| 1. |
- Abbasiverki, Roghayeh, et al.
(författare)
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Analysis of shallowly buried reinforced concrete pipelines subjected to earthquake loads
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; :51, s. 111-130
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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.
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| 2. |
- Ahmed, Lamis, et al.
(författare)
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Finite element simulation of shotcrete exposed to underground explosions
- 2012
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Ingår i: Nordic Concrete Research. - : Nordic Concrete Federation. - 0800-6377. ; :45, s. 59-74
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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.
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| 3. |
- Al-Gburi, Majid, et al.
(författare)
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Effect of the boundary conditions on the crack distribution in early age concrete
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 50, s. 347-351
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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.
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| 4. |
- Al-Gburi, Majid, et al.
(författare)
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Simplified methods for crack risk analyses of early age concrete : Part 2: Restraint factors for typical case wall-on-slab
- 2012
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 46:2, s. 39-56
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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.
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| 5. |
- Al-Gburi, Majid, et al.
(författare)
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Simplified methods for crack risk analyses of early age concrete : Part 1: Development of Equivalent Restraint Method
- 2012
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 46:2, s. 17-38
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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.
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| 6. |
- Babaahmadi, Arezou, 1985, et al.
(författare)
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Mineralogical, Physical and Chemical Characterization of Cementitious Materials Subjected to Accelerated Decalcification by an Electro-Chemical Method
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 1/2014:49, s. 181-198
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Tidskriftsartikel (refereegranskat)abstract
- To facilitate the service life predictions regarding durability of nuclear waste repositories acceleration methods enhancing the decalcification process are needed. In this study an electro-chemical migration method to accelerate leaching of calcium from cementitious specimens of sizes 50×100Ø and 75×50Ø mm is presented. The mineralogical, physical and chemical properties of degraded samples are characterized. The results demonstrate that up to 70% decrease in strength, 50 % decrease in E-modulus, 90 % increase in gas permeability, at least 70% increase in chloride diffusion coefficient and 70 % increase in pore volume could be expected due to leaching of portlandite from concrete.
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| 7. |
- Bagge, Niklas, et al.
(författare)
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Full-Scale Test to Failure of a Prestressed Concrete Bridge in Kiruna
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 50, s. 83-86
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Tidskriftsartikel (refereegranskat)abstract
- To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests areplanned for a 50 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden.Both non-destructive and destructive full-scale tests will be performed. This paper summarisesthe test programme, which comprises evaluation of the structural behaviour of the bridge, theresidual forces in the prestressed steel, methods for strengthening using carbon fibre reinforcedpolymers (CFRP) and the shear resistance of the bridge slab.
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| 8. |
- Bagge, Niklas, et al.
(författare)
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Instrumentation and Full-Scale Test of a Post-Tensioned Concrete Bridge
- 2014
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 51, s. 63-83
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Tidskriftsartikel (refereegranskat)abstract
- To meet new demands, existing bridges might be in need for repair, upgrading or replacement. To assist such efforts a 55-year-old post-tensioned concrete bridge has been comprehensively tested to calibrate methods for assessing bridges more robustly. The programme included strengthening, with two systems based on carbon fibre reinforced polymers (CFRPs), failure loading of the bridge’s girders and slab, and determination of post-tension cables’ condition and the material behaviour. The complete test programme and related instrumentation are summarised, and some general results are presented. The measurements address several current uncertainties, thereby providing foundations for both assessing existing bridges’ condition more accurately and future research.
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| 9. |
- Boubitsas, Dimitrios
(författare)
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Use of limestone in cement : The effect on strength and chloride transport in mortars
- 2013
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Ingår i: Nordic Concrete Research. - 0800-6377. ; :47/1, s. 61-80
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes studies carried out to examine the influence_x000D_ on strength and chloride ingress when Portland cement is replaced_x000D_ with limestone filler. In the chloride ingress study both an_x000D_ accelerated method and field exposure measurements up to one_x000D_ year were employed. The results show that the method of_x000D_ measuring the resistance to chloride ingress can have a major_x000D_ influence on the assessment of the effect of different binders._x000D_ Further, the effect on chloride resistance, when replacing Portland_x000D_ cement with limestone filler is strongly dependent of the_x000D_ replacement ratio. The effect on compressive strength when_x000D_ replacing Portland cement with limestone filler is also strongly_x000D_ dependent of the replacement ratio.
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| 10. |
- Bryne, Lars-Elof, et al.
(författare)
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Laboratory testing of early age bond strength between concrete for shotcrete use and rock
- 2013
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 47, s. 81-100
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Tidskriftsartikel (refereegranskat)abstract
- Shotcrete(sprayed concrete) is, together with rock bolts, the most important material used for reinforcement in hard rock tunnelling. Sprayed concrete differs from ordinary concrete through the application technique and the addition of accelerators which give immediate stiffening. The bond between sprayed concrete and rock is one of the most important properties in the quality assessment of shotcreted concrete. During the very early age after spraying the physical properties of the concrete and the bond to the rockdepend on the accelerator and the micro structure that is formed. In this work a laboratory test method for measuring early bond strength for very young shotcrete is presented.
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