| 1. |
- Abbasiverki, Roghayeh, et al.
(författare)
-
Analysis of shallowly buried reinforced concrete pipelines subjected to earthquake loads
- 2014
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; :51, s. 111-130
-
Tidskriftsartikel (refereegranskat)abstract
- Buried reinforced concrete pipelines are widelyused in e.g. water and wastewater systems. Failure of these infrastructures mayresult in drastic effects and recently they have been brought into focus asvital components in safety systems for nuclear power installations. The highlevel of safety has here lead to a demand for reliable earthquake risk analyses.In this paper, methods are compared and the use of seismic design loadsdemonstrated. FE analysis in 2D of soil-pipe interaction under seismic wavepropagation is performed. The performance of concrete pipes subjected toseismic waves with different frequency content is evaluated with respect todifferent soil condition but also water mass effect.
|
|
| 2. |
- Ahmed, Lamis, et al.
(författare)
-
Dynamic Measurements for Determining Poisson’s Ratio of Young Concrete
- 2018
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; :58, s. 95-105
-
Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the elastic properties of concrete at early age is often a pre-requisite for numerical calculations. This paper discusses the use of a laboratory technique for determining Poisson’s ratio at early concrete age. A non-destructive test set-up using the impact resonance method has been tested and evaluated. With the method, it has been possible to obtain results already at 7 hours of concrete age. Poisson's ratio is found to decrease sharply during the first 24 hours to reach a value of 0.08 and then increase to approximately 0.15 after seven days.
|
|
| 3. |
- Ahmed, Lamis, et al.
(författare)
-
Finite element simulation of shotcrete exposed to underground explosions
- 2012
-
Ingår i: Nordic Concrete Research. - : Nordic Concrete Federation. - 0800-6377. ; :45, s. 59-74
-
Tidskriftsartikel (refereegranskat)abstract
- An elastic finite element model is used tosimulate theinducedstress waves from blasting, propagating in rock towards shotcrete on a tunnel wall. Due to the inhomogeneous nature of the rock, the stress wavesattenuate onitsway from the point of explosiontowardsthe shotcrete on the rock surface. Material damping for the rock-mass is estimated from in-situ measurements. The vibration resistance of the shotcrete-rock support system depends on the material properties of the shotcrete. Age-dependent material properties are varied to investigate the behaviour of young shotcrete subjected to blast loading. Finally, finite element analysis results are presented and verified through comparison with other numerical models, measurements and observations.
|
|
| 4. |
- Al-Gburi, Majid, et al.
(författare)
-
Effect of the boundary conditions on the crack distribution in early age concrete
- 2014
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; 50, s. 347-351
-
Tidskriftsartikel (refereegranskat)abstract
- Restrained movement in early age concrete may cause cracking. The boundary conditions – restraint – influence the possible crack distribution. This study aims at highlighting the effect of such restraint on the crack distribution. This is done by using the “Cracking Model for Concrete” in ABAQUS/Explicit simulating the non-linear behaviour under and after cracking. In the study the typical case wall-on-slab was in focus using a structure previously been tested in laboratory with both fixed and free bottom slab. The result of the modelling shows fairly good agreement with the cracks observed in the tests.
|
|
| 5. |
- Al-Gburi, Majid, et al.
(författare)
-
Reducing Thermal Crack Risks Caused by Restraint in Young Concrete - A Case Study on Walls of Water Tanks
- 2022
-
Ingår i: Nordic Concrete Research. - : Walter de Gruyter. - 0800-6377 .- 2545-2819. ; 66:1, s. 41-54
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
- Al-Gburi, Majid, et al.
(författare)
-
Simplified methods for crack risk analyses of early age concrete : Part 2: Restraint factors for typical case wall-on-slab
- 2012
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; 46:2, s. 39-56
-
Tidskriftsartikel (refereegranskat)abstract
- Existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.
|
|
| 7. |
- Al-Gburi, Majid, et al.
(författare)
-
Simplified methods for crack risk analyses of early age concrete : Part 1: Development of Equivalent Restraint Method
- 2012
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; 46:2, s. 17-38
-
Tidskriftsartikel (refereegranskat)abstract
- The present study deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.
|
|
| 8. |
- Anderberg, Anders, et al.
(författare)
-
Hydroxide ion concentration at an interface between concrete and a self-levelling flooring compound
- 2007
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; 36, s. 37-47
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This article presents results from measurements of hydroxide ion transport between a concrete and a floor screed of a lower alkalinity than the concrete. As many floor coverings and floor adhesives are sensitive to high alkaline conditions it is important to know how hydroxide ions are transported to be able to evaluate the long-term function of floor constructions. It was found that only minor transport of hydroxide ions occurs in the hygroscopic moisture range. One conclusion is therefore that a floor screed of lower alkalinity may protect sensitive floorings from the high alkalinity present in concrete.
|
|
| 9. |
- Anderberg, Anders, et al.
(författare)
-
Moisture in Self-levelling Flooring Compounds. Part I. Water Vapour Diffusion Coefficients
- 2004
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; Publication 32:2/2004, s. 3-15
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Abstract in UndeterminedDiffusion coefficients of three self-levelling flooring compounds (SLC) and water vapour resistance of a primer have been measured with the cup method. The results show that the diffusion coefficient is dependent not only on the vapour content (relative humidity), but also on the absolute moisture content, i.e., there is a hysteresis effect on moisture transport. At RH lower than approximately 90 %, SLC have higher diffusion coefficients than a standard concrete (w/c 0.7 OPC), but the opposite is true at higher RH. This can be explained by the fact that SLC have different pore structure than concrete. The latter may also be an effect of the high amount of polymer in SLC that form a film throughout the material and thereby limits capillary moisture transport.
|
|
| 10. |
- Anderberg, Anders, et al.
(författare)
-
Moisture properties of self-levelling flooring compounds. Part II. Sorption isotherms.
- 2004
-
Ingår i: Nordic Concrete Research. - 0800-6377. ; Publication 32:2/2004, s. 16-30
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Moisture sorption in self-levelling flooring compounds was investigated by using a sorption balance. Results are presented as sorption isotherms. Influence of temperature, age, water to binder ratio and carbonation are also presented. An increased temperature and increased water to binder ratio gives lower moisture sorption. Results from scanning curves indicate that, when changing sorption mode, even a minute change in moisture content may result in a significant change in relative humidity in the material.
|
|
