association (NMEA) messages are used in advance. As a tool for analysis the new Application for SKPOS® Monitoring and R

Schlüsselwörter

  • Initialisation time
  • SKPOS® analysis
  • NMEA message.
access type Uneingeschränkter Zugang

Uncertainties Concerning the Free Vibration of Inhomogeneous Orthotropic Reinforced Concrete Plates

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 21 - 30

Zusammenfassung

Abstract

Analyzing nearly collapsed and broken structures gives good insights into possible architectural and engineering design mistakes and faults in the detailing and mismanagement of a construction by building contractors. Harmful vibration effects of construction operations occur frequently. The background reviews have demonstrated that the problem of the vibration serviceability of long-span concrete floors in buildings is complex and interdisciplinary in nature. In public buildings, floor vibration control is required in order to meet Serviceability Limit States that ensure the comfort of the users of a building. In industrial buildings, machines are often placed on floors. Machines generate vibrations of various frequencies, which are transferred to supporting constructions. Precision machines require a stable floor with defined and known dynamic characteristics. In recent years there has been increasing interest in the motion of elastic bodies whose material properties (density, elastic moduli, etc.) are not constant, but vary with their position, perhaps in a random manner. Concrete is a non-homogeneous and anisotropic material. Modeling the mechanical behavior of reinforced concrete (RC) is still one of the most difficult challenges in the field of structural engineering. One of several methods for determining the dynamic modulus of the elasticity of engineering materials is the vibration frequency procedure. In this method, the required variables except for the modulus of elasticity are accurately and certainly determined. In this research, the uncertainly analysis of the free vibration of inhomogeneous orthotropic reinforced concrete plates has been investigated. Due to the numerous outputs obtained, the software package has been written in Matlab, and an analysis of the data and drawing related charts has been done.

Schlüsselwörter

  • Free vibration
  • concrete plates
  • orthotropic and inhomogeneous behavior
  • uncertainly analysis.
access type Uneingeschränkter Zugang

Constitutive Modeling and Numerical Simulation of Frp Confined Concrete Specimens

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 31 - 36

Zusammenfassung

Abstract

Fiber-reinforced polymer (FRP) composites are generally used for the seismic retrofit of concrete members to enhance their strength and ductility. In the present work, the confining effect of Carbon Fiber-Reinforced Polymer (CFRP) composite layers has been investigated by numerical simulation. The numerical simulation has been carried out using nonlinear finite element analysis (FEA) to predict the response behaviour of CFRP-wrapped concrete cylinders. The nonlinear behaviour of concrete in compression and the linear elastic behaviour of CFRP has been modeled using an appropriate constitutive relationship. A cohesive model has been developed for modeling the interface between the concrete and CFRP. The interaction and damage failure criteria between the concrete to the cohesive element and the cohesive element to the CFRP has also been accounted for in the modeling. The response behaviour of the wrapped concrete specimen has been compared with the proposed interface model and with a perfectly bonded condition. The results obtained from the present study showed good agreement with the experimental load-displacement response and the failure pattern in the literature. Further, a sensitivity analysis has been carried out to study the effect of the number of layers of CFRP on the concrete specimens. It has been observed that wrapping with two layers was found to be the optimum, beyond which the response becomes flexible but with a higher load-carrying capacity

Schlüsselwörter

  • FRP
  • confinement
  • nonlinear analysis
  • interface modelling
  • cohesive model
  • damage model
  • sensitivity analysis
  • finite element method
access type Uneingeschränkter Zugang

Optimal Maintenance Works for the Aborshada Road in the Western Region of Libya

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 37 - 44

Zusammenfassung

Abstract

In this research, the condition of a road pavement was investigated for the Aborshada Road in the Gharian region of Libya to determine the optimal maintenance works. Previously, a simple engineering judgment was the only procedure followed by the Gharian municipal engineers for evaluating pavements and prioritizing maintenance. The surface condition of the Aborshada Road pavement was investigated using “the Pavement Condition Index (PCI)” visual technique. The pavement was inspected to survey the different distresses in each sample unit. Ninteen pavement distresses were classified according to the PCI standards (PCI for roads and parking lots became an ASTM standard in 2007 (D6433-07)). It was necessary to know the most common distresses of the Aborshada Road to provide assistance for the decision maker in his evaluation of the pavement and the optimum repair method to be selected.

