| 1. |
- Abbasi, Rasha, et al.
(författare)
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IceCube search for neutrinos from GRB 221009A
- 2023
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Ingår i: Proceedings of 38th International Cosmic Ray Conference (ICRC 2023). - : Sissa Medialab Srl.
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Konferensbidrag (refereegranskat)abstract
- GRB 221009A is the brightest Gamma Ray Burst (GRB) ever observed. The observed extremelyhigh flux of high and very-high-energy photons provide a unique opportunity to probe the predictedneutrino counterpart to the electromagnetic emission. We have used a variety of methods to searchfor neutrinos in coincidence with the GRB over several time windows during the precursor, promptand afterglow phases of the GRB. MeV scale neutrinos are studied using photo-multiplier ratescalers which are normally used to search for galactic core-collapse supernovae neutrinos. GeVneutrinos are searched starting with DeepCore triggers. These events don’t have directionallocalization, but instead can indicate an excess in the rate of events. 10 GeV - 1 TeV and >TeVneutrinos are searched using traditional neutrino point source methods which take into accountthe direction and time of events with DeepCore and the entire IceCube detector respectively. The>TeV results include both a fast-response analysis conducted by IceCube in real-time with timewindows of T0 − 1 to T0 + 2 hours and T0 ± 1 day around the time of GRB 221009A, as well asan offline analysis with 3 new time windows up to a time window of T0 − 1 to T0 + 14 days, thelongest time period we consider. The combination of observations by IceCube covers 9 ordersof magnitude in neutrino energy, from MeV to PeV, placing upper limits across the range forpredicted neutrino emission.
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| 2. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 3. |
- Falster, Daniel, et al.
(författare)
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AusTraits, a curated plant trait database for the Australian flora
- 2021
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Ingår i: Scientific Data. - : Nature Portfolio. - 2052-4463. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.
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| 4. |
- Hosseini, Seyed Mohammad, et al.
(författare)
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Study of Flame Dynamics and Flashback Mechanism in a Gas Turbine Combustor Using Simultaneous OH-PLIF and PIV
- 2010
-
Ingår i: AIAA 2010-6668. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
-
Konferensbidrag (refereegranskat)abstract
- The present study aims to investigate the effects of burner geometry on flame characteristics, stabilization, and the occurrence of flashback using the Triple Annular Research Swirler (TARS). A premixing tube is placed at the exit of the burner. Simultaneous Planar Laser Induced Fluorescence (PLIF) of OH radicals indicating the reacting zone and Particle Image Velocimetry (PIV) for flow field mapping, were applied to study the flow- and flame-dynamics during transition from flame stabilized in the combustion chamber to flame flashback in the mixing tube. Particular attention was placed on the flame behavior/dynamics near the lean blow out (LBO). The flow field featured a central recirculation zone (CRZ), and an annular swirling jet with internal and external shears layers. The movement of the flame front relative to the upstream stagnation point of the vortex breakdown at different conditions was studied. Simultaneous planar measurements using laser diagnostics, namely, Planar Laser Induced Fluorescence (PLIF) of OH radicals and Particle Image Velocimetry (PIV), have been carried out. With mixing tube and at lean cases, vortex breakdown and the flame holding occurred close to the tube exit. As the equivalence ratio was increased, the flame entered intermittently into the premixing tube. Increasing further the equivalence ratio, the flame was stabilized inside the premixing tube. Different statistical evaluations were performed on the data to obtain better understanding of the flame stabilization mechanism. They included PDF of the axial velocity, mean velocity field and mean intensity of the OH radical, two-dimensional correlation between PIV and LIF data, POD analysis of the velocity vectors, distribution of OH radical intensity and binary images of density distribution of the seeding particles.
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| 5. |
- Iudiciani, Piero, et al.
(författare)
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Characterization of a multi-swirler fuel injector using simultaneous laser based planar measurements of reaction zone, flow field and fuel distribution
- 2009
-
Ingår i: Proceedings Of The Asme Turbo Expo 2009, Vol 2. - 9780791848838 ; 2, s. 1041-1052
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Konferensbidrag (refereegranskat)abstract
- Modern gas turbine spray combustors feature multiple swirlers with distributed fuel injection system for rapid fuel/air mixing and flame stabilization ensuring low NOx operations. In the present paper, we investigate the effects of different swirler designs on flame characteristics, stabilization, and behavior at lean blow out using a Triple Annular Research Swirler (TARS) burner. Simultaneous planar measurements using laser diagnostics, namely, Planar Laser Induced Fluorescence (LW) of OH radicals indicating the reacting zone, LW Acetone indicating unburnt fuel distribution and Particle Image Velocimetry (PIV) for flow field mapping, were applied to study the flow dynamics, fuel distribution and flame dynamics for different swirler geometries, air flow rates, and equivalence ratios. Both axial and nearly perpendicular to axis cross-sectional planes were investigated. The three swirler configurations allowed getting stable and repeatable flames over a wide range of different flow and fuel equivalence ratio conditions, confirming the good flexibility and operability of the TARS burner. Averaged fields are presented to compare the effect of different flow conditions using the same swirler configuration, and the effect of different swirler configurations at the same flow conditions. LIF and PIV instantaneous samples are also shown, both in axial and cross sectional planes, with structures captured in detail. Perfect matching is found between unburnt and burnt field, as well as agreement between axial and cross-sectional measurements. Particular attention has been placed on unstable flames and a highly unsteady flame near the lean blow out (LBO) is shown. Local extinctions are occasionally seen on instantaneous snapshots. Unsteadiness of such flame is suitable to exemplify the use of Proper Orthogonal Decomposition (POD) analysis that identifies the most "energetic" large scale structures or modes of the flame. In particular, rotational and helical modes are observed which can contribute to the swirling flame instability. The results show the effect of the strength and rotation direction of the swirlers can lead to strong flame stratification or to a more homogenous flames. Analysis of the flame dynamics, indicates that the flame can be stabilized dynamically without the presence of a Central Recirculation Zone (CRZ) through flame quenching and flame propagation.
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| 6. |
- Iudiciani, Piero, et al.
(författare)
-
Proper Orthogonal Decomposition for experimental investigation of swirling flame instabilities
- 2010
-
Ingår i: Paper AIAA 2010-584. - Reston, Virigina : American Institute of Aeronautics and Astronautics.
-
Konferensbidrag (refereegranskat)abstract
- An experimental investigation of both confined and unconfined flames on a Triple Annular Research Swirler (TARS) is presented. The paper focuses on post-processing techniques aiming at extracting information on the dynamics that are lost through classical statistics approach. POD together with a derived a-posteriori phase averaging procedure successfully reconstructed the dynamics of flames under thermo-acoustic instabilities in the confined case. For unconfined flames, an analysis of the azimuthal modes is performed.
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| 7. |
- Szász, Robert-Zoltán, et al.
(författare)
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Algorithm for automatic quantification of flashback and flash forward events from high-speed chemiluminescence recordings
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer Science+Business Media B.V.. - 9783319306001 - 9783319306025 ; , s. 519-526
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Konferensbidrag (refereegranskat)abstract
- Three methods are employed to identify and quantify flashback and flash forward events based on chemiluminescence recordings of swirling flames. The approaches differ in the procedure to determine the instantaneous flame position. The results revealed that the most robust method is to determine a threshold relative to the instantaneous maximum intensity. Analysis of the complete dataset indicated that flashback events are significantly slower than flash forward events.
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| 8. |
- Al Shemaili, Jasem, et al.
(författare)
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Pharmacokinetics in Mouse and Comparative Effects of Frondosides in Pancreatic Cancer
- 2016
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Ingår i: Marine Drugs. - : MDPI AG. - 1660-3397. ; 14:6
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Tidskriftsartikel (refereegranskat)abstract
- The frondosides are triterpenoid glycosides from the Atlantic sea cucumber Cucumaria frondosa. Frondoside A inhibits growth, invasion, metastases and angiogenesis and induces apoptosis in diverse cancer types, including pancreatic cancer. We compared the growth inhibitory effects of three frondosides and their aglycone and related this to the pharmocokinetics and route of administration. Frondoside A potently inhibited growth of pancreatic cancer cells with an EC50 of similar to 1 mu M. Frondoside B was less potent (EC50 similar to 2.5 mu M). Frondoside C and the aglycone had no effect. At 100 mu g/kg, frondoside A administered to CD2F1 mice as an i.v. bolus, the Cp-max was 129 nM, Cl-tb was 6.35 mL/min/m(2), and half-life was 510 min. With i.p. administration the Cp-max was 18.3 nM, Cl-tb was 127 mL/min/m(2) and half-life was 840 min. Oral dosing was ineffective. Frondoside A (100 mu g/kg/day i.p.) markedly inhibited growth cancer xenografts in nude mice. The same dose delivered by oral gavage had no effect. No evidence of acute toxicity was seen with frondoside A. Frondoside A is more potent inhibitor of cancer growth than other frondosides. The glycoside component is essential for bioactivity. Frondoside A is only effective when administered systemically. Based on the current and previous studies, frondoside A appears safe and may be valuable in the treatment of cancer.
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| 9. |
- Andersson, Öivind, et al.
(författare)
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Laser-Rayleigh Imaging of DME Sprays in an Optically Accessible DI Diesel Truck Engine
- 2001
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Ingår i: SAE Technical Paper 2001-01-0915. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
-
Konferensbidrag (refereegranskat)abstract
- Laser-Rayleigh imaging has been employed to measure the relative fuel concentration in the gaseous jet region of DME sprays. The measurements were performed in an optically accessible diesel truck engine equipped with a common rail injection system. A one-hole nozzle was used to guarantee that the recorded pressure history was associated with the heat release in the imaged spray. To compensate for the low compression ratio in the modified engine the inlet air was preheated. Spray development was studied for two levels of preheating, from the start of injection to the point where all fuel was consumed. The results indicate that there is a strong correlation between the amount of unburned fuel present in the cylinder and the rate of heat release at a given time. The combustion can not be described as purely premixed or purely mixing-controlled at any time, but always has an element of both. After all fuel appears to have vanished there is still an extended period of heat release. This indicates a rich combustion yielding combustible products.
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| 10. |
- Andersson, Öivind, et al.
(författare)
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Quantitative Imaging of Equivalence Ratios in DME Sprays Using a Chemically Preheated Combustion Vessel
- 2000
-
Ingår i: SAE technical paper series, paper 2000-01-5785. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
-
Konferensbidrag (refereegranskat)abstract
- Dimethyl Ether (DME) has proved to be a promising fuel for diesel engines. It virtually eliminates particulate emissions and reduces the formation of nitrogenous oxides, without negatively affecting engine efficiency. Obtaining a deeper understanding of the mechanisms behind these properties is thus highly desirable. Various authors have suggested that the low NO emissions associated with DME are an effect of the mixing conditions, which are thought to differ from those of diesel sprays. To examine this, laser-Rayleigh imaging was employed for quantitative measurement of the local equivalence ratios in DME sprays. The quantitative images were analyzed using a statistical approach, in which probability distributions of ϕ -values for burning and for non-reacting sprays were compared. It was concluded that the diffusion flame is established in the stoichiometeric or slightly lean regions of the spray. Measurements were performed in an isochoric combustion vessel chemically preheated by igniting a lean mixture of CO and oxygen-enriched air. A multizone combustion model was used to analyze the DME combustion and the effects of preheating on the vessel atmosphere. The benefits and drawbacks of this set-up are discussed.
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| 11. |
- Arason, Magnús, et al.
(författare)
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Strengthening of steel girder bridges using coiled pins
- 2019
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Ingår i: 20th Congress of IABSE 2019. - Zurich, Switzerland : International Association for Bridge and Structural Engineering (IABSE). ; , s. 38-43
-
Konferensbidrag (refereegranskat)abstract
- A requirement for heavier vehicular transport on the Norwegian road network has resulted in a demand for increased bearing capacity for many of the older bridges in the country. Many of the bridges that have been found to have insufficient capacity against present-day demands are steel girder bridges with concrete slabs without a shear connection between steel and concrete. There is a large number of bridges of this type in Norway and the paper presents strengthening of two of those, in Aust-Agder county in the south of the country. These bridges are approximately 30 m long, single span. The bearing capacity has been upgraded by installing composite action between the steel girders and the concrete slab using coiled pins, in conjunction with thickening of the bottom flange of the steel girders. To obtain composite action, the pins are fitted to tightly drilled holes through the top flange of girders up into the concrete slab. Coiled pins have not been used much for bridge applications. In the work presented, the method has been found to have advantages in terms of cost and workability. Furthermore, the method has benefits when viewed from an environmental standpoint, since it allows strengthening of existing non-composite bridges using relatively little new material, and minimizes traffic disruptions.
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| 12. |
- Axelsson, Boman, et al.
(författare)
-
Laser-induced incandescence for soot particle size and volume fraction measurements using on-line extinction calibration
- 2001
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 72:3, s. 367-372
-
Tidskriftsartikel (refereegranskat)abstract
- A novel technique for two-dimensional measurements of soot volume fraction and particle size has been developed. It is based on a combined measurement of extinction and laser-induced incandescence using Nd:YAG laser wavelengths of 532 nm and 1064 nm. A low-energy laser pulse at 532 nm was used for extinction measurements and was followed by a more intense pulse at 1064 nm, delayed by 15 ns, for LII measurements. The 532-nm beam was split into a signal beam passing the flame and a reference beam, both of which were directed to a dye cell. The resulting fluorescence signals, from which the extinction was deduced, together with the LII signal, were registered on a single CCD detector. Thus the two-dimensional LII image could be converted to a soot volume fraction map through a calibration procedure during the same laser shot. The soot particle sizes were evaluated from the ratio of the temporal LII signals at two gate time positions. The uncertainty in the particle sizing arose mainly from the low signal for small particles at long gate times and the uncertainty in the flame temperature. The technique was applied to a well-characterized premixed flat flame, the soot properties of which had been previously thoroughly investigated.
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| 13. |
- Axelsson, Boman, et al.
(författare)
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Laser-Induced Incandescence for Soot Particle Size Measurements in Premixed Flat Flames
- 2000
-
Ingår i: Applied Optics. - 2155-3165. ; 39:21, s. 3683-3690
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of soot properties by means of laser-induced incandescence (LII) and combined scattering–extinction were performed in well-characterized premixed ethylene–air flames. In particular, the possibility of using LII as a tool for quantitative particle sizing was investigated. Particle sizes were evaluated from the temporal decay of the LII signal combined with heat balance modeling of laser-heated particles, and these sizes were compared with the particle sizes deduced from scattering–extinction measurements based on isotropic sphere theory. The correspondence was good early in the soot-formation process but less good at later stages, possibly because aggregation to clusters began to occur. A critical analysis has been made of how uncertainties in different parameters, both experimental and in the model, affect the evaluated particle sizes for LII. A sensitivity analysis of the LII model identified the ambient-flame temperature as a major source of uncertainty in the evaluated particle size, a conclusion that was supported by an analysis based on temporal LII profiles.
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| 14. |
- Baudoin, Eric, et al.
(författare)
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Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames
- 2013
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Ingår i: Flow, Turbulence and Combustion. - : Springer Science and Business Media LLC. - 1573-1987 .- 1386-6184. ; 90:2, s. 269-284
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedThe stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime, significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.
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| 15. |
- Baudoin, Eric, et al.
(författare)
-
Effect of partial premixing on stabilization and local extinction of turbulent methane/air flames
- 2011
-
Ingår i: Proceedings of the 17th Mediterranean Combustion symposium, MCS 7. - 9788888104126
-
Konferensbidrag (refereegranskat)abstract
- The stabilization characteristics and local extinction structures of partially premixed methane/air flames were studied using simultaneous OH-PLIF/PIV techniques, and large eddy simulations employing a two-scalar flamelet model. Partial premixing was made in a mixing chamber comprised of two concentric tubes, where the degree of partial premixing of fuel and air was controlled by varying the mixing length of the chamber. At the exit of the mixing chamber a cone was mounted to stabilize the flames at high turbulence intensities. The stability regime of flames was determined for different degree of partial premixing and Reynolds numbers. It was found that in general partially premixed flames at low Reynolds numbers become more stable when the level of partial premixing of air to the fuel stream decreases. At high Reynolds numbers, for the presently studied burner configuration there is an optimal partial premixing level of air to the fuel stream at which the flame is most stable. OH-PLIF images revealed that for the stable flames not very close to the blowout regime,significant local extinction holes appear already. By increasing premixing air to fuel stream successively, local extinction holes grow in size leading to eventual flame blowout. Local flame extinction was found to frequently attain to locations where locally high velocity flows impinging to the flame. The local flame extinction poses a future challenge for model simulations and the present flames provide a possible test case for such study.
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| 16. |
- Brown, Brielin C., et al.
(författare)
-
Multiset correlation and factor analysis enables exploration of multi-omics data
- 2023
-
Ingår i: Cell Genomics. - : Elsevier BV. - 2666-979X. ; 3:8, s. 100359-
-
Tidskriftsartikel (refereegranskat)abstract
- Multi-omics datasets are becoming more common, necessitating better integration methods to realize their revolutionary potential. Here, we introduce multi-set correlation and factor analysis (MCFA), an unsupervised integration method tailored to the unique challenges of high-dimensional genomics data that enables fast inference of shared and private factors. We used MCFA to integrate methylation markers, protein expression, RNA expression, and metabolite levels in 614 diverse samples from the Trans-Omics for Precision Medicine/Multi-Ethnic Study of Atherosclerosis multi-omics pilot. Samples cluster strongly by ancestry in the shared space, even in the absence of genetic information, while private spaces frequently capture dataset-specific technical variation. Finally, we integrated genetic data by conducting a genome-wide association study (GWAS) of our inferred factors, observing that several factors are enriched for GWAS hits and trans-expression quantitative trait loci. Two of these factors appear to be related to metabolic disease. Our study provides a foundation and framework for further integrative analysis of ever larger multi-modal genomic datasets.
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| 17. |
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| 18. |
- Chartier, Clement, et al.
(författare)
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Analysis of Smokeless Spray Combustion in a Heavy-Duty Diesel Engine by Combined Simultaneous Optical Diagnostics
- 2009
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2009-01-1353
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A heavy-duty diesel engine operating case producing no engine-out smoke was studied using combined simultaneous optical diagnostics. The case was close to a typical low-load modern diesel operating point without EGR. Parallels were drawn to the conceptual model by Dec and results from high-pressure combustion vessels. Optical results revealed that no soot was present in the upstream part of the jet cross-section. Soot was only observed in the recirculation zones close to the bowl perimeter. This indicated very slow soot formation and was explained by a significantly higher air entrainment rate than in Dec's study. The local fuel-air equivalence ratio, Φ, at the lift-off length was estimated to be 40% of the value in Dec's study. The lower Φ in the jet produced a different Φ-T history, explaining the soot results. The increased air entrainment rate was mainly due to smaller nozzle holes and increased TDC density. Furthermore, increased injection pressure was believed to reduce the residence time in the jet, thus reducing the soot formation. OH was detected at the periphery of the jet, upstream of the location where fuel started to react on the jet centerline. The OH region extended relatively far into the jet, further supporting the conclusion of a less fuel-rich jet in the current case. Partially oxidized fuel (POF) was found at the center of the jet, downstream of the lift-off position. This indicated that the temperature needed to start chemical reactions inside the jet had not been obtained at the lift-off position. The high-temperature reaction zone at the periphery thus added heat over a distance before POF was observed on the centerline.
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| 19. |
- Cinthio, Magnus, et al.
(författare)
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Instruktioner för laborationsrapportskrivande
- 2008
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Ingår i: [Host publication title missing].
-
Konferensbidrag (refereegranskat)abstract
- I denna undersökning studeras hur laborations- rapporter vid LTH motiveras som pedagogiskt moment, hur skrivinstruktionerna är relaterade till lärandemomentet, och om detta kan förbättras. Det visar sig att de flesta instruktioner endast mycket kortfattat motiverar varför laborationsrapporter skrivs även om kursansvariga har ambitiösa mål med momentet. I skrivinstruktionerna finns ofta fler dispositions- och formaliainstruktioner än sådana som syftar till reflektion, till att förbättra skrivandet eller som uppmuntrar till vetenskapligt tänkande. Ett intressant angreppssätt, LabWrite, används vid North Carolina State University at Rayleigh, USA, där laboration och rapport används som ett sätt för studenten att också lära sig ett vetenskapligt förhållningssätt. LabWrite är intressant, men som första steg anser vi att instruktionen kan göras tydligare. Ett förslag är att dela upp den i tre distinkta delar; instruktioner som syftar till kritiskt tänkande, instruktioner om disposition och layout och slutligen instruktioner av teknisk karaktär.
