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  • 1.
    Adamaitis, Piotr
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Hollow Core Cross-Laminated Timber: Less material with the same performance2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this work was to study if a hollow and 30 % lighter cross laminated timber (CLT) slab has the same structural performance for out of plane bending compared to a conventional CLT slab. Earlier research where such a hollow core CLT (HCCLT) was investigated has shown promising results. However, when producing a HCCLT slab insufficient gluing pressure may occur in some lamellas when using a hydraulic press method. Therefore, it is suggested that a vacuum press technology is applied to produce HCCLT elements.

    In this study, a five-layered solid CLT model was developed using a finite element (FE) software (Abaqus). Validation of the model was proven by comparing slab deflection at mid span with corresponding hand calculations. Results for the HCCLT slab, both for ultimate limit state (ULS) and serviceability limit state (SLS), were within standard limits for out-of-plane structural behaviour. The mechanical behaviour in out of plane loading with spaced lamellas in CLT is presented. Thereafter, a FE-model for HCCLT was developed.

    In future studies, HCCLT should be manufactured and loaded until failure by certified CLT manufacturers. Delamination tests should be carried out according to FprEN 16351. The empirical collected data from such tests should be used to develop practical calculation methods.

  • 2. Adolfi, Bengt
    et al.
    Hameury, Stephane
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jegerfors, K
    Landström, A
    Trälyftet: Ett byggsystem i massivträ för flervåningshus2005Report (Other (popular science, discussion, etc.))
    Abstract [en]

    Trälyftet" presenterar ett byggsystem - bestående av industriellt tillverkade volymer med stommar av massivträ - som gör det möjligt att bygga moderna, robusta flervåningshus av prefabricerade volymer i massivträ. Vi får ta del av forskningen bakom byggsystemet, funktionen och erfarenheterna från det första prototyphuset. Även konstruktioner och installationer beskrivs.

  • 3.
    Afridi, Muhammad Amjad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Skellefteå Municipal, Skellefteå, Sweden..
    Erlingsson, Sigurdur
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Swedish Natl Rd & Transport Res Inst VTI, Linköping, Sweden.;Univ Iceland, Fac Civil & Environm Engn, Reykjavik, Iceland..
    Sjogren, Leif
    Swedish Natl Rd & Transport Res Inst VTI, Linköping, Sweden..
    Municipal street maintenance challenges and management practices in Sweden2023In: Frontiers in Built Environment, E-ISSN 2297-3362, Vol. 9, article id 1205235Article in journal (Refereed)
    Abstract [en]

    The municipal street network acts as a multifunctional asset by providing people, vehicles and public services with a well-functioning infrastructure. To keep it in good condition, optimal maintenance measures are required which would result in an efficient use of taxpayers' money. This paper investigates the street network deterioration processes and the management practices that the municipal administrations have applied in Sweden. The study is based on a survey with Swedish municipalities using questionnaires and complementary interviews. The answers provide insight into a wide range of common pavement distresses and deterioration factors, along with pavement management practices. The study identifies that potholes, surface unevenness and alligator cracking are the most cited challenges, while pavement ageing, heavy traffic and patches are the most noted causes. Similarly, the cold climate and population density are influential factors in pavement deterioration. Allocation of the maintenance and rehabilitation and reconstruction budget is higher in the northern part of the country as well as in densely populated municipalities. Condition data collection and use of commercial Pavement Management Systems (PMS) are limited. Addressing the challenges effectively may be possible through the enhancement of the budget, feasible/clear guidelines from municipal councils/politicians, and reducing the gap between street network administrations and utility service providers.

  • 4.
    Ahmed, Lamis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Crack propagation under water pressure2018Report (Refereed)
    Abstract [en]

    Cracks in concrete structures such as a concrete dam can be exposed to water pressure, for example, uplift pressure. The water pressure can be significant and may result in cracks propagating through the structures and thus it may result in reduced service life. However, the knowledge of water pressure within the cracks is relatively limited and is often neglected or just roughly estimated. The influence of crack opening rate on the uplift pressure distribution in the crack and the pressure variation during opening or sudden crack closure are questions needed to investigate. As an attempt to answer those questions, a pilot study presented here describes the possibilities and limitations of the proposed experimental setup; and technology (penetrability meter and tomography) as an examination method for water pressure in propagation concrete cracks. The test specimens examined here are exclusively cylinders cast of concrete with or without an initial crack.

    The penetrability meter can be used to apply water pressure and to visualize the crack opening, X-Ray computed tomography test, was performed. KTH Civil and Architectural Engineering department has organized the laboratory resources.

    The examples reported in this work show that the technology and equipment have great potential for future work on crack propagation, however, sample design and preparation, as well as testing need further development.

  • 5.
    Anderson-Skold, Yvonne
    et al.
    Swedish Natl Rd & Transport Res Inst, S-58195 Linköping, Sweden.;Chalmers Univ Technol, Dept Architecture & Civil Engn, S-41296 Gothenburg, Sweden..
    Afridi, Muhammad Amjad
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Skellefteå Municipal, Stromsorgatan 15, S-93134 Skellefteå, Sweden..
    Nordin, Lina
    Swedish Natl Rd & Transport Res Inst, S-58195 Linköping, Sweden..
    Patricio, Joao
    Swedish Natl Rd & Transport Res Inst, S-58195 Linköping, Sweden..
    Lindgren, Asa
    Swedish Transport Adm, POB 3057, S-90302 Umeå, Sweden..
    Johansson, Carl-Martin
    Swedish Transport Adm, POB 3057, S-90302 Umeå, Sweden..
    Olofsson, Alexandra
    Swedish Transport Adm, POB 3057, S-90302 Umeå, Sweden..
    Andersson, Angelica
    Swedish Natl Rd & Transport Res Inst, S-58195 Linköping, Sweden.;Linköping Univ, Dept Sci & Technol, Campus Norrköping, S-60174 Norrköping, Sweden..
    Erlingsson, Sigurdur
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering. Swedish Natl Rd & Transport Res Inst, S-58195 Linköping, Sweden.;Univ Iceland, Fac Civil & Environm Engn, IS-108 Reykjavik, Iceland..
    Development of the SUNRA Tool to Improve Regional and Local Sustainability of the Transportation Sector2022In: Sustainability, E-ISSN 2071-1050, Vol. 14, no 18, p. 11275-, article id 11275Article in journal (Refereed)
    Abstract [en]

    To fulfil the global sustainable development goals (SDGs), achieving sustainable development is becoming urgent, not least in the transportation sector. In response to this, the sustainability framework Sustainability National Road Administrations (SUNRA) was developed to contribute to improving the sustainability performance of national road administrations across Europe. In the present study, the framework has been tested, applied and further developed to be applicable for target setting and follow-up at the project level at both the Swedish Transport Administration (STA) and at municipal levels. The aim was a framework relevant for investment, re-investments, maintenance and operation projects and also to make it more user applicable. The study also investigated how the framework can contribute to sustainability, identified drivers and barriers for applying the framework and examined whether the framework can be applied and adapted to projects of different complexities. The adaptations and developments were done in collaboration between researchers and practitioners. The results show that the framework could easily be used and adapted for investment, re-investment, maintenance and operation projects in the planning stage, as well as for small municipal establishments, construction or reconstruction of residential areas and frequent maintenance. The framework contributes to increased awareness on sustainability, and it provides a common structure and transparency on how infrastructure project goals/targets are set and fulfilled. The framework can also be applied to follow the fulfilment of the goals/targets and thereby adapt the project to better fulfil the goals. Identified barriers include the lack of obligations and lack of experience in using sustainability frameworks.