This study reveals the actual performance of the pavements and suggests the research required for dealing with the pavement maintenance problem in Libya, especially in the western region. The best maintenance alternative for Aborshada Road was Case No. 3 (Potholes, Long. & Trans. Cracking and Alligator Crack Maintenance). Also, the most common pavement distresses on the Aborshada Road were Distress Nos. 1, 3, 6, 7, 10 and 13 according to the ASTM - D6433-07 classification

Schlüsselwörter

  • Pavement distress
  • Optimum Maintenance Policy
  • Pavement Condition Index
  • pavement management
  • pavement scores.
5 Artikel
access type Uneingeschränkter Zugang

Study of Post-Cracking Torsional Behaviour of High-Strength Reinforced Concrete Beams with a Ferrocement Wrap

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 1 - 12

Zusammenfassung

Abstract

The post-cracking behaviour of structures subjected to torsion can be well predicted by Hsu’s softened truss model. The softened truss model is applicable to structures having symmetry in their material properties on all four sides. Wrapping on three faces is a common phenomenon when the top face is provided with a flange or slab. Such a wrapping on three faces of a beam is referred to as a “U” wrap. “U” wraps are better wrapping strategies for distressed structures, as their top face is not accessible for many structures. The material property of an unwrapped face differs from the rest of wrapped faces. For the effective use of wrapping, the unwrapped face needs to be provided with a material having a higher resistance to tension and shear. For this, high-strength concrete in the core is a better option. Here, an attempt is made to predict the torsional capacity of “U” wrapped high-strength concrete beams having an asymmetry in the material using a softened truss model with suitable modifications of the material properties. Efficient algorithms are proposed for the solution of simultaneous equations. The predictions are found to be in good agreement with the experimental test results

Schlüsselwörter

  • High-strength concrete
  • torsional strength
  • twist
  • toughness
  • stiffness.
access type Uneingeschränkter Zugang

Analysis of the Skpos® users Initialisation Times

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 13 - 20

Zusammenfassung

Abstract

From the establishment of the Slovak real time positioning service (SKPOS®), the reference stations’ observations, network solutions and outputs from the user communications with the service control software were set for archiving. Today we know that all those archived data have the potential to give us valuable information about the service’s character and quality and about the conditions during the performance of Real time Kinematic (RTK) measurements. After conducting some analyses, we are able to easily understand how important factors such as the number of satellites used, the state of the ionosphere, network solutions in the border zone, densification of the network, etc., can affect those measurements. For those purposes the users’ initialisation times derived from the archived National Marine Electronics Association (NMEA) messages are used in advance. As a tool for analysis the new Application for SKPOS® Monitoring and R

Schlüsselwörter

  • Initialisation time
  • SKPOS® analysis
  • NMEA message.
access type Uneingeschränkter Zugang

Uncertainties Concerning the Free Vibration of Inhomogeneous Orthotropic Reinforced Concrete Plates

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 21 - 30

Zusammenfassung

Abstract

Analyzing nearly collapsed and broken structures gives good insights into possible architectural and engineering design mistakes and faults in the detailing and mismanagement of a construction by building contractors. Harmful vibration effects of construction operations occur frequently. The background reviews have demonstrated that the problem of the vibration serviceability of long-span concrete floors in buildings is complex and interdisciplinary in nature. In public buildings, floor vibration control is required in order to meet Serviceability Limit States that ensure the comfort of the users of a building. In industrial buildings, machines are often placed on floors. Machines generate vibrations of various frequencies, which are transferred to supporting constructions. Precision machines require a stable floor with defined and known dynamic characteristics. In recent years there has been increasing interest in the motion of elastic bodies whose material properties (density, elastic moduli, etc.) are not constant, but vary with their position, perhaps in a random manner. Concrete is a non-homogeneous and anisotropic material. Modeling the mechanical behavior of reinforced concrete (RC) is still one of the most difficult challenges in the field of structural engineering. One of several methods for determining the dynamic modulus of the elasticity of engineering materials is the vibration frequency procedure. In this method, the required variables except for the modulus of elasticity are accurately and certainly determined. In this research, the uncertainly analysis of the free vibration of inhomogeneous orthotropic reinforced concrete plates has been investigated. Due to the numerous outputs obtained, the software package has been written in Matlab, and an analysis of the data and drawing related charts has been done.

Schlüsselwörter

  • Free vibration
  • concrete plates
  • orthotropic and inhomogeneous behavior
  • uncertainly analysis.
access type Uneingeschränkter Zugang

Constitutive Modeling and Numerical Simulation of Frp Confined Concrete Specimens

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 31 - 36

Zusammenfassung

Abstract

Fiber-reinforced polymer (FRP) composites are generally used for the seismic retrofit of concrete members to enhance their strength and ductility. In the present work, the confining effect of Carbon Fiber-Reinforced Polymer (CFRP) composite layers has been investigated by numerical simulation. The numerical simulation has been carried out using nonlinear finite element analysis (FEA) to predict the response behaviour of CFRP-wrapped concrete cylinders. The nonlinear behaviour of concrete in compression and the linear elastic behaviour of CFRP has been modeled using an appropriate constitutive relationship. A cohesive model has been developed for modeling the interface between the concrete and CFRP. The interaction and damage failure criteria between the concrete to the cohesive element and the cohesive element to the CFRP has also been accounted for in the modeling. The response behaviour of the wrapped concrete specimen has been compared with the proposed interface model and with a perfectly bonded condition. The results obtained from the present study showed good agreement with the experimental load-displacement response and the failure pattern in the literature. Further, a sensitivity analysis has been carried out to study the effect of the number of layers of CFRP on the concrete specimens. It has been observed that wrapping with two layers was found to be the optimum, beyond which the response becomes flexible but with a higher load-carrying capacity

Schlüsselwörter

  • FRP
  • confinement
  • nonlinear analysis
  • interface modelling
  • cohesive model
  • damage model
  • sensitivity analysis
  • finite element method
access type Uneingeschränkter Zugang

Optimal Maintenance Works for the Aborshada Road in the Western Region of Libya

Online veröffentlicht: 05 Nov 2014
Seitenbereich: 37 - 44

Zusammenfassung

Abstract

In this research, the condition of a road pavement was investigated for the Aborshada Road in the Gharian region of Libya to determine the optimal maintenance works. Previously, a simple engineering judgment was the only procedure followed by the Gharian municipal engineers for evaluating pavements and prioritizing maintenance. The surface condition of the Aborshada Road pavement was investigated using “the Pavement Condition Index (PCI)” visual technique. The pavement was inspected to survey the different distresses in each sample unit. Ninteen pavement distresses were classified according to the PCI standards (PCI for roads and parking lots became an ASTM standard in 2007 (D6433-07)). It was necessary to know the most common distresses of the Aborshada Road to provide assistance for the decision maker in his evaluation of the pavement and the optimum repair method to be selected.

This study reveals the actual performance of the pavements and suggests the research required for dealing with the pavement maintenance problem in Libya, especially in the western region. The best maintenance alternative for Aborshada Road was Case No. 3 (Potholes, Long. & Trans. Cracking and Alligator Crack Maintenance). Also, the most common pavement distresses on the Aborshada Road were Distress Nos. 1, 3, 6, 7, 10 and 13 according to the ASTM - D6433-07 classification

Schlüsselwörter

  • Pavement distress
  • Optimum Maintenance Policy
  • Pavement Condition Index
  • pavement management
  • pavement scores.

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