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| 20. |
- Collin, Peter, et al.
(författare)
-
International workshop on strengthening of steel/composite bridges
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The European infrastructure is rapidly aging, and steel/composite bridges are noexception to the rule. With thousands of older steel/composite bridges, there is ademand of rational methods to strengthen the older bridges to compensate not onlyfor their age, but also for higher loads and new codes, of which perhaps the newfatigue rules for highway bridges in EC3-2 will be the hardest to meet.Within the frames of the European R&D project Prolife (RFCS-CT-2015-00025) aworkshop was arranged in Stockholm September 28th 2015. Bridge owners,designers and researchers from 12 countries participated, and the similaritiesbetween the countries as well as the variety of technical solutions were highlighted.The contributions are presented in this report and the organizers want to thank allparticipants for making this seminar successful.
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| 21. |
- Collin, Robert
(författare)
-
Laser Diagnostics for Applications to In-Cylinder Engine Investigations
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the work presented in the thesis laser diagnostics was employed primarily in the investigation of engines, but was also used to study soot in flames. Quantitative measurements were performed for visualizing both in-cylinder soot formation and DME sprays in a combustion vessel. The DME sprays inside a diesel truck engine were also qualitatively investigated. The combustion process in the HCCI engine was studied as well. Two species, formaldehyde and OH, were detected there simultaneously. Laser-induced incandescence (LII) was used in the work with soot diagnostics to measure soot concentrations, the potential for soot particle sizing also being investigated. Early in the work, various fundamental studies were performed in well-characterized flames in which results using the LII technique were compared with measurements performed by means of the scattering-extinction technique. As an extension of this work, LII was combined with an extinction measurement to provide on-line calibration of quantitative measurements of soot volume fractions. LII was also employed to investigate soot production in the cylinder of a gasoline direct-injection engine. Quantitative soot volume fraction distributions were obtained from the engine after calibrating the LII technique against a small, premixed well-defined flame. In the second part of the thesis, the use of dimethyl ether (DME) sprays as fuel for diesel engines was investigated. Laser-Rayleigh imaging was applied to obtain quantitative images of the local equivalence ratios for the DME sprays. Before any of the engine measurements were performed, the mixing conditions of both burning and non-burning DME sprays were investigated in a chemically pre-heated combustion vessel. These measurements were followed up by in-cylinder investigation of the use of DME spray in a diesel truck engine. The development of the spray was studied from the start of injection until all the fuel was consumed. In the final part of the work, ignition and combustion processes in the HCCI engine were investigated by means of laser-induced fluorescence (LIF). Two species, formaldehyde and OH, were imaged simultaneously. The formaldehyde formed as an intermediate during an early stage of the combustion process served as an indicator of low-temperature reactions. The OH radical, in turn, an important intermediate formed in high-temperature regions during combustion, was used as an indicator of regions in which HCCI combustion was underway. How the combustion process is affected by changes in the homogeneity of the fuel-air mixture that arises from early versus late injection timing, was investigated. During the data evaluation there was a need of defining an index of homogeneity in order to compare the homogeneity of the signal distribution in the different measurements. The effect of fuel volatility on HCCI combustion was also investigated, fuels of low and high volatility, respectively, being employed.
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| 22. |
- Collin, Robert, et al.
(författare)
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Simultaneous OH- and Formaldehyde-LIF Measurements in an HCCI Engine
- 2003
-
Ingår i: SAE Transactions, Journal of Fuels and Lubricants. - 0096-736X. ; 112:4, s. 2479-2486
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous OH- and formaldehyde LIF measurements have been performed in an HCCI engine using two laser sources working on 283 and 355 nm, respectively. Two ICCD camera systems, equipped with long-pass filters, were used to collect the LIF signals. The simultaneous images of OH and formaldehyde were compared with heat-release calculated from the pressure-trace matching the cycle for the LIF measurements. The measurements were performed on a 0.5-l, single-cylinder optical engine equipped with port-fuel injection system. A blend of iso-octane and n-heptane was used as fuel and the compression ratio was set to 12:1. The width of the laser sheet was 40 mm and hence covered approximately half of the cylinder bore. At some 20 CAD BTDC low temperature reactions are present and formaldehyde is formed. The formaldehyde signal is then rather constant until the main heat-release starts just before TDC, where the signal decreases rapidly to low values. From some 15 CAD to 5 CAD BTDC the formaldehyde is uniformly distributed in the imaged area. As formaldehyde decreases, OH increases and follows the main rate of heat release curve, though with a slight lag in phase. Thereafter OH is formed in the areas from which the formaldehyde has disappeared and the OH signal is present to some 20 CAD ATDC.
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| 23. |
- Collin, Robert, et al.
(författare)
-
Studies of the Combustion Process with Simultaneous OH- and Formaldehyde-PLIF in a Direct-Injected HCCI engine
- 2004
-
Ingår i: [Host publication title missing]. ; , s. 311-317
-
Konferensbidrag (refereegranskat)abstract
- To run a Diesel engine in Homogeneous Charge Compression Ignition (HCCI) mode has proved to be a highly promising approach towards reduced engine-out emissions of NOx and particulate matter. A crucial issue when utilizing HCCI is the degree of charge homogeneity that is required to achieve the desired low temperature combustion. A very well mixed charge can be created through the use of traditional port injection. This approach would most often result in low emissions of NOx and soot. However, this strategy might also see a penalty in the form of high levels of unburned hydrocarbons due to incomplete combustion, especially under low load conditions. A proposed solution to this is to utilize stratified charge in the lower load range. The creation of a stratified charge imposes no major problems in modern DI engines. The important parameter is the degree of stratification that can be tolerated. If the charge gets too highly stratified, the combustion will become more diesel-like with dramatically increased levels of NOx and soot as a result. This paper presents simultaneous laser based measurements of formaldehyde and OH-radical distributions in an HCCI engine. Formaldehyde is formed as an intermediate species when combusting hydrocarbons. The formation occurs through low temperature reactions in an early phase of the combustion process. Later in the process formaldehyde is being consumed. Formaldehyde is, therefore, used as indicator of the first stage of combustion and a marker of zones with low-temperature reactions. The OH radical is formed as an intermediate during the high temperature reactions, and is used as a marker of zones where the combustion is ongoing. The purpose of the investigation was to study how the combustion process is affected by the change in homogeneity that arises from early and late injection, respectively. A 0.5 liter single-cylinder optical engine equipped with a DI common rail fuel system was operated with a number of different injection timings, resulting in various levels of charge stratification. A blend of iso-octane and n-heptane was used as fuel. The measurement technique used was planar laser-induced fluorescence where formaldehyde was excited at 355nm and OH at 283nm. Two separate ICCD units were used to detect the resulting fluorescence from formaldehyde and OH. Measurement series covering the process from the start of injection until late in the expansion stroke is presented for different injection timings as well as pressure traces and emission analysis. A homogeneity index is calculated and used to compare the level of homogeneity resulting from injection timings. From early injection until about 50CAD BTDC the time, between onset of low temperature reactions and start of the high temperature reactions, is long enough for the formaldehyde to form an almost homogeneous distribution before it is being consumed. For later injection timings the high temperature reactions starts before this mixing is completed and therefore the formaldehyde distribution is not longer homogeneous and the combustion is more diesel like.
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| 24. |
- Collin, Robert, et al.
(författare)
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The Effect of Fuel Volatility on Hcci Using Simultaneous Formaldehyde and Oh Plif
- 2004
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2004-01-2948
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous formaldehyde and OH PLIF have been applied in a direct-injected HCCI engine. The engine is a 0.5 l single-cylinder optical engine equipped with EGR system. PLIF measurements were performed with the engine run with two different fuels of low and high volatility, respectively. Different ratios of EGR were also examined. The aim of the study was to investigate how fuels with different volatility and EGR affect the HCCI combustion and measurements were performed for early and late injection timings. Measurements are presented for different injection timings showing formaldehyde and OH from start of injection until late in the expansion stroke. Also, formaldehyde distributions obtained from after the low temperature regime and before the high temperature regime are studied for different tuning of the start of injection from 300 CAD to 20 CAD before top dead center. In this investigation the spatial homogeneity of the formaldehyde distributions and the surface fraction of LIF signal covering the image are compared for the different fuels and EGR ratios.
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| 25. |
- Cvijovic, Marija, 1977, et al.
(författare)
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Strategies for structuring interdisciplinary education in systems biology: An European perspective
- 2016
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Ingår i: npj Systems Biology and Applications. - : Springer Science and Business Media LLC. - 2056-7189. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- Systems Biology is an approach to biology and medicine that has the potential to lead to a better understanding of how biological properties emerge from the interaction of genes, proteins, molecules, cells and organisms. The approach aims at elucidating how these interactions govern biological function by employing experimental data, mathematical models and computational simulations. As Systems Biology is inherently multidisciplinary, education within this field meets numerous hurdles including departmental barriers, availability of all required expertise locally, appropriate teaching material and example curricula. As university education at the Bachelor’s level is traditionally built upon disciplinary degrees, we believe that the most effective way to implement education in Systems Biology would be at the Master’s level, as it offers a more flexible framework. Our team of experts and active performers of Systems Biology education suggest here (i) a definition of the skills that students should acquire within a Master’s programme in Systems Biology, (ii) a possible basic educational curriculum with flexibility to adjust to different application areas and local research strengths, (iii) a description of possible career paths for students who undergo such an education, (iv) conditions that should improve the recruitment of students to such programmes and (v) mechanisms for collaboration and excellence spreading among education professionals. With the growing interest of industry in applying Systems Biology approaches in their fields, a concerted action between academia and industry is needed to build this expertise. Here we present a reflection of the European situation and expertise, where most of the challenges we discuss are universal, anticipating that our suggestions will be useful internationally. We believe that one of the overriding goals of any Systems Biology education should be a student’s ability to phrase and communicate research questions in such a manner that they can be solved by the integration of experiments and modelling, as well as to communicate and collaborate productively across different experimental and theoretical disciplines in research and development.
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| 26. |
- Gaulton, Kyle J, et al.
(författare)
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Genetic fine mapping and genomic annotation defines causal mechanisms at type 2 diabetes susceptibility loci.
- 2015
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 47:12, s. 1415-1415
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Tidskriftsartikel (refereegranskat)abstract
- We performed fine mapping of 39 established type 2 diabetes (T2D) loci in 27,206 cases and 57,574 controls of European ancestry. We identified 49 distinct association signals at these loci, including five mapping in or near KCNQ1. 'Credible sets' of the variants most likely to drive each distinct signal mapped predominantly to noncoding sequence, implying that association with T2D is mediated through gene regulation. Credible set variants were enriched for overlap with FOXA2 chromatin immunoprecipitation binding sites in human islet and liver cells, including at MTNR1B, where fine mapping implicated rs10830963 as driving T2D association. We confirmed that the T2D risk allele for this SNP increases FOXA2-bound enhancer activity in islet- and liver-derived cells. We observed allele-specific differences in NEUROD1 binding in islet-derived cells, consistent with evidence that the T2D risk allele increases islet MTNR1B expression. Our study demonstrates how integration of genetic and genomic information can define molecular mechanisms through which variants underlying association signals exert their effects on disease.
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| 27. |
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| 28. |
- Hasegawa, Ryo, et al.
(författare)
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Influence of homogeneity on HCCI combustion
- 2005
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Ingår i: AutoTechnology. - 1616-8216. ; 5:3, s. 48-51
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A new laser technique for detecting the air/fuel mixture in the combustion process is presented as a method for improving cycle-by-cycle variations in an HCCI engine.
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| 29. |
- Hermansson, Åke, et al.
(författare)
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Heat Transfer in Soils
- 2009
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Ingår i: Water in Road Structures. - Dordrecht : Springer. ; , s. 69-79
-
Bokkapitel (refereegranskat)abstract
- Temperature highly affects pavement performance. High and low temperatures not only affects the viscosity of asphalt concrete but also has an impact on the moisture flow within pavements. At temperatures below 0°C the freezing of pavements dramatically changes the permeability and frost action might occur forcing water to flow upwards to the freezing front resulting in frost heave and other pavement distress.
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| 30. |
- Hildingsson, Leif, et al.
(författare)
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Optical Diagnostics of Hcci and Low-Temperature Diesel Using Simultaneous 2-D Plif of Oh and Formaldehyde
- 2004
-
Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; :2004-01-2949
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous OH- and formaldehyde planar-LIF measurements have been performed in an optical engine using two laser sources working on 283 and 355 nm, respectively. The engine used for the measurements was a car diesel engine converted to single-cylinder operation and modified for optical access. The fuel, n-heptane, was injected by a direct injection common-rail system and the engine was also fitted with an EGR system. The engine was operated in both HCCI mode and diesel mode. Due to the low load, the diesel mode resulted in low-temperature diesel combustion and because of limitations in maximum pressure and maximum rate of pressure increase of the optical engine, the diesel mode was run at a higher EGR percentage than the HCCI mode to slow down the combustion. A third mode, pilot combustion, was also investigated. This pilot combustion is created by an injection at 30 CAD before TDC followed by a second injection just before TDC. The OH and formaldehyde LIF images were compared with the heat-release calculated from the pressure traces. Analyses of the emissions, of for example NOx and HC, were also performed for the different operating modes.
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| 31. |
- Hildingsson, Leif, et al.
(författare)
-
Optical Diagnostics of HCCI and UNIBUS Using 2-D PLIF of OH and Formaldehyde
- 2005
-
Ingår i: SAE technical paper series.
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous OH- and formaldehyde planar-LIF measurements have been performed in an optical engine using two laser sources working on 283 and 355 nm, respectively. The measurements were performed in a light- duty diesel engine, using n-heptane as fuel, converted to single- cylinder operation and modified for optical access. It was also equipped with a direct-injection, common-rail system as well as an EGR system. The engine was operated in both HCCI mode, using a single fuel injection, and UNIBUS (Uniform Bulky Combustion System) mode, using two injections of fuel with one of the injections at 50 CAD before TDC and the other one just before TDC. The OH and formaldehyde LIF images were compared with the heat- release calculated from the pressure-traces. Analyses of the emissions, for example NOx and HC, were also performed for the different operating conditions.
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| 32. |
- Hult, Johan, et al.
(författare)
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Quantitative three-dimensional imaging of soot volume fraction in turbulent non-premixed flames
- 2002
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Ingår i: Experiments in Fluids. - : Springer Science and Business Media LLC. - 1432-1114 .- 0723-4864. ; 33:2, s. 265-269
-
Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional (3-D) imaging system for studies of reactive and non-reactive flows is described. It can be used to reveal the topology of turbulent structures and to extract 3-D quantities, such as concentration gradients. Measurements are performed using a high repetition rate laser and detector system in combination with a scanning mirror. In this study, the system is used for laser-induced incandescence measurements to obtain quantitative 3-D soot volume fraction distributions in both laminar and turbulent non-premixed flames. From the acquired data, iso-concentration surfaces are visualised and concentration gradients calculated.
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| 33. |
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| 34. |
- Hällmark, Robert, 1981-
(författare)
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Composite Bridges : Innovative ways of achieving composite action
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The topic of this thesis is steel-concrete composite bridges and innovative ways of achieving composite action. The typical superstructure consists of three main components: the steel girders, the concrete deck slab and the shear connectors. The latter connects the steel and the concrete parts to each other, which enables a design where the parts are assumed to act as one structural member, the composite beam.The research presented in this thesis is primarily focused on different construction- and strengthening-methods, developed to reduce the impact on the road users, mainly by reducing the time spent on the construction site and the need of traffic restrictions.The prefabricated steel girders give composite bridges some advantages in the construction stage, in comparison to the more common in-situ cast concrete bridges, since the girders can be launched or lifted into their final positions. Such an installation procedure is often favourable in case of crossings over roads, railways, rivers etc., since it minimizes the impact on the citizens using the infrastructure below the bridges and the need of temporary supports. In order to shorten the time spent on the construction site and to reduce the impact on the road users even more, prefabrication of the concrete deck can also be considered.In this thesis, a review of different prefabrication techniques for composite bridges is presented, along with a study of one specific prefabrication concept that reduces the need of in-situ cast deck joints. This concept, with prefabricated concrete deck elements with dry joints, utilizes concrete shear keys to transfer shear forces over the transverse deck joints, while in-situ cast joints are used for the longitudinal connection between the steel girders and the concrete deck slab.The structural behaviour of composite bridges with dry deck joints has been investigated by large scale beam tests, along with field measurements on a composite bridge built with this prefabrication concept. The load capacity of the shear keys has also been investigated by laboratory tests. The test results have been compared to numerical analyses and different design models, with the aim of developing design recommendations.The results indicate that this type of bridges do not behave as conventional composite bridges with in-situ cast deck slabs. For single span bridges, which only experience positive bending moments, the structural behaviour in the ultimate limit state is close to the structural behaviour of conventional composite bridges. However, the degree of composite action is strongly reduced at lower load levels. This should be taken into account in the design in the fatigue- and the serviceability-limit states. Sections under negative bending moments behave in general as non-composite sections, which was expected due to the dry deck joints.Based on the evaluation of the test results and the state -of-the-art review, design recommendations and design criteria are presented, along with production and execution recommendations for this type of prefabricated bridges.Strengthening of existing bridges is another activity that often leads to traffic restrictions, which causes costs and troubles for the road users and the society. One method for strengthening non-composite steel-concrete bridges is post-installation of shear connectors, to create composite action. The composite cross-section has a larger stiffness and bending capacity, implying that a larger traffic load often can be allowed. It must however also be assured that other structural parts do not limit the load capacity of the structure.There are several different types of shear connectors that can be used for post-installation, and some are more suitable than others. This thesis presents a state-of-the-art review on post-installed shear connectors in general and Coiled Spring Pins in particular. The latter is an interference fit connector that can be installed from below the bridge, with no or minor impact on the traffic on the bridge.The behaviour of Coiled Spring Pins, used as shear connectors in composite bridges, has been investigated by experimental methods. Push-out tests have been used to study the static strength and the fatigue lifetime, while field monitoring of a real bridge structure has been used to study the behaviour on a structural level. The tests results have been evaluated and design criteria and design recommendations have been suggested.The static tests and the following analysis show that Coiled Spring Pins are a very ductile type of shear connector, with a slightly different load-deformation behaviour than headed shear studs. The static strength of the shear connection shows a quite small spread even when different parameters are varied quite a lot. The performed fatigue tests in dicate a fatigue strength that are somewhat lower than headed studs, in terms of detail category, while previous test series by other researchers indicate a higher fatigue strength than headed studs. It can be noted that there is a large scatter between the results from different test series, performed by different researchers. The reasons to this scatter are discussed in the thesis and a conservative fatigue design criterion is presented.The results from the field monitoring indicate that a bridge strengthened with Coiled Spring Pins behaves as a composite structure and that the Coiled Spring Pins reduce the slip significantly. The analysis of the test results shows that a design assuming full composite action, with rigid shear connection, describes the measured behaviour in a good way.Based on the state-of-the-art review and the different tests performed, design recommendations and criteria are presented, along with production and execution recommendations for post-installation of Coiled Spring Pins.
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| 35. |
- Hällmark, Robert, et al.
(författare)
-
Concrete shear keys in prefabricated bridges with dry deck joints
- 2011
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 2011:44
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Tidskriftsartikel (refereegranskat)abstract
- A prefabricated concrete deck with dry joints between deck elements has been developed to make prefabricated bridges even more competitive. This type of bridge deck has been used on single span bridges in Sweden, and is now under development for multi span bridges. This paper describes how the deck system works. Results from laboratory tests of shear keys between deck elements are also presented together with an analysis comparing the predicted capacity with the measured failure load.
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| 36. |
- Hällmark, Robert, et al.
(författare)
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Innovative prefabricated composite bridges
- 2009
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Ingår i: Structural Engineering International. - : Informa UK Limited. - 1016-8664 .- 1683-0350. ; 19:1, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- The competitiveness of composite bridges depends on different circumstances such as site conditions, local costs of material and staff, and the experience of the contractor. Two major advantages of composite bridges compared to concrete bridges are the ability of the steel girders to carry the weight of the formwork and the fresh concrete, and the shorter construction time which not only saves money for the contractor but even more for the road users. A further step is to prefabricate not only the steel girders, but also the concrete deck. In this paper, a new concept for composite bridges is described, with dry joints between the prefabricated concrete elements. The principal of the technique is presented, as well as some laboratory test simulating the load situation at an internal support in a multi-span bridge. Also, some experiences from an already built single span composite bridge with dry joints are presented.
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| 37. |
- Hällmark, Robert, et al.
(författare)
-
Large-scale tests on a composite bridge with prefabricated concrete deck and dry deck joints
- 2013
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Ingår i: Stahlbau. - : Wiley. - 0038-9145 .- 1437-1049. ; 82:2, s. 122-133
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the large-scale tests on a composite bridge with prefabricated deck elements and dry joints between the elements. The work is part of the European R&D project ELEM (RFCS-CT-2008-00039). This type of bridge has been used for three single-span bridges in Sweden and has contributed to minimizing construction time as well as disturbance to traffi c. The behaviour at midspan and the behaviour over an internal support of a continuous bridge were studied in the tests, and the results analysed by FEM and discussed. Conclusions regarding the design of this type of bridge are drawn, with respect to the global analysis as well as cross-section capacity.
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| 38. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Monitoring of a bridge strengthened with post-installed coiled spring pins
- 2017
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Ingår i: IABSE Symposium, Vancouver, 2017. - Zürich, Switzerland : IABSE - International Association for Bridges and Structural Engineering. - 9783857481536 ; , s. 1201-1208
-
Konferensbidrag (refereegranskat)abstract
- Many existing bridges were not originally designed for the traffic loads and the number of load cycles which they now experience. In order to increase the load capacity of non-composite steel-concrete bridges, post installed shear connectors can be used. This paper describes a field monitoring of a steel-concrete bridge which have been strengthened with post-installed coiled spring pins as shear connectors. During the monitoring, the bridge was loaded with a 31 tonnes truck placed in specific positions while strains were measured in the steel main girders, together with the horizontal slip at the steel-concrete interface. The results indicate that the coiled spring pins prevent the slip and that they can be used for strengthening purpose. It is also observed that the friction in the steel-concrete interface can contribute quite a lot to the composite action, even though that effect cannot be accounted for in the design.
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| 39. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Post-installed shear connectors : Fatigue push-out tests of coiled spring pins
- 2019
-
Ingår i: Journal of constructional steel research. - : Elsevier. - 0143-974X .- 1873-5983. ; 153, s. 298-309
-
Tidskriftsartikel (refereegranskat)abstract
- The number of heavy vehicles and their weight have been increasing over time, implying that many bridges are experiencing traffic loads with higher magnitude and frequency than they were originally designed for. In some cases, it will be necessary to either replace or strengthen the structures to keep the bridges in service. For existing non-composite steel girder bridges, post-installation of shear connectors can often be used to increase the traffic load capacity significantly. One type of shear connector that is suitable for post-installation, even though not commonly used, is the Coiled Spring Pin. These interference fit connectors can be installed from below the bridge deck during traffic, in order to minimize the impact on road users. This paper describes an experimental study on the fatigue strength of Coiled Spring Pins and a compilation of previously performed fatigue tests on this type of connector. The new test series, with nine specimens, are evaluated statistically and a fatigue strength design equation is proposed. The results show that there are large variations between different test series, while tests within the same series show good agreement. The reasons for this are discussed in the paper along with recommendations for future testing.
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| 40. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Post-Installed Shear Connectors : Monitoring a Bridge Strengthened with Coiled Spring Pins
- 2019
-
Ingår i: Structural Engineering International. - : Taylor & Francis. - 1016-8664 .- 1683-0350. ; 29:2, s. 225-233
-
Tidskriftsartikel (refereegranskat)abstract
- Traffic density and vehicle weight have been increasing over time, which implies that many existing road bridges were not designed for the high service loads and increased number of load cycles that they are subjected to today. One way to increase the traffic load capacity of non-composite steel–concrete bridges is to post-install shear connectors. This paper presents a study of a steel–concrete bridge that has been strengthened with post-installed coiled spring pins, a type of connector which can be installed from below while the bridge is still in service. The strengthening method and design procedure are presented, along with the results from field monitoring performed to evaluate the behaviour of the strengthened structure. The results from the strengthened and non-strengthened sections show that the coiled spring pins counteract the slip and increases the degree of composite action. Finite-element models of the field tests were created in order to compare the results using different design assumptions and establish a suitable level of detail for modelling the shear connectors.
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| 41. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Post-installed shear connectors : coiled spring pins
- 2016
-
Ingår i: IABSE CONGRESS, STOCKHOLM, 2016. - CH - 8093 Zürich, Switzerland. - 9783857481444 ; , s. 1227-1234
-
Konferensbidrag (refereegranskat)abstract
- Many existing bridges were not originally designed for the traffic loads and the number of load cycles which they now experience. In order to increase the load capacity of steel-concrete bridges, post installed shear connectors can be used. This paper presents a state-of the art study of postinstalled shear connectors in general and coiled spring connectors in particular
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| 42. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Post-installed Shear Connectors : Push-out Tests of Coiled Spring Pins vs. Headed Studs
- 2019
-
Ingår i: Journal of constructional steel research. - : Elsevier. - 0143-974X .- 1873-5983. ; 161, s. 1-16
-
Tidskriftsartikel (refereegranskat)abstract
- Steadily increasing traffic volumes and traffic loads lead to a continuously growing demand for bridge rehabilitation, strengthening and replacement projects. For existing steel girder bridges with non-composite concrete decks, the traffic load capacity can often be increased significantly if composite action can be created afterwards. Different kinds of shear connectors are more or less suitable for post-installation. Coiled spring pins are one type of interference fit connector that can be installed from below the bridge deck during traffic, in order to minimize the impact on road users. This paper describes an experimental study on the static capacity and stiffness of coiled spring pins used as shear connectors at steel-concrete interfaces. Six push-out test series are presented, with a total of 28 tests, together with an alternative type of test set-up. The results show that the failure of the coiled spring pins is very ductile and that the load capacity is predictable and sufficient for a cost-effective application. The tests also indicate a significantly lower stiffness of the connectors in comparison to welded headed studs of similar dimensions, which might be of great importance if an existing shear connection is strengthened.
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| 43. |
- Hällmark, Robert, et al.
(författare)
-
Prefabricated bridge construction across Europe and America
- 2012
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Ingår i: Practice Periodical on Structural Design and Construction. - 1084-0680 .- 1943-5576. ; 17:3, s. 82-92
-
Tidskriftsartikel (refereegranskat)abstract
- Determining the most efficient and economical way to build a new or replacement bridge is not as straightforward a process as it once was. The total cost of a bridge project is not limited to the amount spent on concrete, steel, and labor. Construction activities disrupt the typical flow of traffic around the project and results in additional costs to the public in the form of longer wait times, additional mileage traveled to get around the work zone, or business lost attributable to customers avoiding the construction. The risk of injury to workers because of traffic interactions or construction activities increase with each hour spent at the construction site. Finding a way to shorten the time spent on the jobsite is beneficial to the contractor, the owner, and the traveling public. Prefabricating certain bridge elements reduces the time spent at the construction site and reduces the effects on the road users and the surrounding community. For example, steel beams with composite concrete decks reduce the construction time over cast-in-place concrete superstructures. In some instances, entire structures have been fabricated off-site under strict environmental and quality controls and then shipped to the site and erected in a matter of days instead of months. The total cost of using prefabricated bridge elements (PBE) depends greatly on the scale of the prefabrication. The more that prefabrication is used, the lower the costs. Even under limited use, however, prefabrication is usually comparable to traditional construction techniques. However, when durability and user costs are taken into account, the overall cost may be significantly less than traditional pieceby-piece construction. To improve the competitiveness of prefabricated composite bridges, a European research and development project, ELEM RFSR-CT-2008-00039, was started in 2008. The overall objective of the project is to make prefabricated bridges more competitive through development of new cost-effective, time-efficient, and sustainable bridge structures. The project has started with a knowledge extension, in the form of the workshop on “Composite Bridges with Prefabricated Deck Elements.” This workshop was held in Stockholm, Sweden, in March 2009 to share the knowledge and experience gained by agencies around the globe. During the workshop, experiences from Europe and the United States were presented in an effort to promote the use of accelerated bridge construction (ABC) and prefabricated bridge elements.
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| 44. |
- Hällmark, Robert, et al.
(författare)
-
Prefabricated composite bridges
- 2009
-
Ingår i: Sustainable Infrastructure. - Zürich : International Association for Bridge and Structural Engineering. - 9783857481215 ; , s. 282-283
-
Konferensbidrag (refereegranskat)
|
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| 45. |
- Hällmark, Robert, et al.
(författare)
-
Simulation of low-cycle fatigue in integral abutment piles
- 2007
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Ingår i: Improving Infrastructure Worldwide. - Zürich : International Association for Bridge and Structural Engineering. - 9783857481161
-
Konferensbidrag (refereegranskat)abstract
- Integral abutment bridges are bridges without any expansion joints, and their largest benefits are the lower construction- and maintenance costs. In order to build longer integral bridges it might be necessary to allow plastic hinges to be developed in the piles. Lateral thermal movements are the major reason to plastic deformations, and since temperature variations are cyclic it has to be proved that low-cycle fatigue will not occur. A simulation of the pile strain spectra should be able to take into account the strains caused by temperature variations and traffic loads. Such a model has been created from real temperature data and traffic loads measured by Bridge-Weigh-In-Motion technology. Monte Carlo simulations have been performed in order to simulate daily and annual temperature changes as well as the varying traffic loads. Piles strains have been calculated, and their fatigue effect has been evaluated.
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| 46. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Strengthening Bridges with Postinstalled Coiled Spring Pin Shear Connectors : State-of-the-Art Review
- 2019
-
Ingår i: Practice Periodical on Structural Design and Construction. - : American Society of Civil Engineers (ASCE). - 1084-0680 .- 1943-5576. ; 24:1
-
Tidskriftsartikel (refereegranskat)abstract
- Many existing bridge structures experience much more significant loads and load cycles than were anticipated when the bridges were originally designed. An effective way to increase the load capacity and fatigue resistance of steel girder with non-composite concrete deck bridge structures is to retrofit the structure with shear connectors to create a composite girder-deck structure. This paper presents a state-of the art study of post-installed shear connectors in general and coiled spring connectors in particular. The strengthening method is described together with experiences from real bridge strengthening projects, along with a study of load capacity and structural behavior.
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| 47. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Testing of coiled spring pins as shear connectors
- 2017
-
Ingår i: IABSE Symposium, Vancouver, 2017. - Zürich, Switzerland : IABSE - International Association for Bridges and Structural Engineering. - 9783857481536 ; , s. 1209-1216
-
Konferensbidrag (refereegranskat)abstract
- A few decades ago, steel-concrete composite bridges were quite rare structures, whereas steel girder bridges with non-composite concrete decks were rather common. For the latter type of structure, composite action can be obtained long after the bridges were constructed by post installation of shear connectors. Most installation procedures involve reconstruction of pavement and concrete deck, which will result in traffic disturbance. There are however some types of shear connectors that can be installed from underneath, connecting the top flanges to the concrete deck, without affecting the upper surface. This means that the bridge can be strengthened during traffic. One type of such a shear connector is the coiled spring pin, which is an interference fit connector. This paper presents the results from push-out tests conducted in order to find the static capacity and the load-slip behaviour of coiled spring pins used as shear connectors.
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| 48. |
- Hällmark, Robert, 1981-, et al.
(författare)
-
Testing of composite girders with coiled spring pin shear connectors
- 2021
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Ingår i: IABSE Congress Ghent 2021. - Zurich, Switzerland : International Association for Bridge and Structural Engineering (IABSE). ; , s. 1700-1708
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Konferensbidrag (refereegranskat)abstract
- Today, steel girder bridges with concrete deck slabs are generally constructed as steel-concrete composite structures, to utilize the material and the structural parts in an efficient way. However, many existing bridges constructed before the early 1980´s were designed without shear connectors at the steel-concrete interface. With increasing traffics loads and higher amount of load cycles, there is sometimes a need to strengthen these bridges. One way to increase the bending moment capacity is to create composite action by post-installation of shear connectors. The authors have studied the concept of strengthening by post-installed shear connectors, with a focus on a connector called coiled spring pin. This paper presents the results from the first beam tests performed with this kind of shear connector. In line with the previous push-out tests, the test results indicate a very ductile shear connection, with a potential to be a material- and cost-efficient strengthening alternative.
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| 49. |
- Hällmark, Robert, et al.
(författare)
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The behaviour of a prefabricated composite bridge with dry deck joints
- 2013
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Ingår i: Structural Engineering International. - 1016-8664 .- 1683-0350. ; 23:1, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the monitoring of a one-span composite bridge in northern Sweden. The bridge was built in 2000, with prefabricated deck elements connected to steel girders, and the back walls as well as the piers were also prefabricated. The monitoring was required to clarify the doubts regarding whether a bridge with dry deck joints can be expected to perform as a conventional composite bridge, with in situ cast deck and sections with sagging moments. To get a better understanding of the long-term structural behaviour, the bridge was monitored both during 2001 and 2011, instrumented with equipment measuring the deflections and strains in the steel cross section. The bridge was loaded with a truck in midspan having a total weight of 25 t. When the truck was centred between the girders, the results showed a symmetric behaviour, with respect to deflections and stresses. For the case with the truck stationed right above one of the steel girders, anti-symmetric behaviour was observed and studied by means of finite element calculations, taking into account the stiffness of the composite section as well as the end screens and the earth pressure below them.
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| 50. |
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