  • 6.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ahmed, Lamis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Computed tomography as investigation method for steel fibre reinforced tunnel shotcrete2017Conference paper (Refereed)
  • 7.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Ahmed, Lamis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Datortomografi som undersökningsmetod för ung och gammal, sprutad och gjuten betong för tunnlar2016Report (Other academic)
  • 8.
    Ansell, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Nordström, Erik
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures. Sweco Energuide, Hydro Power & Dams, Stockholm, Sweden.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Laboratory investigation of steel fibre reinforced sprayed concrete using a computed tomography method2018In: Eight International Symposium on SPRAYED CONCRETE - Modern Use of Wet Mix Sprayed Concrete for Underground Support, 2018, p. 24-38Conference paper (Refereed)
    Abstract [en]

    A laboratory method for investigation of cored samples of steel fibre reinforced sprayed concrete (shotcrete) is described. A pilot study on computed tomography (CT) has been conducted, with focus on how the technique can be used for non-destructive testing where the cores remain intact after scanning and evaluation. The CT method require advanced integrated equipment for X-ray scanning and image detection, together with a computerized visualization system that can reproduce a threedimensional virtual, transparent model of the studied object. The method is well suited to describe orientation and distribution of steel fibres within the concrete. Interfaces between rock-concrete and concrete-concrete, between layers of differentsequences ofspraying, can also be identified. The results from the CT investigations can be presented as qualitative data that in 3D shows locations of steel fibres, aggregates, etc., and also as quantitative data showing relative distributions of cement paste, aggregates, steel fibres and voids, which is here demonstrated by a selection of examples. The method is well suited for practical analysis of sprayed concrete in situ specimens and it is recommended that it is established as a standard method for special inspections and performance evaluation of rock support in tunnels and subspace structures.

  • 9. Arm, Maria
    et al.
    Wik, Ola
    Engelsen, Christian J.
    Erlandsson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Hjelmar, Ole
    Wahlström, Margareta
    How Does the European Recovery Target for Construction & Demolition Waste Affect Resource Management?2017In: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265X, Vol. 8, no 5, p. 1491-1504Article in journal (Refereed)
    Abstract [en]

    The revised EU Waste Framework Directive (WFD) includes a 70 % target for recovery of construction and demolition (C&D) waste. In order to study the potential change in the resource management of the main C&D waste fractions, as a consequence of fulfilling the WFD target, a Nordic project (ENCORT-CDW) has been performed. Waste fractions studied included asphalt, concrete, bricks, track ballast, gypsum-based construction materials and wood. Recovery scenarios were identified and estimations were made regarding expected savings of primary materials, impact on transport, and pollution and emissions. For wood waste, the main differences between re-use, material recycling and energy recovery were evaluated in a carbon footprint screening based on life cycle assessment methodology. The study concluded that the EU recovery target does not ensure a resource efficient and environmentally sustainable waste recovery in its present form since: It is very sensitive to how the legal definitions of waste and recovery are interpreted in the Member States. This means that certain construction material cycles might not count in the implementation reports while other, less efficient and environmentally safe, recovery processes of the same material will count. It is weight-based and consequently favours large and heavy waste streams. The result is that smaller flows with equal or larger resource efficiency and environmental benefit will be insignificant for reaching the target. It does not distinguish between the various recovery processes, meaning that resource efficient and environmentally safe recovery cannot be given priority. Improved knowledge on C&D waste generation and handling, as well as on content and emissions of dangerous substances, is required to achieve a sustainable recovery.

  • 10.
    Babic, Nino
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Flyttbara byggnader för bostadsändamål: Kompatibla med de nya tidsbegränsade byggloven2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Bostadsbyggandet i Sverige står inför kommande utmaningar. Bostadsbristen ökar och många av landets kommuner anser att de redan nu har en stor bostadsbrist. En orsak som ofta pekas ut är tiden det tar för kommunen att arbeta fram en detaljplan. Samtidigt skärps kraven avseende energiförbrukning för byggnader som byggs efter år 2020. Som en motåtgärd har riksdagen nyligen röstat igenom en lag som utökar möjligheterna att utnyttja de tidsbegränsade byggloven för att bygga tillfälliga bostäder. Tidsbegränsade bygglov kan då utnyttjas för att tillfälligt tillgodose behovet samtidigt som kommunen kan arbeta fram en detaljplan dit byggnaderna sedan flyttas. I detta examensarbete undersöks det hur detta skulle kunna implementera, och samtidigt bibehålla prestandan som byggnaderna är tänkte att ha.

     

    Syftet med detta arbete är att undersöka om KL-trä kan användas på ett tidigare outnyttjat sätt, genom att bygga flyttbara moduler som är kompatibla med tidsbegränsade bygglov för att på ett snabbt sätt kunna tillgodose det stora bostadsbehovet. Den stora frågan som detta examensarbete försöker att besvara är ”Hur kan man bygga flyttbara bostadshus med KL-trä som når den nya miljömålen som kommer år 2020?”. Målet är därför att göra en kartläggning och presentera lösningar på de frågor och tveksamheter som kan finnas kring flyttbara byggnader med KL-trästomme, både innan och efter flytt.

    Trä har länge använts som ett byggmaterial i norra Europa. I Sverige förstördes många städer under 1700- och 1800-talet av bränder. För att förhindra brand och brandspridning mellan byggnader infördes år 1874 ett förbud mot att bygga fler än två våningar i trä, ett förbud som varade i mer än 100 år. Detta ledde till att andra material utvecklades och tog stora marknadsandelar i flerbostadshusmarknaden. År 1994 tilläts det än en gång att bygga högt i trä i samband med att Sverige gick med i EU. Att använda trä som stommaterial har många fördelar, men innebär också specifika områden som är viktiga att ägna uppmärksamhet. KL-trä är ett relativt nytt stommaterial i Sverige och utvecklingen har lett till praktiska lösningar på de problem som är förknippade med trästommar. 

    Genom att utnyttja fördelarna som KL-trä innebär kan flerbostadshus byggas med volymelement som lever upp till dem krav som ställs på flerbostadshus enligt Boverkets byggregler, BBR. Fördelarna är bland annat låg egenvikt, låg värmekonduktivitet och en trevlig arbetsmiljö. Arbetets slutsatser är bland annat:

    • För att nå ett gott resultat i hela processen är det viktigt att planeringen håller hög kvalitet.
    • Stor vikt bör läggas på utformning av brandskydd och akustisk prestanda som lever upp till kraven på platsen för det tidsbegränsade bygglovet och på återuppställningsplatsen.*
    • I projekteringsskedet är det viktigt att se till att de valda tekniska lösningarna är lätta att installera och plocka isär. 
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    Flyttbara byggnader för bostadsändamål
  • 11.
    Bekele, Abiy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Application of Automated Non-contact Resonance Testing for Low Temperature Behavior of Asphalt Concrete2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Impact resonance testing is a well-documented non-destructive testing method and its applications on asphalt concrete have also been implemented successfully. The test is carried out manually by inducing an impact in order to excite the test specimen and taking measurements of the vibrational response. In an effort to improve the manual procedure of impact resonance testing, an automated non-contact methodology is developed and its applicability with regards to low temperature behaviors of asphalt concrete is investigated. Results from this work show that repeatable fundamental resonance frequency measurements can be performed on a disc shaped specimen in an automated manner without the need to open the thermal chamber. The measurements obtained from the new method have been verified by taking similar resonance frequency measurements using an instrumented impact hammer. It has also been shown in this work that the proposed method is suitable to investigate the lone effects of cyclic thermal conditioning on asphalt concrete without any other possible biasing effects associated with contact in the conventional testing. A hysteretic behavior of stiffness modulus is obtained on three different asphalt concrete specimens subjected to repeated low temperature cyclic conditioning. Reduced modulus values at each temperature are obtained in all the tested specimens after a low temperature stepwise conditioning at temperatures from 0oC to -40 oC. This observed behavior shows that the dynamic modulus of the tested specimens is affected by low temperature conditioning. The norm of the complex modulus decreases and the phase angle or damping ratio increases after low temperature conditioning. Hence, valuable and practical low temperature characteristics of different asphalt concrete mixtures can possibly be obtained by using the proposed methodology.

    Download full text (pdf)
    fulltext
  • 12.
    Bekele, Abiy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Automated Non-contact Resonance Excitation Method for Low Temperature Behavior of Asphalt ConcreteManuscript (preprint) (Other academic)
    Abstract [en]

    This paper studies the applicability of an automated non-destructivetesting method to monitor the stiffness of asphalt concrete at lowtemperatures. A loudspeaker is used as a source of non-contact excitation ofthe axially symmetric fundamental resonance frequencies of a disc-shapedasphalt concrete specimen positioned inside an environmental chamber. Measuredresonance frequencies are used to calculate the dynamic moduli of the specimenat different temperatures. The repeatability of the method as well as theeffect of loudspeaker height above the sample are studied. Results show thatthe main advantage of the non-contact excitation method, compared to manuallyapplied impact hammer excitation, is that repeatable automated measurements canbe performed while the specimen is placed inside an environmental temperaturechamber. This methodology enables to study the effect of only low temperatureconditioning on the dynamic modulus of asphalt concrete without interferencefrom mechanical loading.

    Download full text (pdf)
    fulltext
  • 13.
    Bekele, Abiy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Effect of Cyclic low temperature conditioning on Stiffness Modulus of Asphalt Concrete based on Non-contact Resonance testing methodManuscript (preprint) (Other academic)
    Abstract [en]

    The stiffness modulus behaviors of three different asphalt concrete specimens that are subjected to cyclic cooling and heating are monitored. In an attempt to identify the sole effect of temperature cycles and to avoid any other biasing effects such as thermal contamination that can possibly corrupt measurements, resonance frequency measurements of the specimens are taken using an automated non-contact resonance method. The resonance frequency measurements are based on the fundamental axially symmetric mode of vibration. A hysteretic effect is observed on the measured resonance frequencies of the specimens with an application of cyclic cooling and heating. Lower stiffness moduli are obtained during the heating phase of a complete cooling and heating cycle. The stiffness moduli are calculated from measured resonance frequencies of the specimens in order to show their relative reductions due to the hysteretic effect. This finding is particularly important since it enables us to observe and understand the effect of the thermal history of asphalt concrete with regards to the reversibility behavior of its stiffness modulus. The damping of the specimens is also calculated from the measured resonance frequencies at the temperatures within the applied cyclic cooling and heating. Their observed behavior is also discussed with respect to a presence of potential micro damage.

    Download full text (pdf)
    fulltext
  • 14.
    Bekele, Abiy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Evaluation of Low Temperature Damage in Asphalt Mixtures with Non-Contact Resonance Testing2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thetemperature induceddamage in asphalt mixtureshas always been a major distress that requires a substantialconsiderationin the asphalt industry. One of the most important aspects of studying temperature induceddamage is developing a practical test method for evaluation of the material’s resistanceto it. Hence, there is a growing interest in developing testing methodologieswhich are more efficient, less expensive and simpler to perform than the conventional test methods. Impact resonance testing is a well-documented non-destructive testing method,and ithas been successfully appliedon asphalt mixturesto measure their elastic and viscoelastic properties. This research aims at extending the impact resonance testing methodology to characterization of temperature induced damage in asphalt mixtures and to investigate experimentally and numerically damage induced in asphalt mixtures due to thermomechanical mismatch between the masticand aggregate phases.In order to improve temperature control and thus accuracy of the resonance testing, an automated non-contact test procedure is developedwith a loudspeakerutilized as a source of excitation.The developed methodology has been evaluatedfor a range of asphalt concrete materialsand temperatures. The measurementsobtained from the new method have been verified by taking similar resonance frequency measurements usinganinstrumented impact hammer. Results from this work show that repeatable fundamental resonance frequency measurements can be performed onadisc shaped specimen in an automated manner without the need to open thethermal chamberthat is used to condition test specimens.Investigationsofmicro-damage in asphalt concrete due to differential thermal contraction during cooling cycles havebeen carried out experimentally by using the developedautomated non-contact resonance testingcombined withcyclic cooling. The results of the experimental work haveshown the initiation of low temperature micro-damage and a hysteretic behavior of stiffness modulus during thethermal cycles. Energy based micro-mechanical model is also utilized in order to characterize themicro-crackinitiation and growthin asphalt concrete due to cyclic low temperature variations.Results of this approach have indicated the initiation of micro-cracksat low temperatures as well as the decrease in their length with increase in temperature. In order to obtain a quantitative insight into the temperature induced damage formation, a micromechanical finite element model (FEM) of asphalt mixture

    under thermal loading is developed. The model is used to investigate the damage evolution during the thermal cycles as well as its effect on material’s stiffness. Four cases ofmastic-aggregate combinations aremodelledin order to investigate effects of aggregate gradation as well as of masticpropertieson the thermal damage evolution. Cohesive Zone Model (CZM) isused to define aggregate-masticinterface so that an initiation of micro-damage due to differential thermal contraction can be probedin terms of its effect on the overall stiffness modulus. It is observed numerically that during the thermal cycles, thermal damage is initiated at the aggregate-mastic interface due to the differential contraction of mastic. It is also shown that the modelling observations are in qualitative agreement with the experimental findings from the resonance testing. Accordingly, the proposed modelling approach is a viable tool for evaluation of theeffect of asphalt mixture design on its resistance to thermally induced damage.

    Download full text (pdf)
    Abiy_PhD_Theses
  • 15.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Elaguine, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Gudmarsson, Anders
    Peab Asfalt AB, Drivhjulsvagen 11, S-12630 Hagersten, Sweden..
    Micro-mechanical modelling of low temperature-induced micro-damage initiation in asphalt concrete based on cohesive zone model2021In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 286, article id 122971Article in journal (Refereed)
    Abstract [en]

    Asphalt pavement is subjected to cyclic temperature variations during its service life owing to changes in daily and seasonal climatic conditions. These variations tend to accumulate thermally induced distress leading to initiation and evolution of micro-cracks. The effect of cyclic thermal variations as well as ther-mal incompatibility of mastic and aggregates is of major significance for understanding the behavior of thermally induced damage in pavements. Thermal stress is developed due to differential contraction of mastic relative to aggregates in asphalt concrete at low temperatures. In this paper, low temperature micro-damage initiation in asphalt concrete due to differential thermal contraction is modelled using 2D micro-mechanical volume element. Cohesive zone model (CZM) is adopted to simulate low temper-ature damage initiation at the mastic-aggregate interface (adhesive failure) within the mixtures. A cycle of cooling and heating is applied in the micro-mechanical model in order to capture the effect of thermal damage initiation on the overall stiffness modulus of the mixtures. The results from the model reveal a reduction in stiffness modulus (as compared to the values at similar temperatures within a cycle) after the temperature of-40 degrees C is reached within the applied cyclic cooling and heating. The effects of aggre-gate gradation and binder grade are also monitored by considering four cases of mixtures formed from a combination of two different gradations and two different mastics. Results of the micro-mechanical mod-elling are also compared with experimental observations of comparable mixture types.

  • 16.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Elaguine, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Civil and Architectural Engineering Laboratory.
    Gudmarsson, Anders
    KTH, School of Architecture and the Built Environment (ABE).
    Micro-mechanical Modelling of Low temperature-induced micro-damageinitiation in asphalt concrete based on Cohesive zone model2020In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526Article in journal (Refereed)
  • 17.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    Lytton, Robert L.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Application of Energy-Based Crack Initiation Approach to Low-Temperature Damage and Recovery Based on Noncontact Resonance Testing2020In: Journal of materials in civil engineering, ISSN 0899-1561, E-ISSN 1943-5533, Vol. 32, no 9, article id 04020237Article in journal (Refereed)
    Abstract [en]

    Low temperature has a tendency to cause microdamage in asphalt concrete because of the relative thermal contraction of mastic and subsequent accumulation of thermal stresses. This paper presents the applicability of an energy-based micromechanical approach for assessing low-temperature damage and recovery in asphalt concrete based on a newly developed noncontact resonance testing. The principle of local energy balance and redistribution was applied to estimate average thermal microcrack length by considering local thermal strain energy release zones and surface energy of cracks initiated at preexisting air voids. A damage probing test was carried out by thermal loading and unloading of five different asphalt concrete specimens. The test was carried out by using a recently developed noncontact resonance method. The stiffness modulus was determined from the resonance test and utilized in the energy balance and redistribution formulation. Coefficients of thermal contraction of the specimens were also determined based on the noncontact resonance test and by applying the principle of the impact-echo method and calculating changes in thickness of the test specimens.

  • 18.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Gudmarsson, Anders
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Slow dynamic diagnosis of asphalt concrete specimen to determine level of damage caused by static low temperature conditioning2017In: 43rd Annual Review of Progress in Quantitative Nondestructive Evaluation, American Institute of Physics (AIP), 2017, Vol. 1806, article id 080012Conference paper (Refereed)
    Abstract [en]

    The phenomenon of slow dynamics has been observed in a variety of materials which are considered as relatively homogeneous that exhibit nonlinearity due to the presence of defects or cracks within them. Experimental realizations in previous work suggest that slow dynamics can be in response to acoustic drives with relatively larger amplitude as well as rapid change of temperature. Slow dynamics as a nonlinear elastic response of damaged materials is manifested as a sharp drop and then recovery of resonance frequency linearly with logarithmic time. In this work, slow dynamics recovery is intended to be used as a means of identifying and evaluating thermal damage on an asphalt concrete specimen. The experimental protocol for measuring slow dynamics is based on the technique of nonlinear resonance spectroscopy and is set up with non-contact excitation using a loud speaker and the data acquisition tool box of Matlab. Sweeps of frequency with low amplitude are applied in order to probe the specimen at its linear viscoelastic state. The drop and then recovery in fundamental axially symmetric resonance frequency is observed after the specimen is exposed to sudden temperature change. The investigation of the viscoelastic contribution to the change in resonance frequency and slow dynamics can help identify micro-damage in asphalt concrete samples.

  • 19.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Gudmarsson, Anders
    Peab Asfalt AB, Drivhjulsvägen 11, Hägersten, 126 30, Sweden.
    Birgisson, Björn
    Department of Civil Engineering, Texas A&M University, 3136 TAMU, College Station, 77843-3136, TX, United States.
    Automated Non‑contact Resonance Excitation Method to Assess Low Temperature Dynamic Modulus of Asphalt Concrete2019In: Journal of nondestructive evaluation, ISSN 0195-9298, E-ISSN 1573-4862, Vol. 38, no 2Article in journal (Refereed)
    Abstract [en]

    This paper studies the applicability of an automated non-destructive testing method to monitor the stiffness of asphalt concrete at low temperatures. A loudspeaker is used as a source of non-contact excitation of the axially symmetric fundamental resonant frequencies of a disc-shaped asphalt concrete specimen positioned inside an environmental chamber. Measured resonant frequencies are used to calculate the dynamic moduli of the specimen at different temperatures. The repeatability of the method as well as the effect of loudspeaker height above the sample are studied. Results show that the main advantage of the non-contact excitation method, compared to manually applied impact hammer excitation, is that repeatable automated measurements can be performed while the specimen is placed inside an environmental temperature chamber. This methodology enables to study the effect of only low temperature conditioning on the dynamic modulus of asphalt concrete without interference from mechanical loading.

  • 20.
    Bekele, Abiy
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rydén, Nils
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Gudmarsson, Anders
    Peab Asfalt AB, Drivhjulsvagen 11, S-12630 Hagersten, Sweden..
    Birgisson, Björn
    Department of Civil Engineering, Texas A&M University, 3136 TAMU, College Station, 77843-3136, TX, United States.
    Effect of cyclic low temperature conditioning on stiffness modulus ofasphalt concrete based on non-contact resonance testing method2019In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 225, p. 502-509Article in journal (Refereed)
    Abstract [en]

    The stiffness modulus behaviors of three different asphalt concrete specimens that are subjected to cyclic cooling and heating are monitored. In an attempt to identify the sole effect of temperature cycles and to avoid any other biasing effects such as thermal contamination that can possibly corrupt measurements, resonance frequency measurements of the specimens are taken using an automated non-contact resonance method. The resonance frequency measurements are based on the fundamental axially symmetric mode of vibration. A hysteretic effect is observed on the measured resonance frequencies of the specimens with an application of cyclic cooling and heating. Lower stiffness moduli are obtained during the heating phase of a complete cooling and heating cycle. The stiffness moduli are calculated from measured resonance frequencies of the specimens in order to show their relative reductions due to the hysteretic effect. This finding is particularly important since it enables us to observe and understand the effect of the thermal history of asphalt concrete with regards to the reversibility behavior of its stiffness modulus. The damping of the specimens is also calculated from the measured resonance frequencies at the temperatures within the applied cyclic cooling and heating. Their observed behavior is also discussed with respect to a presence of potential micro damage. 

  • 21.
    Bergenudd, Jens
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Dynamic analysis of a pedestrian timber truss bridge at three construction stagesManuscript (preprint) (Other academic)
  • 22.
    Bergenudd, Jens
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Dynamic analysis of a pedestrian timber truss bridge at three construction stages2024In: Structures, ISSN 2352-0124, Vol. 59, article id 105763Article in journal (Refereed)
    Abstract [en]

    This article investigates the dynamic behaviour of a single span pedestrian timber truss bridge by in situ testing and numerical modelling. The in situ dynamic tests were performed at three different construction stages: (1) on only the truss structure, (2) on the finished bridge without the asphalt layer and (3) on the finished bridge with the asphalt layer. The objective is to better understand how the different parts of the bridge contribute to the overall dynamic properties. The experimental results show that the damping ratios increased significantly for the first lateral mode (from 1.0 to 3.8%) and the first torsional mode (from 1.2 to 3.5%) between stage 2 and stage 3 due to the asphalt layer. The damping ratio is around 1.6% for the first bending mode for the finished bridge. The experimental and numerical results indicate that the stiffness of the asphalt layer is important to consider at stage 3 (10 degrees C) for the first lateral and torsional mode, but not for the first bending mode. Finally, it was concluded that longitudinal springs must be applied at the pot bearings in order to get agreement with the experimental results at all the three stages.

  • 23.
    Bergenudd, Jens
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamic testing and numerical modelling of a pedestrian timber bridge at different construction stages2023In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 279, article id 115429Article in journal (Refereed)
    Abstract [en]

    This article studies the dynamic properties of a single span pedestrian timber bridge by in-situ testing and numerical modelling. The in-situ dynamic tests are performed at four different construction stages: (1) on only the timber structure, (2) on the timber structure with the railings, (3) on the timber structure with railings and an asphalt layer during warm conditions and (4) same as stage 3 but during cold conditions. Finite element models for the four construction stages are thereafter implemented and calibrated against the experimental results. The purpose of the study is to better understand how the different parts of the bridge contribute to the overall dynamic properties. The finite element analysis at stage 1 shows that longitudinal springs must be introduced at the supports of the bridge to get accurate results. The experimental results at stage 2 show that the railings contributes to 10% of both the stiffness and mass of the bridge. A shell model of the railings is implemented and calibrated in order to fit with the experimental results. The resonance frequencies decrease with 10–20% at stage 3 compared to stage 2. At stage 3 it is sufficient to introduce the asphalt as an additional mass in the finite element model. For that, a shell layer with surface elements is the best approach. The resonance frequencies increase with 15–30% between warm (stage 3) and cold conditions (stage 4). The stiffness of the asphalt therefore needs to be considered at stage 4. The continuity of the asphalt layer could also increase the overall stiffness of the bridge. The damping ratios increase at all construction stages. They are around 2% at warm conditions and around 2.5% at cold conditions for the finished bridge.

  • 24.
    Bergenudd, Jens
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Battini, Jean-Marc
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Pacoste, Costin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Study of the dynamic response of a timber pedestrian bridge during different construction stages2022In: Conference Proceedings 4th ICTB (2022) ,ICTB 2021 PLUS 4th International Conference on Timber Bridges / [ed] Franke, Bettina and Franke, Steffen, Biel/Bienne, Switzerland, 2022, p. 167-178Conference paper (Other academic)
    Abstract [en]

    The objective of this article is to study the dynamic behaviour of a timber pedestrian bridge by performing in-situ tests at four different construction stages: 1) on only the timber structure 2) on the timber structure with the railings 3) on the timber structure with railings and an asphalt layer during warm conditions and 4) same as stage 3 but during cold conditions. The study included numerical calculations with a 2D finite element model. Two modal parameter extraction methods were implemented during the post-processing. The modes of vibration were analysed with the modal assurance criterion (MAC) to ensure their validity. The results show that the presence of the railings during stage 2 increases the resonance frequencies with 0-2 % compared to stage 1, despite an approximately 5 % increase of the total mass of the bridge. The vertical resonance frequencies decreased 12-22 % when the asphalt was installed at stage 3 compared to stage 2, due to an approximately 70 % increase of the total mass and the asphalt’s low stiffness due to a high temperature. The resonance frequencies increased 14-27 % during cold conditions at stage 4 compared to stage 3. This was mainly due to an increased stiffness of the asphalt layer due to a low temperature. Adding railings therefore resulted in a higher overall stiffness of the bridge, whereas asphalt essentially only added mass to the bridge at warm conditions but increased the stiffness at cold compared to warm conditions. The damping ratios increased for each construction stage and were approximately 2-3 % for the finished bridge. The two modal parameter extraction methods produced similar results which ensures that reliable results are obtained. The auto-MAC indicated well-separated modes and the cross-MAC ensured comparison of the same modes. The finite element model showed that some stiffness was lacking for the first bending mode. This stiffness could be due to shear deformation of the plastic pads at the bridge supports.

  • 25. Blomqvist, L.
    et al.
    Honfi, D.
    Johansson, M.
    Ziethén, R.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Norén, J.
    Development of novel structural connections - Inspiration from furniture industry2021In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper (Refereed)
    Abstract [en]

    The presented project aims to develop prototypes for building connections inspired by the furniture and interior industry and explore them with representatives from the timber construction industry. The long-term vision is that actors from furniture and building industry together develop a smart system for assembly of building elements, which provide higher precision, faster and more efficient assembly than what is available today. The prototype connection developed in this project shows that the idea is ripe for full-scale investigation. Laboratory tests showed promising results due to the high failure loads obtained with very high stiffness.

  • 26.
    Blomqvist, Lars
    et al.
    RISE Research Institutes of Sweden, Sweden.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claesson, August
    KTH, School of Architecture and the Built Environment (ABE).
    Osmane, Zakaria Ben
    KTH.
    Ziethén, Rune
    RISE Research Institutes of Sweden, Sweden.
    Johansson, Marie
    RISE Research Institutes of Sweden, Sweden.
    Experimental and numerical analyses of a connection for CLT structures2023In: 13th World Conference on Timber Engineering, WCTE 2023, Curran Associates, Inc. , 2023, p. 1154-1159Conference paper (Refereed)
    Abstract [en]

    Although building systems made of cross-laminated timber (CLT) have become common in Sweden in the past 20 years and they have developed rapidly during the same period, steps remain to be taken to simplify the assembly of such systems, especially at construction sites. Current construction methods, however, remain labourintensive and thus show room for improvement. This paper describes a novel connection for the assembly of building elements made of CLT. Simple and inexpensive, the connection is fairly insensitive to manufacturing tolerances and enables rapid, more efficient construction than the connections for CLT structures currently used. Test results show the excellent strength and stiffness of the connection, which also allows the replacement of numerous fasteners, including nails and screws, with only a single steel rod.

  • 27. Bressi, S.
    et al.
    Dumont, A. G.
    Partl, Manfred N.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Carleton University, Ottawa, Canada; Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland.
    A new laboratory methodology for optimization of mixture design of asphalt concrete containing reclaimed asphalt pavement material2016In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 49, no 12, p. 4975-4990Article in journal (Refereed)
    Abstract [en]

    The reduction of virgin bitumen added to asphalt mixtures containing Reclaimed Asphalt Pavement (RAP) is based on the typical assumption that all the aged binder function in the same way as the virgin binder. However, recent studies conducted by the authors for a specific case show that a blend or mobilization of RAP binder are negligible. The aged bitumen becomes softer acting as glue facilitating cluster formation between small-size RAP particles. The reduction of small-size particles causes changes in the target grading curve and in the voids-fill, affecting the compactability of RAP mixtures. Therefore the target grading curve of RAP mixtures needs to be readjusted, using different proportions of virgin aggregates and taking into account the cluster phenomenon. The objective of this paper is to develop a new mix design approach for RAP mixtures, taking into account the cluster phenomenon and the contribution of the aged bitumen in the compactability. The virgin aggregates, filler and RAP are investigated and individually included in the calculation. 3D images of the virgin aggregates allowed the determination of new surface area factors; the concept of critical filler concentration led to the definition of the minimum bitumen quantity required to maintain the mastic in a diluted state and fill the voids. A RAP clustering model was introduced to predict the agglomeration of small-size RAP particles. The readjustment of the target grading curve was analytically calculated, allowing the correct estimation of the amount of virgin bitumen to be added to asphalt mixtures. Finally, a first verification of the entire process was carried out performing laboratory tests. These promising results enable the challenge of a new mix design optimization for HMA with high RAP content to be addressed.

  • 28. Bressi, Sara
    et al.
    Dumont, A. G.
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Carleton Univ, Ottawa, Canada.
    An advanced methodology for the mix design optimization of hot mix asphalt2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, p. 174-185Article in journal (Refereed)
    Abstract [en]

    The bitumen quantity to add to asphalt mixtures depends on the surfaces of aggregates and filler to be coated. The formulas currently available in the literature have limitations such as considering all the fillers with the same specific surface or the aggregates with spherical or cubical shapes. This paper aims to define an analytical approach for the determination of the optimal dosage of bitumen in HMA proposing new methodologies to go a step further in the resolution of the above mentioned approximations. Indeed, new surface area factors were calculated to determine the aggregates surface considering their real shapes and volumes. Afterwards, the authors proposed a detailed characterization of two types of fillers and the critical filler concentration, introduced by Faheem and Bahia, was used to calculate the minimum amount of bitumen for maintaining the mastic in a diluted state and filling the voids in the mixtures. Finally, a verification of the formula developed was carried out with specific laboratory tests. These results allow the challenge of revising the method of calculating the specific surface of the aggregates and filler to be addressed with the final goal to include them in a new mix design optimization for HMA. 

  • 29.
    Bryne, Lars Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lausamaa, J.
    Ernstsson, M.
    Englund, Finn
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Söderström, Ove
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    UV-laser irradiated wood: Some aspects on micromorphology, wettability, surface composition and liquid permeability2008In: Proceedings of the 4th meeting of the Nordic-Baltic network in wood material science and engineering (WSE), 2008, p. 75-82Conference paper (Refereed)
    Abstract [en]

    Many wood products used as building or construction materials involve a combination of the wood material with polymers, such as adhesives, coatings, preservatives and binders in composites. Combinations of wood and polymers in outdoor exposure, however, in general have poor long-term durability. A major cause of the unsatisfactory durability can be related to the high hygroscopicity of wood and the great difference in hygro-thermal properties between the components, resulting in wood-polymer de-bonding. In addition, mechanical processing (e.g. sawing, sanding and planning) of wood in general forms a weak boundary layer of loose and crushed wood cells in the surface which also may interfere with the wood-polymer bonding. The main objective of this work was to study ultra violet (EV), or excimer, laser irradiation on wood as a means to remove, by ablation, the outer deformed layer from a wood substrate. Effects of the UV-laser treatment on wetting and liquid permeability characteristics were studied by Wilhelmy plate experiments, and effects on the wood surface chemistry were studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The micromorphology of wood was studied by low vacuum-scanning electron microscopy (LV-SEM). The pre-treatment of wood substrates by UV-laser ablation resulted in a notable changes in surface micromorphology, liquid permeability, wettability and surface chemistry characteristics.

  • 30.
    Bryne, Lars-Elof
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Aspects on wettability and surface composition of modified wood2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Wood is often combined with other materials such as thermoplastics, adhesives and coatings. In general, combinations of wood and polymers especially in outdoor exposure have poor long-term durability. This behaviour can be related to an insufficient wood-polymer adhesion due to the low intrinsic compatibility between the wood substance and the polymers used. Another source for woodpolymer de-bonding is the high hygroscopicity of wood and great difference in hygro-thermal properties between the components.

    The basic conceptual idea related to this work is to reduce the hygrosensitivity of wood by applying different wood modification methods, in particular, acetylation, furfurylation and heat treatment. The effects of such chemical modifications of wood, also accompanied with ageing effects, on its adhesion properties with commonly used synthetic polymers are, however, not well understood. In this context, the over-all purpose of this thesis is to achieve a better understanding of wood-polymer adhesion and interfacial forces which also may guide us to tailor the interaction between modified wood and e.g. thermoplastics and adhesives. The main focus of this thesis is therefore to apply contact angle analysis based on the Chang-Qin-Chen (CQC) Lewis acid-base model in order to estimate the work of adhesion (Wa) between the wood, modified wood and certain polymers. Contact angle measurements on wood samples were performed based on the Wilhelm plate principle. Related to this, an effort was also made to characterize the studied modified wood surfaces according to morphology and chemical composition. The methods that have been used are low vacuum scanning electron microscopy (LV-SEM), X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS).

    Results show that so-called interaction parameters can be successfully estimated for prediction of Wa between wood and polymers using the applied CQC model. Furthermore, such wetting analysis was successfully related to spectroscopic findings of the chemical composition of the wood samples surface. Ageing effects, i.e. the time after preparation of the wood surface, play a central role for the surface characteristics. In most cases, ageing resulted in a significant decrease of Wa between wood and water and a moderate decrease between wood and thermoplastics. The surface characteristics of acetylated wood were, however, more stable over time compared to unmodified, furfurylated and heat treated wood. The predicted Wa with the adhesives for heat treated and acetylated wood was increased due to ageing. Future work is planned to involve studies in order to relate such predicted adhesion properties with the actual performance of various wood-polymer systems.

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  • 31.
    Bryne, Lars-Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lausmaa, Jukka
    SP Technical Research Institute of Sweden, Chemistry and Materials Technology, Borås, Sweden.
    Ernstsson, Marie
    Institute for Surface Chemistry, Stockholm, Sweden.
    Englund, Finn
    SP Trätek, Technical Research Institute of Sweden, Wood Technology, Borås, Sweden.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ageing of modified wood: Part 2: Determination of surface composition of acetylated, furfurylated, and thermally modified wood by XPS and ToF-SIMS2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 305-313Article in journal (Refereed)
    Abstract [en]

    The main objective of this work was to study the chemical composition of surfaces and ageing effects on acetylated pine (Pinus sylvestris), heat treated spruce (Picea abies), and furfurylated radiata pine (Pinus radiata) in comparison to unmodified wood. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were the instruments of choice. Observation with a low-vacuum scanning electron microscope (LV-SEM) complemented the study. The spectroscopic information was also linked to a parallel wettability study on matched wood samples by the Wilhelmy method. The results show that XPS and ToF-SIMS are two powerful tools that in combination give complementary information, both quantitative and qualitative, and are well suited for observation of the ageing process of different wood surfaces. The hydrophobization process as a result of migration of extractives during ageing was well quantified by the XPS measurements and the results correlated well with wetting results. Several specific hydrophobic substances could be identified by ToF-SIMS measurements.

  • 32.
    Bryne, Lars-Elof
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Ageing of modified wood: Part 1: Wetting properties of acetylated, furfurylated, and thermally modified2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 3, p. 295-304Article in journal (Refereed)
    Abstract [en]

    The main objective of this work was to apply contact angle analysis to predict work of adhesion (W-a) between some modified wood materials and certain thermoplastics and adhesives. Wetting properties, i.e., contact angles, were measured by the Wilhelmy method on both freshly prepared and aged veneer samples of unmodified and acetylated Scots pine, furfurylated radiata pine, and heat treated Norway spruce. The sessile drop method was used to measure contact angles on a phenol resorcinol formaldehyde, an emulsion polymer isocyanate, and a one-component polyurethane adhesive. Contact angle data were also collected from the literature on polyethylene, polyvinyl chloride, polymethyl methacrylate, polystyrene, and Nylon 6. Contact angle analysis based on the Chang-Qin-Chen model was then applied to determine so-called acid-base interaction parameters and W-a between the wood samples and the selected thermoplastics and adhesives. Results show that the ageing process led to an increased hydrophobic character of unmodified, heat treated, and furfurylated wood samples. The freshly prepared acetylated wood samples had a pronounced hydrophobic character which remained approximately constant after ageing. The predicted W-a between the wood and the adhesives was considerably higher than that between the wood and the thermoplastics. Furthermore, the predicted W-a between the acetylated wood and both the thermoplastics and water was approximately unchanged when comparing the fresh and aged samples. In contrast, the ageing of all other wood samples resulted in a dramatic decrease of the wood-water W-a and a moderate decrease of the wood-thermoplastics W-a. The wood-adhesives W-a, however, was unchanged for the unmodified and furfurylated wood when comparing the fresh and aged samples and even increased for heat treated and acetylated wood samples.

  • 33. Bueno, M.
    et al.
    Hugener, M.
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Fracture toughness evaluation of bituminous binders at low temperatures2015In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 48, no 9, p. 3049-3058Article in journal (Refereed)
    Abstract [en]

    When asphalt roads turn brittle at low temperatures, they are no longer able to relax completely from traffic induced stresses and may also suffer damage through crack initiation and propagation. In order to avoid early structural damages, the bituminous binders must be selected very carefully. However, conventional test methods for assessing performance of bituminous binders at low temperatures are often unsatisfactory reliable, in particular in case of polymer modified bituminous binders. In this study, an alternative experimental method based on fracture mechanical principles was performed on pre-notched specimens in the brittle state inside a cooling media. This fracture toughness test was evaluated in terms of its suitability for distinguishing different types of polymer modified and unmodified bituminous binders. In addition, the feasibility to evaluate different ageing states was also analysed by testing samples after artificial short-term and long-term ageing procedures. The repeatability obtained from the experimental results showed that the fracture toughness test is a suitable candidate for being introduced in a standardization framework.

  • 34.
    Bulgarini, Mario
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Technical Optimization of a Long Span Beam made of Glulam Elements2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Timber constructions have during the past two or three decades become more andmore common, mostly due to the easy prefabrication and the cheap, sustainablematerial. For long-span applications it is vital to find design solutions that optimizethe structure from the point of view of material consumption, number of theconnections, structural reliability etc.This thesis focuses on the structural optimization of a long span timber structureearlier developed by a Swedish glulam company for industry buildings and sport hallapplications. The main goal of this study has been the minimization of the volume ofwood required to built the structure, given a set of geometrical restrictions and theassigned loads.The optimal shape of the structure and the arrangement of the different elementshas been investigated by means of theoretical analyses taking into account theprincipal directions of stress which would occurr in similar structures with massivecross sections. The results of this investigations give some guidelines to design newtypes of structures, where both mechanical efficiency and manufacturing issues havebeen taken into consideration.Comparisons of the structural models proposed in this thesis with the originalproposal provided by the Swedish glulam company conclude the work, suggestingsome possible improvements.

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  • 35. Canestrari, F.
    et al.
    Ferrotti, G.
    Lu, X.
    Millien, A.
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. Empa, Swiss Federal Laboratories for Materials Science and Technology.
    Petit, C.
    Phelipot-Mardelé, A.
    Piber, H.
    Raab, C.
    Mechanical testing of interlayer bonding in asphalt pavements2013In: Advances in Interlaboratory Testing and Evaluation of Bituminous Materials, Springer Netherlands, 2013, p. 303-360Chapter in book (Refereed)
    Abstract [en]

    Steadily increasing requirements on pavement performance properties, in terms of bearing capacity and durability, as well as new innovative developments regarding pavement materials and construction, are observed worldwide. In this context interlayer bonding at the interfaces of multi-layered bituminous systems is recognized as a key issue for the evaluation of the effects, in terms of stress-strain distribution, produced by traffic loads in road pavements. For this reason a correct assessment of interlayer bonding is of primary importance, and research efforts should be addressed in order to improve the lack of correlation and/or harmonization among test methods. Following this principle RILEM TG 4 organized an interlaboratory test in order to compare the different test procedures to assess the interlayer bonding properties of asphalt pavement. The results of the experimental research are presented with a preliminary overview of basic elements, test methods and experimental investigations on interlayer bonding. Then the RILEM TG 4 experimental activities, based on the construction of three real- scale pavement sections, are presented in detail. Each pavement section was composed of two layers, and three different interface conditions were chosen. The first pavement was laid without interface treatment and the others with two different types of emulsion. Fourteen laboratories from 11 countries participated in this study and carried out shear or torque tests on 1,400 cores. The maximum shear or torque load and the corresponding displacement were measured, and the shear or torque strength was calculated as a function of the following parameters: diameter, test temperature, test speed, stress applied normal to the interface and age of the specimen. The results of this study are presented in terms of precision and correlations regarding the parameters which results in useful information on asphalt pavement interlayer bond tests.

  • 36.
    Celma Cervera, Carlos
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Partl, Manfred N.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. bEMPA Swiss Federal Laboratories for Materials Testing and Research, Switzerland.
    Larsson, Per-Lennart
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Contact-induced deformation and damage of rocks used in pavement materials2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 133, p. 255-265Article in journal (Refereed)
    Abstract [en]

    Performance of stone-based construction materials, such as asphalt and unbound aggregate mixtures is defined to a great extent by the mechanics of the stone-to-stone interactions. Accordingly, the Discrete Element Method (DEM) is gaining popularity as a modelling tool to investigate the mechanical behavior of these materials. Contact and failure laws defining particles force-displacement relationships and the propensity of particles to break are crucial inputs for the DEM simulations. The present study aims at providing an experimental contact mechanics basis for the development of physically based stone-to-stone interaction laws. The attention is focused on investigating stone's force-displacement relationship and damage characteristics at pure normal loading for two stone materials used by the road industry. Experiments are performed at spherical contact profiles for cyclic and monotonically increasing loads. The emphasis lies on the evolution of contact compliance and accumulation of contact induced damage. The effect of surface roughness on the materials response is examined through comparative experiments performed on the specimens with different roughness values. Optical and environmental scanning electron microscopy (ESEM) observations of the contact induced damage at the material surface are presented and discussed in the context of contact mechanics. The implications of the reported experimental findings on the development of mechanics based contact and failure laws for the DEM modelling of stone-based construction materials are discussed.

  • 37. Chailleux, E.
    et al.
    Partl, M. N.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    General summary and outlook2013In: RILEM State-of-the-Art Reports, Springer, 2013, p. 429-438Conference paper (Refereed)
    Abstract [en]

    Final considerations based on the experience and feedback of this RILEM technical committee TC 206-ATB on “Advanced Testing and Characterization of Bituminous Materials” are given. Some open questions within the general methodology as introduced in Chap. 1 and used as guideline for RILEM activities are listed. Future prospects and direction of activities of joint voluntary research efforts within the frame of such asphalt-related committees are also discussed. It is suggested that these future efforts will most certainly have to focus even more on sustainability and environmental aspects but without neglecting general materials and systems quality aspects during production and construction as well as safety and performance during use. Future activities will also have to dealwith multifunctionality aspects of pavements and multi-scaling approaches as a basis for better understanding and tailoring of pavements and pavement materials.

  • 38.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Elaguine, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Partl, Manfred N.
    EMPA, Uberlandstr 129, CH-8600 Dubendorf, Switzerland..
    Vibration-induced aggregate segregation in asphalt mixtures2020In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 53, no 2, article id 27Article in journal (Refereed)
    Abstract [en]

    Aggregate segregation in asphalt mixture is a bothersome engineering issue during pavement construction. The practitioners have some measures to mitigate the segregation potential based on experiences which, however, can only reduce the risk to a certain extent. In this research, the authors aim to contribute to the discussion in a rational non-empirical way, by using novel experimental and numerical techniques. A case study is carried out to investigate the vibration-induced segregation in asphalt mixtures, corresponding to the circumstance arising during material transportation to the construction site. A novel experimental test is conducted for evaluating the segregation characteristics of asphalt mixtures under vertical vibration in laboratory conditions. A numerical investigation based on discrete element method is further performed to study the phenomenon from a micromechanical point of view. The obtained experimental and numerical results indicate that vibratory loading induces aggregate size segregation in asphalt mixtures, and the degree of segregation is influenced profoundly by the adhesive properties of bituminous binders and the aggregate gradation.

  • 39.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. EMPA–Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland.
    Experimental and numerical analysis of asphalt flow in a slump test2019In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 20, p. S446-S461Article in journal (Refereed)
    Abstract [en]

    The mechanical behaviour of uncompacted asphalt mixtures is still not well understood,threatening directly to the pavement practices such as control of mixture’s workability andsegregation. This situation may become even worse due to the gradually increasing complexityand advances in paving materials and technologies. This study adopts a slump flow testbased on concrete technology and a Discrete Element (DE)-based numerical tool to investigatethe mechanical behaviour of uncompacted asphalt mixture from a microstructural point ofview, particularly focusing on the bituminous binder effects. The combined experimental andnumerical analysis indicates that bitumen distinctly influences the contact interactions withinthe mixture and thus its macroscopic flow, which can be physically interpreted as a combinedeffect of lubricated friction and bonding force. Additional case studies demonstrate that the DEmodel is capable of simulating the flow response of asphalt mixtures under changed particlecontact conditions and driven force.

  • 40. Clemons, Craig M.
    et al.
    Rowell, Roger M.
    Plackett, David
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Chapter 13: Wood/nonwood thermoplastic composites2012In: Handbook of wood chemistry and wood composites, second edition / [ed] Rowell Roger M., Boca Racon, FL: CRC Press, 2012, 2, p. 473-508Chapter in book (Refereed)
  • 41. Cooper, Paul A.
    et al.
    Ung, Y. T.
    Edlund, M.-L.
    Jermer, J.
    Söderström, Ove
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Inorganic wood preservative levels in soil near a noise barrier treated with different preservatives after 8 years in service in Sweden2005In: 36th Annual Meeting of the International Research Group on Wood Protection, 2005Conference paper (Refereed)
  • 42.
    Crocetti, Roberto
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Lappalainen, Kaj
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Backman, Matthias
    KTH.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Norén, J.
    Multiple shear plane connections with timber based gusset plates2021In: World Conference on Timber Engineering 2021, WCTE 2021, World Conference on Timber Engineering (WCTE) , 2021Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an experimental study conducted on multiple-shear joints consisting of gusset plates made of either LVL or plywood connected to the timber members by means of full-threaded self-tapping screw. Both hardwood and softwood timber based gusset plates with different thickness and face grain orientations were investigated. The results show that this type of connection has an excellent structural performance, with not very dissimilar strength from that of comparable connections which makes use of slotted-in steel plates and dowels. It is believed, therefore, that the proposed solution can be a valid alternative to the more traditional timber connection with slotted-in steel plates and dowels.

  • 43.
    Dahlström, Carl
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Giesen, Emma
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Mould resistance design for external wood frame wall systems: Simulation and evaluation of wall structures under varying conditions of exposure using the MRD model2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Moisture induced damages to building envelopes can result in microbial growth possibly affecting the health and wellbeing of occupants. Recent failing structures and damaged buildings indicate a lack of tools to estimate risk of mould growth and moisture damage. In this work a so-called mould resistance design (MRD) model has been applied for mapping the risk for mould growth on a number of wood-containing wall structures. The MRD model introduces an engineering approach to moisture safety design in a similar way as for structural design, where load and resistance is compared. The MRD model introduces and quantifies the concepts of climatic exposure and material resistance and compares them through an MRD index. This MRD index incorporates a limit state, which gives the critical dose of exposure for a given resistance to initiate onset of mould growth.

     

    Three conceptual wall structures were evaluated and analyzed in terms of MRD index: two wall systems with an air gap and one wall system without. A parametric study investigating the effect of parameter variation on MRD index was conducted. Evaluated parameters were: climate (geographic location), orientation, air changes per hour in the air gap, driving rain penetrating the facade layer, exterior plaster properties and wood type. The simulations were performed using the hygrothermal calculation software WUFI. The results indicate that the wall systems with a ventilated air gap performs better in terms of MRD index i.e. suggests a lower risk of initiation of mould growth than the wall system without air gap. The results of orientation variation show that wall systems perform differently dependent on layering structure. The inherent water sorption properties of the exterior plaster are shown to have a large effect on the results. In addition, uncertainties were found on how to accurately include hydrophobicity as a parameter in the model. The report concludes that geographical location and its specific climate is the most important parameter to consider when designing for moisture safety. The MRD model is recommended to be used in combination with traditional moisture safety evaluation.

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  • 44. Das, Prabir
    et al.
    Birgisson, Bjorn
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Importance of Thermal Contraction Coefficient in Low Temperature Cracking of Asphalt Concrete2016In: Proceedings of the Fifty-Ninth Annual Conference of the Canadian Technical Asphalt Association (CTAA): Winnipeg, Manitoba / [ed] Canadian Technical Asphalt Association, 2016Conference paper (Refereed)
    Abstract [en]

    A major distress mode in asphalt pavements is low temperature cracking, which results from the contraction and expansion of the asphalt pavement under extreme temperature changes. The potential for thermal cracking involves interplay between the environment, the road structure, and importantly the properties of the asphalt mixture. In the present study, the low temperature cracking performance of asphalt mixture has been investigated numerically and experimentally. A low temperature cracking model has been utilized, which was developed by integrating fracture energy threshold into an asphalt concrete thermal fracture model considering non-linear thermal contraction coefficients. Based on the asphalt concrete mixture viscoelastic properties, this enhanced model can predict thermally-induced stresses and fracture temperatures. It was observed that the thermal contraction coefficient in asphalt concrete is non-linear in the temperature range of interest for low temperature cracking. The implications of having non-linear thermal contraction coefficient were investigated numerically. From the analysis, it was found that this enhanced model can be utilized to evaluate the low temperature cracking performance of asphalt mixtures and rank them accordingly. Interestingly, non-linear thermal contraction coefficient gave much better prediction than the linear approach.

  • 45.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Olsson, Erik
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Elaguine, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Larsson, Stefan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    DEM model for high-speed railway embankments2018Report (Other academic)
  • 46.
    de Frias Lopez, Ricardo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Soil and Rock Mechanics.
    Silfwerbrand, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory. School of Engineering and Applied Science, Aston University, Birmingham, UK.
    Force transmission and soil fabric of binary granular mixtures2016In: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656, Vol. 66, no 7, p. 578-583Article in journal (Refereed)
    Abstract [en]

    The effect of fines content on force transmission and fabric development of gap-graded mixtures under triaxial compression has been studied using the discrete-element method. Results were used to define load-bearing soil fabrics where the relative contributions of coarse and fine components are explicitly quantified in terms of force transmission. Comparison with previous findings suggests that lower particle size ratios result in higher interaction between components. A potential for instability was detected for underfilled fabrics in agreement with recent findings. It was also found that the threshold fines content provides an accurate macroscopic estimation of the transition between underfilled and overfilled fabrics.

  • 47.
    Debertolis, Mattia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Laurinaviciute, Agne
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Load-bearing wood connections using birch plywood: An experimental study of birch plywood gusset plates behaviour with mechanical connectors2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A growing sustainability concern is pushing the construction industry to seekalternative materials with lower environmental impact. In the last decade useof wood as load-bearing construction has become a common trend, however,connections of timber elements are still performed by the use of steel plates.An alternative to this could be using hardwood plywood instead of steelgusset plates. Connections with plywood are expected to reach a similarcapacity and reduce the environmental impact of wooden construction evenfurther. Hence research on plywood as a load-bearing construction materialis required in order to be able to design and use such connections in reality.Since birch plywood has high strength, it was chosen to study its’ loadbearingcapacity in dowelled connections with wood elements. The aim wasto analyse birch plywood failure modes and load capacity dependence on thevariation of plywood face grain angle and mechanical fasteners positioning inthe connection.

    The study was conducted with a total of 36 specimens of 4 different nailpatterns and 3 plywood load-to-face grain angle directions: 0°, 22.5° and 45°.These specimens were pre-designed to have failure modes either in block shearor net tension in the plywood board. They were later tested in the laboratory byapplying a tension load. Testing results showed that despite the prediction ofblock shear in some of the specimens, plywood plates always had net tensionfailure mode. Also, especially for 0° of face grain angle, plywood specimenswith wider dowels placement in connection resulted in significantly higherload capacity than narrow ones. This showed that the spreading angle of theload plays an important role in the strength of the connection. Additionally,it was observed, that 45° grain-to-load angle specimens, which had the lowestpredicted load capacity, resulted in similar values as 22.5° specimens. Thisimplies that there is no significant effect on connection strength due to plywoodgrain angle variation when it is not parallel to the applied load.

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  • 48.
    Debertolis, Mattia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Wang, Yue
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wang, Tianxiang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Crocetti, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Investigation on mechanical connections with birch plywood gusset plates2023In: 19th Annual Meeting of the Northern European Network for Wood Science and Engineering / [ed] Erik Larnøy, Ås, Norway: The Nordic Forest Research Cooperation Commitee , 2023, p. 96-98Conference paper (Refereed)
    Abstract [en]

    The construction industry is increasingly driven by sustainability concerns, prompting a search for alternative materials with a low environmental footprint, such as engineered wood products. Nowadays, connections of timber elements are still performed by the use of steel plates. However, steel plates can be replaced by plywood made of birch since it has superior mechanical properties compared to plywood made from softwood (Wang et al. 2021, 2022; Crocetti et al. 2021; Werner Åström, 2019). Besides, the capacity calculation for this connection according to the standards is conservative, meaning that the efficiency is low and the actual capacity could be much higher than the design value (Rossi et al. 2016). This research aims to enhance the knowledge and the design process of timber-to-timber connections with birch plywood (BP) plates.

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    WSE2023_Proceedings_MattiaDebertolis
  • 49.
    Digregorio, Giuseppe
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Real - time data and BIM: automated protocol for management and visualisation of data in real time: A case study in the "Teaching House" of the KTH campus2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays BIM and real-time data are becoming a central topic for the AECO (Architecture, Engineering, Construction and Operations) industry, they represent new powerful tools for the design and management of facilities.Building monitoring and real-time data can represent a solution to many important challenges like energy efficiency, indoor climate quality and cost management. Although it is clear the importance of data for a correct use of BIM technology and its potentiality, in literature, are not so common examples of complete workflows for a complete management of data from the input phase to the output one.The scope of the study is to design a protocol for entering, managing and exporting real-time data using Revit and Dynamo where the customers have a central role during the input phase and a dedicated mode for data display including a desktop version and an augmented reality one for a more immersive experience.In order to show the real potentiality of the project, the protocol has been utilised for the calculation of thermal comfort parameters of the “Teaching House” situated in KTH campus. All data entered from the students into a form online, via QR-code, have been inserted into Dynamo in order to calculate the desired parameters values which are successively stored into a database for further analysis, everything automatically.

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    fulltext
  • 50.
    Elaguine, Denis
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Olsson, Erik
    Department Engineering Sciences and Mathematics, Luleå University of Technology, Luleå, Sweden.
    Raab, Christiane
    Concrete and Asphalt, Empa, Swiss Federal Laboratories for Material Science and Technology, Duebendorf, Switzerland.
    Partl, Manfred N.
    PaRRC Partl Road Research Consulting, Oeschgen, Switzerland.
    Experimental and numerical modelling of shear bonding between asphalt layers2023In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 24, no S1, p. 176-191Article in journal (Refereed)
    Abstract [en]

    Interlayers in asphalt pavements are potential structural damage initiators. In order to better understand the quantitative role of interlayer parameters, such as surface roughness, binder type, binder content and loading type on interlayer shear strength, this paper focuses on the effects of particle interlock and contact conditions on interlayer strength through experimental and numerical modelling. Experimentally, interlayer shear box strength tests on a model material consisting of stiff binder blended with steel balls are performed with and without normal force confinement. A Discrete Element method model of the test is developed using measurements of the model material for calibrating the contact law and for validating the model. It is shown that this model captures adequately the measured force-displacement response of the specimens. It is thus a feasible starting point for numerically and experimentally studying the role of binder and tack coat regarding interlayer shear strength of real asphalt layers.

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