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  • 51.
    Alfredsson, Magnus
    et al.
    NCC.
    Karlsson, Robert
    Swedish National Road and Transport Research Institute, Infrastructure, Pavement Technology.
    Sjögren, Leif
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Hintze, Staffan
    NCC.
    Johansson, Bo
    NCC.
    Lundström, Robert
    NCC.
    Winnerholt, Tomas
    Trafikverket.
    Funktionskriterier för vägkonstruktioner: Förstudie2010Report (Other academic)
    Abstract [sv]

    Det projekt som här rapporteras har som syfte att identifiera och beskriva de svårigheter och möjligheter som totalentreprenader medför, respektive erbjuder, för alla parter. Målet är att utveckla totalentreprenader på ett sådant sätt att branschens effektivitet ökas. Denna rapport är en förstudie där det studerats vilka krav som byggherren ska ställa på utföraren av en vägkonstruktion i en totalentreprenad med funktionsansvar och hur utföraren ska verifiera kraven. Arbetet har genomförts med medlemmar från olika aktörer i branschen och omfattat främst litteraturstudier och intervjuer. Kunskaper och erfarenheter har sammanställts och analyserats för att slutligen kondenseras ned till ett antal förslag till fortsatt arbete.

    Förstudien har pekat ut ett antal områden som viktiga för att påskynda framtida utveckling av totalentreprenader:

    Terminologi – idag råder viss begreppsförvirring

    Analys av funktionella krav i tidigare projekt

    Trafikantkrav

    Miljökrav

    Utveckling av funktionella krav i samverkan

    Väghållarekonomi

    Regelbetingade begränsningar av funktionella krav

    Uppföljning och underlättande av erfarenhetsackumulering

    Implementering av nya mått och mätmetoder

  • 52.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint Calculation in Concrete Culvert First Casting2014Report (Other academic)
  • 53.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint Calculation in Concrete Culvert Second Casting2014Report (Other academic)
  • 54.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint Effects in Early Age Concrete Structures2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks.Volumetric deformations in early age concrete are caused by changes in temperature and/or the moisture state. If such movements are restrained, stresses will occur. If the tensile stresses are high enough, there will be a damage failure in tension and visible cracks arise. These stresses are always resulting from a self-balancing of forces, either within the young concrete bodyalone, i.e. without structural joints to other structures, or from the young concrete in combination with adjacent structures through structural joints.The decisive situation within a young concrete body alone is typically high stresses at the surface when the temperature is near the peak temperature within the body. This situation occur rather early for ordinary structures, say within a few days after casting for structures up to about some meters thickness, but for very massive structures like large concrete dams, it might take months and even years to reach the maximum tensile stresses at the surface. Usually this type of cracks is denoted "surface cracks", and in some cases only a temperature calculation may give a good perception to make decisions of the risk of surface cracking.On the other hand, the decisive situation within a young concrete body connected to adjacent structures, might include both risk of surface cracking at some distance away from the structural joint and risk of through cracking starting in the neighborhood of the structural joint. If the young concrete body is small in accordance to the adjacent structure, or, in other words, if thereis an overall high restraint situation in the young concrete, the risk of early surface cracking might be out of question. So, restraint from adjacent structures represents one of the main sources of thermal and shrinkage stresses in a young concrete body.This study is mainly concentrated on establishing the restraint inside the young concrete body counteracted by adjacent structures, and how to estimate the risk of through cracking based on such restraint distributions. The restraint values in the young concrete are calculated with use of the finite element method, FEM. Any spatial structure may be analyzed with respect to the level of restraint. Calculations of risk of cracking are demonstrated with use of existing compensation plane methods, and a novel method denoted equivalent restraint method, ERM, is developed for the use of restraint curves. ERM enables the use of both heating ofthe adjacent structure and/or cooling of the young concrete, which are the most common measures used on site to reduce the risk of early cracking.In a design situation many parameters are to be considered, like type of cement, different concrete mixes, temperature in the fresh concrete, surrounding temperatures, temperature in the adjacent structure, measures on site (heating/cooling/insulation), sequence order of casting.Therefore, in general a lot of estimations concerning risks of cracking are to be performed. The main objective with the present study is to develop methods speeding up and shorten the design process.Furthermore, established restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the slab, wall, and roof for the typical structure Tunnel. It has been shown that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, results from the neural network can be represented by a series of basic weight and response functions, which enables that the restraint curves easily can be made available to any engineer without use of complicated software.A new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that the lower part of the wall is cast together with the slab, and that part is called a kicker. It hasbeen proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers.Restraint is affected by casting sequence as well as boundary conditions and joint position between old and new concrete elements. This study discusses the influence of different possible casting sequences for the typical structure wall-on-slab and slab-on-ground. The aim is to identify the sequence with the lowest restraint to reduce the risk of cracking.

  • 55.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint formulation for wall on slab at early age concrete structures by using ANN2012Report (Other academic)
    Abstract [en]

    Existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.

  • 56.
    Al-Gburi, Majid
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Restraint in structures with young concrete: Tools and estimations for practical use2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks. Restraint represents one of the main sources of thermal and shrinkage stresses at early age concrete. Paper I, deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.In Paper II, existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.Paper III, discusses the influence of five casting sequences for the typical structure slab-on-ground. The aim is to map restraints from adjacent structures for a number of possible casting sequences, and to identify the sequence with the lowest restraint. The paper covers both continuous and jumped casting sequences, which include one, two and three contact edges. The result shows that the best casting sequence is the continuous technique with one contact edge.

  • 57.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Effect of casting sequences on the restraint in slab-on-ground2014Conference paper (Refereed)
    Abstract [en]

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks. Restraint represents one of the main sources of thermal and shrinkage stresses at early age concrete. The casting sequence is affected by the restraint from adjacent structures. The present study discusses the influence of five casting sequences for the typical structure slab-on-ground. The aim is to map restraints for a number of possible casting sequences, and to identify the sequence with the lowest restraint. The study covers both continuous and jumped casting sequences, which include one, two and three contact edges. The result shows that the best casting sequence is the continuous technique with one contact edge

  • 58.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Effect of the boundary conditions on the crack distribution in early age concrete2014In: Nordic Concrete Research, ISSN 0800-6377, Vol. 50, p. 347-351Article in journal (Refereed)
    Abstract [en]

    Restrained movement in early age concrete may cause cracking. The boundary conditions – restraint – influence the possible crack distribution. This study aims at highlighting the effect of such restraint on the crack distribution. This is done by using the “Cracking Model for Concrete” in ABAQUS/Explicit simulating the non-linear behaviour under and after cracking. In the study the typical case wall-on-slab was in focus using a structure previously been tested in laboratory with both fixed and free bottom slab. The result of the modelling shows fairly good agreement with the cracks observed in the tests.

  • 59.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. College of engineering, University of Mosul, Iraq.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Prediction of Restraint in Second Cast Sections of Concrete Culverts using Artificial Neural Networks2018In: European Journal of Environmental and Civil Engineering, ISSN 1964-8189, E-ISSN 2116-7214, Vol. 22, no 2, p. 226-245Article in journal (Refereed)
    Abstract [en]

    Estimation of restraint is very important for accurately predicting the risk of early thermal and shrinkage cracking in concrete structures. The stress in young concrete is affected by changes in its dimensions during hydration and the restraint imposed by adjoining structures. In concrete culverts, the restraints from existing structures acting upon the first and second casting sections to be cast are different, causing them to exhibit different early cracking behaviour. This work presents a new method for predicting restraint in complex concrete structures using artificial neural networks (ANNs). Finite element calculations were performed to predict restraint in 108 slabs, 324 walls and 972 roofs from second sections of concrete culverts, and the results obtained were used to train and validate ANN models. The ANN models were then used to study the effects of varying selected parameters (the thickness and width of the roof and slab, the thickness and height of the walls, and the length of the culvert section) on the predicted restraint. Mathematical expressions for predicting restraint values in slabs, walls and roofs were derived based on the ANN models’ output and implemented in an Excel spreadsheet that provides a simple way of predicting restraint in practical applications. Restraint values predicted in this way agree well with the results of finite-element calculations

  • 60.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Reduction of Early Age Crack Risks in Concrete Walls by Using a New Casting Technique2016In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 26, no 3, p. 216-224Article in journal (Refereed)
    Abstract [en]

    Volumetric changes in early age concrete that are restrained might lead to cracks. The degree of restraint is influenced by the casting sequence and the dimensions of the castings. In the current study a new casting technique is proposed to reduce restraint in the newly cast concrete with a new arrangement of the structural joint to the existing old concrete. The proposed technique is valid for the typical structure wall-on-slab using one structural joint. This casting method means that lower part of the wall is cast together with the slab, and that part is called a kicker. Hereby, the behavior of the structure changes from a typical case wall-on-slab to a typical case wall-on-wall. It has been proven by the beam theory and demonstrated by numerical calculations that there is a clear reduction in the restraint from the slab to the wall using kickers. In the paper different kicker heights are studied with the aim of determining the minimum restraint in the upper part of the wall cast in contact with the kicker. The technique using kickers is compared with common measures used in the field to avoid cracking, such as cooling pipes in the new casting and/or heating cables in the adjoining old concrete. The presented method is both cost and time effective, as it opens the possibility to use larger structural length of each casting sequence.

  • 61.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Using Artificial Neural Network to Predict the Restraint in Concrete Culvert at Early Age2015In: Structural Engineering International, ISSN 1016-8664, E-ISSN 1683-0350, Vol. 25, no 3, p. 258-265Article in journal (Refereed)
    Abstract [en]

    Estimation of restraint is very important for accurate prediction of the risk of concrete cracking at early age. The present study predicts the restraint in 324 walls and 972 roofs for a concrete culvert. A parametric study included the thickness and width of the roofs, thickness and height of the walls, thickness and width of the slab, and length of the structures. Each parameter increased or decreased the restraint in the walls and the roofs. The calculation of the restraint was done elastically by the finite-element method (FE). The results were used by an artificial neural network (ANN) tool, where firstly an influential percentage was investigated as input parameters on the restraint prediction. Equations have been derived by the ANN model to calculate the restraint in the walls and the roofs. It was then used in an Excel sheet to calculate the restraint and compare the result with the result from the finite-element calculations giving high accuracy between the ANN model and the FE calculations

  • 62.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hedlund, Hans
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hösthagen, Anders
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simplified methods for crack risk analyses of early age concrete: Part 1: Development of Equivalent Restraint Method2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, p. 17-38Article in journal (Refereed)
    Abstract [en]

    The present study deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.

  • 63.
    Al-Gburi, Majid
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Jonasson, Jan-Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Yousif, Salim T
    Mosul University.
    Nilsson, Martin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Simplified methods for crack risk analyses of early age concrete: Part 2: Restraint factors for typical case wall-on-slab2012In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, p. 39-56Article in journal (Refereed)
    Abstract [en]

    Existing restraint curves have been applied to the method of artificial neural networks (ANN) to model restraint in the wall for the typical structure wall-on-slab. It has been proven that ANN is capable of modeling the restraint with good accuracy. The usage of the neural network has been demonstrated to give a clear picture of the relative importance of the input parameters. Further, it is shown that the results from the neural network can be represented by a series of basic weight and response functions. Thus, the results can easily be made available to any engineer without use of complicated software.

  • 64.
    Alizadeh Khameneh, Mohammad Amin
    et al.
    KTH.
    Eshagh, Mehdi
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering.
    Sjöberg, Lars E.
    KTH.
    Optimisation of Lilla Edet Landslide GPS Monitoring Network2015In: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943, Vol. 5, no 1, p. 57-66Article in journal (Refereed)
    Abstract [en]

    Since the year 2000, some periodic investigations have been performed in the Lilla Edet region to monitor and possibly determine the landslide of the area with GPS measurements. The responsible consultant has conducted this project by setting up some stable stations for GPS receivers in the risky areas of Lilla Edet and measured the independent baselines amongst the stations according to their observation plan. Here, we optimise the existing surveying network and determine the optimal configuration of the observation plan based on different criteria.We aim to optimise the current network to become sensitive to detect 5 mm possible displacements in each net point. The network quality criteria of precision, reliability and cost are used as object functions to perform single-, bi- and multi-objective optimisation models. It has been shown in the results that the single-objective model of reliability, which is constrained to the precision, provides much higher precision than the defined criterion by preserving almost all of the observations. However, in this study, the multi-objective model can fulfil all the mentioned quality criteria of the network by 17% less measurements than the original observation plan, meaning 17%of saving time, cost and effort in the project.

  • 65.
    Allirani, Hemanthini
    et al.
    National Institute of Technology, Tiruchirappalli.
    Santhakumar, Moses
    National Institute of Technology, Tiruchirappalli.
    Kumar, Kavitha
    National Institute of Technology, Tiruchirappalli.
    Analysis of factors influencing traffic accidents: a case study of Tiruchirappalli city2018Conference paper (Refereed)
    Abstract [en]

     Road safety is a major concern in many developing countries including India. Road accidents are responsible for an increase in deaths and disability throughout the world. Road accidents lead to loss of life, property and affect the general welfare of the people and the economy. India accounts for 10% of global road accidents and has the highest death rate in the world. In India, traffic fatalities have increased by 4.6% from 2014 to 2015. The analysis of road accident data reveals that about 57 accidents and 17 deaths take place every hour on an average in Indian roads. Road accidents have been increasing alarmingly in Tamil Nadu, being a major state contributing to total no. of accidents in India. Tamil Nadu reported the highest number of road accidents in 2015 sharing about 13.8% of the total accidents in the country. Tamil Nadu accounts for about 10.7% and 15.9% of total road fatalities and injury accidents in the entire country. Tamil Nadu ranked second highest and first in the country for fatalities and minor injury accidents.

    A case study of Tiruchirappalli city is considered for the present study. Tiruchirappalli city is situated at the geographical center of Tamil Nadu. Every year, a number of people are killed or injured due to road accidents. In Tiruchirappalli between the year 2010 and 2015, about 924 fatal accidents were reported and 974 people were killed due to road accidents. Hence, it is essential to find solutions to mitigate the problem. Road accidents are influenced by many factors such as traffic flow, geometric design of road sections, horizontal curvature, vertical grade, lane width, and shoulder width etc. Predicting the exact cause for the road accident is complex. Studies were done relating the factors like traffic volume, speed, road characteristics, road geometrics etc., with the road accidents. This study focuses on analysing road accident data and the relationship between various factors influencing road accidents so that suitable accident remedial measures can be suggested to enhance road safety.

  • 66.
    Alm, Ove
    et al.
    Luleå tekniska universitet.
    Norin, Jonas
    Luleå tekniska universitet.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Experimentella bestämningar av mekaniska egenskaper för hårdmetallpulver: slutrapport över pilotstudie1982Report (Other academic)
  • 67.
    Alm, Ove
    et al.
    Luleå tekniska universitet.
    Olofsson, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Attempt to make accurate measurements of deformations of compressible soilds at high pressure and different states of stress1982In: High pressure in research and industry: 8th AIRAPT Conference, 19th EHPRG Conference, 17 - 22 August 1981, Institte of Physical Chemistry, University of Uppsala, Sweden ; proceedings / [ed] C.-M. Backman, Uppsala: Fysikalisk-kemiska inst., Univ , 1982, p. 619-622Conference paper (Refereed)
  • 68.
    Al-Taie, Entidhar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Al-Ansari, Nadhir
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Saaed, Tarek Edrees
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Foundation assessment in different parts of Iraq using STAAD Pro v8i2013In: Journal of Civil Engineering and Architecture, ISSN 1934-7359, E-ISSN 1934-7367, Vol. 7, no 3, p. 273-281Article in journal (Refereed)
    Abstract [en]

    Foundation is considered as one of the main parts of any structure such as buildings, railways, bridges, etc. The type of foundation used is highly dependent on the type and properties of soil. The design of foundations requires many factors that should be defined such as the load that the foundation is going to hold, geological conditions of the soil under the foundation, type of soil and the local building code criteria.There are number of differences in the geological and soil conditions in Iraq. As a consequence, these differences are reflected on the type of foundation to be used. Despite these differences, same materials and style of buildings are used all over Iraq. The main problems of Iraqi soil are high gypsum content, salinity and shallow water table depth. These factors that influence the foundations are the soil properties and the amount of loads that transmitted by the superstructure.The situation had been analysed through a case study which illustrated the link between soil and foundation types in three different parts of Iraq (Mosul, Baghdad and Basra). One building was analysed using STAAD. Pro software in these regions. It is evident that Iraqi designers and engineers require local code to define all the loads, materials and design of the foundation to be used. The use of local materials might be very effective from both engineering and economic perspectives.

  • 69. Alten, Karoline
    et al.
    Deix, Stefan
    Peelen, Willy
    Wessels, Jos
    Courage, Wim
    Ravnikar Turk, Mojca
    Skaric Palic, Sandra
    Acalin, Nina
    Lundkvist, Sven-Olof
    Swedish National Road and Transport Research Institute, Traffic and road users, Human-vehicle-transport system interaction.
    Asset service condition assessment methodology (ASCAM Project)2012In: EPAM 2012, Malmö, Sweden, 5–7 September: 4th European pavement and asset management conference, Linköping: Statens väg- och transportforskningsinstitut, 2012, , p. 12Conference paper (Other academic)
    Abstract [en]

    Allocating financial resources among different sub-assets of a country’s road infrastructure is a challenge that is highly dependent on the strategic priorities and organisational structure of the infrastructure operator. While some agencies in Europe deal with pavements, bridges, tunnels or road furniture completely independently, others find that they have one mutual budget that needs to be shared out among the different assets in a way that represents their respective need for maintenance. The criteria upon which such allocations are based may be political, empirical, or based on stakeholder/user interests. The goal of the project ASCAM – Asset Service Condition Assessment Methodology – was to develop a framework for cross-asset management that can be used to objectively assign a budget to certain assets. While previous research projects have already compiled lists of various key performance indicators, ASCAM aimed to find mutual indices such as an “end user service level” that could be used to judge all sub-assets on equal terms and thus compare their condition on the same scale.

    By looking at asset management in the ASCAM partner countries and other European road agencies, the best-practice in individual asset management was extracted to develop the framework and perform a proof-of-concept for the project. While other projects such as PROCROSS within the same ERA-NET call also worked on cross-asset management – but from a top-down approach – ASCAM’s bottom-up approach looked at the more technical aspects of evaluating infrastructure condition and making a budgetary assignment based on the current and predicted state of the assets.

  • 70.
    Alzubaidi, Hossein
    Swedish National Road and Transport Research Institute.
    Drift och underhåll av grusvägar: litteraturstudie1999Report (Other academic)
    Abstract [sv]

    Grusvägarna omfattar en väsentlig del av det svenska vägnätet. Det statliga vägnätet omfattar 98 015 km väg varav 22 136 km (22%) är grusvägar (1997). Förutom de statliga grusvägarna finns även ca 35000 km enskilda grusvägar med statsbidrag och ca 210 000 km skogsbilvägar.

    Föreliggande litteraturstudie ingår som en första del i doktorandprojektet "”Effektiva produktionsmetoder inom drift och underhåll av grusvägar”".

    Denna rapport behandlar drift och underhåll av grusvägar huvudsakligen med inriktning mot grusslitlagret under barmarksperioden. I Sverige och de nordiska länderna infaller denna period normalt mellan maj och oktober. Med begreppet ”Drift och underhåll av grusvägar” menas i denna rapport all verksamhet som berör skötsel av grusvägar så att vägen hålls i farbart skick. Litteraturstudien består av tio kapitel vars rubriker finns i följande avsnitt:

    Kapitel 1 "Inledning", kapitel 2 "Grundläggande begrepp", kapitel 3 "Allmänt om vägnätet", kapitel 4 "Nedbrytning av grusvägar", kapitel 5 "Tekniska krav på grusvägar i Sverige", kapitel 6 "Faktorer som påverkar underhållet av grusvägar", kapitel 7 "Metoder för drift och underhåll av grusvägar", kapitel 8 "Tillståndsbedömning av grusvägar", kapitel 9 "Planering och värdering av drift- och underhålls-åtgärder", kapitel 10 "Referenser", Kapitel 11 "Figur- och tabellförteckning".

  • 71.
    Alzubaidi, Hossein
    Swedish National Road and Transport Research Institute.
    Miljöeffekter av dammbindning av grusvägar1999Report (Other academic)
  • 72.
    Alzubaidi, Hossein
    Swedish National Road and Transport Research Institute.
    Operation and maintenance of gravel roads: a literature study1999Report (Other academic)
    Abstract [en]

    Gravel roads form a large percentage of the road network in Sweden. The public road network under the jurisdiction of the Swedish National Road Administration has a total length of some 98,000 kilometres. About 22,000 km of this network consists of gravel roads. In addition, there are about 74,000 kilometres of private road and 210,000 kilometres of forest roads. The report describes the present position in the operation and maintenance of gravel roads. It presents a comprehensive literature survey of current and recent national and international research. It deals only with summer maintenance and focuses primarily on roads surfaced with aggregate. The following areas are treated in the report: - Definitions and terms regarding the operation and maintenance of gravel roads.- General description of the Swedish road network. - Major factors causing deterioration of gravel roads. - Technical requirements for Swedish gravel roads. - Factors, which influence the operation and maintenance of gravel roads. - Operation and maintenance methods. - Condition assessment of gravel roads. - Planning and evaluation of operation and maintenance measures.

  • 73.
    Alzubaidi, Hossein
    Swedish National Road and Transport Research Institute.
    Tillståndsbedömning av grusvägar: en sammanfattning av: On rating of gravel roads. Doctoral thesis at the Division of Highway Engineering, Royal Institute of Technology, Stockholm2002Report (Other academic)
    Abstract [sv]

    Bakgrunden till avhandlingen är att en metod for tillståndsbedömning av grusvägar utgör en viktig del av ett styrsystem som skall leda till effektivitet i underhållsverksamheter. Vägverket tillämpar en metod för tillståndsbedömning av grusvägar, förkortad VVMB 106, vilken tar hänsyn till jämnhet, löst grus samt damm. Representativa 100 m långa slumpvalda grusvägsdelsträckor används för själva bedömningen. Delsträckans tillstånd indelas i klass 1 (god), klass 2 (godtagbar) eller klass 3 (dålig). Tillståndet bedöms tillfredsställande om delsträckan placeras i klass 1 eller klass 2 avseende jämnhet och bundenhet, annars bedöms det otillfredsställande. Syftet med avhandlingen är dels att analysera VVMB 106 för att finna dess svagheter, dels att utveckla en ny och förbättrad metod.

  • 74.
    Amer, Wadi
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Soil Steel Composite Bridges: A comparison between the Pettersson-Sundquist design method and the Klöppel & Glock design method including finite element modelling2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 75.
    Amer, Wadi
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Lars, Pettersson
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Structural response of a high profile arch flexible culvert in sloping terrain using finite element modeling2018Conference paper (Refereed)
    Abstract [en]

    Flexible culverts are generally considered cost-effective structures for their simplicity in construction and the short time involved in the erection process. This has constantly motivated practitioners to explore the different areas of application including their performance in sloping environment. Yet, the complex nature of the interaction between the soil and steel materials marks a challenge, where the performance of these structures is fundamentally influenced by the quality of the backfill soil and its configuration around the conduit/arch. Surface slopes may affect the structural response by inducing an asymmetrical soil support and an unbalanced earth loading.

    The use of numerical simulation is utilized to provide insights about the performance of flexible culvert in sloping environment, where a case study of a high profile arch is investigated under different construction schemes. The paper focuses mainly on predicting the structural behavior of soil loading effects. The study includes the influence of different slopes in combination with various depths of soil cover.

    The results enabled to realize the importance of soil configuration around the steel arch and its influence on the structural response. While the presence of surface slopes emphasizes the susceptibility of flexible culverts with low depths of soil cover, higher covers may help in reducing the effect of steep slopes. Sectional forces were found to increase with the increase of surface slopes. The study also highlighted recent research efforts on the topic and briefly discussed some design implications when building flexible culverts in sloping terrain.

  • 76.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Adaptive and semi-active vibration control of railway bridge dynamics2012Report (Other academic)
    Abstract [en]

    Long Life Bridges is a Marie Curie 7th Framework Project funded under the Industry and Academia Partnerships and Pathways call, Grant Agreement No. 286276. The Project commenced in September 2011 and is continuing for 4 years until August 2015. The project vision is to extend the service lives of bridges through development of advanced assessment methods. The author wishes to acknowledge the financial contribution by the European Commission in supporting the project and funding this research.

    The work presented in this report has been conducted at Roughan & O’Donovan Innovative Solutions, Dublin, Ireland, during the period of January to December 2012, under supervision of Associate Professor Alan O’Connor. The author has been seconded from the Royal Institute of Technology (KTH), Division of Structural Engineering and Bridges.

    Within the project, experimental work to develop a prototype damper has been carried out at Trinity College Dublin (TCD), Department of Civil, Structural and Environmental Engineering. A special thank goes to Dr. Kevin Ryan and the laboratory staff at the Department for the help in manufacturing and testing the prototype damper.

    Full-scale testing has been performed on a railway bridge in Sweden. The tests were funded directly by the Swedish Transport Administration (Trafikverket). The instrumentation and field measurements were performed by KTH in collaboration with the author.

    The work presented, denoted secondment 1.1b, deals with development of adaptive and semi-active damping systems for railway bridges. The aim of the project is to develop methods for structural vibration control with applications for railway bridge dynamics. Much of the work has been related to a case study bridge.

    There is constant demand on rail authorities to increase both the allowable axle loads and the allowable speed on existing railway lines. As an example, the Swedish Transport Administration has recently investigated the possibility of upgrading part of the main lines to allow for future high-speed trains. Some lines are also being investigated with the aim of allowing ore transports with higher axle loads and longer trains. A large portion of the bridge stock was designed for significantly lower axle loads and only very few have been designed to account for dynamic effects. Increased dynamic effects may result in exceedance of dynamic design criteria, reduced service life due to fatigue, or even failure. Through better quantification of risk, it is often possible to prove that speeds can be increased with no adverse effect. However, for bridges where the level of risk is too high, a cost-effective means of reducing dynamic effects on bridges are active and semi-active control system. Semi-active control is well established in other fields and could prove to be a beneficial technique to allow train speeds to be increased.

    The concept of structural vibration control is to attenuate the dynamic response of a structure by means of an external damping device. Due to changes in either loading or structural behaviour, the properties of the damper device may need to be changed to efficiently mitigate vibrations. Two main principles of damper devices are commonly used; tuned mass dampers and shock absorbers. Tuned mass dampers consist of a suspended mass mounted on the main structure. Due to a phase-shift, the vibration of the suspended mass partly counteracts the corresponding motion of the main structure. Changing the stiffness of the suspended mass results in a variable adaptive tuned mass damper. Shock absorbers rely on producing the counteracting force by means of increased viscous damping. Devices with variable viscous damping are often categorised as semi-active. Fully active systems rely on producing the counteracting force by means of a load actuator. Adaptive and semi-active systems generally require much less energy to operate compared to fully active systems.

  • 77.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Impact loading on concrete slabs: Experimental tests and numerical simulations2014Report (Other academic)
    Abstract [en]

    In this report, the load capacity of concrete slabs subjected to concentrated loads is studied, considering both the static load capacity and the response due to impact of a falling mass. The purpose of the study is to gain more knowledge on the static and dynamic behaviour of the slabs and to use that knowledge in the assessment of the load capacity of inner lining systems in tunnels. The methodology involves experimental testing of a series of slabs, validation of numerical models and simulating the response of the inner lining system.

    A total of 18 slabs were manufactured, consisting of shotcrete and reinforcement mesh. Some of the slabs also included steel fibre reinforced concrete (SRFC). The size of the slabs were 1.75×1.75×0.12 m, suspended in four hangers #1.2 m and loaded centric on an area of 0.2×0.2 m. In addition, a series of core samples and beams were cut from two of the slabs for material testing and verification of numerical models.

    From the static load tests of the slabs, the load at cracking was obtained at 50 – 60 kN with a vertical midpoint displacement of 0.6 – 1.0 mm. The ultimate load ranged from 60 – 80 kN. The slabs showed significant ductility with a peak displacement of about 70 – 80 mm at post-failure. All slabs showed a two-way flexural failure. The concrete cover was in average 30 mm, measured from the compressive side, resulting in little difference between the crack load and the ultimate load. A vertical displacement of about 1 – 2 mm was required to obtain a crack width of 0.2 mm. Three slabs with only SRFC were tested until static failure, the ultimate load ranged from 85 – 90 kN but with less ductility compared to the slabs with rebar mesh.

    Impact load tests were performed using a steel mass of 600 kg. The free fall height was varied from 1 – 2 m. The peak impact load varied from 200 – 250 kN, without any clear correlation with the height. The corresponding impulse load varied from 4.0 – 5.5 kNs with a clear correlation to the height. All slabs subjected to impact load showed a one-way flexural failure, the residual strength after impact was sufficient to carry the static load of the steel weight. Several of the slabs showed significant fallout of concrete during impact, in one extreme case a total of 16 kg. Three slabs were tested with an outer layer of 30 mm of SRFC, none of these slabs showed any significant fallout.

    The static and dynamic response of the slabs have been simulated using nonlinear FE-models. The models generally show good agreement, both for static load, crack widths and response during impact. Similar models were used to simulate the response of the inner lining system. The results indicate a significant load capacity, both due to static and impact loading. The models are however not able to account for potential punching failure.

  • 78.
    Andersson, Andreas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Load capacity assessment and strengthening of a railway arch bridge with backfill2013Conference paper (Refereed)
    Abstract [en]

    In this paper, a load capacity assessment and strengthening measures of a multi-span railway arch bridge with backfill are presented. The bridge is located in Stockholm, Sweden, and constitute a vital link for the national railway network. The bridge consists of 20 concrete arches with overlying backfill, each with a span of 20 m. After more than 80 years of service, severe deterioration of the concrete was found during conditional assessments. A load capacity assessment was performed and the theoretical ultimate load was found to be highly dependent on the development of soil pressures along the arch barrel. The demands from the railway authority are to increase the allowable axle load from 22,5 to 25 tonnes and extend the service life by 50 years. Due to the uncertainties in structural behaviour and progressing degradation, extensive strengthening measures for the arch barrels were decided. To allow for full traffic at all times, the strengthening was performed in stages, to minimize any temporary reduction in load capacity due to removal of existing material. The strengthening was designed using non-linear finite element analysis and each stage of strengthening has been verified using in-situ field measurements.

  • 79.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Arvidsson, Therese
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Train-Track-Bridge Interaction for non-ballasted Railway Bridges on High-Speed Lines2017Report (Other academic)
    Abstract [en]

    This report contains a comprehensive parametric study on the coupled dynamic train–track–bridge interaction (TTBI) system for non-ballasted railway bridges. The existing design limits in Eurocode EN 1990 A2 regarding vertical deck acceleration and vertical deck displacement is compared with the wheel–rail forces and car body acceleration from simulations.

    The simulations are based on a 2D TTBI model with linear Hertzian contact that allows for loss of contact. The model has been verified against both other numerical simulations as well as experiments, all with good agreement. The parametric study consists of a large number of theoretical bridges, all optimized to reach the limit of either vertical deck acceleration or vertical deck displacement. The study comprises both single- and double track bridges.

    The track irregularities are found to be of paramount importance. Two different levels are therefore studied; “higher track quality” corresponding to a well-maintained track for high-speed railways and “lower track quality” corresponding to the Alert Limit in EN 13848-5. The final conclusions are based on the “lower track quality” in order not to underestimate the risk of running safety and passenger comfort. Simulations with the bridge excluded show that the additional contribution from the bridge is low, especially for the lower track quality.

    The existing limit for vertical deck acceleration is set to 5 m/s2 in EN 1990 A2 and is based on a very simple assumption of the gravity acceleration reduced by a factor 2. The results in this report show that this likely is a too conservative measure of the running safety. Based on the wheel–rail forces from the simulations, the resulting wheel unloading factor and duration of contact loss does not reach critical values before the deck acceleration is beyond 30 m/s2.

    In EN 1990 A2, a vertical car body acceleration of 1 m/s2 is stipulated as “very good level of comfort” and is indirectly limited by the vertical deck displacement. Good agreement is generally found in the simulations between deck displacement and expected car body acceleration. In the simulations, the limit for car body acceleration is always exceeded before the running safety is compromised.

  • 80.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Christoffer, Svedholm
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamisk kontroll av järnvägsbroar, inverkan av 3D-effekter2016Report (Other academic)
    Abstract [en]

    This report present result from dynamic analyses of railway bridges for high-speed trains. A comparison of the dynamic response in 2D vs. 3D has been performed for a limited selection of slab bridges, beam bridges and box girder bridges. Each cross-section has been optimized based on the dynamic requirements for dynamics in 2D, without any consideration of the static design. In many cases, the cross-section probably needs to be increased to fulfil the static load capacity.

    Slab bridges with a span length from 10 – 25 m and 1 – 4 spans have been analysed. In several cases, mostly for shorter spans, the natural frequency for bending is lower in 3D compared to 2D. The reason is due to a smaller contributing width, owing to shear-lag. This results in a lower resonance speed and therefore often a larger dynamic response within the same speed range. Apart from that, the dynamic response is found to be similar in 3D compared to 2D. The influence of torsional does not appear to be governing the response for the studied cases.

    Using the same method, beam bridges with span length from 20 – 40 m and 1 – 4 spans have been analysed. Similar to the slab bridges, the 3D-model of the beam bridges show lower natural frequency in bending compared to the 2D-model, owing to shear-lag. For double-track bridges, the difference in response between 2D and 3D-models are similar to the findings for the slab bridges. For single-track bridges, some cases of the 3D-model shows significantly lower response without pronounced resonance peaks in the same speed interval as the 2D-model. The reason is likely a combination of the support eccentricity and the mass of the bridge, which for vertical bending results in horizontal inertia. It is shown that this can be simulated with a modified 2D-model in most cases.

    Box girder bridges with span length from 40 – 70 m in 1 – 3 spans have also been analysed. Due to the larger torsional stiffness, the torsional mode is often much higher than the first bending mode. Also, the shear-lag effect seems to be smaller and the response from the 3D-model agrees well with the corresponding 2D-model.

    In the case dynamic assessment is performed using the simplified methods according to (Svedholm & Andersson, 2016), it is suggested that the following is considered:

    • Shear-lag and the eccentricity at the supports should be considered when estimating the first natural frequency for bending, n0, preferably using a 3D-model.

    • If the first torsional mode nT < 1.2n0, a full dynamic analysis in 3D should be performed.

    • In the case a 3D-model shows several closely spaced bending modes with similar shape, a full dynamic analysis in 3D should be performed.

  • 81.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Attenuating resonant behavior of a tied arch railway bridge using increased hanger damping2012In: Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management, Taylor & Francis Group, 2012, p. 2572-2577Conference paper (Refereed)
    Abstract [en]

    In this paper, dynamic analyses and field measurements of a tied arch railway bridge is presented. Excessive vibrations of the hangers were obtained, caused by resonance during train passages. The resulting increase of the stress level and number of stress cycles were shown to decrease the fatigue service life significantly. The most critical section is a threaded turnbuckle connection of the hangers. Due to low damping of the hangers, more than 50 % of the cumulative fatigue damage was related to free vibrations after train passage. Passive dampers were installed to attenuate the vibrations by means of increased damping. A combination of field measurements and numerical models are used to investigate the behavior of the bridge and the impact of increased hanger damping.

  • 82.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dynamics of railway bridges, analysis and verification by field tests2015In: EVACES'15, 6th International Conference On Experimental Vibration Analysis For Civil Engineering Structures / [ed] Glauco Feltrin, EDP Sciences, 2015, Vol. 24Conference paper (Refereed)
    Abstract [en]

    The following paper discusses different aspects of railway bridge dynamics, comprising analysis, modelling procedures and experimental testing. The importance of realistic models is discussed, especially regarding boundary conditions, load distribution and soil-structure interaction. Two theoretical case studies are presented, involving both deterministic and probabilistic assessment of a large number of railway bridges using simplified and computationally efficient models. A total of four experimental case studies are also introduced, illustrating different aspects and phenomena in bridge dynamics. The excitation consists of both ambient vibrations, train induced vibrations, free vibrations after train passages and controlled forced excitation.

  • 83.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Trinity College Dublin.
    Development of a multi-passive tuned mass damper, theory and experiments2014In: Proceedings of the 9th International Conference on Structural Dynamics, EURODYN 2014, Porto, 2014, p. 1551-1556Conference paper (Refereed)
    Abstract [en]

    In this paper, a bi-directional multi-passive tuned mass damper is presented. The applicationfor the damper is on vertical hangers of an existing steel arch railway bridge.The hangers have been found susceptible to resonance and the resulting stressesresults in a reduced service life due to fatigue. Due to different boundaryconditions, the natural frequencies of the hangers are different in thelongitudinal and the transverse direction. In addition, the natural frequenciesincrease during train passage, due to increased tensile force in the hangers. Aprototype of the damper has been developed, consisting of two suspended massescoupled in series. Different lateral suspensions are used to obtain differentnatural frequencies in the longitudinal and the transverse direction. One massis tuned to the conditions of the fully loaded bridge and the other mass to theunloaded bridge. The performance of the damper is verified using controlledloading under laboratory conditions and the results are compared with a finiteelement model. The damper is shown to perform as expected and the motion of thetwo masses is near uncoupled. Finally, the performance of the damper isverified by in-situ testing on the case study bridge.

  • 84.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    External damping of stay cables using adaptive and semi-active vibration control2013In: Proceedings of the 8th International Cable Supported Bridge Operators Conference, Edinburgh, Scotland, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, the performances of different external damping systems for stay cables are studied based on numerical simulations. Two types of dampers have been analysed; a near anchorage viscous damper and a tuned mass damper (TMD) mounted near the midspan of the stay cable. For the passive case, both dampers are tuned to the fundamental mode of vibration of the cable. The optimal viscous damping for the near anchorage damper is determined based on well-known equations for a taut string. For the TMD, parametrical studies have been performed to determine the optimal damping ratio as function of the damper mass. The resulting vibration mitigation from the two systems are also studied for higher modes of vibration and the potential increase in performance using an adaptive or semi-active vibration control system is studied.

  • 85.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Semi-active damping systems for railway bridges2012In: / [ed] Colin Caprani, Alan O'Connor, Dublin, 2012, p. 177-182Conference paper (Refereed)
    Abstract [en]

    In this paper, a semi-active control system for vibration mitigation of railway bridges is presented. The real time frequency response is estimated using a short-time Fourier transform, employing curve fitting to relevant peaks for increased accuracy. A control algorithm developed in Matlab® is linked to a commercial FE-software, facilitating application on arbitrary structures. A numerical study of an existing tied arch railway bridge is presented. From earlier field measurements and numerical analysis, resonance of several hangers during train passage was observed. This was shown to significantly reduce the fatigue service life of the hangers and for the most critical section about 50% of the cumulative damage was related to free vibrations. A system of passive dampers was later installed and the increase in resulting damping was measured. Within the present study, the previous results are reanalysed and compared with a semi-active approach. The natural frequencies of the hangers vary as a result of the variation in axial force. A semi-active control system has the potential to improve the vibration response of the structure when compared to the installed passive system.

  • 86.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Vibration mitigation of railway bridges using adaptive damping control2013In: Assessment, Upgrading and Refurbishment of Infrastructures, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, the advantage of an adaptive damping system is presented. A damper with variable stiffness is tuned based on estimates of the real-time frequency response, facilitating optimal vibration mitigation. The performance of the developed routines is investigated on an existing tied arch railway bridge. Based on previous field measurements, resonant behaviour of several hangers was found. In combination with low structural damping, the induced stresses resulted in a reduced fatigue service life. Passive dampers are currently installed on the longer hangers, each tuned to the fundamental natural frequency of the individual hanger. However, increased axial force during train passage results in a significant variation in natural frequency, with an apparent risk of detuning the passive dampers. The predicted performance of an adaptive damping system to account for this variation in dynamic behaviour is presented and its potential application is discussed.

  • 87.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Leander, John
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Extending the fatigue service life of a railway bridge by local approaches2013Conference paper (Refereed)
    Abstract [en]

    In this paper, fatigue assessment of a steel railway bridge is presented. The bridge is located in central Stockholm, Sweden, and is one of the most vital links for the railway network. The bridge services both freight trains and commuter trains with more than 500 passages per day. The main load bearing structure is designed as a steel grillage of welded I-beams. Fatigue critical sections have been identified at locations where secondary bracing systems are welded to the flanges of the I-beams. Both numerical simulations and extensive field measurements have shown a significant exceedance of the theoretical fatigue service life. Based on analysis of local stress concentrations, improvement of fatigue critical details have been suggested. The decrease in stress concentration is demonstrated both by numerical simulations and in-situ field measurements and shows a significant improvement when estimating the remaining fatigue service life.

  • 88.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Development and testing of a bi-directional multi-passive tuned mass damperIn: Computer-Aided Civil and Infrastructure Engineering, ISSN 1093-9687, E-ISSN 1467-8667Article in journal (Other academic)
    Abstract [en]

    This paper presentsthe development and testing of a bi-directional multi-passive tuned mass damper(bi-MTMD). A prototype of the damper has been built and tested under laboratoryconditions. The damper was developed for application to a vertical hanger on anexisting tied-arch railway bridge. During train passage, resonance has beenobserved in several hangers, resulting in a reduction in the predicted fatigueservice life. The objective of the damper is to mitigate the vibrations toreduce the resulting stresses and consequently to extend the life of thehanger. The hanger has different natural frequencies for longitudinal andtransversal bending. In addition, a significant difference in natural frequencyis obtained for the loaded and unloaded bridge, due to the increase in axialforce in the hangers. The developed damper accounts for both scenarios and istuned based on previous field measurements. The results from the laboratoryexperiments are compared with a 3D FE-model of the damper.

  • 89.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Development of a Bi-directional Multi-Passive Tuned Mass DamperIn: Journal of Structural Engineering, ISSN 0733-9445, E-ISSN 1943-541XArticle in journal (Refereed)
    Abstract [en]

    This paper presents the development and testing of a bi-directional multi-passivetuned mass damper (bi-MTMD). A prototype of the damper has been built andtested under laboratory conditions. The damper was developed for application toa vertical hanger on an existing tied-arch railway bridge. During trainpassage, resonance has been observed in several hangers, resulting in areduction in the predicted fatigue service life. The objective of the damper isto mitigate the vibrations to reduce the resulting stresses and consequently toextend the life of the hanger. The hanger has different natural frequencies forlongitudinal and transversal bending. In addition, a significant difference innatural frequency is obtained for the loaded and unloaded bridge, due to theincrease in axial force in the hangers. The developed damper accounts for bothscenarios and is tuned based on previous field measurements. The results fromthe laboratory experiments are compared with a 3D FE-model of the damper.

  • 90.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Swedish Transport Adm Trafikverket, Solna, Sweden.
    O'Connor, Alan
    Trinity College Dublin.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Passive and Adaptive Damping Systems for Vibration Mitigation and Increased Fatigue Service Life of a Tied Arch Railway Bridge2015In: Journal of Bridge Engineering, ISSN 1084-0702, E-ISSN 1943-5592, Vol. 30, no 9, p. 748-757Article in journal (Refereed)
    Abstract [en]

    n this article, the use of external damping systems for vibration mitigation of railway bridge dynamics is studied. For a presented case study bridge, the performance of different tuned mass damper systems (TMDs) is studied. During train passage, the change in dynamic characteristics of the bridge may produce a significant detune to a passive TMD. Therefore, routines for a variable stiffness TMD using incremental frequency estimates are developed. Based on numerical simulations, the cumulative fatigue damage is calculated for different damper systems. Due to resonant behavior, the results are found to highly depend on the train speed. Based on an assumed probability density function for the train speed, fragility curves are produced to express the probability of fatigue failure as a function of the number of train passages.

  • 91.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Roslin, Mattias
    Trafikverket.
    Load capacity of inner lining system s due to impact from falling rocks2015In: SEE Tunnel: Promoting Tunneling in SEE Region / [ed] Davorin Kolic, Dubrovnik, 2015Conference paper (Other academic)
    Abstract [en]

    The inner lining concept is a method to prevent water leakage and the risk of icing inside tunnels and is frequently used in countries with cold climate. Blocks of falling ice may result is a severe safety risk in both road and railway tunnels. Although several established inner lining systems exist, finding the optimal solution considering function, maintenance- and investment cost is a challenging task. A new system has recently been used in Sweden and is due to its success planned to be used for the Stockholm Bypass, an 18 km road tunnel project in Stockholm.

    A set of design criterions has been stipulated for the inner lining system. In this paper, the case of impact loading from falling rocks is studied. The inner lining system is required to withstand the impact of a 600 kg block landing on a square surface of 0.2x0.2 m. The free fall height, i.e. the distance to the rock surface, is typically less than 0.5 m but may span up to 1.5 m in some cases. A too conservative design may result in an unnecessary thick structure and lack of knowledge of the impact phenomena may result in an unsafe design.

    An extensive experimental program has been performed, consisting of representative parts of the inner lining system. A mass of 600 kg is dropped onto the structure and the results are compared with numerical simulations. The experiments show that the current system is rather ductile but that local concrete fallouts may occur at extreme free fall heights.

  • 92.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Roslin, Mattias
    Trafikverket.
    Taube, Arvid
    Trafikverket.
    Bärförmåga hos inklädnadssystem vid stödbelastning från fallande bergblock2015In: Bergmekanikdag 2015 / [ed] BeFo, Stockholm: Stiftelsen Bergteknisk forskning , 2015Conference paper (Other academic)
    Abstract [en]

    Inner lining system in tunnels is a method to prevent water ingress and forming of ice in the traffic area. A solution that is common in Norway is based on stretching a sealing membrane between rock anchorages that forms a gap to the primary rock strengthening. The membrane is in turn protected by a layer of shotcrete towards the traffic area. The rock strengthening is designed to resist all loads from the rock mass independent of the inner lining system. A problem is however how to perform inspections and conditional assessment of the rock strengthening, since the gap is usually small. Other topics are what loads the inner lining system should be designed for. In TRVK Tunnel 11, the load of a local falling rock of 600 kg is stipulated, assuming to act on a surface of 0.2×0.2 m. Furthermore, the inner lining system should be designed to resist what is connoted as an extreme rock load of 6 metric ton, acting on a 1×1 m area, even when a primary rock strengthening is present. Similar inner lining systems have been used in e.g. Norra länken, parts of Citybanan in Stockholm and is planned to be used for the Stockholm Bypass project.

    In the present paper, results from a recent research project are presented, aiming at investigating the structural manner of action of the aforementioned inner lining system. A series of concrete slabs have been tested, both until static failure and with a 600 kg drop weight from different heights. All tested slabs resulted in flexural failure and showed a significant ductility. For several of the slabs tested for impact loading, significant spalling from the soffit was obtained, at the most corresponding to a mass of 16 kg. Three of the slabs tested for impact load were manufactured with an outer layer of steel fibre reinforced shotcrete. None of these slabs showed any significant spalling, despite a free fall height up to 2 m.

    Several FE-analyses have also been performed, accounting for the nonlinear material properties of concrete. The results showed good agreement with the conducted experiments, both regarding static loading, cracking and impact load. A similar analysis was also done for the whole inner lining system. The results showed a larger load capacity compared to the experiments, but still with a rather localised failure.

  • 93.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Full Scale Tests and Structural Evaluation of Soil-Steel Flexible Culverts for High-Speed Railways2012In: Second European conference on Buried Flexible Steel structures Rydzyna April 23rd – 24th 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper, results from full-scale tests on a corrugated soil-steel flexible culvert for railway traffic are presented. The bridge was instrumented with strain gauges, accelerometers and displacement gauges, measuring the response from passing trains. The aim of the measurement campaign was to gain knowledge of the dynamic behaviour due to train induced vibrations, both of the bridge structure and the overlying railway embankment. From the measured data, the load distribution and soil-stiffness can be estimated. The results also serve as input for calibration of numerical models that are used for predicting the behaviour due to high-speed trains.

  • 94.
    Andersson, Andreas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. The Swedish Transport Administration (Trafikverket), Sweden.
    Ülker-Kaustell, Mahir
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. Tyréns AB, Sweden.
    Borg, Richard
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Dymén, Olivier
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Carolin, Anders
    Trafikverket.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Pilot testing of a hydraulic bridge exciter2015In: EVACES'15, 6th International Conference on Experimental Vibration Analysis For Civil Engineering Structures / [ed] Glauco Feltrin, Zurich: EDP Sciences, 2015, Vol. 24, p. 02001-Conference paper (Refereed)
    Abstract [en]

    This paper describes the development of a hydraulic bridge exciter and its first pilot testing on a full scale railway bridge in service. The exciter is based on a hydraulic load cylinder with a capacity of 50 kN and is intended for controlled dynamic loading up to at least 50 Hz. The load is applied from underneath the bridge, enabling testing while the railway line is in service. The system is shown to produce constant load amplitude even at resonance. The exciter is used to experimentally determine frequency response functions at all sensor locations, which serve as valuable input for model updating and verification. An FE-model of the case study bridge has been developed that is in good agreement with the experimental results.

  • 95.
    Andersson, Anna-Lena
    Swedish Transport Administration.
    Suicide And Accident Classification Method Used In Sweden2018Conference paper (Refereed)
    Abstract [en]

    Since 2010 Sweden has been presenting statistics on suicides in road traffic separately from that on fatalities caused by accidents. To undertake this, a method has been developed for classification of road traffic fatalities in order to determine if the fatality was caused by an accident or by a suicide. For more information, see abstract nr 180: “Suicide and accident classification methodology”.

  • 96.
    Andersson, Anna-Lena
    et al.
    Trafikverket.
    Svensson, Kenneth
    Trafikverket.
    Suicide and accident classification methodology2018Conference paper (Refereed)
    Abstract [en]

    Fatalities in road traffic are not only due to accidents, some of them are suicides. Sweden has since 2010 described statistics on suicides in road traffic separately from fatalities caused by accidents. To implement this, a method has been developed for classification of road traffic fatalities in order to determine if the fatality was caused by an accident or by a suicide.The work has been carried out in cooperation between The Swedish Transport Administration, The Swedish Transport Agency, The National Board of Forensic Medicine and Suicide Prevention Western Sweden.

  • 97.
    Andersson, Arne
    et al.
    AB Previa/ARA miljö.
    Jacobson, Torbjörn
    Swedish National Road and Transport Research Institute, Infrastructure, Infrastructure maintenance.
    Persson, Bengt-Olle
    Peab Asfalt.
    Tillsatsmedel i asfalt: påverkan på arbetsmiljö och omgivning (2006-02-06). Slutrapport2006Report (Other academic)
    Abstract [sv]

    Vissa tillsatsmedel upplevs idag som besvärliga för arbetsmiljön vid tillverkning och utläggning av asfaltmassa. Vidstående projekt som finansierats av SBUF och Peab Asfalt AB syftar till att ta fram relevanta fakta om tillsatsmedel och dess hälso- och miljöproblem. Projektet har dels inriktats som en förstudie av vad som hitintills har gjorts inom asfaltmiljöområdet både i Sverige och i utlandet, dels kompletterande fältmätningar vid asfaltläggning av polymermodifierad asfalt. Studien har utförts i samarbete mellan Peab Asfalt AB, VTI och Previa/ARA-miljö.

  • 98.
    Andersson, G
    et al.
    Svenska Väginstitutet.
    Lundeberg, Erik
    Svenska Väginstitutet.
    Undersökningar rörande bromslängden för bilar vid olika väglag1931Report (Other academic)
  • 99.
    Andersson, Jenny
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Widening of The Nockeby Bridge: Methods for strengthening the torsional resistance2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    i Abstract The Nockeby Bridge, in the western part of Stockholm, is a prestressed concrete bridge with an openable swing span of steel. The bridge was built during 1970 and should now be widened with 0.5 meters on each side. The concrete bridge deck is supported by two main-beams and cross-beams are located at the position of all supports. Previous studies of the bridge show that the torsional resistance is too low and the bridge needs strengthening while widened. The aim of this master  thesis  was  to  study  and  compare  different  strengthening  methods  for  The  Nockeby Bridge.  Eight  different  bridges  in  Sweden  and  China  were  reviewed  to  find  possible  strengthening  methods  for  The  Nockeby  Bridge.  External  prestressing  tendons  and  additional  cross-beams between  the  two  main-beams  were  seen  to  have  good  influence  on  the  resistance.  The  effect from strengthening with carbon-fiber reinforced polymer was questioned during small loads and was not seen as a suitable strengthening method for The Nockeby Bridge.  Four different FE-models were generated to be able to compare two strengthening methods. The compared strengthening methods were a method with additional cross-beams between the main-beams and a method with external prestressing tendons. All FE-models were built up by solid- and  truss  elements  where  the  concrete  was  modelled  with  solid  elements  and  the  prestressed reinforcement was modelled with truss elements.  Only a few load-cases were included to limit the scope of the study. The included load-cases were deadweight,  prestressing  forces  and  vehicle  load  from  standard  vehicle  F,  G,  H  and  I.  Two influence lines were created to be able to place the vehicle loads in an unfavorable way. From the FE-models, shear  stresses were  extracted  along two  lines, one  on  each  side  of the main-beam. The torsional part of the shear stresses was calculated from these two results and compared with the torsional resistance of the bridge. While calculating the torsional resistance, the normal force in the cross-section from prestress was extracted with the function “free body cut”. The results showed that none of the tested strengthening methods were enough to  strengthen The  Nockeby  Bridge.  However, the  method  with additional  cross-beams  was  seen  as  a  better method than external prestressing tendons. A combination of the two methods might be suitable but  was  not  tested.  Adding  four  cross-beams  in  each  span  might  also  increase  the  resistance enough, but this was neither tested. It was also seen that a reduction of the torsional stiffness had a large influence on the result. Such a reduction is allowed in some cases and should be utilized if possible. Furthermore,  it  was  seen  that  solid-models  were  extremely  time  consuming  and  there  is  not  a  good alternative to design a bridge with only a solid model.

  • 100.
    Andersson, Mats
    Swedish National Road and Transport Research Institute, Society, environment and transport, Transport economics Stockholm.
    Marginal railway renewal costs: a survival data approach2007Report (Other academic)
    Abstract [en]

    In this paper, renewal costs for railway tracks are investigated using survival analysis. The purpose is to derive the effect from increased traffic volumes on rail renewal cycle lengths and to calculate associated marginal costs. A flow sample of censored data containing almost 1 500 observations on the Swedish main railway network is used. We specify Weibull accelerated failure time regression models, and estimate deterioration elasticities for total tonnage as well as for passenger and freight tonnages separately. Marginal costs are calculated as a change in present values of renewal costs from premature renewal following increased traffic volumes.

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