Change search
Refine search result
1234 151 - 177 of 177
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 151.
    Onifade, Ibrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway Engineering Laboratory.
    Dinegdae, Yared H.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Birgisson, Björn
    Hierarchical approach for fatigue cracking performance evaluation in asphalt pavements2017In: Frontiers of Structural and Civil Engineering, ISSN 2095-2430, E-ISSN 2095-2449, Vol. 11, no 3, p. 257-269Article in journal (Refereed)
    Abstract [en]

    In this paper, a hierarchical approach is proposed for the evaluation of fatigue cracking in asphalt concrete pavements considering three different levels of complexities in the representation of the material behaviour, design parameters characterization and the determination of the pavement response as well as damage computation. Based on the developed hierarchical approach, three damage computation levels are identified and proposed. The levels of fatigue damage analysis provides pavement engineers a variety of tools that can be used for pavement analysis depending on the availability of data, required level of prediction accuracy and computational power at their disposal. The hierarchical approach also provides a systematic approach for the understanding of the fundamental mechanisms of pavement deterioration, the elimination of the empiricism associated with pavement design today and the transition towards the use of sound principles of mechanics in pavement analysis and design.

  • 152.
    Onifade, Ibrahim
    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.
    Birgisson, Björn
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Towards Asphalt Mixture Morphology Evaluation with the Virtual Specimen Approach2015In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402Article in journal (Refereed)
    Abstract [en]

    The morphology of asphalt mixture can be defined as a set of parameters describing the geo-metrical characteristics of its constituent materials, their relative proportions as well as spatialarrangement in the mixture. The present study is carried out to investigate the effect of themorphology on its meso- and macro-mechanical response. An analysis approach is used forthe meso-structural characterisation based on the X-ray computed tomography (CT) data.Image processing techniques are used to systematically vary the internal structure to obtaindifferent morphology structures. A morphology framework is used to characterise the aver-age mastic coating thickness around the main load carrying structure in the structures. Theuniaxial tension simulation shows that the mixtures with the lowest coating thickness exhibitbetter inter-particle interaction with more continuous load distribution chains between adja-cent aggregate particles, less stress concentrations and less strain localisation in the masticphase.

  • 153.
    Onifade, Ibrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Asphalt Internal Structure Characterization with X-Ray Computed Tomography and Digital Image Processing2013In: Multi-Scale Modeling and Characterization of Infrastructure Materials: Proceedings of the International RILEM Symposium Stockholm, June 2013, Springer Netherlands, 2013, p. 139-158Conference paper (Refereed)
    Abstract [en]

    In this paper, detailed study is carried out to develop a new workflow from image acquisition to numerical simulation for the asphalt concrete microstructures. High resolution computed tomography scanned images are acquired and the image quality is improved using digital image processing techniques. Nonuniform illumination is corrected by applying an illumination profile to correct the background and flat-fields in the image. Distance map based watershed segmentation are used to segment the phases and separate the aggregates. Quantitative analysis of the micro-structure is used to determine the phase volumetric relationship and aggregates characteristics. The result of the quantitative analysis showed a very high level of reliability. Finite Element simulations were carried out with the developed micro-mechanical meshes to capture the strength and deformation mechanisms of the asphalt concrete micro-structure. From the micro-mechanical investigation the load transfer chains, higher strength characteristics and high stress localization at the mastic interface between adjacent aggregates was shown.

  • 154.
    Onifade, Ibrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Effect of micro-scale morphological parameters on meso-scale response of Asphalt Concrete2014In: Asphalt Pavements - Proceedings of the International Conference on Asphalt Pavements, ISAP 2014, CRC Press, 2014, p. 1775-1784Conference paper (Refereed)
    Abstract [en]

    With recent advancement in the use of X-Ray Computed Tomography to capture the internal structure of Asphalt Concrete (AC), results have shown several possibilities to account for the distribution of the different phases in the mix and quantify them in a reliable way. The morphology of asphalt mixtures which includes the aggregate size gradation and the distribution of the air-voids and bitumen phase are captured in a single morphological parameter called the Primary Structure (PS) coating thickness-(Tps). In this study, the effect of variations in the morphological micro-structural property on the mesoscale response of three (3) AC samples is examined using the 3D Finite Element Method (FEM). The AC internal geometry is acquired using X-Ray Computed Tomography (CT); the distribution of the aggregates, mastic and air-voids phase is considered and obtained using Digital Imaging Processing (DIP) techniques. Using a surface-based cohesive behavior and assuming a predominant adhesive failure at the interface between the mastic and aggregate, a maximum traction criterion is used to obtain the damage propensity of the different mixtures. The result of the analysis shows that the microstructural morphological parameter Tps adequately captures the meso-scale response of the mixtures; there exist an inverse relationship between mixture strength characterization and the morphological parameter Tps.

  • 155. Ovik, J
    et al.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Newcomb, David
    Characterizing Seasonal Variations in Flexible Pavement Material Properties2000In: Transportation Research Record, Vol. 1684Article in journal (Refereed)
  • 156. Ovik, J
    et al.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Newcomb, David
    Seasonal Variations in Backcalculated Pavement Layer Moduli at MN/ROAD2000In: Journal of ASTM International, Vol. STP1375Article in journal (Refereed)
  • 157. Paikowsky, S.G.
    et al.
    Birgisson, Björn
    McVay, M
    Nguyen, T
    Kuo, C
    Baecher, G.
    Ayyub, B.
    Stenerson, K.
    O'Malley, K.
    Chernauskas, L.
    O'Neill, M.
    Load and Resistance Factor Design (LRFD) for Deep Foundations2004Book (Refereed)
  • 158. Romeo, Elena
    et al.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering.
    Montepara, Antonio
    Tebaldi, Gabriele
    The effect of polymer modification on hot mix asphalt fracture at tensile loading conditions2010In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 11, no 5, p. 403-413Article in journal (Refereed)
    Abstract [en]

    A laboratory investigation was conducted to evaluate the effect of both cross-linked and linear styrene-butadiene-styrene (SBS) modifiers on the cracking resistance of hot mix asphalt (HMA) mixtures. Five types of asphalt mixtures composed by the same aggregate gradation but different asphalt binders were produced in the laboratory. The cracking performances of the mixtures were evaluated using a viscoelastic fracture mechanics-based model entitled 'HMA Fracture Mechanics'. Crack localisation and crack growth were investigated performing the indirect tensile test and the semi-circular bending test. A digital image correlation system capable of providing full-field strain maps was applied. The results show the benefit of SBS modifiers to the mixture's cracking resistance in terms of reduced rate of damage accumulation and increased tensile limits to failure. Finally, significant damage and first fracture have shown to be strongly more localised in modified specimens than in the unmodified one.

  • 159. Roque, R.
    et al.
    Birgisson, Björn
    University of Florida, Gainesville, FL.
    Drakos, C.
    Dietrich, B.
    Development and Field Evaluation of Energy-Based Criteria for Top-down Cracking Performance of Hot Mix Asphalt2004In: 2004 JOURNAL OF THE ASSOCIATION OF ASPHALT PAVING TECHNOLOGISTS: FROM THE PROCEEDINGS OF THE TECHNICAL SESSIONS, VOL 73, 2004, Vol. 73, p. 229-260Conference paper (Refereed)
    Abstract [en]

    It is now well-recognized that top-down cracking is a major form of distress in hot mix asphalt pavements A detailed analysis and evaluation of 22 field test sections throughout the state of Florida resulted in the development and verification of energy-based criteria for top-down cracking of hot mix asphalt. The work clearly indicated that there is no single mixture property or characteristic that can reliably predict top-down cracking performance of hot mix asphalt. A parameter termed the Energy Ratio, which was derived using the HMA Fracture Mechanics Model developed at the University of Florida, was determined to accurately distinguish between pavements that exhibited top-down cracking and those that did not, except for mixtures with excessively low or unusually high dissipated creep strain energy thresholds. The Energy Ratio, which is defined as the dissipated creep strain energy threshold of the mixture divided by the minimum dissipated creep strain energy required, is determined on the basis of tensile properties that can be obtained from a modulus, creep, and strength test performed with the Superpave IDT at a temperature of 10degreesC. The Energy Ratio accounts for the effects of pavement structural characteristics on top-down cracking performance. Therefore, it can be used to suitably integrate asphalt mixture properties in the pavement design process. In addition, a rational approach was developed to adjust the minimum Energy Ratio criterion for different traffic level pavements. In conclusion, two energy-based criteria were recommended to control top-down cracking of hot mix asphalt: 1) a minimum dissipated creep strain energy threshold; and 2) a minimum Energy Ratio for mixtures with a dissipated creep strain energy threshold greater than the minimum.

  • 160. Roque, R
    et al.
    Myers, L
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of Measured Tire Contact Stresses for the Prediction of Pavement Response and Performance2000In: Transportation Research Record, Vol. 1716Article in journal (Refereed)
  • 161. Roque, R
    et al.
    Myers, L
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Use of Two-Dimensional Finite Element Analysis to Represent Bending Response of Asphalt Pavement Structures2002In: International Journal of Pavement Engineering, Vol. 2Article in journal (Refereed)
  • 162. Sangpetgnam, S.
    et al.
    Birgisson, Björn
    Roque, R.
    A Multi-Layer Boundary Element Method for the Evaluation of Top-Down Cracking in Hot Mix Asphalt Pavements2004In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1896Article in journal (Refereed)
  • 163. Sangpetgnam, S
    et al.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Roque, R
    Development of an Efficient Hot Mix Asphalt Fracture Mechanics-Based Crack Growth Simulator2003In: Transportation Research Record, Vol. 1832Article in journal (Refereed)
  • 164. Sangpetgnam, S.
    et al.
    Birgisson, Björn
    Roque, R.
    Prediction of Top-Down Crack Initiation and Crack Growth in Hot Mix Asphalt Pavements2004In: Proceedings, Fifth International RILEM Conference on Cracking in Pavements – Mitigation, Risk Assessment and Prevention, Limoges, France, 2004Conference paper (Refereed)
  • 165.
    TAŞDEMİR, Yuksel
    et al.
    Engineering and Architecture Faculty, Bozok University.
    Das, Prabir
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Determination of Mixture Fracture Performance with the Help of Fracture Mechanics2010Conference paper (Refereed)
    Abstract [en]

    Cracking is one of the most influential distresses that mostly affect the service life of asphalt concrete pavements. These cracks start as microcracks that later coalesce to form macrocracks, which propagate due to tensile and/or shear stress. As the cracks propagate, the pavement serviceability starts to reduce dramatically. In order to improve the cracking performance of asphalt pavements, it is important to acquire a good understanding of the cracking mechanism and to have a reliable system to determine mixture’s resistance to crack development and propagation.

     

    An HMA (Hot Mix Asphalt) fracture mechanics framework based on Superpave IDT (InDirect Tension test) has been developed in the US. The main ideology of this framework is the concept of the existence of a damage threshold. The dissipated creep strain energy (DCSE) limit and the fracture energy (FE) limit of asphalt mixtures are the lower and upper thresholds, respectively. According to this fracture mechanics framework, three types of testing are performed in the IDT testing device for predicting the fracture resistance of bituminous mixtures. Testing comprises resilient modulus, static creep and tensile strength. In this study, theory of this framework and application to field will be explained extensively.

  • 166. Wang, J.
    et al.
    Birgisson, Björn
    Department of Civil and Coastal Engineering, University of Florida.
    Roque, R.
    Effects of Viscoelastic Stress Redistribution on the Cracking Performance of Asphalt Pavements2006In: 2006 Journal of the Association of Asphalt Paving Technologists: From the Proceedings of the Technical Sessions, Vol 75, 2006, Vol. 75, p. 637-676Conference paper (Refereed)
    Abstract [en]

    Although the theological behavior of hot mix asphalt (HMA) mixtures has been well recognized, it has rarely been taken into account in predicting the pavement response and evaluating its cracking performance. In this paper, a detailed analysis of the rheological behavior of asphalt concrete (AC) and its effect on the pavement response is carried out using a viscoelastic boundary element method developed recently by the authors. The research findings show that the stress distribution in flexible pavements is continuously changing as the pavement is loaded, because viscoelastic bituminous materials relax stresses. Generally, both compressive stresses at the top and tensile stresses at the bottom of the AC layer reduce with increased loading time or number of repeated loads. Continuous repeated loads may lead to accumulation of residual tensile stresses at the surface of the pavement and residual compressive stresses at the bottom of the AC layer. The presence of significant tensile stresses at the top of the pavement layer results in an accumulation of dissipated creep strain energy (DCSE) over time (or with number of loads) and may eventually lead to the formation of a crack. As time increases, the tension at the bottom of AC layer reduces significantly and may finally turn into compression. At the same time, a considerable level of tension builds up at the surface of the AC layer through loading and unloading cycles. This could possibly explain why bottom-up cracking does not appear as frequently as top-down cracking. Interestingly, these findings also appear to explain why top-down cracks have not been observed in parking lots. In summary, this paper clearly shows that the theological behavior of the HMA mixture results in load-induced stress redistributions that may dominate the failure mode of pavement structure. The results presented imply a wide range of consequences for pavement engineers. The nature of the viscoelastic stress redistributions depends on the rheology of the binder, mixtures, pavement structure, and the loads applied. Therefore, successful optimization of a pavement structure and mixtures for enhanced cracking performance may require the inclusion of viscoelastic effects. The research findings reported in this paper open a door for the evaluation of the cracking performance of asphalt pavements considering the rheology of asphalt mixtures and for the subsequent adjustment of the current criteria for selection and design of mixtures and binder types.

  • 167. Wang, Jianlin
    et al.
    Birgisson, Björn
    A time domain boundary element method for modeling the quasi-static viscoelastic behavior of asphalt pavements2007In: Engineering analysis with boundary elements, ISSN 0955-7997, E-ISSN 1873-197X, Vol. 31, no 3, p. 226-240Article in journal (Refereed)
    Abstract [en]

    A time domain boundary element method (BEM) is presented to model the quasi-static linear viscoelastic behavior of asphalt pavements. In the viscoelastic analysis, the fundamental solution is derived in terms of elemental displacement discontinuities (DDs) and a boundary integral equation is formulated in the time domain. The unknown DDs are assumed to vary quadratically in the spatial domain and to vary linearly in the time domain. The equation is then solved incrementally through the whole time history using an explicit time-marching approach. All the spatial and temporal integrations can be performed analytically, which guarantees the accuracy of the method and the stability of the numerical procedure. Several viscoelastic models such as Boltzmann, Burgers, and power-law models are considered to characterize the time-dependent behavior of linear viscoelastic materials. The numerical method is applied to study the load-induced stress redistribution and its effects on the cracking performance of asphalt pavements. Some benchmark problems are solved to verify the accuracy and efficiency of the approach. Numerical experiments are also carried out to demonstrate application of the method in pavement engineering.

  • 168. Wang, Jianlin
    et al.
    Birgisson, Björn
    Roque, Reynaldo
    Windows-based top-down cracking design tool for Florida: Using energy ratio concept2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2037, p. 86-96Article in journal (Refereed)
    Abstract [en]

    Top-down cracking has been found to be a predominant mode of distresses of asphalt pavements in Florida. Therefore, it is important to accommodate top-down cracking in the design of asphalt mixtures and pavement structures. After a multiyear study on top-down cracking supported by the Florida Department of Transportation, the University of Florida developed a top-down cracking model based on hot-mix asphalt fracture mechanics. This paper presents the implementation of the Florida cracking model into a mechanistic-empirical (M-E) flexible pavement design framework. Based on the energy ratio concept, a new M-E pavement design tool for top-down cracking has been developed. In the Level 3 M-E design, a series of semiempirical models were developed for estimation of time-dependent material properties. With incorporation of the material properties models, the design tool is capable of performing pavement thickness design as well as pavement life prediction for top-down cracking in Florida. The thickness design is optimized for different traffic levels, mixture types, and binder selections, and the optimization is an automated process. This design tool has been packed into Windows-based software, making it convenient to use for pavement design engineers.

