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  • 851.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Pre-flashover Compartment Fires: Two-Zone Models2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 175-183Chapter in book (Refereed)
    Abstract [en]

    Two-zone models are applied to pre-flashover fires, i.e. compartment fires which have not reached ventilation controlled combustion conditions as defined in Chap. 10. Several more or less advanced computer codes have been developed to calculate temperature under such assumptions. The most fundamental principles of the theory are outlined below.

  • 852.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Steady-State Conduction2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 17-24Chapter in book (Refereed)
    Abstract [en]

    In one dimension in the x-direction the rate of heat transfer or heat flux is expressed according to Fourier’s law as outlined in Sect. 1.​1.q . ′′ x =−k⋅dTdx q.x′′=−k⋅dTdxwhere k is the thermal conductivity. For simplicity the mathematical presentation of the heat transfer phenomena is here in general made for one-dimensional cases only. Corresponding presentations in two and three dimensions can be found in several textbooks such as [1, 2].

  • 853.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperature Calculation in Fire Safety Engineering2016Book (Refereed)
    Abstract [en]

    This book provides a consistent scientific background to engineering calculation methods applicable to analyses of materials reaction-to-fire, as well as fire resistance of structures. Several new and unique formulas and diagrams which facilitate calculations are presented. It focuses on problems involving high temperature conditions and, in particular, defines boundary conditions in a suitable way for calculations. A large portion of the book is devoted to boundary conditions and measurements of thermal exposure by radiation and convection. The concepts and theories of adiabatic surface temperature and measurements of temperature with plate thermometers are thoroughly explained.Also presented is a renewed method for modeling compartment fires, with the resulting simple and accurate prediction tools for both pre- and post-flashover fires. The final chapters deal with temperature calculations in steel, concrete and timber structures exposed to standard time-temperature fire curves. Useful temperature calculation tools are included, and several examples demonstrate how the finite element code TASEF can be used to calculate temperature in various configurations. Temperature Calculation in Fire Safety Engineering is intended for researchers, students, teachers, and consultants in fire safety engineering. It is also suitable for others interested in analyzing and understanding fire, fire dynamics, and temperature development. Review questions and exercises are provided for instructor use.

  • 854.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperature of Steel Structures2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 195-216Chapter in book (Refereed)
    Abstract [en]

    Steel is sensitive to high temperature. The critical temperature of a steel member is the temperature at which it cannot safely support its load.

  • 855.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperature of Timber Structures2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 227-233Chapter in book (Refereed)
    Abstract [en]

    Modelling the thermal behaviour of wood is complicated as phenomenas such as moisture vaporization and migration, and the formation of char have decisive influences on the temperature development within timber structures. Nevertheless it has been shown that general finite element codes can be used to predict temperature in, for example, fire-exposed cross sections of glued laminated beams [52], provided, of course, that apparent thermal material properties and appropriate boundary conditions are used. Other specialized numerical codes for timber structures have been developed, e.g. by Fung

  • 856.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Temperatures of Concrete Structures2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 217-225Chapter in book (Refereed)
    Abstract [en]

    Reinforced concrete structures are sensitive to fire exposure of mainly two reasons. They may be subject to explosive spalling, and they may lose their load-bearing capacity due to high temperatures. Spalling is particularly hazardous as it may occur more or less abruptly and unanticipated. It usually starts within 30 min of severe fire exposure. It may depend on several mechanisms or combinations thereof such as pore pressure, stresses due to temperature gradients, differences of thermal dilatation and chemical degradations at elevated temperatures. Reinforcement bars of steel lose their strength at temperature levels above 400 °C. Prestressed steel may even loose strength below that level. Concrete loose as well both strength and stiffness at elevated temperature.

  • 857.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The adiabatic surface temperature and the plate thermometer2011In: Fire safety science: proceedings of the 10th international symposium : [held at College Park, MD, 19-24 June 2011], London: International Association for Fire Safety Science, 2011, p. 1001-1011Conference paper (Refereed)
    Abstract [en]

    The concept of adiabatic surface temperature (AST) opens possibilities to calculate heat transfer to a solid surface based on one temperature instead of two as is needed when heat transfer by both radiation and convection must be considered. The adiabatic surface temperature is defined as the temperature of a surface which cannot absorb or lose heat to the environment, i.e. a perfect insulator. Accordingly, the AST is a weighted mean temperature of the radiation temperature and the gas temperature depending on the heat transfer coefficients. A determining factor for introducing the concept of AST is that it can be measured with an inexpensive and robust method called the plate thermometer (PT) even under harsh fire conditions. Alternative methods for measuring thermal exposure under similar conditions involve water cooled heat flux meters that are in most realistic situations difficult to use and very costly and impractical. This paper presents examples concerning how the concept of AST can be used in practice both in reaction-to-fire tests and in large scale scenarios where structures are exposed to high and inhomogeneous temperature conditions

  • 858.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    The term ‘heat flux’ is used ambiguously: Clear definitions are needed on how to express thermal exposure2016In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 40, no 3, p. 507-510Article in journal (Refereed)
    Abstract [en]

    The expression ‘heat flux’ without any qualifier like ‘to a surface at ambient temperature’ as frequently used in fire safety science and engineering literature and standards is ambiguous and misleading. Boundary conditions in fire safety engineering problems cannot be expressed as a given heat flux (or net heat flux), as the heat flux depends on and varies with the exposed surface temperature and thereby the properties of the target body. Therefore, it is important that the terminology is reviewed and that an agreement is reached on how to express thermal exposure in a well-defined and unambiguous way. A proposal is given on how the boundary conditions can be defined in a consistent way that is applicable to fire resistance and reaction-to-fire problems

  • 859.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Thermal Ignition Theory2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 125-132Chapter in book (Refereed)
    Abstract [en]

    The various aspects of the subject ignition of unwanted fires has been thoroughly investigated by Babrauskas and presented in the comprehensive Ignition Handbook. This book is concentrating on the calculation of the development of surface temperature. Despite many limitations, it is often assumed that a solid ignites due to external heating when its exposed surface reaches a particular ignition temperature.

  • 860.
    Wickström, Ulf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Unsteady-State Conduction2016In: Temperature Calculation in Fire Safety Engineering, Encyclopedia of Global Archaeology/Springer Verlag, 2016, p. 25-44Chapter in book (Refereed)
    Abstract [en]

    When a body is exposed to unsteady or transient thermal conditions, its temperature changes gradually, and if the exposure conditions remain constant it will eventually come to a new steady state or equilibrium. The rate of this process depends on the mass and thermal properties of the exposed body, and on the heat transfer conditions. As a general rule the lighter a body is (i.e. the less mass) and the larger its surface is, the quicker it adjusts to a new temperature level, and vice versa. The temperature development is governed by the heat conduction equation (Eq. 1.29) with the assigned boundary conditions. It can be solved analytically in some cases, see textbooks such as [1, 2], but usually numerical methods are needed. This is particular the case in fire protection engineering problems where temperature generally varies over a wide range, often several hundred degrees.

  • 861.
    Wickström, Ulf
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Anderson, Johan
    RISE Research Institutes of SwedenBorås, Sweden.
    Sjöström, Johan
    RISE Research Institutes of SwedenBorås, Sweden.
    Measuring incident heat flux and adiabatic surface temperature with plate thermometers in ambient and high temperatures2019In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 43, no 1, p. 51-56Article in journal (Refereed)
    Abstract [en]

    A new more insulated and faster responding plate thermometer (PT) is introduced, which has been developed for measurements particularly in air at ambient temperature. It is a cheaper and more practical alternative to water‐cooled heat flux meters (HFMs). The theory and use of PTs measuring incident radiation heat flux and adiabatic surface temperature are presented. Comparisons of measurements with PTs and HFMs are made. Finally, it is concluded that incident radiation in ambient air can be measured with HFMs as well as with the new insulated type of PT. In hot gases and flames, however, only PTs can be recommended. At elevated gas temperatures, convection makes measurements with HFMs difficult to interpret and use for calculations. However, they can be used in standard or well‐defined configurations for comparisons.

  • 862.
    Wickström, Ulf
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Byström, Alexandra
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Compartment fire temperature: a new simple calculation method2015In: IAFSS - The International Association for Fire Safety Science: proceedings, ISSN 1817-4299, Vol. 11, p. 289-301Article in journal (Refereed)
    Abstract [en]

    In this paper a new simple calculation method for compartment temperatures is derived. The method is applicable to post-flashover ventilation controlled fires. A parameter termed the ultimate compartment fire temperature is defined as the temperature obtained when thermal equilibrium is reached and thick compartment boundaries cannot absorb any more heat from the fire gases. This temperature depends only on the product of the heat of combustion and the combustion efficiency over the specific heat capacity of air. It is, however, independent of the air mass flow rate, and of the fire compartment geometry and the thermal properties of the compartment boundary materials. These parameters on the other hand govern the rate at which the fire temperature is increasing towards the ultimate temperature. It is shown how the fire temperature development as a function of time in some idealized cases may be calculated by a simple analytical closed form formula.The fire temperature developments of two types of compartment boundaries are presented, semi-infinitely thick and thin structures. It is also shown that for the semi-infinite case, the solution resembles the standard ISO 834/EN 1363-1 curve and the parametric fire curves according to Eurocode 1, EN 1991-1-2.

  • 863.
    Wickström, Ulf
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Byström, Alexandra
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sjöström, Johan
    SP Sveriges Tekniska Forskningsinstitut, Brandteknik.
    Temperature measurements and modelling of flashed over compartment fires2016In: Proceedings of 14th International Conference and Exhibition on Fire Science and Engineering, 2016, Vol. 2, p. 949-960, article id 12Conference paper (Refereed)
    Abstract [en]

    This paper describes and validates by comparisons with test results a one-zone model for computing temperatures of compartment fires where flashover is reached. The model is based on an analysis of the energy and mass balance of a fully developed (ventilation controlled) compartment fire. It is demonstrated in this paper that the model can be used to predict fire temperatures in compartments with semi-infinite boundaries as well as with boundaries of insulated or uninsulated steel sheets where so called lumped heat capacity can be assumed. Comparisons are made with a series of experiments in compartments of light weight concrete, and insulated and non-insulated single sheet steel structures. A general finite element code has been used to calculate the temperature in the surrounding structures. The in this manner calculated surface temperatures yield the fire temperature as a function of time. By using a numerical tool like a finite element code it is possible to analyse fire compartment surrounding structures of various kinds and combinations of materials.Two new characteristic compartment fire temperatures have been introduced in this paper. They are the ultimate compartment fire temperature, which is the temperature reached when heat losses to surrounding structures as well radiation out through openings can be neglected, and the maximum compartment fire temperature, which is the temperature when only the losses to surrounding structures are neglected.The experiments referred to were accurately defined and surveyed. In all the tests a propane gas burner was used as the only fire source. Temperatures were measured with thermocouples and plate thermometers at several positions, and oxygen concentrations were measured in the fire compartment only opening. In some tests the heat release rate as well as the CO2 and CO concentrations were measured as well (Sjöström, et al., 2016).

  • 864.
    Wickström, Ulf
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Hunt, Sean
    JENSEN HUGHES.
    Lattimer, Brian
    JENSEN HUGHES.
    Barnett, Jonathan
    RED Fire Engineers Pty Ltd.
    Beyler, Craig
    JENSEN HUGHES .
    Technical comment: ten fundamental principles on defining and expressing thermal exposure as boundary conditions in fire safety engineering2018In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 42, no 8, p. 985-988Article in journal (Refereed)
    Abstract [en]

    Predicting the temperature of an exposed object or even a person is one of the most common tasks of fire safety engineering. However, the nonlinear nature of heat transfer and the challenge of changing material properties with temperature have plagued precise predictions. In addition, as methodologies are developed, one of the biggest challenges is to apply them to known scenarios where temperatures and heat fluxes have been measured. The interpretations of such measurements are, however, often clouded by the lack of common understanding of the reported values and how they shall be translated into boundary conditions to be used for calculations. This technical comment summarizes the Fundamental Principles that are crucial to properly identifying the fire exposure so that appropriate temperature predictions can be made.

  • 865.
    Widman, J.
    Luleå tekniska universitet.
    Environmental impact assessment of steel bridges1998In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 46, no 1-3, p. 291-293Article in journal (Refereed)
    Abstract [en]

    The Swedish Institute of Steel Construction has made LCAs on steel and concrete composite road bridges in order to detect important environmental impact parameters and to find areas where improvements are necessary. Two of the most common bridge types were studied. Combustion engines in vehicles contribute to a big share of the airborne emissions, such as CO2 and NOx. In spite of the small amounts, alloys as Molybdenum contribute to most of the environmental burden from the materials according to one assessment method. This put steel in a less favourable position when comparing LCA results with other materials. The concrete in steel bridges contributes to almost 50% of the environmental impact and the fact that steel bridges need less material than concrete bridges, shows that steel bridges are good environmental choices. Three assessment methods have been used to get multi-comparable and objective assessment results. The use of the bridge (traffic) is the most polluting part during the life cycle. The study has resulted in a report, SBI Report 183:1. (LCA: life cycle assessment.)

  • 866.
    Wikström, Samuel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Påbyggnation av befintlig betongbyggnad2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The investigation whether an extension of an office building can be built or not is received through several things that have been calculated, reasoned about and decided in order to be able to move forward. The aim with the investigation, or project, was to find out if an existing building could be fitted with additional floors and if any conclusions concerning similar projects could be made.The project started with looking at the existing house, House B, and making necessary assumptions regarding wind loads and how the concrete of the building looks after more than 50 years and also determine which ways the loads take through the building by identifying critical sections. The calculations start with deciding the loads and doing a calculation of cumulative loads throughout the building until the utilization rate for the columns, walls and foundation elements are known. The calculation of cumulative loads throughout the building came to play a big part in the project as it was necessary to figure out how much load the elements are carrying and compare it to the load bearing capacity of every single element. With known utilization rates, for all of House B, an extension of the building began to come in to focus. It was there decided that the roof and its columns should be removed with regards to weight and functionality. After the removal of the top floor the new utilization rates for the building were deemed suitable for extension. The extension is then chosen to be made out of wooden columns with wood floors and the positions of the new columns will be aligned with the existing rows of columns. This placement of the columns was derived from an investigation on what would work best regarding on how to spread the loads throughout the building and on the suitability of carrying a floor. The building material for the extension of the building was not predetermined but was chosen to be wood for its properties and relatively low weight after a shorter reasoning.The limitations for the extension did not come from the existing load bearing elements but from the foundation. Why the utilization rates concerning the foundation should be considered to be sufficient for an extension of the building is motivated through discussion.The procedure of calculating the extension is an iterative process and this process gave the result that without reinforcements in the foundation another two floors and a roof could be built. With reinforcements another 6 floors and a roof could be built. The floor that is suggested to be demolished is incorporated in the concept of a new floor thus giving that two new floors and a new roof is a raise of the building by one floor and one roof.Finally some conclusions are made from the purposes stated early on and these conclusions are motivated from the projects calculations and conditions.

  • 867.
    Witkowski, Artur
    et al.
    Centre for Fire and Hazards Science, University of Central Lancashire.
    Girdin, Bertrand
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Hewitt, Fiona
    Centre for Fire and Hazards Science, University of Central Lancashire.
    Fontaine, Geêlle
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq.
    Duquesne, Sophie
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq.
    Bourbignot, Serge
    R2Fire / UMET – UMR CNRS 8207, ENSCL, Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq.
    Hull, T. Richard
    Centre for Fire and Hazards Science, University of Central Lancashire.
    Development of an Anaerobic Pyrolysis Model for Fire Retardant Cable Sheathing Materials2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 113, p. 208-217Article in journal (Refereed)
    Abstract [en]

    Wire and cable coverings are potentially a major cause of fire in buildings and other installations. As they need to breach fire walls and are frequently located in vertical ducting, they have significant potential to increase the fire hazard. It is therefore important to understand the ignition and burning characteristics of cables by developing a model capable of predicting their burning behaviour for a range of scenarios. The fire performance of electrical cables is usually dominated by the fire performance of the sheathing materials. The complexity of the problem increases when cable sheathing incorporates fire retardants. One-dimensional pyrolysis models have been constructed for cable sheathing materials, based on milligram-scale and bench-scale test data by comparing the performance of three different software tools (ThermaKin, Comsol Multiphysics and FDS, version 6.0.1). Thermogravimetric analysis and differential scanning calorimetry were conducted on powdered cable coatings to determine the thermal degradation mechanism, the enthalpy of decomposition reactions, and the heat capacities of all apparent species. The emissivity and the in-depth absorption coefficient were determined using reflectance and transmittance measurements, with dispersive and non-dispersive spectrometers and integrating spheres. Bench-scale tests were conducted with a mass loss calorimeter flushed with nitrogen on samples in a horizontal orientation, for comparison with the pyrolysis model of non-flaming decomposition at an external heat flux of 50 kW m-2. The parameters determined through analysis of the milligram-scale data were used to construct a pyrolysis model that predicted the total mass loss from calorimeter tests in anaerobic conditions. A condensed phase pyrolysis model that accurately predicts in-depth temperature profiles of a solid fuel, and the mass flux of volatiles evolved during degradation of the fuel, is an essential component of a comprehensive fire model, which when coupled to a computational fluid dynamics code can be used to predict the burning processes in a fire scenario. Pyrolysis models vary considerably in complexity based on the assumptions incorporated into the development of the model.

  • 868.
    Wright, Howard D.
    et al.
    University of Strathclyde.
    Veljkovic, Milan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
    Towards a numerical procedure for composite slab assessment1996In: Recent Research and Developments in Cold-Formed Steel Design and Construction: Recent Research and Developments in Cold-Formed Steel Design and Construction / [ed] Wei-Wen Yu, Rolla, Mo: University of Missouri-Rolla , 1996, p. 415-435Conference paper (Refereed)
    Abstract [en]

    Composite slab design relies upon adequate shear bond resistance between the steel and concrete. This is achieved by friction between the materials and the mechanical interlock of embossments pressed in the steel. The behaviour of this shear bond resistance is complex and is obtainable only from model tests. This paper explores the potential for numerical modelling to provide the required design information.

  • 869.
    Öhlin, Emil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Industrilized and sustainable construction.
    Höghusbyggande med korslaminerade träskivor2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Historicly speaking wood is our moste important building material and it’s usage streches far back in time. Todyay it’s low density makes it possible to prefabricate whole wood bodies in factories that are later shiped out to building sites where they can be asembled. To meet the requierments of todays housing market, Lindbäcks Bygg AB has started a project where a 14-stories house is the be developed. To build on the height is a necessity due to rising land prices and the land has to be used mor efficient. A build of this high put a great demand on the constructual soulution in order for the wood body to withstand high columnloads on the lower flear, while it is stable enough to withstand the wind.

    The purpose of this report is to show you a possible way of constructing a 42 m high 14-stories hos usinga cross laminated timber(CLT). For the calculation a preliminary floor used, that has not been entirely completed. This gives the calcultations and arbitrary soulution that can work for similar buildings with varying floor plans. For this reason utilization of the CLT is a bit lower than what is otherwise wanted for cost optimization.

    In order to wind stabilize the building two differet methods are beging evaluated. In the first one the stabilazation is acheived by stairwells made of concrete In the other one it’s acheived by using 120 mm thick CLT-panels. In both cases the CLT is supporting the vertikal loads that are acting on each floor. On every fifht floor concrete slabs are placed of which the task is to miminize the load effect on the weaker parts of the body.

    By using composit theory according to (Blass & Fellmoser, 2004), the CLT-panels are controlled if they are in risk form shear, deformation or compression. The CLT-panel can be concidered as gluam wood, GL28h if it consists of C24 timber, which  this report is based on. Since the CLT panel is concidered as a solid element it experienced a reduced compressive and lifting forces, that it would otherwise if it was mad by a column system. The calculations shows that the CLT is strong enogugh to withstand the compressive and horisontal forces that is acting on them. When the building is stabilized using a concrete stairwell, this leads to and horisontal load that the concrete needs to be strong enough to withstand.

    The result shows that when concidering static loads, it is possible to construct a 14-stories building wtih a CLT-body that meets the requirements of Eurocode. However, when the building is stabilized with concrete towers it generates a load on against the stairwells. It has not been investigated whether or not the concrete is strong enough to withstand this load.

  • 870.
    Öhman, Kristoffer
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    The Crocodile Nose Connection: Design and laboratory tests on a novel connection for structural hollow sections2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The great properties and clear form makes the circular hollow section (CHS) appreciated by architects. When connecting these sections today it is common to use gusset plates. The knifeplate connection where the gusset plate is inserted into a slot made at the end of a circular section, is the most used connection today. This type of connections is not seen as aesthetically pleasingby architects because of its abrupt cut of the CHS.

    An alternative for the knife-plate connection is the Crocodile nose connection (CN-connection). The benefits of the CN-connection is the absence of the abrupt cut and the protruding gusset plate, which makes it appreciated by architects. In this connection the CHS’s ends are tapered, which creates two semi-elliptical cuts at both sides of the member. On these cuts, appropriate plates arefillet welded. These plates are shaped and bended so that when they are welded in place, the orientation of the extending part is parallel to the member axis. A gap is made between the extending parts so that a gusset plate can be inserted and bolted together with the member.

    Four different specimens of the CN-connection are tested in order to find the best shape. Two specimens have a stiffener between the plates, at a small distance from the end of the CHS. The difference between the presence of a stiffener and the lack of it, is investigated. The results showed that the specimens with the connecting piece obtained a much higher ultimate load, up to 413 %higher. Two different angles of the CHS’s cut is also investigated in order to see the most appropriate bevelling angle. In this case the results showed that the specimens with the smaller bevelling angle obtained a higher ultimate load, up to 40 % higher. A check of the weld connecting the plates and the CHS is also performed. This check was made with an assumed calculation model. The results showed that the calculation model only was valid for the specimens without the connecting piece. The calculation model must therefore be enhanced, in order to work for all dimensioning cases.

  • 871. Veljkovic, Milan (Editor)
    Uppfeldt, Björn (Editor)
    International workshop on new fire safety regulations for single storey building and on-going projects2012Report (Other academic)
  • 872. Collin, Peter (Editor)
    Nilsson, Mattias (Editor)
    Veljkovic, Milan (Editor)
    International Workshop Strengthening of Steel Bridges: Topics of relevance for the BRIFAG project2011Report (Other academic)
  • 873. Björnfot, Anders (Editor)
    Lean Wood Engineering goes Japan2011Report (Other academic)
  • 874. Johnsson, Helena (Editor)
    Proceedings from the Nordic Workshop in Wood Engineering: Skellefteå, February 21 20072007Report (Other academic)
    Abstract [en]

    On February 21st 2007 the Nordic Workshop in Wood Engineering was held in Skellefteå as part of Woodtech Sweden Research School. The proceedings contain seven original research papers presented by Ph.D. students in the field of wood material science, wood physics and timber engineering.

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