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| 2. |
- 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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| 3. |
- Edrees, Tarek, et al.
(författare)
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A state-of-the-art review of Structural Control Systems
- 2015
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Ingår i: Journal of Vibration and Control. - : SAGE Publications. - 1077-5463 .- 1741-2986. ; 21:5, s. 919-937
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Tidskriftsartikel (refereegranskat)abstract
- Nowadays the utilization of structural control systems for alleviating the responses of civil engineering structures, under the effects of different kinds of dynamics loadings, has become a standard technology, while still there are numerous of current research approaches for advancing the effectiveness of these methodologies. The aim of this article is to review the state of the art technologies in structural control systems by introducing a general literature review for all the types of vibrations control systems that have been appeared till now. These systems can be classified into four main groups: a) passive, b) semi active, c) active, and d) hybrid based on their operational mechanism. A brief description of each of these main groups and their subgroups, with their corresponding advantages and disadvantages will be also extendedly reported in this review. This article will conclude by providing an overview of some innovative practical implementations of devices, which are able to demonstrate their potentials and future directions of structural control systems in civil engineering.
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| 4. |
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| 5. |
- Elfgren, Lennart, et al.
(författare)
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Tillståndsbedömning av betongbroar
- 2006
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Ingår i: Bygg och Teknik. - 0281-658X .- 2002-8350. ; 98:7, s. 35-40
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- En vanlig frågeställning för befintliga broar är deras tillstånd: Har bärförmågan minskat med tiden så att bron behöver repareras eller förstärkas? Eller, är det rentav så att man med bättre beräkningsmetoder kan visa att en bro idag klarar att bära en högre last än den som den ursprungligen dimensionerades för?
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| 6. |
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| 7. |
- Emborg, Mats, et al.
(författare)
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Temperatursprickor i betong p g a hydratationen för några vanliga typfall
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I samråd mellan Vägverket, Div. Väg och Trafik, Sekt. Broteknik (VTb) och Luleå Tekniska Högskola, Avd. för Konstruktionsteknik har ett antal förekommande typfall vid gjutning av betong studerats med avseende på temperaturspänningar på grund av hydratationen. För de studerade typfallen har spänningsanalyser utförtss och diagram framtagits över sprickrisk vid olika förutsättningar t ex gjutförhållanden och dimensioner. Diagrammen ger underlag för mer säkra sprickriskbedömningar än diagraam enbart baserade på temperaturberäkningar. Rapporten är indelad i tre delar. Del A berör hur temperatursprickor kan uppkomma, vilka huvudfaktorer som inverkar på sprickrisken, vilka förhållanden som gäller för aktuella typfall samt hur sprickrisker kan beräknas. I Del B sker en redogörelse för vilka förutsättningar som gäller allmänt vid sprickriskberäkningar och speciellt vid beräkningarna för typfallen. I Del B kommenteras de diagram över sprickrisker som redovisas i Del C. Del B och Del C kan användas separat vid sprickriskbedömningar.
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| 8. |
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| 9. |
- Fjellström, Peter, et al.
(författare)
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Heat loss compensation for semi-adiabatic calorimetric tests
- 2013
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 47:1, s. 39-60
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Tidskriftsartikel (refereegranskat)abstract
- Heat of hydration has long been of importance since it affects the temperature levels within a concrete structure, and thus, potentially affects its durability. The only source of energy is the reaction between cement and water. This energy warms up the concrete sample and all the ambient materials. Therefore, in order to model these energies, the TSA (traditional semi-adiabat) setup is transformed into an associated sphere. By this, the temperature distribution and the energies within each layer of the TSA can be calculated. The sum of all energies gives the total heat of hydration. A refined model using a correction factor is introduced, which accounts for energies lost to the TSA setup materials. Results show that the effect of this factor cannot be disregarded, especially not for TSAs with low cooling factors.
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| 10. |
- Fjellström, Peter, et al.
(författare)
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Model for concrete strength development including strength reduction at elevated temperatures
- 2012
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 45:1, s. 25-44
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Tidskriftsartikel (refereegranskat)abstract
- When casting concrete structures, one of the most important properties is the concrete strength development. The need of actions on site is different at various stages of hardening, from the fresh concrete to the hardened concrete. The paper defines a model analysing maturity and associated strength growth within three important time periods. The model can be applied separately within each of these periods depending on test data available.It is shown in the paper that the temperature plays an important role on the strength development of concrete structures. The hydration rate increases with increased temperatures, which can be described by maturity functions. If the concrete temperature remains high, strength reduction at later ages usually occurs compared to hardening at lower temperature, which may be denoted strength reduction at elevated temperatures or cross over effects. Both these phenomena have been implemented in the model for strength growth presented in the paper. The functionality of the model is demonstrated by evaluation of laboratory tests for five concrete mixes and two types of cement.
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