  • 169.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    A new moisture distribution model for unbound granular materialsIn: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656Article in journal (Other academic)
    Abstract [en]

    The presence of waterin the unbound granular materials significantly influences the mechanicalperformance of the material. The ability to estimate the soil watercharacteristic curve (SWCC) is crucial thus to determine the effect themoisture has on the mechanical behaviour of granular materials. In this paper,an analytical moisture distribution model is proposed. A packing theory-based framework to evaluateperformance of unbound granular materials reported previously by the authorsallows identifying the two basic components of the unbound granular materialsskeleton: primary structure (PS) - a range of interactive coarse grain sizes thatforms the main load carrying network in granular materials and secondarystructure (SS) - a range of grain sizes smaller than the PS providing stabilityto the aggregate skeleton. In the new moisture distribution model presented inthis paper, moisture wasconsidered to be stored as meniscus water between SS particles and water thatfilled in small voids.The volume of meniscus water between SS particles and the measured matricsuction values are the two key parameters in the model. In order to validatethe model predicted results are then compared with measuredmatric suction of granite granular materials with different gradations. Theresults showed that the model developed is capable of predicting theexperimentally measured matric suction values for a range of gradations. 

  • 170.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Influence of aggregate packing structure on California bearing ratio values of unbound granular materials2014In: International Journal on Road Materials and Pavement Design, ISSN 1468-0629, E-ISSN 2164-7402, Vol. 15, no 1, p. 102-113Article in journal (Refereed)
    Abstract [en]

    Over the past several decades, California bearing ratio (CBR) value has been used in many countries for empirical pavement designs and still many countries are using it for unbound granular materials strength measurement and as input to their pavement design chart. Furthermore, CBR value of unbound granular material is frequently correlated with its fundamental mechanical properties such as resilient modulus, which in turn is often used as an input to a mechanistic pavement design procedure. In the present study, the effect the aggregate packing has on the CBR values of unbound materials is investigated. A packing theory-based framework that allows to identify the load-carrying part of the aggregate skeleton is presented. Aggregate packing parameters controlling the CBR performance of the unbound materials are introduced and evaluated with the experimentally measured CBR values of 20 unbound granular materials found in the literature. It is shown that the CBR values of granular materials are to a great extent controlled by the packing characteristics of their load-carrying skeleton.

  • 171.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Packing theory-based framework for evaluating resilient modulus of unbound granular materials2014In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 15, no 8, p. 689-697Article in journal (Refereed)
    Abstract [en]

    Enhancing the quality of granular layers is fundamental to optimise the structural performance of the pavements. The objective of this study is to investigate whether previously developed packing theory-based aggregate parameters can evaluate the resilient modulus of unbound granular materials. In this study, 19 differently graded unbound granular materials from two countries (USA and Sweden) were evaluated. This study validated both porosity of primary structure (PS) and contact points per particle (coordination number) as key parameters for evaluating the resilient modulus of unbound granular materials. This study showed that decreasing the PS porosity - higher coordination number - calculated based on the proposed gradation model, yields higher resilient modulus. Good correlation was observed between the proposed packing parameters and resilient modulus of several types of aggregates. The packing theory-based framework successfully recognised granular materials that exhibited poor performance in terms of resilient modulus.

  • 172.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Jelagin, Denis
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Guarin, Alvaro
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Packing theory-based framework to evaluate permanent deformation of unbound granular materials2013In: The international journal of pavement engineering, ISSN 1029-8436, E-ISSN 1477-268X, Vol. 14, no 3, p. 309-320Article in journal (Refereed)
    Abstract [en]

    Permanent deformation of unbound granular materials plays an essential role in the long-term performance of a pavement structure. Stability of unbound granular materials is defined by the particle-to-particle contact of the system, the particle size distribution and the packing arrangement. This paper presents a gradation model based on packing theory to evaluate permanent deformation of unbound granular materials. The framework was evaluated by using 10 unbound granular materials from different countries. The disruption potential, which determines the ability of secondary structure (SS) to disrupt the primary structure (PS), is introduced. This study also identified the amount of PS and SS that may eventually be used as a design parameter for permanent deformation of unbound road layers. The evaluation of the model regarding permanent deformation behaviour of granular materials is found to compare favourably with experimental results.

  • 173.
    Yideti, Tatek Fekadu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Dawson, Andrew
    The University of Nottingham.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Implementation of Shakedown and Packing theories for Unbound Granular materialsIn: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526Article in journal (Other academic)
    Abstract [en]

    The shakedown theory is a tool to characterize the state of the structural system of an unbound granular material that is subjected to repeated loading when its response has become resilient in nature and no further accumulation of plastic strain occurs. This paper demonstrates the application of both shakedown and packing theories to characterize permanent deformation behaviour of unbound aggregate materials. Ranges of shakedown phenomenon (Ranges A, B and C) for some selected unbound materials have first been investigated based on their permanent strain responses. The disruption potential (DP) of the primary structure (PS) of the aggregate assemblage has then been determined for each grain size distribution based on a packing theory model. The DP was found to characterize satisfactorily the three types of shakedown ranges. A sensitivity analysis has also been done on DP values by changing the dry density and specific gravity, revealing the importance of these characteristics for shakedown. Further, a finite element analysis was performed to determine the shakedown limit load as a mean stress and a dimensionless shakedown load. The analysis was simulated using the Mohr-coulomb yield criteria for a three-dimensional cylindrical sample. From this study the DP value was found to compare favorably with the predicted mean stress and dimensionless shakedown load.

     

  • 174.
    Yideti, Tatek
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Jelagin, Denis
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.). 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.
    Moisture Distribution Model to Predict Matric Suction in Unbound Granular Materials as a Function of Fines Content2016In: TRB 95th Annual Meeting Compendium of Papers, 2016Conference paper (Refereed)
    Abstract [en]

    The existence of water in the layers of unbound road aggregates significantly influences the performance of pavement structure. Thus, the ability to estimate volumetric water content and its capillary effect is very important. Several models have been suggested to link the matric suction of unbound materials to their water retention properties. In this paper, an analytical moisture distribution model is proposed by using packing theory-based framework for unbound granular materials. The framework was previously developed by the authors of this paper and identifies two basic components of unbound granular materials skeleton: primary structure (PS) - a range of interactive coarse grain sizes that forms the main load-carrying network in granular materials and secondary structure (SS) - a range of grain sizes smaller than the PS providing stability to the aggregate skeleton. In the new moisture model, water was considered to be stored as both menisci water between SS particles and water that fully filled in very small voids. In order to validate the model, predicted results are compared with measured matric suction of a granite material with different gradations. The results showed that the model is capable of predicting the experimentally measured matric suction values for a range of gradations.

  • 175. Zhang, Z
    et al.
    Roque, R
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of Laboratory Measured Crack Growth Rate for Asphalt Mixtures2001In: Transportation Research Record, Vol. 1767Article in journal (Refereed)
  • 176. Zhang, Z
    et al.
    Roque, R
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Sangpetgnam, S
    Identification and Verification of a Suitable Crack Growth Law for Asphalt Mixtures2001In: Journal of Asphalt Paving Technologists, Vol. 70Article in journal (Refereed)
  • 177.
    Zhu, Jiqing
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Polymer modification of bitumen: Advances and challenges2014In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 54, no 1, p. 18-38Article, review/survey (Refereed)
    Abstract [en]

    Advances and challenges in the field of bitumen polymer modification for road construction during the last 40 years are reviewed in this paper. The history of bitumen polymer modification is described chronologically. Some popular plastomers and thermoplastic elastomers in bitumen modification are discussed regarding their advantages and disadvantages, including polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate (EVA), ethylene-butyl acrylate (EBA), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS) and styrene-ethylene/butylene-styrene (SEBS). Although these polymers all improve bitumen properties to some extent, there are still some drawbacks limiting the future development of bitumen polymer modification, such as high cost, low ageing resistance and poor storage stability of polymer modified bitumen (PMB). Researchers attempted various ways to remove these drawbacks. Some technical developments for removing drawbacks are reviewed in this paper, including saturation, sulfur vulcanization, adding antioxidants, using hydrophobic clay minerals, functionalization and application of reactive polymers. The future development of polymers for bitumen modification is analyzed as well. Since it is currently challenging to perfectly achieve all expected PMB properties at the same time, some compromised recommendations are given in this paper, among which greatly enhancing the properties with an acceptably high cost, significantly reducing the cost with relatively poor properties and their combinations. Functionalization is emphasized as a promising way to enhance the properties of currently used polymers and develop new-type polymer modifiers with much greater success in the future. It is also recommended that future research on bitumen polymer modification focuses more on function development towards enhancing: adhesion with aggregates, long-term performance and recyclability.

1234 151 - 177 of 177
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf