Edizioni

Rivista e Edizione

Volume 66 (2022): Edizione 1 (July 2022)

Volume 65 (2021): Edizione 2 (December 2021)

Volume 64 (2021): Edizione 1 (June 2021)

Volume 63 (2020): Edizione 2 (December 2020)

Volume 62 (2020): Edizione 1 (June 2020)

Volume 61 (2019): Edizione 2 (December 2019)

Volume 60 (2019): Edizione 1 (June 2019)

Volume 59 (2018): Edizione 1 (December 2018)

Volume 58 (2018): Edizione 1 (June 2018)

Dettagli della rivista
Formato
Rivista
eISSN
2545-2819
Pubblicato per la prima volta
30 Sep 2018
Periodo di pubblicazione
2 volte all'anno
Lingue
Inglese

Cerca

Volume 66 (2022): Edizione 1 (July 2022)

Dettagli della rivista
Formato
Rivista
eISSN
2545-2819
Pubblicato per la prima volta
30 Sep 2018
Periodo di pubblicazione
2 volte all'anno
Lingue
Inglese

Cerca

8 Articoli
Accesso libero

Preface

Pubblicato online: 11 Jul 2022
Pagine: I - I

Astratto

Accesso libero

When and How Should Chloride Profiles be Calibrated for Paste Fraction?

Pubblicato online: 11 Jul 2022
Pagine: 1 - 18

Astratto

Abstract

Due to stochastic and systematic variations in the paste fraction, data for total chloride content are occasionally calibrated using parallelly measured calcium content as a measure of the actual paste fraction − assuming non-calcareous aggregates and no calcium leaching. Data from concrete exposed at the marine Fehmarn Belt Exposure Site questions the latter assumption. In the outer zone experiencing calcium leaching (ten mm after ten years), errors will be introduced by calcium calibration. To account for the wall effect, calcium profiles from cores taken before exposure might be used to correct for the systematically higher paste fraction at cast surfaces.

Parole chiave

  • Chloride profiles
  • Calcium calibration
  • Wall effect
  • Calcium profiles
Accesso libero

Effect of Set Accelerator on Properties of Wet Sprayed Concrete

Pubblicato online: 11 Jul 2022
Pagine: 19 - 39

Astratto

Abstract

This paper describes sprayed concrete experiments varying the set accelerator dose. Literature on the hydration of cement with modern alkali-free set accelerators is reviewed and two full scale wet spraying experiments have been conducted, varying the dose of set accelerator in each. The effects on the properties of the hardening and hardened sprayed concrete were investigated by field and laboratory testing. Increasing the set accelerator dose was found to increase the rate of early age strength development but reduce density, long term strength and increase suction porosity of hardened sprayed concrete.

Parole chiave

  • Sprayed concrete
  • shotcrete
  • accelerator
  • porosity
Accesso libero

Reducing Thermal Crack Risks Caused by Restraint in Young Concrete - A Case Study on Walls of Water Tanks

Pubblicato online: 11 Jul 2022
Pagine: 41 - 54

Astratto

Abstract

Concrete cracks in structures such as water tanks and nuclear power stations cause anxiety to owners, contractors and engineers. These cracks may significantly increase the structure’s permeability and thus increase leakage, reduce durability, and eventually lead to loss of structural functionality. Therefore it is important to minimize their occurrence and size. To identify effective ways of minimizing cracking in young concrete segments, a parametric study was conducted using the finite element method (FEM). Parameters considered include casting sequence, joint position, wall height, and cooling. The study examined continuous and jumped casting approaches to the casting of a cylindrical reinforced concrete tank for a sewage-treatment plant, with and without the application of the ‘kicker’ technique in which the lower part of the wall is cast with the slab. The main cause of cracking is thermal change and restraint imposed by adjacent older structures, and the FEM predictions agree well with experimental observations. Continuous casting is most effective at minimizing cracking because it creates only two contact edges between newly cast and existing structures producing the lowest level of restraint. The kicker technique is shown to be very effective for reducing restraint and consider rephasing.

Parole chiave

  • Restraint cracks
  • early age
  • casting sequence
  • water tank walls
Accesso libero

Nonlinear Cyclic Analysis of Reinforced Concrete Columns Using Fiber Section Approach

Pubblicato online: 11 Jul 2022
Pagine: 55 - 71

Astratto

Abstract

This study investigates nonlinear modeling and verification of a reinforced concrete element using the fiber section method. At first, the theory related to the fiber section approach and hysteresis models used for cyclic analysis is given. Then, a reinforced concrete column tested previously in the literature is modeled and simulation results are compared with the test results. An acceptable approximation is made utilizing only a few input parameters: Uniaxial stress-strain curves of the materials, location and length of the plastic hinge, and geometry of the model. Moreover, the axial force-moments interaction curve from Eurocode is compared with the one obtained from the nonlinear model. It is shown that by conducting nonlinear analysis a larger capacity of the element is considered which results in a more realistic and economic design.

Parole chiave

  • Column
  • Fiber section
  • Nonlinear analysis
  • Reinforced concrete
  • Time history analysis
Accesso libero

Grading Material Properties in 3D Printed Concrete Structures

Pubblicato online: 11 Jul 2022
Pagine: 73 - 89

Astratto

Abstract

Functionally graded materials (FGMs) describe composite materials with a gradual change in properties along one or several axes. A major advantage with this approach is the avoidance of discontinuities between different layers of material. 3D Printing offers the possibility to control the material composition and spatial placement along the printing process to create structures with graded properties. However, there are very few examples of the application of this approach to 3D concrete printing (3DCP). This paper presents a review of the current approaches of and methods to grade the material properties of a 3DCP structure, as well as a review of similar methods used in other 3D printing processes. Finally, the potential applicability of these principles into concrete are presented and discussed.

Parole chiave

  • 3D concrete printing
  • additive manufacturing
  • functionally graded materials
  • digital fabrication
Accesso libero

Asset Management of Existing Concrete Bridges Using Digital Twins and BIM: a State-of-the-Art Literature Review

Pubblicato online: 11 Jul 2022
Pagine: 91 - 111

Astratto

Abstract

The need to optimize investments in bridge maintenance has created a demand for improved bridge management systems (BMS). Outdated practices in bridge inspection and constant advances in information technology have also contributed to this demand. The use of Digital Twins (DT), although well established in other industries, is still incipient for asset management and structural analysis of bridges. There is a great deal of research on Building Information Modelling (BIM) for bridge inspection, but its post-construction potential is still under-explored. This study presents a state-of-the-art review of the literature on asset management for bridges using digital models such as BIM and digital twins. The review was conducting using a systematic approach. Despite the rapid increase in research on DT and the amount of existing research on BIM, several gaps remain to be addressed, such as the lack of consensus about the definition of digital twins, which has led to wrongful categorisation of digital models as DT. The complex data flow and software compatibility required to develop a functional DT have hindered the exploitation of their full potential so far. The integration of BIM post-construction to BMS and existing automation technologies can also significantly improve current practices of bridge management.

Parole chiave

  • digital twins
  • bridges
  • bridge maintenance
  • bridge management systems
  • BIM
  • review
Accesso libero

Nordic Concrete Research workshop: “Accelerated freeze-thaw testing of concrete”, Lyngby, 20th April 2022

Pubblicato online: 11 Jul 2022
Pagine: 113 - 133

Astratto

Abstract

A one-day Nordic Concrete Research workshop on “Accelerated freeze-thaw testing of concrete” attracted approx. 30 participants. The workshop included presentations on various aspects, such as observed frost damage in the field and the importance of the temperature curve during testing as well as other interactions with the surroundings of the concrete. The workshop also included examples of recent research, which can improve our knowledge about the frost damage mechanism and therefore provide input to improving the standardised test methods. The present paper is a summary of the nine presentations and the discussion arising from the presentations.

Parole chiave

  • Frost deterioration
  • accelerated testing
  • field studies
  • temperature curve
  • frost damage mechanism
8 Articoli
Accesso libero

Preface

Pubblicato online: 11 Jul 2022
Pagine: I - I

Astratto

Accesso libero

When and How Should Chloride Profiles be Calibrated for Paste Fraction?

Pubblicato online: 11 Jul 2022
Pagine: 1 - 18

Astratto

Abstract

Due to stochastic and systematic variations in the paste fraction, data for total chloride content are occasionally calibrated using parallelly measured calcium content as a measure of the actual paste fraction − assuming non-calcareous aggregates and no calcium leaching. Data from concrete exposed at the marine Fehmarn Belt Exposure Site questions the latter assumption. In the outer zone experiencing calcium leaching (ten mm after ten years), errors will be introduced by calcium calibration. To account for the wall effect, calcium profiles from cores taken before exposure might be used to correct for the systematically higher paste fraction at cast surfaces.

Parole chiave

  • Chloride profiles
  • Calcium calibration
  • Wall effect
  • Calcium profiles
Accesso libero

Effect of Set Accelerator on Properties of Wet Sprayed Concrete

Pubblicato online: 11 Jul 2022
Pagine: 19 - 39

Astratto

Abstract

This paper describes sprayed concrete experiments varying the set accelerator dose. Literature on the hydration of cement with modern alkali-free set accelerators is reviewed and two full scale wet spraying experiments have been conducted, varying the dose of set accelerator in each. The effects on the properties of the hardening and hardened sprayed concrete were investigated by field and laboratory testing. Increasing the set accelerator dose was found to increase the rate of early age strength development but reduce density, long term strength and increase suction porosity of hardened sprayed concrete.

Parole chiave

  • Sprayed concrete
  • shotcrete
  • accelerator
  • porosity
Accesso libero

Reducing Thermal Crack Risks Caused by Restraint in Young Concrete - A Case Study on Walls of Water Tanks

Pubblicato online: 11 Jul 2022
Pagine: 41 - 54

Astratto

Abstract

Concrete cracks in structures such as water tanks and nuclear power stations cause anxiety to owners, contractors and engineers. These cracks may significantly increase the structure’s permeability and thus increase leakage, reduce durability, and eventually lead to loss of structural functionality. Therefore it is important to minimize their occurrence and size. To identify effective ways of minimizing cracking in young concrete segments, a parametric study was conducted using the finite element method (FEM). Parameters considered include casting sequence, joint position, wall height, and cooling. The study examined continuous and jumped casting approaches to the casting of a cylindrical reinforced concrete tank for a sewage-treatment plant, with and without the application of the ‘kicker’ technique in which the lower part of the wall is cast with the slab. The main cause of cracking is thermal change and restraint imposed by adjacent older structures, and the FEM predictions agree well with experimental observations. Continuous casting is most effective at minimizing cracking because it creates only two contact edges between newly cast and existing structures producing the lowest level of restraint. The kicker technique is shown to be very effective for reducing restraint and consider rephasing.

Parole chiave

  • Restraint cracks
  • early age
  • casting sequence
  • water tank walls
Accesso libero

Nonlinear Cyclic Analysis of Reinforced Concrete Columns Using Fiber Section Approach

Pubblicato online: 11 Jul 2022
Pagine: 55 - 71

Astratto

Abstract

This study investigates nonlinear modeling and verification of a reinforced concrete element using the fiber section method. At first, the theory related to the fiber section approach and hysteresis models used for cyclic analysis is given. Then, a reinforced concrete column tested previously in the literature is modeled and simulation results are compared with the test results. An acceptable approximation is made utilizing only a few input parameters: Uniaxial stress-strain curves of the materials, location and length of the plastic hinge, and geometry of the model. Moreover, the axial force-moments interaction curve from Eurocode is compared with the one obtained from the nonlinear model. It is shown that by conducting nonlinear analysis a larger capacity of the element is considered which results in a more realistic and economic design.

Parole chiave

  • Column
  • Fiber section
  • Nonlinear analysis
  • Reinforced concrete
  • Time history analysis
Accesso libero

Grading Material Properties in 3D Printed Concrete Structures

Pubblicato online: 11 Jul 2022
Pagine: 73 - 89

Astratto

Abstract

Functionally graded materials (FGMs) describe composite materials with a gradual change in properties along one or several axes. A major advantage with this approach is the avoidance of discontinuities between different layers of material. 3D Printing offers the possibility to control the material composition and spatial placement along the printing process to create structures with graded properties. However, there are very few examples of the application of this approach to 3D concrete printing (3DCP). This paper presents a review of the current approaches of and methods to grade the material properties of a 3DCP structure, as well as a review of similar methods used in other 3D printing processes. Finally, the potential applicability of these principles into concrete are presented and discussed.

Parole chiave

  • 3D concrete printing
  • additive manufacturing
  • functionally graded materials
  • digital fabrication
Accesso libero

Asset Management of Existing Concrete Bridges Using Digital Twins and BIM: a State-of-the-Art Literature Review

Pubblicato online: 11 Jul 2022
Pagine: 91 - 111

Astratto

Abstract

The need to optimize investments in bridge maintenance has created a demand for improved bridge management systems (BMS). Outdated practices in bridge inspection and constant advances in information technology have also contributed to this demand. The use of Digital Twins (DT), although well established in other industries, is still incipient for asset management and structural analysis of bridges. There is a great deal of research on Building Information Modelling (BIM) for bridge inspection, but its post-construction potential is still under-explored. This study presents a state-of-the-art review of the literature on asset management for bridges using digital models such as BIM and digital twins. The review was conducting using a systematic approach. Despite the rapid increase in research on DT and the amount of existing research on BIM, several gaps remain to be addressed, such as the lack of consensus about the definition of digital twins, which has led to wrongful categorisation of digital models as DT. The complex data flow and software compatibility required to develop a functional DT have hindered the exploitation of their full potential so far. The integration of BIM post-construction to BMS and existing automation technologies can also significantly improve current practices of bridge management.

Parole chiave

  • digital twins
  • bridges
  • bridge maintenance
  • bridge management systems
  • BIM
  • review
Accesso libero

Nordic Concrete Research workshop: “Accelerated freeze-thaw testing of concrete”, Lyngby, 20th April 2022

Pubblicato online: 11 Jul 2022
Pagine: 113 - 133

Astratto

Abstract

A one-day Nordic Concrete Research workshop on “Accelerated freeze-thaw testing of concrete” attracted approx. 30 participants. The workshop included presentations on various aspects, such as observed frost damage in the field and the importance of the temperature curve during testing as well as other interactions with the surroundings of the concrete. The workshop also included examples of recent research, which can improve our knowledge about the frost damage mechanism and therefore provide input to improving the standardised test methods. The present paper is a summary of the nine presentations and the discussion arising from the presentations.

Parole chiave

  • Frost deterioration
  • accelerated testing
  • field studies
  • temperature curve
  • frost damage mechanism

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