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  • 1.
    Boutzas, John-Alexander
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Zeka, Dafina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Patch loading resistance of welded I-beams: with respect to misaligned web stiffeners2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When a concentrated load is introduced perpendicular to the flanges of a steel beam, this condition

    is referred to as Patch loading (Gozzi, 2007). This occurrence is common in many steel

    structures, for example at supports or during launching of bridges. Because of the usual slenderness

    of I-beams and other plated structures, these are sometimes reinforced with stiffeners

    in order to avoid buckling. Modifications, such as adding stiffeners to a beam, are done to

    make greater plastic deformations possible before buckling can occur; thereby increasing the

    resistance against failure.

    Transverse stiffeners are added in areas where the beam is exposed to concentrated loads

    (Lagerqvist, 1994). The descriptions of calculating patch loading in the Eurocode are presented

    for cases of double stiffeners, with the load applied in between two stiffeners with

    same distance to each of them, or when there is one single stiffener that is acting in line with

    the load. In the Eurocode there are also descriptions on how to calculate on the resistance

    against patch loading when there are no stiffeners added. However, the Eurocode lacks descriptions

    for cases when the stiffeners are misaligned.

    The purpose of this paper is the evaluation of the impact from transverse stiffeners to the resistance

    of welded I-beams, when the stiffeners are misaligned and where the length of the

    beam varies. Because of the complexity of such of problems it is almost impossible to find

    theoretical solutions (Lagerqvist & Johansson, 1996). Therefore, in this study as well as in

    almost all studies that aim to predict the ultimate resistances of steel beams subjected to patch

    loading, the results are gained empirically. The tests herein were done by FE-modeling and

    the results from the physical experiments done in Lagerkvist’s doctoral thesis were used for

    validation of the model, as conducting experiments ourselves was not economically possible.

    6

    The study was made in two steps. In the first step FE-models were produced under the same

    circumstances as the results obtained by Lagerqvist (1994). Those analyses were not part of

    the aim of the study; the intention for making the initial analyses was to strengthen the reliability

    of the results. From there, the final analyses were made with the aim in investigating the

    influence of stiffeners on the resistance, when these are misaligned. In this step, observations

    were also made with regards to the impact of the bending moment of the beam on its resistance.

    The initial analyses, which were made for validation of the modeling, had a satisfying correspondence

    to the physical experiments; hence the final analyses are assumed valid of acceptance.

    From observations of the results in the final analyses it is noticed that adding stiffeners

    is a highly preferred way of increasing the resistance for slender beams. For full utilization

    it is however important to have the stiffeners optimally placed, because a small deviation

    from this position gives an unwanted decrease in resistance.

  • 2.
    Dahlvik, Mathias
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Eriksson, Johan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Load Effect Modelling in Fatigue Design of Composite Bridges: An assessment of Fatigue Load Models 3, 4 and 5 according to SS-EN-1991-2 Actions on Structures – Part 2: Traffic loads on Bridges2014Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    At the turn of 2010/2011, Sweden went from designing structures according to nationaldesign codes to the new European standards Eurocode. For bridge engineers, this implieda change from a combination of BRO 2004 and BSK 07 to the Eurocode as the maindocuments, complemented by national documents such as TRVK Bro 11. The normtransition did not only change the calculation methods, but also turned a phenomenonthat never was of great importance for road bridges before into something that could limitthe carrying capacity of the structure. This phenomenon is called fatigue, i.e. repeatedload cycles, where each load is much lower than the ultimate limit state capacity, thatfinally results in collapse.

    This master thesis investigates why fatigue is significant in the design today. This is donethrough a comparison of how the new and old regulations assesses fatigue. A bridge builtin 2011, designed by ELU Konsult AB according to the old regulations, was modelledin the finite element program LUSAS. Several lorry crossings from different fatigue loadmodels were then simulated. The output from LUSAS was then used to calculate theutilization ratios for three critical points along the bridge.

    The result indicates that both regulations give rise to similar stress ranges, i.e. thedifference between the maximum and minimum stress obtained during a crossing. Thedifferences between the regulations are instead within the fatigue calculations, where themajor difference is the number of lorries crossing the bridge during its lifetime. Theutilization ratio according to the old regulations for the worst exposed point is 27.0 %,corresponding to 9.13 daily crossings by heavy lorries, which is the maximum numberof daily crossings provided by BRO 2004. The lowest utilization ratio according tothe Eurocode is 70.0 %, calculated for 137 daily crossings which is the lowest amountof crossings allowed. An interpretation of the Eurocode, which allows usage of fatigue loadmodel 5 even for smaller bridges, results in a utilization ratio of 56.0% which correspondsto 90.0 daily crossings, i.e. lower than the other fatigue load models provided by theEurocode but clearly above the old regulations.

    The conclusion is that an alternative way of deciding the number of crossings shouldbe provided by the Eurocode. Today, the classification consists of four steps, which arevery rough. Instead, a proposal is given in this thesis which advocates usage of a linearfunction for deciding the number of design crossings based on the number of daily crossingsby lorries. The proposed alternative design method is between the two regulations withrespect to daily crossings and utilization ratio.

  • 3.
    Hamodi, Sara
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Fahandezh Sadi, Taha
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Analysis of Tension-Zone Resistance in Bolted Steel Connections: Component Method according to Eurocode32017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to predict the behaviour of bolted steel connections, different methods can be applied to calculate the design tension resistance. In this thesis, the tension resistance is evaluated in the context of the so called Component Method according to Eurocode 3 part 1-8. The design approach establishes a unified procedure of modelling steel joints. Each joint configuration is decomposed into its basic components depending on loading type. In order to design the resistance of components subjected to tensile forces, a simple substitute model, the so-called Tstub flange is adopted. The Component Method is rather complicated to apply for all joint configurations. Therefore, the aim of this thesis is to create a brief and facilitated handbook covering the most common types of connections Kadesjös’ engineers deal with. The topic to be studied is rather comprehensive. Thus, this work is only focusing on the resistance calculation of components located in tension zone of HEA-sections in order to go deeper into the equivalent T-stub approach. To get a complete view about the designing procedure, general information about the Component Method are gathered by a literature study. Thereafter, the technical rules for calculation introduced in codes and standards were used to generate a general solution algorithm for two different connection configurations. The calculations have been performed using Mathcad, and the obtained results from a parametric analysis for particular profiles in each example are then summarised in tables and diagrams using Microsoft Excel.

  • 4.
    Nilsson Almqvist, Tom
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Applicering av flexibilitetskoncept på trästomme: En fallstudierapport2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Developers and architects have limited possibilities to design and offer customized apartments. The use of conventional construction systems, with load-bearing walls in concrete and vertical HVAC shafts, tends to lead to standardized floor layouts, which are difficult to modify over time.

    In this thesis, a timber structural system that promotes flexible housing is developed. The structural system allows free positioning of apartment dividing walls, independent plan layouts on each floor and free window positioning in the facades. The structural system is also designed so that renovation and remodeling of the building can be performed in an easy and efficient way, so that flexibility is maintained during the lifetime of the building.

    The study focuses on the structural aspects of the building, but also includes assessments with regard to fire safety, acoustic properties and production.

    Omniplan AB's project BoLag has been used as a case study. The project is a part of the building exhibition LinköpingsBo2017, and omniplan has high ambitions for this project to be at the forefront of innovation. Two main concepts are applied to the building: Flexibility and the use of a timber structural system. The shape of the building plot, regulations in the zoning plan and omniplans visions were used as preconditions in the work.

    Modern timber structures normally use some level of prefabrication. Many suppliers of timber structural systems have developed their own building systems, more or less open. None of these standardized systems provides the flexibility that omniplans project demands. Therefore, a high level of planning is required.

    The result shows that it is possible to apply a flexibility concept on residential buildings with a timber structural system. The objectives are reaches by utilizing a concept that is commonly used in office buildings, where flexibility often is crucial. A beam and post system of laminated timber eliminates the need for load-bearing walls, allowing for a plan layout that varies from floor to floor. A HVAC space in the floor slabs, instead of vertical shafts, facilitates free placement of bathrooms and kitchens.

    Timber building technology is developing rapidly, and hopefully the specific properties of timber can be used to develop the housing industry in general. This study shows that the use of timber has potential for innovative construction.

  • 5.
    Strömgren, Anders
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Wallentin, Martin
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Steel Structures.
    Konsekvenser när full anliggning saknas vid livförstärkning av HSQ-balk2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is written to evaluate a web reinforcement method for a joint in a beam- and column system with continuous beams that is loaded with a given load case. The joint consists of HSQ-beams and VKR-pipes where prefabricated concrete decks are supported by the bottom flange of the beams. The phenomenon that has been studied in detail is how the joint is affected if full contact between the reinforcement plates and the top flange is not achieved. With other words, what is happening with the load carrying capacity when the reinforcement plates are not perfectly straight or when the execution is not done correctly? Three different types of the joint was studied, one that had full connection between all the plates, and then two where full connection was missing between either the web reinforcement plates that goes across the length of the beam or the one directed along the beam. An ultimate load carrying capacity test was also performed to easier be able to measure the consequences on the ultimate strength when full connection between the plates was missing.

    A space of 1 mm, which according to the Swedish execution standard is the largest value that is approved locally (for 1/3 of the section), will in the end not affect the joint with any larger reduction of the load carrying capacity. The plates were then pressed together approximately 0.6 mm. When the joint on the other hand was analyzed with an ultimate load carrying capacity analysis with a spacing of 10 mm between the plates, the load carrying capacity was reduced with approximately 30 % in both cases.

    The dimension of the reinforcement plates in the joint was of the magnitude that the columns were not able to press them to failure without going to failure themselves. This means that the columns are the dimensioning factor for the load carrying capacity of the joint. The size of the reinforcement plates could be reduced without risking the load carrying capacity for the joint, they could then be reduced to the same dimension as the columns. The influence of the uniformly distributed load seems to be neglectable since the load carrying capacity for the joint barely changed when the uniformly distributed load was varying. This means that the reinforcement plates could be designed as a welded column with fixed supports clamped in between the top- and bottom flange of the beam.

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