Change search
Refine search result
1234567 1 - 50 of 831
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Cebecauer, Matej
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Gundlegård, David
    Department of Science and Technology,Linköping University.
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    3D Speed Maps and Mean Observations Vectors for Short-Term Urban Traffic Prediction2019In: TRB Annual Meeting Online, Washington DC, US, 2019, p. 1-20Conference paper (Refereed)
    Abstract [en]

    City-wide travel time prediction in real-time is an important enabler for efficient use of the road network. It can be used in traveler information to enable more efficient routing of individual vehicles as well as decision support for traffic management applications such as directed information campaigns or incident management. 3D speed maps have been shown to be a promising methodology for revealing day-to-day regularities of city-level travel times and possibly also for short-term prediction. In this paper, we aim to further evaluate and benchmark the use of 3D speed maps for short-term travel time prediction and to enable scenario-based evaluation of traffic management actions we also evaluate the framework for traffic flow prediction. The 3D speed map methodology is adapted to short-term prediction and benchmarked against historical mean as well as against Probabilistic Principal Component Analysis (PPCA). The benchmarking and analysis are made using one year of travel time and traffic flow data for the city of Stockholm, Sweden. The result of the case study shows very promising results of the 3D speed map methodology for short-term prediction of both travel times and traffic flows. The modified version of the 3D speed map prediction outperforms the historical mean prediction as well as the PPCA method. Further work includes an extended evaluation of the method for different conditions in terms of underlying sensor infrastructure, preprocessing and spatio-temporal aggregation as well as benchmarking against other prediction methods.

  • 2.
    Possidente, Luca
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Tondini, N.
    Univ Trento, Trento, Italy..
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A 3D beam element to study torsion of steel open sections exposed to fire2019In: Advances in Engineering Materials, Structures and Systems: Innovations, Mechanics and Applications / [ed] Zingoni, A, CRC Press, 2019, p. 561-565Conference paper (Refereed)
    Abstract [en]

    In the analysis of structures in fire, numerical models must account for the effects of increasing temperatures. Although different finite elements capable of effectively tackling the problem are available, 3D beam elements employed in many commercial software do not properly account for the degradation of the torsional properties with temperature. In this context, an enhanced 3D beam element based on a co-rotational formulation is proposed. The element was specifically developed for steel elements and is well suited for the analysis of structures that exhibit a significant torsional behavior. The Timoshenko beam theory was employed and the steel stress-strain law and thermal expansion were implemented according to EN1993-1-2. Two different case studies are presented in this paper. Numerical analyses by means of two different software (ABAQUS and SAFIR) were performed and compared to the results. The outcomes confirmed the effectiveness of the proposed element.

  • 3.
    Leander, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Skoglund, Oskar
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A calibrated verification model for fatigue assessment of road bridges2019In: Proceeding of Nordic Steel 2019, 2019Conference paper (Refereed)
    Abstract [en]

    The format suggested in the Eurocode for fatigue verification of road bridges is under scrutiny in thispaper. The model is easy to use in practice, which is important for design purposes, but its accuracyhas been questioned. For this reason, a reliability-based evaluation of the safety level has beenperformed and is briefly recapitulated in this paper. It shows a large scatter in reliability index rangingfrom unacceptably low to overly conservative. A calibration of the existing model has been performedshowing a more consistent reliability level. Results from comparisons of the existing and calibratedmodels are shown for real bridges considering the influence on design stress ranges. The results showthat the Eurocode model is conservative for short span bridges subjected to low traffic volume. Forother cases, the Eurocode model is non-conservative.

  • 4.
    Shamu, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Zou, Liangchao
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska Sweden AB.
    An experimental study of 2D radial flow of a yield stress fluid between parallel disks2019In: September 2-3, 2019, Helsinki. Nordic Grouting Symposium 2019, Helsinki: Nordic Grouting Symposium , 2019Conference paper (Refereed)
  • 5.
    Malm, Richard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Könönen, Mattias
    Vattenfall.
    Bernstone, Christian
    Vattenfall.
    Persson, Mats
    Vattenfall.
    Assessing the structural safety of cracked concrete dams subjectedto harsh environment2019In: Sustainable and Safe Dams Around the World / [ed] Tournier, Bennett & Bibeau, Canada, 2019, p. 383-397, article id 33Conference 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.

  • 6.
    Warg, Jennifer
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport Planning, Economics and Engineering.
    Ait-Ali, Abderrahman
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport Planning, Economics and Engineering.
    Eliasson, Jonas
    Assessment of Commuter Train Timetables Including Transfers2019In: 21st EURO Working Group on Transportation Meeting, EWGT 2018, 17th – 19th September 2018, Braunschweig, Germany, 2019, Vol. 37, p. 11-18Conference paper (Refereed)
    Abstract [en]

    Many railway networks suffer from high capacity utilisation. For scheduling all services, adjustments to the desired slots are often needed. Such adjustments might lead to longer travel times, crowded trains, longer waiting times for boarding and for transfers. All of this has an important socio-economic impact on both travellers and train operators. This raises the question of the socio-economic assessment of changes in commuter train timetables including transfers. Thus, the aim of this study is to evaluate the effects of adjustments of commuter train timetables on the traveller (i.e. consumer costs) and the train operator (i.e. producer costs). These costs are estimated based on all train trips and operations in the network. In a case study, the effect of changes in departure times (resulting in non-regular interval timetables) is analysed. Further, the price of cancelling a two-way service during different times of the day is compared. The results show that changing departure times can both decrease and increase the total costs, and that regularity for parallel services might not be as important as expected if it is kept for each separate service. For the second study, waiting times for transfers were indicated to have a (too) large impact which can lead to misleading results and might be adjusted in future work. The model is adequate for such kind of questions but needs some more adjustments. For railway networks with dense and heterogeneous traffic (as is the case in Sweden), the contributions of this model are useful for making the challenging timetabling process easier and commuter train services less costly.

  • 7.
    Eriksson, Daniel
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hellgren, Rikard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Assessment of frost damage in hydraulic structures using a hygro-thermo-mechanical multiphase model2019In: Sustainable and Safe Dams Around the World / [ed] Jean-Pierre Tournier, Tony Bennett & Johanne Bibeau, 2019, Vol. 2, p. 332-346Conference 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.

  • 8.
    Rogers, Patrick
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. RISE Research Institutes of Sweden AB.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Selander, Anders
    CEMENTA AB.
    Gram, Annika
    RISE Research Institutes of Sweden AB.
    Bulk Hydrophobic Civil Engineering Concrete For Nordic Conditions – Freeze Thaw Action2019In: / [ed] Wit Derkowski et al., 2019Conference paper (Refereed)
    Abstract [en]

    Concrete is a compositebuilding material which long term function can be modified for example bychanging the water to cement ratio (w/c) or by adding in other chemicaladmixtures to change the fresh and hardened properties of the concrete. Theoverall goal of this study is to reduce the water absorption capacity of thecement paste/microstructure by at least 85 %. This is achieved by using bulkhydrophobic agents in the mixing phase rather than post hardened surfaceapplication. Numerous commercial agents and triglycerides (vegetable oils) weretested and showed promising results at a dosage equal to 3% of cement weight.This though affected compressive strengths negatively. As these concretes willbe exposed to Nordic winter conditions, the concrete should perform well underrepeated salt water freezing and thawing. This continued study will show how aselection of these bulk hydrophobic concretes performed during this part of thestudy. The concrete has a w/c = 0.4 with a cement content (CEM I) of 430 kg/m3

  • 9.
    Rogers, Patrick
    et al.
    RISE CBI, Research Institutes of Sweden AB, Drottning Kristinas väg 26, Stockholm, Sweden.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Gram, Annika
    RISE CBI, Research Institutes of Sweden AB, Drottning Kristinas väg 26, Stockholm, Sweden.
    Selander, Anders
    Cementa AB, Sweden.
    Bulk Hydrophobic Civil Engineering Concrete for Nordic Conditions: Freeze Thaw Action2019Conference paper (Refereed)
    Abstract [en]

    Concrete is a composite building material which long term function can be modified for example by changing the water to cement ratio (w/c) or by adding in other chemical admixtures to change the fresh and hardened properties of the concrete. The overall goal of this study is to reduce the water absorption capacity of the cement paste/microstructure by at least 85 %. This is achieved by using bulk hydrophobic agents in the mixing phase rather than post hardened surface application. Numerous commercial agents and vegetable oils were tested and showed promising results at a dosage equal to 3% of cement weight. This though affected compressive strengths negatively. As these concretes will be exposed to Nordic winter conditions, the concrete should perform well under repeated salt water freezing and thawing. This continued study will show how a selection of these bulk hydrophobic concretes performed during this part of the study. The concrete has a w/c = 0.4 with a cement content (CEM I) of 430 kg/m3.

  • 10.
    Zou, Liangchao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska AB, Stockholm.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Cement grout propagation in 2D fracture networks: impact of rheology2019In: Proceedings in Earth and Geosciences: Rock Mechanics for Natural Resources and Infrastructure Development / [ed] Sergio A.B. da Fontoura, Ricardo Jose Rocca, José Pavón Mendoza, CRC Press, 2019, Vol. 6, p. 2486-2493Conference paper (Refereed)
    Abstract [en]

    Cement grouts propagation into a two-dimensional water-saturated fracture networks with different values of rheological properties are simulated by using an extended two-phase flow model. The cement grouts are typical non-Newtonian fluids that contain yield stress, which are often assumed as Bingham fluids. The aim of this study is to investigate the impact of Bingham rheological properties, i.e. yield stress and plastic viscosity, on cement gouts propagation in two-dimensional fracture networks. The results generally show that the rheological properties of cement grouts, i.e. yield stress and plastic viscosity, significantly affect cement grouts propagation in the fracture network. The propagation rate in the fracture networks reduces with the increase of the yield stress and the plastic viscosity of the cement grouts.

  • 11.
    Shamu, John
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Zou, Liangchao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska Sweden AB.
    Cementbaserade Injekteringsmedels Reogram: Instabilt Flöde Och Inverkan På Injektering2019In: Proceedings Bergdagarna 2019, Stockholm, 2019Conference paper (Other academic)
  • 12.
    Zou, Liangchao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Skanska AB, Stockholm.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Characterization of effective transmissivity for cement grout flow in rock fractures2019In: Proceedings of Nordic Grouting Symposium 2019, 2019Conference paper (Refereed)
    Abstract [en]

    Cement grouting has been widely used in rock engineering. Proper characterization of the effective transmissivity for cement grout flow in rock fractures is primarily important for the design of rock grouting. In practice, the hydraulic transmissivity of groundwater flow in rock fractures characterized by hydraulic tests, i.e., pumping or slug test, is often used for the design of rock grouting. However, cement grouts used in rock grouting practice are typical non-Newtonian fluids contain yield stress, which has different effective transmissivity from the Newtonian groundwater. Therefore, using the groundwater transmissivity characterized by hydraulic tests may cause significant uncertainty in modeling and design of cement rock grouting. In this study, we focus on the effective transmissivity of non-Newtonian cement grout flow in a single fracture, aiming to illustrate the difference between the effective transmissivity of non-Newtonian cement grouts and the hydraulic transmissivity of the Newtonian groundwater. The cement grout is assumed as a Bingham fluid. The theoretical solution for the effective transmissivity of Bingham grout for homogeneous fractures is presented. This solution is compared with the theoretical hydraulic transmissivity, i.e., the cubic law. The results generally illustrate the significant differences between the effective transmissivity of non-Newtonian cement grouts and the hydraulic transmissivity of groundwater. The effective transmissivity of non-Newtonian cement grout is nonlinear which a function of injection pressure. Using the hydraulic transmissivity for rock grouting may underestimate the propagation length of the cement grout in rock fractures. The obtained result is helpful for rock grouting design in practice to reduce the potential uncertainties caused by using the hydraulic transmissivity.

  • 13.
    Wang, Ruoqi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology and Design.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Comparison of simulation methods applied to steel bridge reliability evaluations2019Conference paper (Refereed)
    Abstract [en]

    Steel bridges are in general subjected to fatigue deterioration and the structural reliability of bridges will thus reduce over time. There are multiple simulation-based procedures available to perform structural probabilistic studies with several classes of uncertainty taken into account. Since the crack propagation is highly nonlinear and the limit state function (LSF) is multi-dimensional, it imposes specific demands on the simulation methods. Monte Carlo simulation (MCS) has been widely applied in various of fields, however, it requires a great amount of samples and long computation time to reach a high level of accuracy. A more advanced method, Subset Simulation (SS), compensates this shortage. It calculates the product of conditional probabilities of several chosen intermediate failure events. In this paper, the performance of each method was evaluated and compared against fatigue deterioration for aselected bridge detail. A probabilistic model was defined and both prior and updated reliability estimation were performed. The results showed that SS is a good option to deal with fatigue problem with high nonlinearity and multi-dimensional LSF, and shows outstanding time efficiency compared to MCS to reach a comparable accuracy.

  • 14.
    Andersson, Louise
    et al.
    RISE.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Selander, Anders
    Cementa.
    Trägårdh, Jan
    RISE.
    Continuous Preventive Bridge Maintenance in Sweden – Field Experiment on the Effect of Washing on Concrete Bridges2019In: Proceedings of the fib Symposium 2019: Concrete - Innovations in Materials, Design and Structures, 2019Conference paper (Refereed)
    Abstract [en]

    Bridges are an important part of the infrastructure. For the bridges to have the longest possible service life with minimum repairs, the maintenance is of great importance. One type of bridge maintenance that is rarely researched is the continuous preventive maintenance. The continuous preventive maintenance consists of removal of vegetation, cleaning of bridge joints and drainage systems as well as high-pressure washing of the structure. The effects of washing is heavily discussed but not properly researched. A study on the effectiveness of washing concrete is therefore being conducted. A field experiment has been initiated where concrete specimens are installed on an edge beam of a road bridge. The specimens are of two recipes where one represents an old bridge with rather high water-cement ratio and the other one represents a new bridge with a low water-cement ratio. 50% of the specimens are washed annually, while the others are not. Each year samples are collected and tested for a chloride profile. The results for the first year of exposure have been determined. They are promising but are still only very preliminary. The effect of washing, if any, will be visible after a longer exposure.

  • 15.
    Neves, Ana C.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. KTH, School of Engineering Sciences (SCI), Centres, The KTH Railway Group.
    González Silva, Ignacio
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Cost-based optimization of the performance of a damage detection system2019In: Life-Cycle Analysis and Assessment in Civil Engineering: Towards an Integrated Vision - Proceedings of the 6th International Symposium on Life-Cycle Civil Engineering, IALCCE 2018, CRC Press/Balkema , 2019, p. 2103-2112Conference paper (Refereed)
    Abstract [en]

    Situations such as the collapse of civil engineering structures can be avoided if Structural Health Monitoring (SHM) systems can detect early potential failures and timely withdraw the structure from service ahead of a likely disaster. Structural safety is the leading reason for the implementation of SHM but also noteworthy is the cost reduction associated with routine maintenance and inspection. One of the remaining obstacles to fully implement SHM systems in our infrastructure deals with justifying their economic advantage. This paper proposes a rational framework for the use of SHM in the decision making process regarding the maintenance of civil engineering structures, based on the optimal setup of the damage detection system that yields the minimum associated deployment cost. Concepts such as Bayesian Theorem, Damage Index and Receiver Operating Characteristic curve are used in the proposed framework.

  • 16.
    Högdahl, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Transport planning.
    Delay Prediction with Flexible Train Order in a MILP Simulation-Optimization Approach for Railway Timetabling2019Conference paper (Refereed)
    Abstract [en]

    This paper considers the problem of minimizing travel times and maximizing travel time reliability, which are important socio-economic properties of a railway transport service, for a given set of departures on a double-track line. In this paper travel time reliability is measured as the average delay, and a delay prediction model for MILP timetable optimization is presented. The average delay prediction model takes into consideration time supplements, buffer times and propagation of delays in the railway network and is not restricted to a fixed order of the trains. Validation of the average delay prediction model, and an evaluation of the approach with combined simulation-optimization for improving railway timetables, are conducted by a simulation study on a part of the Swedish Southern Main Line. Results from the simulation study show that the average delays are reduced by up to approximately 40% and that the punctuality is improved by up to approximately 8%.

  • 17.
    Wersäll, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Åkesson, Fredrik
    Persson, Andreas
    Dynamic roller characteristics and CCC using automatic frequency control2019Conference paper (Refereed)
  • 18.
    Wang, Cong
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Sadeghian, Parastoo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Effect of staff number on the bacteria contamination in operating rooms with temperature-controlled airflow ventilation and turbulent mixing ventilation2019In: Proceedings of Building Simulation 2019: 16th Conference of IBPSA, 2019Conference paper (Refereed)
  • 19.
    Damasceno, Davi Rodrigues
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Jan
    Naturgasteknik.
    Efficiency of subset simulation in the design of lined rock caverns for storage of hydrogen gas2019In: Proceedings of the 13th International Conference on Applications of Statistics and Probability in Civil Engineering, Seoul, South Korea, 2019, article id 124Conference paper (Refereed)
    Abstract [en]

    Efforts to substitute the use of fossil fuels in industry by hydrogen gas requires the storage of large volumes of gas with a reliable pressure vessel design. The Hydrogen Breakthrough Ironmaking Technology (HYBRIT) initiative aims to make the whole steel making process in Sweden fossil-free with the storage of industrial scale quantities of hydrogen in underground Lined Rock Cavers (LRCs). The LRC concept is a relatively new design methodology that can be further developed with respect to safety and economic efficiency and reliability-based design methods provide one option to comply with codes and regulations. High reliability is required for the storage of hydrogen gas and the computational time becomes unpractical for the evaluation of a complex system such as the LRC. In this paper, the efficiency of Subset Simulation (SuS) regarding accuracy, precision and required number of samples is studied for the calculation of probability of failure against fatigue of the steel lining. It can be observed that by increasing the number of samples per level and increasing the conditional probability of failure the precision increases as well as the total number of samples. The accuracy of the SuS is checked with respect to Monte Carlo simulation (MCS) showing good agreement and with greater precision for fewer number of samples. A case study is performed for the geologic conditions of Sweden showing that the considered failure mode is unlikely for high stresses and good rock mass quality.

  • 20. Kayo, G.
    et al.
    Shukuya, M.
    Martinac, Ivo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Energy and exergy analysis of waste-water heat recovery in a multi-family residential complex2019In: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing (IOPP), 2019, Vol. 609, no 6, article id 062014Conference paper (Refereed)
    Abstract [en]

    This article provides an approach to analysing the energy and exergy efficiency of a waste-water heat recovery system. The system studied is installed in a multi-family residential complex in Stockholm, Sweden. The heat recovery unit in question consists of eight coaxial, counter-flow heat-exchangers connected in parallel, with waste-water flowing through the internal pipe and cold brine (propylene glycol 25%) ducted through the external pipe. The analysis was carried out based on data collected by a building monitoring system (BMS) during five winter months (heating season). The energy analysis (using average hourly values) showed that on average 10.7 kW (Span: 1.1-38.7 kW) of waste-water heat was delivered to the cold brine. On the other hand, the exergy analysis (using the same data) showed that on average 12% (Span: 3-24%) of the exergy contained in the waste-water was delivered to the cold brine, while on average 76% (Span: 60-88%) was consumed during the process. Access to accurate and detailed performance measurement data was found to be essential for analysing the exergy and energy performance of the heat recovery system. In conclusion, this article demonstrates that it is vitally important to consider both the first and second laws of thermodynamics to achieve a wholesome understanding of heat recovery from waste-water systems.

  • 21.
    Olsson, Lars
    et al.
    Geostatistik AB.
    Spross, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Hintze, Staffan
    NCC.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Båtelsson, Olle
    Trafikverket.
    Framtidens riskhantering – nu med systemförståelse2019Conference paper (Other (popular science, discussion, etc.))
    Abstract [sv]

    Geoteknikern hanterar i sin vardag många och ofta stora risker. Men trots att kostnaden för negativa utfall av geotekniska risker årligen bedöms ligga på flera miljarder kronor, används tillgängliga verktyg för strukturerad riskhantering sparsamt. I ett SBUF-projekt har vi tagit fram en vägledning för hur sådana verktyg kan användas i praktiken. Vi har i denna vägledning särskilt fokuserat på den för riskhanteringen så viktiga systemförståelsen av det geotekniska sammanhanget som man verkar i. Denna artikel är en sammanfattande kortversion av den slutrapport som författarna skrivit inom ramen för SBUF-projektet.

  • 22.
    Härer, Simon
    et al.
    Faculty of Engineering, Reutlingen University, Reutlingen, Germany.
    Nourozi, Behrouz
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Uponor AB, Västerås, Sweden.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings. Bravida Holding AB, Hägersten, Sweden.
    Frost reduction in mechanical balanced ventilation by efficient means of preheating cold supply air2019Conference paper (Refereed)
    Abstract [en]

    This study has focused on evaluating the financial potential of wastewater and geothermal heat recovery systems in a multi-family building. The recovered heat was used to improve the performance of mechanical ventilation with heat recovery (MVHR) system during the coldest days in central Sweden. The main issue, which was targeted with these solutions, was to reduce frost formation in the system and hence increase its thermal efficiency. By looking at the life cycle cost over a lifespan of 20 years, the observed systems were being evaluated economically. Furthermore, statistical analyses were carried-out to counter the uncertainty that comes with the calculation. It was found that the studied wastewater systems have a high possibility of generating savings in this period, while the one fed by geothermal energy is less likely to compensate for its high initial cost. All designed systems however, managed to reduce operational cost by 35-45% due to lower energy usage.

  • 23.
    Lițiu, Andrei Vladimir
    et al.
    KTH, School of Architecture and the Built Environment (ABE).
    Barthelmes, V.M.
    Becchio, C.
    Fabi, V.
    Tarantini, M.
    Vergerio, G.
    Corgnati, S. P.
    Martinac, Ivo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Graphical visualization of behavioural patterns in relation to indoor environment quality and energy use2019In: E3S Web of Conferences, EDP Sciences, 2019, Vol. 111, article id 04060Conference paper (Refereed)
    Abstract [en]

    In this paper, the authors provide a general overview on the methodological framework behind the monitoring and evaluation strategies of Mobistyle project that are used as reference for the demonstration cases. The strategies identify parameters that need to be evaluated during several phases regarding the impact (energy, IEQ, health, behavioural patterns) and the strategy (effectiveness of the process) of the project, and how these parameters can be numerically evaluated. In particular, the paper focuses on the graphical visualization method for behavioural patterns analysis in relation to indoor environment quality and energy use. The proposed approach is illustrated based on measured data from one Mobistyle Project case study i.e. a hotel for long term stay located in Turin, Italy.

  • 24.
    Nordström, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hassanzadeh, Manouchehr
    Sweco.
    Ekström, Tomas
    ÅF.
    Janz, Mårten
    ÅF.
    Guideline for structural safety in cracked concrete dams2019In: 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 (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.

  • 25.
    De Roode, Alexander Francois
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Martinac, Ivo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Kayo, Genku
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    High-Performance and Energy Resilient Communities: Disaster prevention through community engagement2019In: IOP Conference Series: Earth and Environmental Science, Institute of Physics Publishing (IOPP), 2019, no 1, article id 012026Conference paper (Refereed)
    Abstract [en]

    As a part of an integrated approach to formulating a plan and comprehensive program for facing natural disasters, human settlements need to first understand the strengths, weaknesses, opportunities and threats (SWOT) within their own localized communities with respect to such disasters. A starting point is to engage local communities in order to assess their baseline understanding of community capacity and capabilities, and to identify and synergize already established disaster prevention and response programs, systems and initiatives. Maui Island, located in the State of Hawaii within the United States of America, was used as a case study to highlight specific opportunities and constraints that selected communities located on Maui Island face in their decision making for energy resilience. Relevant stakeholder groups and their respective roles in disaster mitigation and response are described. Methods for how best to engage local communities around such topics are described, including community surveys, stakeholder workshops, community working groups, and community forums. Methods for how to assess community capacity and capabilities around disaster resilience are also described, including identifying key stakeholders representing a cross section of the local community and studying community response to past disaster events in order to identify successes, best practices, failures and lessons learned. More specifically, this paper provides a deeper understanding of the opportunities and constraints associated with energy infrastructure on Maui Island when seeking to optimize for energy resilience in the face of natural disasters such as hurricanes, tsunamis, flooding and earthquakes. This baseline inventory of energy resilience for selected Maui communities is assessed at the community level. Further research will then apply an adapted methodology to an analysis at the building cluster or district level. This framework can serve to inform similar communities seeking to enhance their energy resilience through bottom-up community engagement.

  • 26.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Stille, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Palmström, Arild
    Rock Mass AS.
    Hur ska bergbyggande kunna inkluderas i Eurokod 7: How to include rock engineering in Eurocode 72019In: Proceedings Bergdagarna 2019, 2019Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Sweden, among other countries, has chosen not to apply Eurocode 7 to rock engineer­ing design. However, Eurocode 7 is currently under revision, with one purpose being to improve its applicability to rock engineering. Such a revision would however require that the code accommodates the current principles of rock engineering design and exe­cution, since rock engineering in many cases fundamentally differs from other types of construction. In this presentation, we give our view on how a design code for rock engineering needs to be organized, in order to ensure that new rock engineering struc­tures become both sufficiently safe and cost-effectively constructed. An important pre­requisite is having a decision-theoretical connection between design and risk manage­ment that always should permeate geotechnical design and construction. The presented research is based on the results from a research project funded by the Rock Engineering Research Foundation (BeFo) that was finalized in January 2019.

  • 27.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Uponor AB.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holding AB.
    Identifying frost threshold in a balanced mechanical ventilation system by inlet and exhaust air temperature control2019Conference paper (Refereed)
    Abstract [en]

    Frosting is a common issue in air-to-air heat recovery exchangers installed in buildings in cold climate countries. Further to the developed defrosting methods, frost prevention by preheating the outdoor air can reduce the energy usage in buildings. In this study, residential wastewater as a renewable heat source is used to preheat the outdoor air. Due to limited wastewater hourly flowrate and the impact of preheated air temperature on the efficiency of heat exchanger, controlling the preheating temperature is of utmost importance. In this investigation, preheated and exhaust air temperatures are monitored to generate an operational signal to the wastewater circulation pump. The cold surface at the heat exchanger and the dew point of the return air are analyzed to comprehend the condensation and frosting temperatures. The results show that in case of 30% relative humidity in the return air, the frosting threshold is at preheated and exhaust air temperatures below -2.2°C and 2.1°C, respectively. Using these temperatures as controlling parameters, the frosting period has decreased by 23%.

  • 28. Wei, Y.
    et al.
    Liu, Wei
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Xue, Y.
    Zhai, Z.
    Chen, Q.
    Zhang, T.
    Integrated inverse design of ventilation for an aircraft cabin2019In: E3S Web of Conferences, EDP Sciences , 2019Conference paper (Refereed)
    Abstract [en]

    Cabin ventilation is crucial for maintaining thermal comfort and air quality for passengers and crew. The genetic algorithm, proper orthogonal decomposition (POD), and adjoint method have been proposed to inversely design the cabin ventilation. However, each method has its cons and pros. This paper proposed to integrate the above three methods in cascades. The genetic algorithm was applied first in the first stage to roughly circumscribe the ranges of design parameters. Then POD was applied in the next stage to further narrow the ranges and estimate the optimal parametric sets for each design criterion. The estimated optimal design from POD was supplied to the adjoint method for fine tuning. The air-supply parameters of a five-row aircraft cabin were inversely designed to achieve the minimum absolute value of the predicted mean vote (PMV) and the minimum averaged mean age of air. The results showed that the integrated method was able to improve the design stage by stage. The integrated method has superior advantages to assure the optimal design while minimizing the computing expense.

  • 29.
    Liu, Wei
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Chen, C.
    Integration of fast fluid dynamics and Markov chain model for predicting transient particle transport in buildings2019In: E3S Web of Conferences, EDP Sciences, 2019, Vol. 111, article id 04030Conference paper (Refereed)
    Abstract [en]

    Fast simulation tools for the prediction of transient particle transport are critical in designing the air distribution indoors to reduce the exposure to indoor particles and associated health risks. This investigation proposed a combined fast fluid dynamics (FFD) and Markov chain model for fast predicting transient particle transport indoors. The solver for FFD-Markov-chain model was programmed in OpenFOAM, an open-source CFD toolbox. This study used a case from the literature to validate the developed model and found well agreement between the transient particle concentrations predicted by the FFD-Markov-chain model and the experimental data. This investigation further compared the FFD-Markov-chain model with the CFD-Eulerian model and CFD-Lagrangian model in terms of accuracy and efficiency. The accuracy of the FFD-Markov-chain model was similar to that of the other two models. For the studied case, the FFD-Markov-chain model was 4.7 times faster than the CFD-Eulerian model, and it was 137.4 times faster than the CFD-Lagrangian model in predicting the steady-state airflow and transient particle transport. Therefore, the FFD-Markov-chain model is able to greatly reduce the computing cost for predicting transient particle transport in indoor environments.

  • 30. Tang, Q.
    et al.
    Jin, Junchen
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Left turn phasing type determination at isolated intersections solved by a genetic algorithm2019In: 2019 IEEE Intelligent Transportation Systems Conference (ITSC), Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 4236-4241, article id 8917423Conference paper (Refereed)
    Abstract [en]

    A left turn could be treated as a permitted or protected left turn. Good left turn treatment could improve the efficiency at intersections. This paper aims to solve the left turn phasing type problem with the goal of minimizing the total delay. The determination of left turn phasing types extends the lane-based signal optimization method by introducing the decision variables of left turn phasing type indicators. This problem is solved with a genetic algorithm with penalty functions. It is found that permitted left turns contribute to total delay reduction.

  • 31.
    Zhang, Tong
    et al.
    State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China.
    Jin, Junchen
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Smart Transportation Research Institute, Enjoyor Co. Ltd, Hangzhou, 310030, China and Engineering Research Center of Intelligent Transport of Zhejiang Province, Hangzhou 310030, China..
    Yang, Hui
    State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China.
    Guo, Haifeng
    College of Information Engineering, Zhejiang University of Technology, Hangzhou 310013, China ; Enjoyor Co., Ltd, Hangzhou 310030, China..
    Ma, Xiaoliang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Link speed prediction for signalized urban traffic network using a hybrid deep learning approach2019Conference paper (Refereed)
  • 32.
    Nordström, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Tornberg, Robert
    Sweco.
    Kamanga, Romas
    Zesco.
    Management of ASR affected spillway structures at Kafue Gorge, Zambia2019Conference paper (Refereed)
    Abstract [en]

    The Kafue Gorge dam along Kafue River in Zambia was commissioned in 1971. In 1988 one of the spillway gates was jammed due to concrete expansion. Measures were taken, but signs of expansion and cracking continued. After rehabilitation works on one of the spillway gates in 2011 five stop-logs were stuck in position due to concrete expansion. In 2012, ZESCO and SWECO performed an in-depth assessment of the spillway structure with crack mapping and core sampling. Extensive cracking on the upstream side of the spillway piers with crack widths of up to 30 mm was found under water. Concrete analysis verified ongoing ASR. Numerical simulations on the behavior of the dam (with major cracks and ASR-expansion) showed that there was a need for stabilizing measures. SWECO designed remedial measures to restore full integrity of the dam and resolve the problem with the jammed stop-logs that caused reduced discharge capacity. During 2019 post-tensioned tendons are installed to ensure a monolithic behavior of the structure and improve the stability. All major cracks will be sealed to reduce the contact area of concrete and water. Finally, the jammed stop-logs will be removed to restore the discharge capacity of the spillway.

  • 33.
    Nordström, Erik
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Tornberg, Robert
    Sweco.
    Kamanga, Romas
    Zesco.
    Management of ASR-affected spillway structures at Kafue Gorge, Zambia2019Conference paper (Other academic)
  • 34.
    Lövqvist, Lisa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Architecture, Architectural Technologies. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Modeling the evolution of winter damage in an asphalt concrete microstructure2019Conference paper (Refereed)
    Abstract [en]

    Winter damage in asphalt pavements is a complex phenomenon which may cause pothole formation, dislodging of stones and structural layer separation. In order to reduce the winter damage, knowledge about the process in both the pavement and on a microstructural level is required. This paper focuses on modeling the process of damage evolution on a microstructural level in order to identify and understand the different phenomena influencing the degradation process. In this paper the evolution of winter damage in an asphalt concrete microstructure was modeled throughout the course of two winter seasons. The simulations include freezing and thawing cycles as well as additional damage originating from snow plows, both based on real weather data from Luleå in the north of Sweden. The results show a large increase of damage in both the mastic and the aggregate-mastic interface, and thereby also vertical displacement of the top surface, after the first freeze-thaw cycle. During the following freeze-thaw cycles the mastic damage continuous to increase but with a decreasing rate while the damage in the aggregate-mastic interface is only affected by the manually added damage from the snow plow. These results indicate a need to include the growth of -and emergence of new air voids in the model as well as an investigation of the actual behavior and influence of the damage evolution in the interface regions.

  • 35.
    Hellgren, Rikard
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Malm, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Eriksson, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Modelling of the ice load on a Swedish concrete dam using semi-empirical models based on Canadian ice load measurements2019In: Sustainable and Safe Dams Around the World / [ed] Jean-Pierre Tournier, Tony Bennett & Johanne Bibeau, 2019, Vol. 2, p. 3068-3080Conference 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.

  • 36.
    Zou, Liangchao
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Håkansson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Skanska AB .
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Resources, Energy and Infrastructure.
    Non-Newtonian grout flow in single rough-walled rock fractures2019Conference paper (Refereed)
    Abstract [en]

    Modeling of cement grout flow in rock fractures plays an important role in the design of rock grouting. Cement grouts used in rock grouting practice are typical non-Newtonian fluids containing yield stress, and are often assumed as Bingham fluids. Natural rock fractures typically consist of rough surfaces. Therefore, in reality, rock grouting process actually involves non-Newtonian fluid flow in rough-walled fractures, which is rarely studied in the literature. In this work, we focus on the impact of surface roughness and present direct numerical simulations of non-Newtonian grouts flow in single rough-walled fractures, using a regularized method to approximate the yield-stress. The rough-walled rock fracture models are created from a laser-scanned surface of a granite rock sample, to represent realistic features of natural rock fractures. The numerical results generally show nonlinear behaviors of non-Newtonian fluid flow in rough-walled fractures. The surface roughness significantly reduces the effective transmissivity when Reynolds number is relatively large. The obtained result can be used for upscaling analysis in practice, in order to reduce the potential uncertainties caused by the surface roughness of the rock fractures.

  • 37.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Numerical investigation of thermal comfort in an aircraft passenger cabin2019In: E3S Web of Conferences, EDP Sciences, 2019, Vol. 111, article id 01027Conference paper (Refereed)
    Abstract [en]

    This study presents the results of a pilot numerical study of the thermal comfort in the aircraft passenger cabin. The computations have been performed using the Computational Fluid Dynamics (CFD) technique. The overall thermal comfort at temperatures of 15 °C - 20 °C was discussed based on the PMV (Predicted Mean Vote) and PPD (Predicted Percentage of Dissatisfied) indexes. Results indicate that the air velocity and its direction toward the passengers have a considerable impact on their thermal comfort. However, a small variation in temperature has a limited effect on thermal sensation and thus do not jeopardize the overall thermal comfort.

  • 38.
    Sadeghian, Parastoo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Polak, J.
    Afshari, A.
    Sadrizadeh, Sasan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
    Numerical investigation on the impact of different supply air terminal devices on the performance of the newly combined ventilation and heating system2019In: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing (IOPP), 2019, no 5, article id 10th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, IAQVEC 2019; Bari; Italy; 5 September 2019 through 7 September 2019Conference paper (Refereed)
    Abstract [en]

    An increased focus on energy saving has led to a rapid development of energy-efficient buildings. In the residential buildings, space heating, ventilation and air conditioning (HVAC) have the highest energy use. The ventilation system is the main tool to provide acceptable indoor air quality and thermal comfort for occupants. This study presents an investigation of the thermal environment in a room served by new developed, combined ventilation and heating system. The focus is on different configurations of the supply air terminal device in the studied system. The main goal is to investigate the influence of different supply air parameters, which in this study are flowrate and temperature, on the airflow behaviour and performance of the mixing ventilation. In this regards, three different supply air conditions with two inlet configurations were considered. This work has been carried out numerically and validated with the laboratory measurements. Computational Fluid Dynamics (CFD) simulation was applied in this study to map the airflow patterns and air temperature distribution. The results showed that decreasing supply air temperature and increasing the flowrate provided a uniform temperature distribution for both inlet configurations. Inlet configuration investigated in case1 has lower vertical temperature differences in comparison with case 2.

  • 39.
    Karlsson, Freddie
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Department of Civil Engineering, KU Leuven, Leuven, Belgium.
    Maes, K.
    Lombaert, G.
    Online tracking of inputs, states and parameters of structural dynamic systems2019In: Life-Cycle Analysis and Assessment in Civil Engineering: Towards an Integrated Vision - Proceedings of the 6th International Symposium on Life-Cycle Civil Engineering, IALCCE 2018, CRC Press, 2019, p. 211-217Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel filtering algorithm for joint input-state-parameter estimation. The algorithm is derived from an existing joint input-state estimation algorithm. In each step, the system model is linearized around the current state, yielding an algorithm which is similar to the Extended Kalman filter. It is shown that, in the application to linear structural dynamic systems, the analytical expressions for the Jacobian matrices involved in the linearization are readily available due to the choice of parametrization. The proposed methodology is verified by numerical simulations for a four story shear building.

  • 40.
    Strömberg, Larissa
    et al.
    NCC Nordic Construction Company, Infrastructure Business Area, Solna, Sweden.
    Löfsjögård, Malin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Hintze, Staffan
    NCC Nordic Construction Company, Infrastructure Business Area, Solna, Sweden.
    Optimization parameter sets for sustainable concrete in tunnels2019In: ISEC 2019 - 10th International Structural Engineering and Construction Conference2019, ISEC Press , 2019Conference paper (Refereed)
    Abstract [en]

    Public and private clients are beginning to set complex optimization requirements, taking into consideration environmental and cost-efficiency parameters over the built construction’s lifetime. The early design process is currently irreversible and this makes it difficult to change a concrete structure in the later detailed design stage, when more accurate information is available regarding environmental impact and life-cycle costs. There is a dilemma in complying with existing standards to achieve technical requirements while optimizing a concrete structure in order to reduce the climate impact. The long-term goal of the project is to develop a new theoretical concept for dynamic optimization strategies which can be applicable to the early design, the client-requirement preparation, the detailed design, the production and the follow-up stages. This paper presents the results of the up-start phase of the project. Our work has focused on the identification of current practice regarding clients’ requirements for technical, environmental and cost-efficiency parameters. An analysis of these requirements with sprayed concrete in a number of ongoing projects has led to the identification of optimization parameter sets. The project has also shown how the physical values of those parameters can be collected from existing statistics, experience recovery databases and previous project requirements, or calculated according to standardized methods and tools. The concept developed will be used in a demonstrative modeling in the next project step.

  • 41.
    Ahmed, Samih
    et al.
    Tyréns AB.
    Minchot, Guayente
    Tyréns AB.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    King, Fritz
    Tyréns AB.
    Hallgren, Mikael
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Post-Tensioned Stress Ribbon Systems in Long Span Roofs2019In: 20th Congress of IABSE, New York City 2019: The Evolving Metropolis - Report2019, International Association for Bridge and Structural Engineering , 2019, p. 534-540Conference paper (Refereed)
    Abstract [en]

    Cable systems have numerous advantages, such as: large column-free areas, and reduced materials consumption, which reduces the load and the cost. Nevertheless, they are rarely used in long span roofs due to large deflections, and the insufficient space for end supports, or/and back-stayed cables. This work suggests the use of post-tension stress ribbon system in long span roofs in order to reduce the pull-out forces, deflections and concrete stresses compared to a conventional cable system. A comparison is carried out through meticulous and accurate finite element simulations, using SAP2000, implemented for the new +200m roof of Västerås Travel Center (Sweden), which will become one of the longest cable suspended roofs in the world, if not the longest. Results confirm the suitability and superiority of stress ribbon systems as it reduces concrete stresses, deflections, pull-out forces and vertical reactions. These reductions are found highly correlated to the applied prestressing forces.

  • 42.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Practical guidelines for shotcrete work close to blasting and vibration in hard rock2019In: Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art- Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress, 2019, p. 4659-4668Conference paper (Refereed)
    Abstract [en]

    Limited knowledge on safe vibration levels near newly sprayed concrete (shotcrete) often leads to over-conservative limits in underground construction and tunnelling, with additional costs and planning uncertainties as a consequence. Work on compiling a database of practical vibration levels for shotcrete work close to blasting in hard rock have been initiated and will provide guidelines for safe distances and waiting times for newly sprayed wet-mix shotcrete. A large number of calculations are carried out with a previously developed and relatively computationally effective numerical elastic stress wave propagation model, which will result in a systematically compiled database. These guidelines, giving relationships between the amount of explosives, distance, rock type, shotcrete type, age and thickness, will be of great value as reference for design work and facilitate comparisons with in situ data. It will be possible to adopt the design to ensure undamaged and safer shotcrete constructions with longer service life.

  • 43.
    Nourozi, Behrouz
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Wang, Qian
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Uponor AB.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Bravida Holdings AB.
    Preheating Cold Supply Air to Mechanical Balanced Ventilation using Wastewater or Passive Geothermal Energy2019Conference paper (Refereed)
    Abstract [en]

    This study investigated the thermal potential of two renewable heat sources, residential wastewater and geothermal energy, for preheating the incoming air to the air-handling unit (AHU) in a multi-family building. The main purpose of preheating the inlet air was to avoid the frost formation inside AHU due to low outdoor temperatures during winter. Wastewater extraction flowrate and temperature, as two design parameters, were studied in detail by employing two types of wastewater storage tanks.The suggested outdoor air preheating systems equally reduced the defrosting period to 26% compared to the mechanical ventilation with heat recovery system (MVHR) without air preheating. The system that utilized a temperature stratified wastewater storage tank provided a higher ratio of heat output to electricity input. The other outdoor air preheating system, which was equipped with an unstratified wastewater storage tank, provided a lower ratio of heat output to pumping power. However, this ratio was not disturbed by variations in outdoor air temperature.

  • 44.
    Spross, Johan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Prästings, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Probabilistic evaluation of settlement monitoring with the observational method during construction of embankments on clay2019In: Proceedings of the 7th International Symposium on Geotechnical Safety and Risk (ISGSR 2019): State-of-the-Practice in Geotechnical Safety and Risk / [ed] Jianye Ching, Dian-Qing Li and Jie Zhang, 2019, article id IS3-3Conference paper (Refereed)
    Abstract [en]

    Preloading  is  commonly  used  to  accelerate  primary  consolidation  and  increase  strength  under  embankments founded on highly compressible clay. By installing prefabricated vertical drains, this process can be even further accelerated. Because of significant geotechnical uncertainties, primarily regarding the vertical and horizontal coefficients of consolidation, prediction of settlement development with time is difficult. This paper shows how Bayesian statistics can be used to update a prior prediction of  the  final  settlement  from  the design  stage, with observations of  settlement made during  the preloading. With  this  approach,  the  observations  during  construction  are  used  to  significantly  reduce  the  considerable  epistemic uncertainty present at the design stage. This allows the surcharge design to be adjusted to suit the actual ground conditions, which is done by increasing the surcharge height if the settlement develops too slowly.

  • 45.
    Sjölander, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ansell, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Probabilistic modelling of fibre reinforced shotcrete2019In: Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art- Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress, CRC Press, 2019, p. 3105-3112Conference paper (Refereed)
    Abstract [en]

    Shotcrete is widely used as rock support and can support the load from blocks either by bonding to the rock or by bending between rock bolts. By introducing fibres, the ductility of the shotcrete will increase and the crack widths decrease. Predictions of the structural behaviour for fibre reinforced shotcrete (FRS) are however complicated due to the large scatter normally seen in test results. The reason is mainly related to the non-uniform distribution and orientation of the fibres which could lead to uncertainties regarding the quality of in-situ shot-crete. The aim with this paper is therefore to investigate if a probabilistic material model for FRS can be used to capture the scatter in the results. An isotropic damage model that combines an exponential softening curve for unreinforced shotcrete and a bi-linear curve to account for the effect of fibres were used. Suitable distributions for each of the parameters in the model have been proposed based on fitting of experimental results. Thereafter, Monte Carlo simula-tions were used to produce results for a large number of lab tests. Results show that the model together with the proposed distributions was able to capture the scatter in test results.

  • 46.
    Tell, Sarah
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Najafi, Ali
    Spencer, Jr., Bill F.
    Real-time hybrid simulation of a bridge-damper system2019In: Advances in Engineering Materials, Structures and Systems: Innovations, Mechanics and Applications: Proceedings of the 7th International Conference on Structural Engineering, Mechanics and Computation (SEMC 2019), September 2-4, 2019, Cape Town, South Africa / [ed] Alphose Zingoni, Cape Town: CRC Press, 2019, p. 1810-1813Conference paper (Refereed)
    Abstract [en]

    This paper presents the use of external dampers for vibration mitigation of railway bridges subjected to passing trains. A numerical model of the bridge combined with an experimental setup of a full-scale magnetorheological damper is used. The combined bridge-damper system is analyzed in real-time using a hybrid simulation technique. The approach is illustrated on a simply supported steel-concrete composite bridge. Due to the large eccentricity between the neutral axis and the roller support, the resulting displacement motivates the use of a near support damper. It is shown that sufficient vibration mitigation can be obtained with a single damper. A parametric study is performed to determine the optimal damper position and inclination.

  • 47.
    Stille, B.
    et al.
    Department of Civil Infrastructure, AECOM Nordic AB, Stockholm, Sweden.
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Department of Civil Infrastructure, AECOM Nordic AB, Stockholm, Sweden.
    Ríos Bayona, Francisco
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics. Department of Civil Infrastructure, AECOM Nordic AB, Stockholm, Sweden.
    Batres Estrada, R.
    Department of Civil Infrastructure, AECOM Nordic AB, Stockholm, Sweden.
    Roslin, M.
    Swedish Transport Administration, Stockholm, Sweden.
    Stockholm bypass project – passage under the Lake Mälaren2019In: Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art- Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress (WTC 2019), May 3-9, 2019, Naples, Italy / [ed] Daniele Peila, Giulia Viggiani, Tarcisio Celestino, London: CRC Press, 2019, p. 1569-1578Conference paper (Refereed)
    Abstract [en]

    In the last years, the Swedish Transport Administration has been working on improving and expanding road communications in Sweden. The Stockholm Bypass Project, one of the biggest projects in Swedish history, consists of a 21 km long highway that goes around the city from north to south. In order to reduce the environmental impact, 17 km of the total length will be excavated underground passing through several regional fault zones and subsea passages. One of the most difficult technical challenges in this project is the passage under the Lake Mälaren and the regional fault zone in the Fiskar fjord. This paper presents the utilized methodology to design the temporary rock support and to manage the risks and uncertainties for the excavation through the fault zone, which mainly originate from the limited information about the rock conditions and the relatively large width of the tunnels.

  • 48. Leurent, F.
    et al.
    Li, S.
    Badia, Hugo
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Structural design of a hierarchical urban transit network integrating modal choice and environmental impacts2019In: 21st EURO Working Group on Transportation Meeting, EWGT 2018, 17th – 19th September 2018, Braunschweig, Germany, Elsevier, 2019, Vol. 37, p. 99-106Conference paper (Refereed)
    Abstract [en]

    The paper develops a structural model and a design methodology for transit system planning in an urban area. Transit "components" are modelled by subarea and by sub-mode in terms of line length, station spacing, and fleet size, in order to determine both quality of service and production costs. Roadway networks are modeled with a Macroscopic Fundamental Diagram that relates speed to network capacity and vehicle demand. Local and global environmental impacts are considered. Travel demand includes both mode-dependent users and mode-choosers able to adopt the mode that offers higher utility. The design methodology involves a mathematical program of welfare optimization with respect to transit factors and fares. Two definitions of welfare are given, one that takes into account only demand surplus and supply profit, the other including environmental impacts. An example of application to Greater Paris shows that there is room for system optimization under current subsidy conditions, and that the explicit inclusion of environmental impacts brings about a significant shift in the "optimal" policy package.

  • 49.
    Skoglund, Oskar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    The impact of local geometry on the fatigue life of a welded structural detail2019In: Proceeding of Nordic Steel 2019, 2019Conference paper (Refereed)
    Abstract [en]

    Fatigue often limits the capacity of welded steel bridges, and thus often governs the amount of steel required. The fatigue life is, to a large extent, governed by stress concentrations and the magnitude is controlled by local as well as global geometry; by improving the local geometry the stress raising effects can be lowered and by increasing the global dimensions the nominal stress can be reduced. The fatigue assessment format presented in the Eurocode gives little or no room for the designer to control the local geometry of the structural detail, and is often left with increasing the overall dimensions in order to improve the fatigue life of the structure. This paper aims at investigating the possible impact on the fatigue life of welded steel structures by different weld geometries. In this paper a vertical stiffener will be studied by fracture mechanics. The study showed that significant improvements in fatigue life can be made by small changes to the weld geometry and the most pronounced effect was by changing the weld toe radius, and

  • 50. Tondini, N.
    et al.
    Morbioli, A.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    A 2D beam element for the analysis of flexural buckling of steel structures at elevated temperatures2018In: Applications of Fire Engineering - Proceedings of the International Conference of Applications of Structural Fire Engineering, ASFE 2017, CRC Press/Balkema , 2018, p. 199-208Conference paper (Refereed)
    Abstract [en]

    The paper describes the development of a two-dimensional (2D) nonlinear beam finite element that includes advanced path-following capabilities for detecting bifurcation instability of steel elements subjected to fire loading. A co-rotational formulation was used for describing the beam kinematic. The degradation of the steel mechanical properties at high temperature according to the Eurocode 1993-1-2 was considered by integrating the material constitutive law based on a predetermined temperature field in the cross section. Advanced path-following methods were implemented to analyse the elastic-plastic post-buckling behaviour of compressed steel elements at high temperature without the need of introducing geometrical imperfections. To highlight the practical implications, a parametric analysis showed that the element could reproduce the EN1993-1-2 buckling curve. The obtained outcomes were validated against experimental and numerical data obtained with commercial software ABAQUS and SAFIR. 

1234567 1 - 50 of 831
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf