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Hellgren, R., Malm, R., Fransson, L., Johansson, F. & Westberg Wilde, M. (2020). Measurement of ice pressure on a concrete dam with a prototype ice load panel. Cold Regions Science and Technology, 170, Article ID 102923.
Open this publication in new window or tab >>Measurement of ice pressure on a concrete dam with a prototype ice load panel
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2020 (English)In: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441, Vol. 170, article id 102923Article in journal (Refereed) Published
Abstract [en]

This paper presents the development and installation of a prototype ice load panel and measurements of ice load from February 2016 to February 2018 at the Rätan hydropower dam in Sweden. The design of the 1 × 3 m2 panel enables direct measurement of ice pressure on the concrete surface is based on previous experience from similar measurements with sea ice. Important features of the design are sufficient height and width to reduce scale effects and to cover the ice thickness and variations in water level. The Rätan dam was chosen based on several criteria so that the ice load is considered to be reasonably idealized against the dam structure.

For the three winters 2016, 2016/2017, 2017/2018, the maximum ice load recorded was 161 kN/m, 164 kN/m and 61 kN/m respectively. There were significant daily fluctuations during the cold winter months, and the daily peak ice loads showed a visual correlation with the daily average temperature and with the daily pattern of operation of the power station with its corresponding water level variations.

Place, publisher, year, edition, pages
Elsevier, 2020
National Category
Engineering and Technology Building Technologies
Research subject
Civil and Architectural Engineering, Structural Engineering and Bridges
Identifiers
urn:nbn:se:kth:diva-264210 (URN)10.1016/j.coldregions.2019.102923 (DOI)2-s2.0-85075037308 (Scopus ID)
Note

QC 20191125

Available from: 2019-11-23 Created: 2019-11-23 Last updated: 2019-11-25Bibliographically approved
Malm, R., Könönen, M., Bernstone, C. & Persson, M. (2019). Assessing the structural safety of cracked concrete dams subjectedto harsh environment. In: Tournier, Bennett & Bibeau (Ed.), Sustainable and Safe Dams Around the World: . Paper presented at ICOLD 2019 Symposium, (ICOLD 2019), June 9-14, 2019, Ottawa, Canada (pp. 383-397). Canada, Article ID 33.
Open this publication in new window or tab >>Assessing the structural safety of cracked concrete dams subjectedto harsh environment
2019 (English)In: Sustainable and Safe Dams Around the World / [ed] Tournier, Bennett & Bibeau, Canada, 2019, p. 383-397, article id 33Conference paper, Published paper (Refereed)
Abstract [en]

As the dams are aging and the design requirements continuously increase, complexanalyses may be required that consider aspects previously excluded in the original design.Due to the harsh environment in cold regions with significant seasonal temperature variations,many con- crete dams have cracked. The development of cracks may result in internal failuremodes, where parts of the dam may fail. These internal failure modes are thereby primarily governedby the material failure of reinforcement and concrete. When assessing cracked hydraulicstructures, how- ever, many design guidelines are based on global safety factors for stability failuremodes, i.e. overturning and sliding, while the partial coefficient methods are used for thestructural design related to material failures. By using a developed design methodology basedon finite element analysis, all these failure modes but also combinations of different failuremodes can be consid- ered. In this paper, the design methodology is presented and implementedto assess the structural safety of a cracked concrete spillway section. The result provides supportfor dam owners on how to manage pillars of concrete dams subjected to extensive cracking.

Place, publisher, year, edition, pages
Canada: , 2019
Keywords
concrete dams, cracks, FEA, structural safety, harsh environment
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering, Concrete Structures
Identifiers
urn:nbn:se:kth:diva-261148 (URN)978-0-367-33422-2 (ISBN)
Conference
ICOLD 2019 Symposium, (ICOLD 2019), June 9-14, 2019, Ottawa, Canada
Note

QC 20191007

Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-07Bibliographically approved
Eriksson, D., Malm, R. & Hellgren, R. (2019). Assessment of frost damage in hydraulic structures using a hygro-thermo-mechanical multiphase model. In: Jean-Pierre Tournier, Tony Bennett & Johanne Bibeau (Ed.), Sustainable and Safe Dams Around the World: . Paper presented at ICOLD 2019 Symposium (pp. 332-346). , 2
Open this publication in new window or tab >>Assessment of frost damage in hydraulic structures using a hygro-thermo-mechanical multiphase model
2019 (English)In: Sustainable and Safe Dams Around the World / [ed] Jean-Pierre Tournier, Tony Bennett & Johanne Bibeau, 2019, Vol. 2, p. 332-346Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents an extension of a novel hygro-thermo-mechanical multiphase model for simulation of freezing of partially saturated air-entrained concrete on the structural scale to account for the effect of damage in the material. The model is applied in an example which investigates the extent and severity of frost damage caused by extremely cold climate conditions in a typical concrete wall in a waterway constructed with air-entrained concrete. The results were concluded to comply with observations made in experimental work and testing of freezing air-entrained concrete under exposure conditions similar to those in hydraulic structures. Furthermore, the results indicate that the effect of short periods of time with high rates of freezing was rather small on the obtained damage. Additionally, increasing the depth of the boundary region with an initially high degree of water saturation on the upstream side had also a rather small effect on the damaged zone.

National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-253820 (URN)
Conference
ICOLD 2019 Symposium
Note

QC 20190624

Available from: 2019-06-18 Created: 2019-06-18 Last updated: 2019-06-24Bibliographically approved
Nordström, E., Malm, R., Hassanzadeh, M., Ekström, T. & Janz, M. (2019). Guideline for structural safety in cracked concrete dams. In: Sustainable and safe dams around the world : proceedings of the ICOLD 2019 symposium, (ICOLD 2019), June 9-14, 2019, Ottawa, Canada = Un monde de barrages durables et sécuritaires : publications du symposium CIGB 2019, Juin 9-14, 2019, Ottawa, Canada: . Paper presented at ICOLD 2019 Annual Meeting/Symposium. June 9-14, Ottawa, Canada (pp. 1681-1696). CRC Press
Open this publication in new window or tab >>Guideline for structural safety in cracked concrete dams
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2019 (English)In: Sustainable and safe dams around the world : proceedings of the ICOLD 2019 symposium, (ICOLD 2019), June 9-14, 2019, Ottawa, Canada = Un monde de barrages durables et sécuritaires : publications du symposium CIGB 2019, Juin 9-14, 2019, Ottawa, Canada, CRC Press, 2019, p. 1681-1696Conference paper, Published paper (Refereed)
Abstract [en]

Several concrete dams show cracking, and their condition and remaining service

life must be determined. Assessment and service life prediction of cracked dams should include an investigation to determine the cause and consequences of cracks. Cracks can be caused by different mechanisms, which also may act together. Some mechanisms act during a short period of time, e.g. in the beginning after construction, while other mechanisms may influence the dam during the whole service-life. Therefore, it is important to combine observations, measurements, laboratory tests and theoretical analyses investigating the causes of the cracks, their future development and the influence they may have on the performance of the dam. Lessons learned and knowledge concerning crack propagation in concrete and rock, general material engineering, durability concerns caused by cracks, structural analysis issues connected to cracks, field measurements and design of remedial measures has been compiled in a Swedish guideline. The guideline highlights issues that should be looked for in inspections and contains a methodology to determine the residual strength and serviceability of cracked concrete dams and how to review dam safety criteria’s. This in turn will provide the dam owner with a better means to manage and prioritize rehabilitation and maintenance work.

Place, publisher, year, edition, pages
CRC Press, 2019
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-261090 (URN)978-0-367-33422-2 (ISBN)
Conference
ICOLD 2019 Annual Meeting/Symposium. June 9-14, Ottawa, Canada
Note

QC 20191011

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-10-11Bibliographically approved
Hellgren, R., Malm, R. & Nordström, E. (2019). Modeller för övervakning av betongdammar: Energiforskrapport 2019:580. Stockholm, Sweden, 580
Open this publication in new window or tab >>Modeller för övervakning av betongdammar: Energiforskrapport 2019:580
2019 (Swedish)Report (Other academic)
Alternative title[en]
Models for monitoting of concrete dams
Abstract [sv]

Inom dammövervakning används begreppen larm och varning för meddelanden om upptäckten av en potentiell dammsäkerhetsrisk. Larm är kopplade till ett akut farligt beteende och en varning till ett oförväntat beteende. Dammövervakning är således ett klassificeringsproblem där varje nytt uppmätt beteende ska klassificeras som säkert eller osäkert, alternativt som förväntat eller oförväntat. Ett farligt beteende innebär att dammsäkerheten är hotad akut medan ett oförväntat värde uppstår när dammen inte beter sig enligt förväntan utifrån rådande yttre förhållanden. En sådan avvikelse betyder inte per automatik att något är fel eller att säkerheten är hotad men en oskadad damm bör bete sig enligt ett förväntat mönster och en avvikelse från det förväntade beteende kan indikera en initiering av en skada hos dammen.För att bestämma det förväntade mätvärdet behövs någon typ av prediktionsmodell som förutsäger dammens beteende utifrån de yttre förhållandena. I denna rapport delas prediktionsmodellerna upp i teoribaserade och databaserade modeller. De teoribaserade modellerna bygger på en fysikalisk koppling mellan yttre förhållanden så som vattennivå och temperaturer och dammens beteende. I de databaserade modellerna är denna koppling istället empirisk och utan fysikalisk koppling.Det finns flertalet olika typer av instrument och givare för dammövervakning. I denna rapport sammanfattas vanliga typer avsedda för dammätningar, inklusive dess mätnoggrannhet. Dessutom diskuteras användningen av olika givare baserat på om de lämpar sig som detektorer vid ett potentiellt dammbrott eller om givarna främst är att anse som stödinstrumentering vars syfte är att bidra mer information om dammens beteende eller yttre förhållanden.Varje modelltyp har unika egenskaper med för- och nackdelar. Det är därför viktigt att välja modelltyp utifrån behov och syfte. En teoribaserad modell, t.ex. FE-modell, ger möjligheten att tolka resultaten och hitta fysikaliska samband, men är sämre på att förutsäga exakt beteende. De mest avancerade databaserade modellerna är utan fysikalisk mening, men kan förutsäga framtida beteenden väldigt bra. Att välja den ena modelltypen framför den andra innebär, något tillspetsat, ett val mellan förståelse och prestation. Lyckligtvis utesluter inte användandet av en modelltyp en annan. De fysikbaserade modellerna som hjälper oss att förstå och tolka en damms beteende kommer alltid ha en plats i dammsäkerhetsarbetet. Det är dessutom den modelltyp som bäst kan användas för att studera dammbrottsscenarion och därmed användas för definition av eventuella larmnivåer. Som ett komplement till dessa kan de databaserade modellerna användas för att ge tidiga indikationer när dammens beteende skiljer sig från det förväntade och lämpar sig därmed väl för val av varningsnivåer. De databaserade metoderna ger tidigare indikationer på eventuella avvikelser eftersom de generellt presterar bättre med mindre spridningsmått än motsvarande teoribaserade modeller.

Abstract [en]

In the field of dam surveillance, alert and alarm values are used for error detection to notify about the discovery of a potential dam safety risk. Alarm values are used to notify that a dangerous behavior have been reached. Alert values (warnings) are used to notify that the measured data is out of the expected range. Dam surveillance can thereby be considered as a classification problem where every measured response should be classified as safe or unsafe, or alternatively as expected or unexpected. Dangerous behavior implies that the safety of the dam may be compromised (e.g. the coefficient of safety may be surpassed), while an unexpected value occurs when the dam no longer acts according to the predicted behavior based on current conditions. Such a discrepancy does not necessarily mean that the dam safety is compromised, but could indicate that the dam is damaged.In order to determine the expected behavior, some type of prediction model is required that can predict the dam behavior based on ambient conditions. In this report, the prediction models are defined as either theory-based or empirical. The theory-based models are based on physics with correlation between ambient conditions such as water level and temperatures and the response of the dam. In the empirical models, this coupling is purely empirical without any physical meaning.There are several types of sensors that can be used for dam surveillance. In this report, the instruments commonly used within the field of dam engineering and their expected accuracy are discussed. In addition, the use of different sensors based on their purpose in the surveillance program is discussed where sensors are denoted as detectors or support instruments. The detectors are considered as sensors suitable to be used to monitor a potential failure mode while the purpose of the support instruments is to provide additional information about the dam response or the ambient conditions.Every type of model has unique properties with different pros and cons. It is therefore important to choose the type of model based on the need and purpose of the monitoring or evaluation of the dam response. A finite element model gives good possibilities to interpret the results and find the physical meaning of a specific behavior, but is not as good to give exact predictions. The most advanced empirical models are defined without any physical meaning, but are capable to give precise predictions of the expected response. To choose one type of model over another can thereby be described as choosing between understanding and performance. Luckily, the use of one model does not exclude the use of others. The models based on physics helps us understand and interpret the dam behavior and will therefore always have a use in the dam safety work. It is also the type of model that best can be used to study scenarios during dam failure and thereby to define alarm values. As a compliment to these, the empirical models can be used to give early warnings when the dam behavior is out of the ordinary and is therefore most suited for definition of alert values. These models generally perform better and has smaller deviation than the corresponding theoretical models.The case studies presented in this report shows that the simple empirical models with some physical meaning gives very good predictions of the expected behavior.

Place, publisher, year, edition, pages
Stockholm, Sweden: , 2019. p. 83
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-255284 (URN)9789176735800 (ISBN)
Note

QC 20190828

Available from: 2019-07-28 Created: 2019-07-28 Last updated: 2019-08-28Bibliographically approved
Hellgren, R., Malm, R. & Eriksson, D. (2019). Modelling of the ice load on a Swedish concrete dam using semi-empirical models based on Canadian ice load measurements. In: Jean-Pierre Tournier, Tony Bennett & Johanne Bibeau (Ed.), Sustainable and Safe Dams Around the World: . Paper presented at ICOLD 2019 Symposium (pp. 3068-3080). , 2
Open this publication in new window or tab >>Modelling of the ice load on a Swedish concrete dam using semi-empirical models based on Canadian ice load measurements
2019 (English)In: Sustainable and Safe Dams Around the World / [ed] Jean-Pierre Tournier, Tony Bennett & Johanne Bibeau, 2019, Vol. 2, p. 3068-3080Conference paper, Published paper (Refereed)
Abstract [en]

In cold regions where the water surface of a river or lake freezes during the winter, concrete dams may be subjected to a pressure load from the ice sheet. This pressure load may constitute a large portion of the total horizontal load acting on a small dam. From a dam safety perspective, it is important to determine the design value of the ice load. In February 2016, a prototype of an ice load panel was installed on a Swedish concrete dam. The 1x3m2 panel measures the ice pressure with three load cells. In this paper, the ice load measured on the Swedish dam is predicted using a Canadian empirical model, previously developed from a 9-year field program to estimate the ice loads caused by thermal effects and variation in water level. The predictions from the model could not accurately predict the measured ice loads. Since the current understanding of ice load is limited, it is not possible to determine whether the measurement, the model or both are inaccurate.

National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-253821 (URN)
Conference
ICOLD 2019 Symposium
Note

QC 20190624

Available from: 2019-06-18 Created: 2019-06-18 Last updated: 2019-09-25Bibliographically approved
Magnusson, J., Hallgren, M., Malm, R. & Ansell, A. (2019). Numerical analyses of shear in concrete structures subjected to distributed blast loads. Engineering structures
Open this publication in new window or tab >>Numerical analyses of shear in concrete structures subjected to distributed blast loads
2019 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Dynamic loading, shear failure, numerical modelling, FEM, shear span
National Category
Other Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-250797 (URN)
Note

QC 20190509

Available from: 2019-05-06 Created: 2019-05-06 Last updated: 2019-05-13Bibliographically approved
Gasch, T., Malm, R. & Ansell, A. (2019). Three-dimensional simulations of ageing concrete structures using a multiphase model formulation. Materials and Structures, 52(4), Article ID 85.
Open this publication in new window or tab >>Three-dimensional simulations of ageing concrete structures using a multiphase model formulation
2019 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 52, no 4, article id 85Article in journal (Refereed) Published
Abstract [en]

The durability of concrete structures is in no small degree determined by the quality and integrity of the concrete, where structural damages such as cracks negatively affect many of the functions of the structure. Often cracks are formed due to restrained thermal and hygral deformations, where the risk is exceptionally high during the early stages after casting. This study presents a hygro-thermo-chemo-mechanical model that accounts for phenomena such as hydration, external and internal drying, self-heating, creep, shrinkage and fracture. The model is derived as a modified version of a fully-coupled multiphase model recently proposed by Gasch et al. (Cem Concrete Res 116:202–216, 2019. https://doi.org/10.1016/j.cemconres.2018.09.009) and implemented in the Finite Element Method. Here the governing equations are simplified, and a more efficient solution method is proposed. These modifications are made with the intention to obtain a model more suitable for structural scale simulations. To validate the model, one of the end-restrained beams tested within the French research project CEOS.fr is analyzed. Laboratory data on the concrete is used to calibrate to model and recordings of ambient conditions makes it possible to define accurate boundary conditions. Results from the simulation are compared to measured temperatures and deformations from the first 60 days after casting and are found to generally be in good agreement. Compared to the fully-coupled model by Gasch et al. (2019), the modifications proposed in this study reduce the computational cost by a factor five; without any noticeable differences to the structural results.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
Concrete, Early-age, Finite Element Method, Hygro-thermo-chemo-mechanical, Structural application
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-262551 (URN)10.1617/s11527-019-1383-4 (DOI)000478086000001 ()2-s2.0-85069913179 (Scopus ID)
Note

QC 20191021

Available from: 2019-10-21 Created: 2019-10-21 Last updated: 2019-10-21Bibliographically approved
Eriksson, D., Gasch, T., Malm, R. & Ansell, A. (2018). Freezing of partially saturated air-entrained concrete: A multiphase description of the hygro-thermo-mechanical behaviour. International Journal of Solids and Structures, 152-153, 294-304
Open this publication in new window or tab >>Freezing of partially saturated air-entrained concrete: A multiphase description of the hygro-thermo-mechanical behaviour
2018 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 152-153, p. 294-304Article in journal (Refereed) Published
Abstract [en]

Even though air-entrained concrete is usually used for concrete structures located in cold climates that are exposed to wet environments, frost damage is frequently detected during inspections. However, it is often hard to assess the extent and severity of the damage and, thus, there is a need for better tools and aids that can complement already established assessment methods. Several studies have successfully shown that models based on poromechanics and a multiphase approach can be used to describe the freezing behaviour of air-entrained concrete. However, these models are often limited to the scale of the air pore system and, hence, hard to use in applications involving real structures. This study proposes a hygro-thermo-mechanical multiphase model which describes the freezing behaviour of partially saturated air-entrained concrete on the structural scale. The model is implemented in a general FE-code and two numerical examples are presented to validate and show the capabilities of the model. The first concerns a series of experimental tests of air-entrained cement pastes, whereas the second aims to show the capability of the model to account for an initial non-uniform distribution of moisture. While the model predictions underestimate the magnitude of the measured strains, the results still show that the model can capture the general freezing behaviour observed in the experimental tests on the structural scale. Furthermore, the results demonstrate that the model is capable of describing freezing induced deformations caused by non-uniform moisture distributions.

Keywords
Freezing, Partially saturated, Air-entrained concrete, Structural scale, Finite element modelling
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-237303 (URN)10.1016/j.ijsolstr.2018.07.004 (DOI)000447576100023 ()2-s2.0-85051402406 (Scopus ID)
Note

QC 20181114

Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2019-01-07Bibliographically approved
Malm, R. (2018). Full-scale test of an unreinforced concrete dome plug for the spent nuclear fuel repository. Nordic Concrete Research, 58(1), 55-75
Open this publication in new window or tab >>Full-scale test of an unreinforced concrete dome plug for the spent nuclear fuel repository
2018 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 58, no 1, p. 55-75Article in journal (Refereed) Published
Abstract [en]

In the planned Swedish repository for spent nuclear fuel, plugs are designed to close the deposition tunnels. The outer part of these plugs consists of a concrete dome made with selfcompacting-concrete, designed to have low pH to reduce negative effects on the bentonite clay buffer. A full-scale test has been performed to evaluate the performance of the plug, to test the installation and to verify underlying design assumptions. In this paper, the behaviour of the concrete dome is evaluated based on measurements, from casting the concrete until it was subjected to 4 MPa hydrostatic water pressure.

Place, publisher, year, edition, pages
The Nordic Concrete Federation, 2018
National Category
Infrastructure Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-237450 (URN)10.2478/ncr-2018-0004 (DOI)000448381900005 ()
Note

QC 20181213

Available from: 2018-10-28 Created: 2018-10-28 Last updated: 2018-12-13Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3586-8988

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