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1.	Desivyana, Nindya, 1997, et al. (författare) Challenges in the adoption of sustainable criteria in the Swedish property development industry 2023 Ingår i: Procedia Computer Science. - : Elsevier BV. - 1877-0509. ; 219, s. 1752-1759 Konferensbidrag (refereegranskat)abstract The construction industry is facing an increased focus on sustainability and climate neutrality, causing property developers to implement new requirements into the procurement documents, which are also driven by the national agenda. This study explores the current state of sustainability practice among Swedish property developers and identifies the main obstacles to expand further the implementation of the sustainability criteria. How the property developers define and implement sustainability requirements has been assessed through qualitative semi-structured interviews, focusing on sustainability certification systems, Life Cycle Assessment (LCA), and social sustainability. The results show usage of sustainability certification systems for marketing purposes and high awareness and practice of LCA, even though the accuracy of LCA was questioned. This study also identified guideline gaps for circular economy and social sustainability measurements, which could relate to low initiatives from the certification systems.
2.	Rempling, Rasmus, 1976, et al. (författare) Utmattning 2021 Ingår i: Betonghandbok material - Hårdnad betong, fysikaliska egenskaper och beständighet. - 9789179170882 ; , s. 485-510 Bokkapitel (övrigt vetenskapligt/konstnärligt)
3.	Mathern, Alexandre, 1986 (författare) Addressing the complexity of sustainability-driven structural design: Computational design, optimization, and decision making 2021 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Being one of the sectors with the largest environmental burden and high socio-economic impacts sets high requirements on the construction industry. At the same time, this provides the sector with great opportunities to contribute to the globally pursued sustainability transition. To cope with the increasing need for infrastructure and, at the same time, limit their sustainability impacts, changes and innovation in the construction sector are required. The greatest possibility to limit the sustainability impact of construction works is at the early design phase of construction projects, as many of the choices influencing sustainability are made at that point. Traditionally, an early choice of a preferred design is often made based on limited knowledge and past experience, considering only a handful of options. This preferred design is then taken on to the successive stages in the stepwise design process, leading to suboptimization. Alternatively, many different design choices could be considered and evaluated in a more holistic approach in order to find the most sustainable design for a particular application. However, finding design solutions that offer the best sustainability performance and fulfil all structural, performance and buildability requirements, require methods that allow considering different design options, analysing them, and assessing their sustainability. The aim of this thesis is to explore and develop methods enabling structural engineers to take sustainability objectives into account in the design of structures. Throughout this thesis, a number of methods have been explored to take sustainability aspects into account in the structural design process. As a first step, highly parameterized computer codes for sustainability-driven design have been developed. These codes interoperate with FE analysis software to automatically model and analyse design concepts over the whole design space and verify compliance with structural design standards. The codes were complemented with a harmonized method for life cycle sustainability performance assessment, in line with the state-of-the-art standards. Here, sustainability criteria were defined covering environmental, social, economic, buildability and structural performance for multi-criteria assessment of design concepts. To identify the most sustainable designs within the set, multi-objective optimization algorithms were used. Algorithms that address the high expense of constraint function evaluations of structural design problems were developed and integrated in the parameterized computer codes for sustainability-driven design. To ensure the applicability and validity of these methods, case studies based on real-world projects and common structural engineering problems were used in this thesis. Case studies for bridges and wind turbine foundations as well as a benchmark case of a reinforced concrete beam were investigated. The case studies highlight the potential of the methods explored to support the design of more sustainable structures, as well as the applicability of the methods in structural engineering practice. It is concluded that it is possible and beneficial to combine computational design, life cycle sustainability assessment, and multi-objective design optimization as a basis for decision making in the design phase of civil engineering projects. A wide adoption of such a sustainability-driven design optimization approach in structural engineering practice can directly improve the sustainability of the construction sector.
4.	Mathern, Alexandre, 1986, et al. (författare) Concrete Support Structures for Offshore Wind Turbines: Current Status, Challenges, and Future Trends 2021 Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 14:7 Forskningsöversikt (refereegranskat)abstract Today’s offshore wind turbine support structures market is largely dominated by steel structures, since steel monopiles account for the vast majority of installations in the last decade and new types of multi-leg steel structures have been developed in recent years. However, as wind turbines become bigger, and potential sites for offshore wind farms are located in ever deeper waters and ever further from the shore, the conditions for the design, transport, and installation of support structures are changing. In light of these facts, this paper identifies and categorizes the challenges and future trends related to the use of concrete for support structures of future offshore wind projects. To do so, recent advances and technologies still under development for both bottom-fixed and floating concrete support structures have been reviewed. It was found that these new developments meet the challenges associated with the use of concrete support structures, as they will allow the production costs to be lowered and transport and installation to be facilitated. New technologies for concrete support structures used at medium and great water depths are also being developed and are expected to become more common in future offshore wind installations. Therefore, the new developments identified in this paper show the likelihood of an increase in the use of concrete support structures in future offshore wind farms. These developments also indicate that the complexity of future support structures will increase due to the development of hybrid structures combining steel and concrete. These evolutions call for new knowledge and technical know-how in order to allow reliable structures to be built and risk-free offshore installation to be executed.
5.	Mathern, Alexandre, 1986, et al. (författare) Lessons learned from the construction, inspection, and defect assessment of reinforced concrete foundations for wind turbines 2022 Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 12:3 Tidskriftsartikel (refereegranskat)abstract Foundations of wind turbines are subject to challenging conditions during their service life as they support ever larger wind turbines under complex loading situations. There have been numerous reports of cracked concrete foundations of wind turbines. Cracking can impair the durability and serviceability of the foundations, thereby leading to very expensive repairs or even to premature failure of the structure. To avoid cracking-related problems and improve the quality of concrete foundations, it is important to gather information and experience from the production stage and its outcome. However, although problems and defects in the construction of wind turbine foundations are widespread, they have very seldom been documented and reported, in particular from a contractor’s perspective. This article analyses and critically reviews data collected during the production, inspection, diagnosis, and repair activities conducted in relation to the construction of foundations for a wind farm project in Sweden. The extent of defects observed on individual foundations is assessed and used to investigate the eventual relation between the observed deviations and different production aspects. Investigation methods to determine the importance of these defects and their consequences and possible remediation measures are also discussed. Finally, recommendations are proposed to improve the quality control of wind turbine foundations.
6.	Rempling, Rasmus, 1976, et al. (författare) Performance requirements for Swedish transport infrastructure - A pre-study of challenges and possibilities 2022 Rapport (övrigt vetenskapligt/konstnärligt)abstract In recent years, significant worldwide research has been conducted regarding the performance assessment of bridges and the concept of performance indicator has been introduced However, there are still significant discrepancies in how these indicators are obtained and used. Simultaneously, it is desirable to achieve processes and methods that are direct, i.e. that measured values are directly compared with projected values over time. This project concerns methods for verification of technical performance requirements. The feasibility study brought together interdisciplinary researchers, consultants, and entrepreneurs to gather knowledge, anchor the research agenda, and implement performance requirements. The project concludes that there is a need for a “Holistic multi-parameter verification/validation system” that relies on the knowledge gained in structural health monitoring research.
7.	van Eldert, Jeroen, 1987-, et al. (författare) Application of Measurement While Drilling Technology to Predict Rock Mass Quality and Rock Support for Tunnelling 2020 Ingår i: Rock Mechanics and Rock Engineering. - : Springer. - 0723-2632 .- 1434-453X. ; 53:3, s. 1349-1358 Tidskriftsartikel (refereegranskat)abstract A tunnelling project is normally initiated with a site investigation to determine the in situ rock mass conditions and to generate the basis for the tunnel design and rock support. However, since site investigations often are based on limited information (surface mapping, geophysical profiles, few bore holes, etc.), the estimation of the rock mass conditions may contain inaccuracies, resulting in underestimating the required rock support. The study hypothesised that these inaccuracies could be reduced using Measurement While Drilling (MWD) technology to assist in the decision-making process. A case study of two tunnels in the Stockholm bypass found the rock mass quality was severely overestimated by the site investigation; more than 45% of the investigated sections had a lower rock mass quality than expected. MWD data were recorded in 25 m grout holes and 6 m blast holes. The MWD data were normalised so that the long grout holes with larger hole diameters and the shorter blast holes with smaller hole diameters gave similar results. With normalised MWD data, it was possible to mimic the tunnel contour mapping; results showed good correlation with mapped Q-value and installed rock support. MWD technology can improve the accuracy of forecasting the rock mass ahead of the face. It can bridge the information gap between the early, somewhat uncertain geotechnical site investigation and the geological mapping done after excavation to optimise rock support.
8.	Desivyana, Nindya, 1997, et al. (författare) Sustainability Driven Procurement of Building Projects Incentives and Driving Factors from the Clients’ Perspective 2023 Rapport (övrigt vetenskapligt/konstnärligt)abstract The construction industry is reported as one of the biggest global industries which accounted 30% global greenhouse gas emissions. The challenge of the construction industry is not merely on the reduction of emissions, but also extended towards other aspects of sustainability, consisting of the environmental, social, and economic pillars of sustainability. Sweden took action to handle the environmental issues by targeting on being climate neutral by 2045. Hence, the Swedish National Board of Housing, Building, and Planning, commonly known as Boverket, took more detailed action by stipulating climate declaration for all new buildings. The property developers play a vital role to boost sustainability in Sweden, since they have an increased influence in the hierarchy of the construction industry. In this case, the drivers of sustainable development in the construction industry are partially reliant on the clients’ requirements requested in every project, as well as their ethics and initiatives. Therefore, this study investigates the state-of-the-art sustainable practices among property developers in Sweden to identify the main challenges in applying sustainable criteria during the procurement phase. This study was carried out by qualitative research which consists of a literature review and an empirical study of semi-structured interviews. This study resulted in the identification of several common sustainable criteria, covering the three pillars of sustainability and also emphasising the fact that currently the property developers have an increased interest in environmental and economic sustainability, rather than social sustainability. The results of the study also raised the notion of long-term perspective, how it affects the business strategy on sustainability and the different perceptions that exist. The study concludes that the market demand drives the implementation of the agenda on sustainability, among property developers in Sweden, while providing substantial information that could prove useful in the future development of the national agenda and its regulations.
9.	Löfgren, Simon (författare) Set-Based Design of Frame Bridges - Development and Implementation 2020 Rapport (övrigt vetenskapligt/konstnärligt)abstract The traditional design process of bridges in structural engineering is based on the design approach called Point-Based design. To minimize environmental impact and industrialize the design process, the theory of Set-Based design (SBD) has been recognized as a promising approach. Since frame bridges is one of the most common bridge types in Sweden, the main objective of this thesis is to develop and implement a SBD tool for frame bridges. To be able to evaluate the different design alternatives generated by the design tool, evaluation criteria within buildability and sustainability are identified. Buildability is a concept within building industry that aims to improve productivity and safety within on-site production while also reducing the costs of the construction process. The building industry is one of the major contributors regarding impact on its surrounding. Therefore, there is a huge potential in improving the sustainability within the building industry. Sustainability is divided in Environment, Social and Economy aspects. The design tool allows performing an automated and iterative structural preliminary design of several frame bridge alternatives specified within ranges of design parameters. The design alternatives are analyzed with Finite Element Analysis (FEA) and evaluated according to predefined evaluation criteria. By scripting the design tool in programing language Python, it is possible to control an FEA program, such as Brigade Plus, from the design tool as well as performing a preliminary design of frame bridges. The preliminary design is performed according to requirements in national building codes, Eurocode. Finally, a case study is performed to investigate how a SBD tool can be implemented in an infrastructure project containing several frame bridges. In a large infrastructure project and with a SBD tool it is possible to find one optimum bridge solution that fulfills the need of several bridges in a set of bridges. The contractor can then industrialize parts of the construction of frame bridges, hopefully leading to a more sustainable and cost-effective building of frame bridges.
10.	Täljsten, Björn, 1961-, et al. (författare) Assessment of prestressed concrete bridges - challenges 2020 Ingår i: IABSE Symposium, Wroclaw 2020. - Zürich : International Association For Bridge And Structural Engineering (IABSE). ; , s. 487-494 Konferensbidrag (refereegranskat)abstract Prestressed concrete bridges are important parts of our infrastructure. They are susceptible to different kinds of deterioration processes. Examples of damages and deficiencies are cracking, corrosion, voids, bond loss, reduction of cover layer, delamination, fatigue and loss of stiffness and strength. This necessitates methods to continuously assess their condition in order to avoid problems that might lead to shorter service life or reduction of structural integrity. Many of the existing prestressed bridges in Europe are now approaching their design life length. However, with proper and continuous inspection, monitoring and assessment, we may plan proactive maintenance and the structural safety can be assured or – if necessary - increased. This will save both money and decrease the environmental impact of the structure.
11.	Ståhle, Alexander, et al. (författare) Designguide för Smarta gator 2022 Bok (övrigt vetenskapligt/konstnärligt)abstract Designguiden för smarta gator konkretiserar hur de fyra megatrenderna urbanisering, digitalisering, samhällsförändringar och miljöförändringar leder till nya krav och utformningsprinciper för framtidens gator. Guiden är tänkt att fungera som en inspiration och ett underlag för att förnya svensk gatupolicy på nationell, regional och kommunal nivå.Guiden innehåller utöver en inledning följande kapitel: en historisk tillbakablick (gatans utveckling), gatans användning, gatans delar, gatans design, designprocessen, guidens genomförande.
12.	Nasrollahi, Kourosh, 1991 (författare) Differential railway track settlement in a transition zone – Field measurements and numerical simulations 2023 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract In a transition zone between two different railway track forms, there is a discontinuity in track structure leading to a gradient in track stiffness. Examples include transitions between different superstructures, e.g., slab track to ballasted track, and/or between different substructures, e.g., embankment to a bridge or tunnel structure. Differences in loading and support conditions at the interfaces between track superstructure and substructure on either side of the transition may lead to differential track settlement and an irregularity in longitudinal rail level soon after construction because of densification of ballast and consolidation in the subsoil. This results in an amplification of the dynamic traffic loading along the transition. To ensure the safety of railway operation and reduce maintenance costs, it is necessary to monitor the condition of the transition zone and detect any operational change at an early stage. A methodology for the simulation of long-term differential track settlement, the development of voided sleepers leading to a redistribution of rail seat loads, and the evolving irregularity in vertical track geometry at a transition between two track forms, is presented. For a prescribed traffic load, the accumulated settlement is predicted using an iterative approach. It is based on a time-domain model of vertical dynamic vehicle–track interaction to calculate the contact forces between sleepers and ballast in the short term. These are used in an empirical model to determine the long-term settlement of the ballast and subgrade below each sleeper. Gravity loads and state-dependent track conditions are accounted for. The methodology is applied to a transition zone between a ballasted track and a slab track that is subjected to heavy haul traffic. The influence of higher axle loads and the implementation of under sleeper pads on sleeper settlement is assessed. Based on fibre Bragg grating sensors, a setup for in-situ long-term condition monitoring of track bed degradation in a transition zone has been developed and implemented to provide data for verification and calibration of the simulation model. The system is designed for measurements in an operational railway track in harsh conditions in the north of Sweden. The instrumentation along the transition comprises four clusters, each with an optical strain gauge array on the rail web in one sleeper bay, and an accelerometer and a displacement transducer on the sleeper end. Two additional accelerometers are installed far from the transition zone to measure a reference state. Combined, the data should not only provide details on long-term settlements, but also the change in dynamic response it underpins.
13.	Robuschi, Samanta, 1991 (författare) Natural corrosion in reinforced concrete structures 2021 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Among the threats to the durability of concrete structures, corrosion of the reinforcement bars is undoubtedly the most common one. Corrosion damages impair safety and durability of infrastructure, and assessment of the safety is challenging due to the complex nature of the corrosion process. Furthermore, research on the topic often requires adapting results from short-time laboratory tests, where corrosion of the reinforcement bars is induced using impressed current, to the reality of existing structures. The use of impressed current results in differences in type and distribution of corrosion products. Naturally corroded specimens are hence the necessary bridge between the knowledge acquired from artificially corroded specimens and the application to real structures. This works investigates the structural effects of natural, chloride-induced corrosion in reinforced concrete structures. Specifically, three research questions were investigated. First, the bond and anchorage of naturally corroded plain bars was studied using 3-point bending and pull-out tests. The tests were designed to be applied to specimens taken from a decommissioned bridge from the 1930s. The bond capacity of plain bars was observed to be significantly higher than in results obtained from laboratory tests on similar bars. Significant factors influencing the effect of corrosion damages on the bond were casting position and presence of stirrups. Finite element analyses were used to further investigate the bond-slip behaviour of the tested specimens. The results highlighted the effect of the loss of bond at yielding on the structural behaviour of the specimens. The second question looked into the characteristics of the corrosion products and the surrounding concrete; this is relevant to assess corrosion damages in existing structures. Neutron imaging and X-ray computed tomography were used to obtain qualitative and quantitative data on corrosion damages in a naturally corroded specimens, including iron to rust ratio. Comparison with an artificially corroded specimen showed differences in distribution of the corrosion products. Finally, possible correlations between transversal cracks and corrosion damages was investigated. A dataset was compiled from experiments available in literature. In the selected studies, corrosion of the steel reinforcement resulted from exposing laboratory specimens, pre-cracked in 3-point bending, to chloride environments. No clear correlation between surface crack width and corrosion characteristics was found, but corrosion pits were shown to likely appear in the proximity of transveral cracks. To conclude, this work highlights the complexity of the corrosion process and argues that a thorough understanding of the material and environmental characteristics influencing this process is necessary to properly assess existing structures. Tests on naturally corroded structures are a fundamental step towards acquiring this knowledge.
14.	Armesto Barros, Jesús, et al. (författare) Recent and future trends of onshore wind turbine foundations 2022 Ingår i: Proceedings of the IABSE Symposium Prague 2022: Challenges for Existing and Oncoming Structures. - 9783857481819 Konferensbidrag (refereegranskat)abstract The decarbonization of the economy and the growing need for electricity are two trends that call for greener energy sources. Wind is a growing renewable energy source, which is expected to become the first source of power in the European Union in the next decade. In particular, onshore wind energy is expected to double by then. Fundamental structural components of wind turbines are their foundations, which are large structures associated with important material consumption and many construction challenges. The dimensions of these foundations are continuously increasing as turbines with taller towers and larger rotor diameters are being built. Designing cost- and material-efficient foundations is crucial to reduce the economic and environmental impact of wind energy. An important factor to successfully address these evolving requirements in the planning and design process is to build on the experience from previous projects. The aim of this work is to investigate the evolution of onshore wind turbines and its consequences on the design and climate impact of gravity foundations by analysing data from Swedish wind farms set in operation between 2013 and 2022. The evolution of turbine size, and foundation dimensions, reinforcement layout, material types and quantities, and embodied carbon are analysed in this paper.
15.	Bergenram, Felicia, et al. (författare) Parametric Optimization of Slab Frame Bridges Considering Investment Cost, Environmental Impact and Buildability 2023 Ingår i: Procedia Computer Science. - 1877-0509. Konferensbidrag (refereegranskat)abstract This paper presents research performed on set-based multi-criteria optimization for the preliminary design of slab frame bridges. As a result of immense CO2 emissions emerging from concrete production, there is a need for optimization methods decreasing the volume of concrete without affecting the function of the structure. Previous research suggests a general correlation between CO2 footprint- and cost reduction, due to minimized material use. However, the aspect of buildability may conflict with lessened material, as optimized designs might simultaneously be less buildable. This research aimed to develop an optimization method with respect to the investment cost and environmental impact while also considering buildability cost aspects. The optimization algorithm shows the possibilities of reducing the environmental impact by up to 13.7% for a slightly increased cost of 2.3%. Thus, by implementing optimization procedures in the early stages of the planning process the holistic cost effects related to green solutions can be presented, favoring the choice of sustainable designs amongst clients during tendering procedures.
16.	Mathern, Alexandre, 1986, et al. (författare) Practical metamodel‑assisted multi‑objective design optimization for improved sustainability and buildability of wind turbine foundations 2022 Ingår i: Structural and Multidisciplinary Optimization. - : Springer Science and Business Media LLC. - 1615-1488 .- 1615-147X. ; 65:2 Tidskriftsartikel (refereegranskat)abstract In this work, we study the potential of using kriging metamodelling to perform multi-objective structural design optimization using finite element analysis software and design standards while keeping the computational efforts low. A method is proposed, which includes sustainability and buildability objectives, and it is applied to a case study of reinforced concrete foundations for wind turbines based on data from a large Swedish wind farm project. Sensitivity analyses are conducted to investigate the influence of the penalty factor applied to unfeasible solutions and the size of the initial sample generated by Latin hypercube sampling. A multi-objective optimization is then performed to obtain the optimum designs for different weight combinations for the four objectives considered. Results show that the kriging-obtained designs from samples of 20 designs outperform the best designs in the samples of 1000 designs. The optimum designs obtained by the proposed method have a sustainability impact 8–15% lower than the designs developed by traditional methods.
17.	Baba Ahmadi, Arezou, 1985, et al. (författare) Utilization of Bio Ashes in Cement-based Materials: A Case Study in Cooperation with Pulp and Paper and Energy Production Industries in Sweden 2020 Ingår i: Nordic Concrete Research. - : Walter de Gruyter GmbH. - 0800-6377 .- 2545-2819. ; 63:2, s. 63-78 Tidskriftsartikel (refereegranskat)abstract Worldwide increased concern of the CO2 emissions has led to the replacement of coal by biomass in combustion-based power plants. However, this would cause the scarcity of fly ash, one of the most well-known rest products from coal combustion, which is used as supplementary cementitious materials (SCM) in construction sector to reduce the large environmental footprint of cement production. Seeking to find alternative SCMs, this article aims to demonstrate the viability of using bio ashes in Sweden as SCM, which, due to lack of studies validating their value, are landfilled today. According to the obtained results, bio ashes produced at pulp and paper industries have a considerably consistent chemical composition and exhibit a satisfactory pozzolanic behaviour. Nevertheless, according to the conclusions of this study, the pozzolanicity of these alternative binders is not reflected equally with respect to the most known reactivity tests for common SCMs. The results imply that although “R3” tests method infers the pozzolanic characteristics of the bio ashes in focus of this study, the “activity index test” as well as “calcium consumption test” indicate otherwise.
18.	Hlal, Fatima, 1989 (författare) Stainless Steel Corrugated Web Girders for Composite Road Bridges: Concept Evaluation and Flange Buckling Resistance 2023 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract Achieving a sustainable bridge design requires careful consideration of economic viability and environmental impact over the entire lifespan of the structure. While stainless steel is recognized for its excellent life cycle performance, its high cost prevents it from being used to a larger extent in bridges. In this thesis work, a new solution is investigated to mitigate this issue. The new solution comprises the use of corrugated webs in stainless steel girders which is expected to result in reduced material consumption and cost. The work in this thesis focuses on two problem areas in this field. First, a study is performed to examine the competitiveness of the new concept in relation to conventional designs of steel-concrete composite road bridges. The second part of the work focuses on the problem of flange buckling in girders with corrugated webs. Previous research has shown that the design models developed for flange buckling resistance, including the one in EN 1993-1-5, frequently result in unsafe design. Furthermore, these models were developed for carbon steel and have not been updated for stainless steel. To explore the economic and environmental benefits of the new concept, two studies have been conducted. Firstly, three design solutions are examined on a case study bridge with three continuous spans. These design solutions include carbon steel flat web, stainless steel flat web, and stainless steel corrugated web girder bridges. A genetic algorithm is used to optimize each design solution in terms of weight. The three optimal solutions are then assessed in terms of investment costs, life cycle costs (LCC), and environmental life cycle impact. Secondly, two of the considered design solutions, namely carbon steel flat web and stainless-steel corrugated web girders, are employed to conduct multiple parametric studies using a simply supported reference bridge. For both design solutions, the effects of optimization targets on weight, investment cost, life cycle cost, and environmental life cycle impact are initially investigated. Following that, the focus is put on the life cycle cost (LCC) as an optimization target, and the impact of various design input parameters is investigated. These parameters include span length, girder depth, average daily traffic (ADT) with the associated number of heavy vehicles per slow lane (Nobs), and time intervals and expenses for maintenance activities. Furthermore, a sensitivity analysis is conducted to study the influence of the inflation rate and discount rate. The results indicate that the new concept offers considerable potential saving in weight, life cycle costs, and life cycle impacts for both simply supported and continuous bridges. The saving is more apparent with deeper girders, higher ADT, and more intense maintenance activities. Saving is also larger when inflation is high and discount rate is low. After studying the potential of corrugated web girders to reduce costs and environmental impacts in the case of employing stainless steel, a study of the flange buckling behaviour in duplex stainless-steel girders is conducted in this work. A parametric finite element model is developed and validated with tests conducted on beams made of carbon steel. The material is then changed to EN1.4162, and linear buckling analysis (LBA) and geometrically and materially nonlinear analysis with imperfections (GMNIA) are carried out on 410 girders with typical bridge girder dimensions. The results are compared to previously developed models for carbon steel, and a new buckling curve and flange local buckling design procedure for duplex stainless-steel girders with corrugated webs are proposed. The study shows that the new proposed design model generates more accurate estimates of flange buckling resistance than previous proposed models.
19.	Sciegaj, Adam, 1990 (författare) Multiscale Modelling of Reinforced Concrete Structures 2020 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Concrete cracks at relatively low tensile stresses; cracks open up for ingress of harmful substances, negatively affecting the durability of reinforced concrete structures. Crack widths are thus limited in the design codes, and accurate predictions are needed, especially for large reinforced concrete structures such as bridges or nuclear reactor containment buildings. On the one hand, cracking of concrete, constitutive behaviour of steel, and the bond between them must be accounted for in order to properly describe crack growth. On the other hand, explicitly resolving these features in large structures could prove computationally intractable. This thesis concerns multiscale modelling of reinforced concrete structures. More specifically, different two-scale models, based on Variationally Consistent Homogenisation (VCH), are developed. In these models, the response of a Representative Volume Element (RVE) is upscaled to a few popular structural models: a homogenised solid in plane stress, the effective Euler-Bernoulli beam and the effective Kirchhoff-Love plate. The effective response of the RVE is defined through a boundary value problem, for which different types of boundary conditions are developed and discussed. Furthermore, in order to allow for reinforcement slip transfer across the large-scale elements, a novel macroscopic reinforcement slip field is introduced. The developed two-scale models are used to analyse reinforced concrete deep beams subjected to membrane loads, reinforced concrete beams subjected to uniaxial tension and bending, and reinforced concrete panels subjected to combinations of membrane and bending loads. The results show that the general structural behaviour is reflected well by the multiscale models compared to single-scale analyses. By enriching the model with a macroscopic reinforcement slip field prescribed at the boundary of the RVE, the crack width predictions given by the two-scale models are improved and localisation of effective strain is observed at the large-scale. However, the results were dependent on the large-scale mesh and RVE sizes. In order to improve the objectivity of the model, a novel boundary condition type, prescribing the effective slip in the volume of the RVE, was developed. The macroscopic reinforcement slip became no longer RVE-size dependent, and the maximum crack width predictions were more consistent and showed a smaller variance for different large-scale meshes and sizes of RVEs. In conclusion, the developed two-scale models allow for the analysis of a wide range of reinforced concrete structures, and show potential in saving computational time in comparison to single-scale analyses.
20.	Shu, Jiangpeng, 1987, et al. (författare) Field Destructive Testing of a Reinforced Concrete Bridge Deck Slab 2020 Ingår i: Journal of Bridge Engineering. - : American Society of Civil Engineers (ASCE). - 1084-0702 .- 1943-5592. ; 25:9 Tidskriftsartikel (refereegranskat)abstract Many bridge deck slabs in Europe are rated insufficient load-carrying capacity in shear and punching according to the Eurocodes. In the past, assessment models have mainly been developed from laboratory studies that simplified real-world conditions. Large-scale or full-scale field experiments are needed to validate more recent improved models. The goal of this study is to calibrate improved models using data obtained from a full-scale bridge deck slab shear test; the objective is to exploit and share our findings and to make recommendations for the planning, design, and implementation of such a complex experiment. Full-scale destructive tests of a 55-year-old reinforced concrete bridge deck slab on prestressed concrete girders were conducted to calibrate a model used to assess existing bridges. Concrete properties were also tested to evaluate the condition of the bridge. Results show that both the load-carrying capacity of the bridge deck slab and the strength of the concrete were much greater than were assumed in design. Finite-element analysis of the parameters governing loading positions and prestress in the girders showed that arch action and boundary condition simplification had important effects on shear distribution.
21.	Carneiro, Erica, et al. (författare) Potential improvements in the life-cycle performance of support structures for onshore wind turbines – an interview study in Sweden 2022 Ingår i: Proceedings of XXIV Nordic Concrete Research Symposium. Konferensbidrag (refereegranskat)abstract Wind energy is one of the fastest growing renewable energy sources thanks to its cost-effectivity and sustainability. This paper investigates how construction and maintenance of support structures for onshore wind turbines can be improved. Interviews were performed to identify potential areas for improvement in design, construction, operation, maintenance, and end-of-life. Defects due to poor detailing in design and construction have been recurring and may have important consequences. More structured data collection during the construction stages and more robust inspection protocols can help to ensure adequate life-cycle performance of the support structures. Possibilities to reuse and recycle foundations by the end of the turbine’s operational lifetime, which remain unexploited and unresearched, are also discussed.
22.	Rempling, Rasmus, 1976, et al. (författare) The need for research and innovation to facilitate upscaling of low-carbon concrete 2023 Ingår i: IABSE Congress New Delhi 2023 Engineering for Sustainable Development. - : International Association for Bridge and Structural Engineering (IABSE). - 9781713883128 ; , s. 1199-1206 Konferensbidrag (refereegranskat)abstract For decades, research has been carried out with a focus on concrete structures during curing to mitigate the risk of thermal cracking. Computer programs and aids/tools have also been developed to assess stress and cracking risk analysis of concrete structures during curing. However, today with the recent introduction of low-carbon concretes to reduce the environmental impact of constructions, the reliability of the tools and working procedures, i.e. concrete characterization, is questioned, and a roadmap for research and innovation is called for. The project's primary purpose is to investigate the need for research and innovation regarding upscaling the usage of low-carbon concrete. The nature of the study is based on an industry-focused workshop with specialists from Scandinavia. Increased knowledge of hardening concrete's cracking risk-related properties is of the utmost importance for the construction industry as the need for its understanding has recently increased.
23.	Altintas, Atilla, 1979, et al. (författare) EMD-SVR: A Hybrid Machine Learning Method to Improve the Forecasting Accuracy of Highway Tollgates Traveling Time to Improve the Road Safety 2021 Ingår i: Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering. - Cham : Springer International Publishing. - 1867-8211 .- 1867-822X. ; 364 LNICST, s. 241-251 Konferensbidrag (refereegranskat)abstract Tollgates are known as the bottleneck of the highways, which cause long waiting queues in rush-hour times of the day. This brings many undesirable consequences such as higher carbon emission and road safety issues. To avoid this scenario, traffic control authorities need accurate travel time forecasts at tollgates to take effective action to monitor potential traffic load and improve traffic safety. Accurate forecasting of the traffic travel time will help traffic regulators to prevent arising problems by taking action. The main objective of this study is to improve the short-term forecasting (minutes) of the traffic flow on highway tollgates by improving a novel hybrid forecasting method that combines Empirical Mode Decomposition with Support Vector Regression (EMD-SVR). Results claim that compared with SVR, the new proposed hybrid prediction model, EMD-SVR, can effectively improve prediction accuracy. Better forecasting of the traffic load will provide safer roads but will also lower the carbon emissions caused by longer traveling times.
24.	Basso, Rafael, 1979, et al. (författare) Electric Vehicle Routing Problem with Machine Learning for Energy Prediction 2021 Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 145, s. 24-55 Tidskriftsartikel (refereegranskat)abstract Routing electric commercial vehicles requires taking into account their limited driving range, which is affected by several uncertain factors such as traffic conditions. This paper presents the time-dependent Electric Vehicle Routing Problem with Chance- Constraints (EVRP-CC) and partial recharging. The routing method is divided into two stages, where the first finds the best paths and the second optimizes the routes. A probabilistic Bayesian machine learning approach is proposed for predicting the expected energy consumption and variance for the road links, paths and routes. Hence it is possible to consider the uncertainty in energy demand by planning charging within a confidence interval. The energy estimation is validated with data from electric buses driving a public transport route in Gothenburg-Sweden as well as with realistic simulations for 24 hours traffic in the city of Luxembourg connected to a high fidelity vehicle model. Routing solutions are compared with a deterministic formulation of the problem similar to the ones found in the literature. The results indicate high accuracy for the energy prediction as well as energy savings and more reliability for the routes.
25.	Berghauser Pont, Meta, 1972, et al. (författare) INTEGRATED URBAN ENVIRONMENT EFFECT ANALYSIS OF INFRASTRUCTURAL TRANSFORMATIONS 2022 Rapport (övrigt vetenskapligt/konstnärligt)abstract The report presents the method developed within the research project ‘Stadsmiljöanalys- Analys av tätbebyggda miljöer i infrastrukturprojekt’, funded by Trafikverket (Swedish Transport Authority). This project sets up an integrated methodology for analysing and estimating the local impact of road and rail infrastructure projects in urban environments, either by way of new infrastructure or by way of retrofits, focusing on socioeconomic, environmental, and cultural-historical effects. While the focus is on national transport infrastructure investments, the method addresses local effects. This stems from the acknowledgement that each infrastructure investments results in a redistribution of accessibility where increasing accessibility on a regional and interurban scale might create encroachments on a local scale including the reduction of the usability of areas near to the infrastructure due to emissions and noise, risk of accidents, negative impacts on wildlife as well as barrier effects. It is these encroachments this method aims to highlight with the aim to reduce negative trade-offs of new or transformed transport infrastructure and recognize both local opportunities and sensitivities. In this project the direct effects of infrastructure projects in relation to the three perspectives (socioeconomic, environmental, and cultural-historical are described and measured in a precise manner through a series of spatial analyses. The cumulative, indirect, effects and broader consequences are also assessed, in relation to the sustainable development goals. The overall assessment methodology is based on a before-and-after analysis workflow, systematically comparing the existing situation (how it is, how it functions, how it affects people) to the future scenarios proposed by planning. The methodology is showcased using two infrastructural transformations projects in Söderköping and Mölndal, Sweden, as case studies. The overarching goal of the research project is to contribute to an improved integration between infrastructure and local urban areas and communities in projects initiated and developed by the Swedish Transport Authority, Trafikverket. The presented methodology builds on the ILKA (Integrerad landskapskaraktärsanalys) method, currently used by the Swedish Transport Authority. While ILKA focuses mainly on the inventory of the current landscape on a regional scale, this project widens the scope to also address urban areas and to include, besides the ecological descriptions, also socio-economic and cultural-historical analysis that are currently less emphasized. Such an integrated method can improve the ability of the Swedish Transport Authority to develop projects that contribute to sustainable urban development and, furthermore, create a unified work procedure in the organization.
26.	Bi, Hui, et al. (författare) Bicycle safety outside the crosswalks: Investigating cyclists' risky street-crossing behavior and its relationship with built environment 2023 Ingår i: Journal of Transport Geography. - : Elsevier BV. - 0966-6923. ; 108 Tidskriftsartikel (refereegranskat)abstract Most bicycle accidents are inextricably bound up with risky riding behaviors, which crossing the street illegally at unprotected mid-block locations is nothing to sneeze at. Compared with cyclists crossing the street at the crosswalk or intersections, there is a huge risk of accidents when they ignore or disobey road rules and across recklessly. Yet, the misbehavior of cyclists is an under-explored area in cyclist research due to the limited availability of detailed cycling data. This study creatively develops a GPS-based detection framework to capture risky street-crossing actions for the cyclists from large-scale bike sharing trajectory data. A data-driven modeling approach, based on structural topic modeling (STM), is developed to reveal the complexity and regularity of cyclists' habitual risky crossing behavior. Since objective built environment is one of the key factors associated with cycling, another goal of this paper is to apply a gradient boosting decision tree (GBDT) model to disentangle how the features of built environment may influence the frequency of risky crossing events. The case study results show that risky street-crossing behavior is prevalent in bicycle traffic – for example, 16.94% of cycling trips are involved in illegal crossing action. Most cyclists engage in illegal crossing behavior at the approximate central part of the streets and during the day, which reveals the presence of heterogeneity over space and time. Strong correlations between commuting activities and risky street-crossing behaviors are identified from topic modeling. Meanwhile, the latent illegal crossing patterns unraveled here highlight that typical reasons for committing the risky riding action include the lure of the travel destination across the road and the inconvenience of riding round in distant legal crossing facilities. GBDT findings provide new insights on the existence of the association between built environment and cyclists' illegal crossing action. The places related employment and catering play a dominant role in contributing risky street-crossing behavior, and the influences of road length, road level, bus stop and metro station are not neglectable. Most built environment attributes show nonlinear correlations with crossing frequency. It is anticipated that this study would successfully shed a first light on the pattern of cyclists' risky street-crossing behavior at the metropolitan scale, and compliment engineering practices to improve crossing behaviors and bicycle safety.
27.	Cao, Danni, et al. (författare) Quantification of the impact of traffic incidents on speed reduction: A causal inference based approach 2021 Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575. ; 157 Tidskriftsartikel (refereegranskat)abstract This paper designs a systemic framework to quantify speed reduction induced by traffic incidents using a causal inference framework. The results can provide a reference to traffic managers for evaluating incident severities, thus take proper control measures after the incident in order not to underestimate or overestimate the negative impact. A two-phase scheme is proposed, including impacted region determination and speed reduction quantification. We first propose a Frame Region (FR) method, based on the shockwave propagation, to determine the spatiotemporal impacted region (SIR) using speed map. It is worth-noting that we design a statistical experiment to prove the rationality of congestion threshold selection. Secondly, we introduce a causal inference method for identifying the matched freeway segments. The traffic condition of finally matched freeway segments can be served as non-incident traffic condition of the incident occurred location, which contributes to quantifying the incident impact on speed reduction. We further demonstrate the proposed method in a case study by taking advantage of an incident record and related real freeway speed data in China. An interesting observation is that, along with the freeway segments away from the incident location, the congestion duration time of different freeway segments firstly rises and then decreases. The case study also illustrates the impact of incident on speed lasts almost 3 h and the congestion caused by the incident spreads 11 km, while the average causal effect of incident on all the impacted freeway segments is 42.3 km/h.
28.	Castrellon, Juan Pablo, 1989, et al. (författare) Enabling Factors and Durations Data Analytics for Dynamic Freight Parking Limits 2023 Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; 2677:2, s. 219-234 Tidskriftsartikel (refereegranskat)abstract Freight parking operations occur amid conflicting conditions of public space scarcity, competition with other users, and the inefficient management of loading zones (LZ) at cities’ curbside. The dynamic nature of freight operations, and the static LZ provision and regulation, accentuate these conflicting conditions at specific peak times. This generates supply–demand mismatches of parking infrastructure. These mismatches have motivated the development of Smart LZ that bring together technology, parking infrastructure, and data analytics to allocate space and define dynamic duration limits based on users’ needs. Although the dynamic duration limits unlock the possibility of a responsive LZ management, there is a narrow understanding of factors and analytical tools that support their definition. Therefore, the aim of this paper is twofold. Firstly, to identify factors for enabling dynamic parking durations policies. Secondly, to assess data analytics tools that estimate freight parking durations and LZ occupation levels based on operational and locational features. Semi-structured interviews and focus group analyses showed that public space use assessment, parking demand estimation, enforcement capabilities, and data sharing strategies are the most relevant factors when defining dynamic parking limits. This paper used quantitative models to assess different analytical tools that study LZ occupation and parking durations using tracked freight parking data from the City of Vic (Spain). CatBoost outperformed other machine learning (ML) algorithms and queuing models in estimating LZ occupation and parking durations. This paper contributes to the freight parking field by understanding how data analytics support dynamic parking limits definition, enabling responsive curbside management.
29.	Hörteborn, Axel, 1986 (författare) Ship Behaviour and Ship Bridge Allision Analysis 2021 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract The demand for maritime transport has increased with the growing demand for worldwide trade. This has led to a major increase in maritime traffic and ship sizes over the last decades, which raises the probability of accidents. The methods used in maritime risk assessments today are based on old hypotheses that do not include all data available today. The main objective of this thesis is to develop numerical models and methods for the analysis of what is considered as normal navigation behaviour at sea today and improve the analysis of probability for ship-bridge allisions. The first part of the thesis describes what is considered as normal meeting distance at sea today. This information is later used while identifying failure events to ensure that the event behaviour was not caused by other ships. These few cases are excluded from the methodology since the communication and situational awareness in the situations are not known. However, while studying the probability of ship-bridge accidents, it is also important to understand how waterway restrictions may affect the probability of ship-ship collisions. Therefore, this thesis also includes a study of how the improved knowledge concerning meeting distance could be used in a near ship-ship collision identification model. One of the main findings considering normal meeting distance is that small and large ships meet each other at a similar distance at sea. In the second part of the thesis, a methodology is proposed to estimate the probability of ship-bridge allision. The presented methodology uses Automatic Identification System (AIS) data and a ship manoeuvring simulator to simulate and analyse marine traffic with regards to risks for accidents, such as ship-bridge allisions. A failure event identification method is also presented, which is needed to determine the frequency, duration and behaviour for the accident scenarios. The three events that were modelled and simulated in the simulator were: drifting ship, sharp turning ship and missing turning point. The probability of the different failure events corresponded to previous statistics confirming the AIS-based methodology. This means the methods to obtain the probability and duration of the failure events could be utilised in other areas. The simulation methodology was confirmed with the probability of grounding in the Great Belt VTS area. This thesis firstly contributes to a better understanding of the modelling of probability for ship-bridge allisions. This will support bridge-building engineers who need to take into account accidental loads from ship-bridge allision while designing bridges. Secondly, this thesis also contributes to a better representation of normal behaviour at sea, which is used both in fairway designs and in estimations of ship-ship collisions.
30.	Khosravi, Mahdi, 1988-, et al. (författare) Assessment of Railway Track Preventive and Corrective Tamping Recovery 2023 Konferensbidrag (refereegranskat)abstract Railway track, as a critical infrastructure, plays a significant role in freight transportation. However, Railway track degrades with age and usage and can impact negatively track availability and safety. Tamping actions are used to rejuvenate the degradation and recover the functionality of the track to an acceptable level. Tamping actions are performed in a form of preventive and corrective regimes. In performing an effective tamping regime, the recovery of both preventive and corrective tamping should be taken into account. In addition, the occurrence of isolated defects should be considered. By combining the recovery model with the degradation model, the long-term behavior of the track geometry can be predicted, and an accurate estimation of tamping needs can be provided, leading to optimum tamping scheduling. In this study, the effects of tamping recovery are modeled for both preventive and corrective strategies. For this aim, the values of both standard deviation (SD) and isolated defects have been predicted and their values before tamping are used as explanatory variables in a multivariable regression model. Finally, the effect of tamping recovery on the values of both SD and isolated defects is estimated. A case study is performed on a heavy haul line located in Sweden’s rail network to evaluate the performance of the proposed multivariable regression model. Observations showed that the model and its coefficients are significant with P-values close to zero, and the R-squared value suggests that the model explains approximately 70% of the variability in the response variable recovery.
31.	Lu, Yichen, et al. (författare) Analytical Method of Traffic Conflict at Urban Road Intersections Based on Risk Region 2021 Ingår i: Tongji Daxue Xuebao/Journal of Tongji University. - 0253-374X. ; 49:7, s. 941-948 Tidskriftsartikel (refereegranskat)abstract A two-stage method of traffic conflict analysis was proposed based on risk region. By using the inD dataset, traffic conflicts were recognized with the calculation of time to risk region(tTTR), and then the degree of traffic conflict risk was judged by risk region duration. Compared with the method based on time-to-collision(tTTC), the proposed method can not only identify rear-end conflicts and crossing conflicts more effectively, but also characterize the degree of traffic conflict risk at different times.
32.	Ouyang, Pengying, et al. (författare) Traffic safety analysis of inter-tunnel weaving section with conflict prediction models 2022 Ingår i: Journal of Transportation Safety and Security. - : Informa UK Limited. - 1943-9962 .- 1943-9970. ; 14:4, s. 630-654 Tidskriftsartikel (refereegranskat)abstract With increasing traffic demand in urban areas of metropolises, many tunnels have been constructed to improve road capacity and traffic mobility. The distance between two consecutive tunnels is relatively short which usually forms a weaving section, leading to considerable traffic conflicts. The objective of this study is to evaluate the safety performance of such inter-tunnel sections. Conflict prediction models based on negative binomial regression were developed to identify influential factors. Field data were collected at ten selected sites in Nanjing, China, and used for calibrating and validating the proposed models. Two types of inter-tunnel weaving sections (type 1 and type 2) were found in the field with distinct lane markings and operation rules. The unique lane markings in type 1 weaving sections are designed to isolate weaving traffic flows and thus reduce conflicts, but in practice, contradictory to its design intention, lead to more traffic conflicts compared with type 2 weaving sections. In addition, the length of the diverging section, merging section, and whole weaving section are found to be significant influencing factors on the conflict occurrence. The findings in the present study are expected to help engineers better design inter-tunnel sections.
33.	Wu, Jiaming, 1989, et al. (författare) Emergency vehicle lane pre-clearing: From microscopic cooperation to routing decision making 2020 Ingår i: Transportation Research Part B: Methodological. - : Elsevier BV. - 0191-2615. ; 141, s. 223-239 Tidskriftsartikel (refereegranskat)abstract Emergency vehicles (EVs) play a crucial role in providing timely help for the general public in saving lives and avoiding property loss. However, very few efforts have been made for EV prioritization on normal road segments, such as the road section between intersections or highways between ramps. In this paper, we propose an EV lane pre-clearing strategy to prioritize EVs on such roads through cooperative driving with surrounding connected vehicles (CVs). The cooperative driving problem is formulated as a mixed-integer nonlinear programming (MINP) problem aiming at (i) guaranteeing the desired speed of EVs, and (ii) minimizing the disturbances on CVs. To tackle this NP-hard MINP problem, we formulate the model in a bi-level optimization manner to address these two objectives, respectively. In the lower-level problem, CVs in front of the emergency vehicle will be divided into several blocks. For each block, we developed an EV sorting algorithm to design optimal merging trajectories for CVs. With resultant sorting trajectories, a constrained optimization problem is solved in the upper-level to determine the initiation time/distance to conduct the sorting trajectories. Case studies show that with the proposed algorithm, emergency vehicles are able to drive at a desired speed while minimizing disturbances on normal traffic flows. We further reveal a linear relationship between the optimal solution and road density, which could help to improve EV routing decision makings when high-resolution data is not available.
34.	Forssén, Jens, 1968, et al. (författare) How can we plan for a good urban sound environment, focusing on road traffic noise? 2020 Ingår i: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:5 Konferensbidrag (refereegranskat)abstract The sound environments in our cities are affected by unwanted sounds, i.e. noise, to an extent that is largely undesired, affecting health and wellbeing. The World Health Organization (WHO) has estimated the burden of disease from traffic-related noise within the western part of Europe and concluded that we each year lose at least one million disability-adjusted life years (DALYs) and that only air pollution has a larger disease burden among environmental factors. The burden of environmental noise is mainly sleep disturbance and annoyance. And the dominant source is road traffic. Methods. This paper describes the mechanisms behind road traffic noise and how we can use them in an urban sound planning perspective to improve the sound environment, as an integral part of sustainable cities and communities. The results are based on calculations and measurements made in previous and ongoing projects. Results. Treatments at source consider tyre, road, engine (whether electric or combustion), driving speed and acceleration, and further vehicle restrictions. Methods for reduction of noise during propagation and more general urban planning aspects include low-height barriers and ground treatments; acoustically absorbing facades and roofs of buildings, e.g. including vegetation; and building morphology and quiet side. Quantitative reductions, in decibels, as well as qualitative aspects are presented. Conclusions. The described possible improvements to the urban sound environment, with focus on road traffic noise as the dominant impairing factor, inform us about how a good urban sound environment can be reachable. However, to reach a good sound environment in reality, the work process of applied urban sound planning demands work across disciplines, also at early-stage planning, instead of traditional noise control applied late in the planning process.
35.	Berghauser Pont, Meta, 1972, et al. (författare) Förtätning av stationsnära områden för god tillgänglighet. Utveckling av en analys - och utvärderingsmetod 2022 Rapport (övrigt vetenskapligt/konstnärligt)abstract Det finns en vilja att förtäta i närheten av stationer för att öka användningen av kollektivtrafik och därmed minska klimatpåverkan kopplad till transpor- ter. Förtätning bidrar bland annat till att skapa levande stationssamhällen, med blandade funktioner, god tillgäng- lighet och miljöer som är trygga och vistelsevänliga där olika grupper och behov möts. Potentialerna är många men så även utmaningarna. Förtätning av stationsnära områden kan också leda till oönskade konsekven- ser för social, ekonomisk och ekologisk hållbarhet. Den här rap- porten kan förhoppningsvis ge ökad förståelse för förtätning i relation till regional tillgänglighet samt för positiva och negativa konsekvenser av förtätning i stationsnära områden. Den kan också skapa insikter om hur olika alternativ för utveckling av stations- nära områden kan värderas utifrån Agenda 2030, särskilt Mål 11: Hållbara städer och samhällen. Rapporten är framtagen inom projektet Urbana stationssamhäll- en – förtätning av stationsnära områden för god tillgänglighet (2020–2022) som finansierats av Trafikverket och bedrivits i sam- verkan mellan Urban Futures vid GMV (projektägare), Arkitektur och samhällsbyggnadsteknik vid Chalmers tekniska högskola, Gö- teborgsregionen (GR), Samhällsplanering vid Högskolan Dalarna och Samhällsplanering och miljö vid KTH.
36.	al-Karawi, Hassan, 1993, et al. (författare) Fatigue life extension of existing welded structures via high frequency mechanical impact (HFMI) treatment 2021 Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 239 Tidskriftsartikel (refereegranskat)abstract High-Frequency Mechanical Impact (HFMI) is one of the post-weld treatment methods. In this study, comparative axial fatigue tests were conducted on as-welded and HFMI-treated welded transverse attachment details. The test results demonstrated the efficiency of HFMI-treatment in fatigue life extension of cracked welded structures, providing that the existing crack size is less than 1.2 mm. Cracks were created in some specimens through fatigue testing before HFMI-treatment, while other specimens were not subjected to any fatigue loading prior to treatment. Many of the treated specimens ran out after 10 million cycles of loading when tested at a stress range of 150 MPa. Therefore, the stress range was increased to 180 MPa or 210 MPa. No remarkable difference was found between the fatigue strength of the crack-free and the cracked treated specimens. It was found that the induced compressive residual stress can exceed the material yield limit, and reach a depth larger than 1.5 mm in most cases. The induced compressive residual stress, the local material hardening, the increase in weld toe radius, the change in crack orientation and the shallowness of the crack size were the causatives of the obtained long fatigue lives of the HFMI-treated specimens. Besides, linear elastic fracture mechanics calculations were conducted to predict the fatigue lives of as-welded and HFMI-treated details. The results were in agreement with the experiment. Moreover, the calculations showed that the initial crack size, the clamping stress and the induced compressive residual stress were the main factors behind the scatter in fatigue lives.
37.	Chen, Teresa E, 1988, et al. (författare) Comparison of the service life, life-cycle costs and assessment of hybrid and traditional reinforced concrete through a case study of bridge edge beams in Sweden 2023 Ingår i: Structure and Infrastructure Engineering. - : Informa UK Limited. - 1573-2479 .- 1744-8980. ; 19:1, s. 39-57 Tidskriftsartikel (refereegranskat)abstract The edge beams of reinforced concrete bridges with de-icing salts sprayed experience extensive corrosion damage. The average service life of edge beams needing replacement in Sweden has been reported as only 45 years, causing great economic loss to both owners and users. Hence, finding a durable solution for edge beams would benefit society. Hybrid reinforced concrete structures, produced by adding a low-to-moderate fibre content into traditional reinforced concrete, can effectively limit the service crack width and improve resistance to chloride-induced corrosion damage. In this paper, different alternatives of hybrid and traditional reinforced edge beams were designed for a case study. The service life of the alternatives was compared by conducting chloride diffusion calculations and by applying a corrosion-induced cracking model. The economic and environmental (indicated by greenhouse gas emissions) benefits of using hybrid reinforced edge beams were assessed by life-cycle cost analysis and life-cycle assessment. The results showed that the service life of edge beams made of hybrid reinforced concrete can be prolonged by over 58%, thereby enabling a significant reduction in the total life-cycle costs and annual total greenhouse gas emissions.
38.	Cornell, Per, 1962 (författare) Town and Fortification in the Early Modern. A complex relationship 2021 Ingår i: Defensive Architecture of the Mediteranean, XI, Proceedings of the International Conference on Fortifications of the Mediterranean Coast. FORTMED 2020, Granada, 26-28 March 2020 / Navarro Palazón, García-Pulido (eds.). - Granada : Universitat Politècnica de València. - 9788490488638 Konferensbidrag (refereegranskat)
39.	Fonsati, Arianna, et al. (författare) OpenBIM methods and tools for schedule and cost management 2021 Ingår i: Sustainability and Automation in Smart Constructions. - Cham : Springer. ; , s. 37-43 Bokkapitel (refereegranskat)abstract Building Information Modeling (BIM) methodologies and approaches are becoming topics of increasing interest within several infrastructural engineering applications. As far as Construction Management (CM) is concerned, BIM technologies provide a valid support-decision tool, which includes a repository of CM related data, useful for any further development and use. This work presents current Infrastructural Building Information Modeling (InfraBIM) implementation possibilities regarding the correlation between information digital modeling, schedule, and cost management dimensions. The methodology is applied to case studies simulation of excavation and construction phases in underground structures to generate budgeted cost and time schedules linked to BIM models. The major benefit in applying such an approach results in obtaining a model with different types of information that can be updated during the design and construction phases. Also, the associated workflow management system allows to update the 3D model, time schedule, and cost estimation while maintaining relations and interconnections previously defined between model components and specific information on their activities and cost. Another key result is about the chance to communicate design and construction schedules via Virtual and Augmented Reality (VAR) techniques, which provide a consistent support tool for the visualization of infrastructure projects.
40.	Hazarika, Amrita, 1993, et al. (författare) Reactivity of Mixed Layer Clays – The Effect of Polycarboxylate Based Superplasticizers on Effective Particle Size Distributions 2023 Ingår i: RILEM Bookseries. - 2211-0844 .- 2211-0852. ; 44, s. 300-310 Konferensbidrag (refereegranskat)abstract The declining availability of promising supplementary cementitious materials (SCMs) in the recent past, such as fly ash and ggbfs, has opened new recesses in the domain of alternative binders. It is therefore imperative and urgent to develop more lasting and consistent alternatives, for addressing the need to diminish the carbon footprint of cement production. The potentialities of utilizing mixed layer excavated clays that are obtained as by-products of repair and construction activities, as possible SCMs have been well established in past literature. However, understanding the relationship between particle deagglomeration and pozzolanic properties via non-energy-intensive methods, is still an open niche yet to be fully explored. This study is an attempt at understanding the use of dispersive mechanisms such as super-plasticizers and storage in suspension to possibly impact surface charges of clay agglomerates and eventually, their reactivity. It is found that dispersive agents added to ground clay particles can enhance pozzolanicity of mixed layer clay particles and thereby reduce dependence on energy intensive methods such as grinding for activation.
41.	Karim, Ali Naman, 1992, et al. (författare) Knowledge gaps regarding the hygrothermal and long-term performance of aerogel-based coating mortars 2022 Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 314:Part A Forskningsöversikt (refereegranskat)abstract Aerogel-based coating mortars are an emerging class of multifunctional wall finishes that stand out for their thermal insulation performance. Commercial and trial mixtures, studied under laboratory conditions, have a declared thermal conductivity of about 30–50 mW/(m∙K). This is comparable to conventional insulation ma-terials such as polystyrene and mineral wool. Aerogel-based coating mortars are primarily intended for use in existing and uninsulated building envelopes. Currently, there is a high research interest in the development of aerogel-based coating mortars. Nevertheless, the knowledge about their hygrothermal and mechanical properties have not been fully explored yet. These properties are needed to assess the moisture risks and long-term dura-bility in different applications and to justify the higher investment costs for aerogel-based coating mortars compared to conventional ones. Apart from the material properties of aerogel-based coating mortars, results from full-scale studies focusing on hygrothermal performance are scattered and representative for limited number of climate conditions and specific products. In this article, available information on hygrothermal and mechanical properties of aerogel-based coating mortars is collected and systematized. The aim is to map the missing data needed for moisture risk assessments. This study focuses on knowledge gaps regarding the hygrothermal and long-term performance of aerogel-based coating mortars, both commercial products and laboratory-based trial mixtures. In addition, economic perspective and health related concerns of the material are discussed. The results indicate that future research efforts should focus more on moisture risk assessments of the material to ensure moisture safe designs especially in areas with humid climates and freeze-thawing. More information needs to be readably available on the me-chanical and hygrothermal compatibility of aerogel-based coating mortars with other materials in multilayer wall systems. In addition, available information on the hygrothermal and mechanical properties and long-term performance of aerogel-based coating mortars need to be further explored.
42.	Kuai, Le, et al. (författare) A numerical and experimental investigation of non-linear deformation behaviours in light-frame timber walls 2022 Ingår i: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 252 Tidskriftsartikel (refereegranskat)abstract In recent decades, there is a trend in Scandinavian countries to build multi-storey residential houses using prefabricated timber modules. It is a highly efficient construction process with less environmental impact and less material waste. A significant building element in the timber modules is the light-frame timber wall, which has to be carefully analysed and optimized in this process. This paper presents a new parametric Finite Element (FE) model that can simulate both in-plane and out-of-plane deformations in the light-frame walls. A new and flexible (Eurocode based) approach to define the properties of the mechanical connections is introduced. A numerical model is presented through simulations of several walls that were verified with full-scale experiments. The results indicate that the numerical model could achieve fairly reasonable accuracy with the new approach. Furthermore, several parametric studies are presented and discussed from global and local points of view, to investigate the effects of certain parameters that are not considered in the design method according to Eurocode 5.
43.	Löfgren, Ingemar, 1972 (författare) Betydelsen av betongens koldioxidupptag ur ett livscykelperspektiv 2021 Ingår i: Husbyggaren. - 0018-7968. ; 1/2021:1, s. 27-31 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract I denna artikel beskriver Ingemar Löfgren, FoU chef C-lab, Thomas Concrete Group hur betong tar upp koldioxid ur luften och hur det beräknas. Här visas också några exempel för olika konstruktioner där koldioxidupptaget anges i kg koldioxid per kvadratmeter exponerad yta. Koldioxidupptaget för ett er familjshus redovisas och exempel ges på hur upptaget kan ökas genom alternativa lösningar. Redovisade resultat och nomenklatur är baserad på metodik enligt den europeiska standarden EN 155804.
44.	Sehlström, Alexander, 1987, et al. (författare) Should Torroja’s prestressed concrete Alloz aqueduct be thought of as a beam or a shell? 2022 Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 264 Tidskriftsartikel (refereegranskat)abstract This paper examines the structural action of Eduardo Torroja’s Alloz aqueduct, completed in 1939, to see whether we should think of it as acting as a beam or a shell. This is of interest regarding the Alloz aqueduct itself, but also in the design of similar structures in the future, where we must have a simple conceptual understanding of how we want it to work. We apply two alternative approaches available at that time, before computers. Firstly, the membrane theory of shells, effectively assuming the aqueduct walls are infinitely flexible in bending, and secondly, the Euler–Bernoulli ‘plane sections remain plane’ elementary beam theory. We also review Torroja’s calculations which were based on an elaboration of the Euler–Bernoulli beam theory know as the Griffith–Taylor theory for the bending of cantilevers, although we are uncertain as to why he decided to use the Griffith–Taylor theory for a thin walled structure. Both the membrane shell and Euler–Bernoulli beam theory require a prestress to be applied along the longitudinal edges of the channel. However, the level of prestress in the Alloz aqueduct is consistent with the beam theory, which seams the most appropriate approach. Whether or not a structure of this type acts as a shell depends upon the thickness of the wall. The thinner the wall, the more it act as a shell. The wall thickness of the Alloz aqueduct is sufficient for it to act mainly as a beam.
45.	Shams Hakimi, Poja, 1988, et al. (författare) Assessment of in-service stresses in steel bridges for high-frequency mechanical impact applications 2021 Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 241 Tidskriftsartikel (refereegranskat)abstract The application of high-frequency mechanical impact (HFMI) treatment to improve the fatigue performance of composite steel and concrete road bridges was studied through a state-of-the-art review in conjunction with simulations of variable amplitude in-service stresses in four case-study bridges in Sweden. Empirical stress range spectra with associated mean stresses were characterised for HFMI-treated bridges. It was shown that the fatigue-critical locations in HFMI-treated bridges remain unchanged compared with conventional bridges and that compressive overloads pose no detrimental effect that requires additional attention in the fatigue assessment. Calculations also showed a considerably better fatigue performance if HFMI treatment is performed on-site, after the application of self-weight stresses.
46.	Williams Portal, Natalie, et al. (författare) Analysis of tensile behavior of recycled aggregate concrete using acoustic emission technique 2020 Ingår i: RILEM Technical Letters. - Bagneux, France : RILEM Publications SARL. - 2518-0231. ; 5, s. 131-140 Tidskriftsartikel (refereegranskat)abstract Recycled concrete aggregate (RCA) was processed from reinforced concrete edge beams sourced from a demolished bridge in Sweden. This material replaced different ratios of coarse aggregate in a benchmark concrete. The tensile behavior of the developed concrete mixes was characterized via monotonic and cyclic uniaxial tensile tests performed on notched cylinders. Such tensile tests allow for the quantification of the fracture energy and softening behavior of the concrete. Moreover, acoustic emission (AE) measurements were conducted in conjunction with the cyclic tests to characterize e.g. micro‐crack initiation and development, as well as crack localization. The tensile behavior of the various materials was found to be similar with minimal variation in the results. However, the softening behavior suggests that the RCA materials are slightly more brittle compared to both the mother and benchmark materials, which could be indicative of differences in the interface transition zones. The corresponding AE measurements also indicated similarities between the micro‐crack initiation and development for these mixes. It can be constituted that if the concrete used to produce RCA is of high quality and from one source, the resulting RAC will have adequate tensile properties with minimal variation, despite the aggregate replacement ratio. © The Author(s) 2020.
47.	Forssén, Jens, 1968, et al. (författare) Road traffic noise disease burden estimates for a model study of varying urban morphology cases 2021 Ingår i: Proceedings of INTER-NOISE 2021 - 2021 International Congress and Exposition of Noise Control Engineering. - : Institute of Noise Control Engineering (INCE). Konferensbidrag (refereegranskat)abstract In a model study containing 31 different building morphologies in an urban setting, road traffic noise exposure has been calculated and analysed. For five of the building morphologies also vegetation surfaces on facades and roofs were studied. The facade exposure levels were analysed for both smaller (single-sided) flats and larger (floor-through) flats, considering the direct exposure from the roads as well as the non-direct exposure at noise-shielded positions like inner yards, applying a noise mapping software in combination with a prediction model for the non-direct exposure. Using noise indicators Lden and Lnight, the disease burden, in terms of DALY (Disability-Adjusted Life Years) per person, was estimated and analysed, via predictions of annoyance and sleep disturbance. As general trends, perimeter blocks were shown to perform better than morphologies with less enclosed yards and densification was shown to result in improved performance, assuming a constant traffic flow. In addition, complementing the perimeter blocks with towers was shown to enable improvement. Furthermore, traffic concentration by locating all local traffic to a single road was shown to be beneficial, increasingly so by widening the road. The use of facade vegetation was shown to result in significant overall improvement.
48.	Stavroulaki, Ioanna, 1976, et al. (författare) A SYSTEMATIC REVIEW OF MULTIFUNCTIONAL STREETS_Final research report 2020 Rapport (övrigt vetenskapligt/konstnärligt)abstract A state-of-the-art, quantitative systematic review of scientific literature on the theme of multifunctional streets was conducted, including scientific papers of the last 10 years, filtered from Web of Science and Scopus. The review is part of a 3-year research project (2019-2021) named: “Smart streets” (Smarta gator) led by Alexander Ståhle (KTH Royal Institute of Technology) and financed by Vinnova (Swedish governmental agency for Innovation systems). The research project aims to develop a Street Multifunctionality Index (Gatufunktionsindex) to assess how existing and designed streets combine five different street functions - Social, Ecologic, Economic, Technical and Traffic - and also produce design guidelines for the design and planning of future multifunctional streets, either in new infrastructure or via retrofits. Within this project, the aim of the systematic review is twofold: first, to assess the degree in which the multifunctionality of streets is addressed in recent literature and provide an overview of the field by identifying where the general literature on the subject is trending, which are the recurrent issues studied, what themes are missing or being understudied; second, since an end product of the research project is to provide guidelines for urban design and planning practice, the review aims to identify the physical factors which have been empirically proven to support the different street functions, and especially those which support multiple functions. The second aim is pursued through focused thematic reviews, which complement the general overview of the field.
49.	Stojanovski, Todor (författare) Urban design and public transportation : public spaces, visual proximity and Transit-Oriented Development (TOD) 2020 Ingår i: Journal of Urban Design. - : Taylor & Francis. - 1357-4809 .- 1469-9664. ; 25:1, s. 134-154 Tidskriftsartikel (refereegranskat)abstract Walking distances conventionally define service areas for public transportation and urban growth boundaries for Transit-Oriented Development (TOD). Urban designers accordingly draw rings around transit stops and arrange transit-supportive land uses within 10-minute walksheds. This approach to TOD neglects processes of creating public spaces in visual proximity of transit stops. This paper proposes a methodology to analyze public spaces and looks at how commercialization and public space patterns unfold through viewsheds around transit stops. The results reveal amoebic TOD patterns of public spaces that are much smaller than conventional walking radii. This alternative viewshed approach can be helpful in designing TODs.
50.	Ait Ali, Abderrahman, 1991-, et al. (författare) Evaluating the mix of maintenance activities on railway crossings with respect to life-cycle costs 2024 Ingår i: European Journal of Transport and Infrastructure Research. - : TU Delft. - 1567-7141 .- 1567-7133. ; 24:1, s. 1-29 Tidskriftsartikel (refereegranskat)abstract Switches & crossings (S&Cs) are vital assets as they allow for increased railway capacity by introducing flexibility and connectivity in railway networks. At the same time, this makes them critical since they can cause costly delays and disruptions if they are not well maintained. This motivates studies to improve maintenance strategies of S&Cs, considering both the life-cycle costs (LCCs) of the assets and socio-economic transportation costs for passengers and freight customers. In this paper, the interdependence between deterioration mechanisms, maintenance activities, and expected LCC (including transportation costs) for the crossing panel – an S&C subsystem – is investigated using a combination of mechanical and econometric modelling. The interrelation between the degradation of contact geometry and track settlement is analysed using simulations of dynamic vehicle– turnout interaction. Long-term mechanical degradation of the crossing panel is simulated for different maintenance strategies that correspond to different timing of the associated maintenance measures (crossing repair welding and tamping). This provides the basis for analysing the interdependence between preventive and corrective activities using econometric modelling. Based on a case study of a common type of S&Cs in the Swedish infrastructure, the impact of different maintenance strategies on LCC and transportation costs is analysed. Opportunities and challenges in the development of more economically effective maintenance strategies of S&Cs are discussed.

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