Yes / Steel concrete composite beams have been increasingly used in practice due to their advantages with respect to their structural features and constructability. However, in conventional composite beam systems composite action is applied via shear connectors welded at the top flange of the down-stand steel beam and embedded in the concrete slabs, making it less favourable for the beam system to be disassembled and reused. This paper presents a numerical study of a new composite beam system consisting of a cellular steel beam, metal deck flooring and demountable shear connectors. According to the experimental study, this composite beam system made the demounting, reassembly, and member reuse possible, and did not compromise the loading capacity. In the numerical study presented in the paper, a finite element model was developed and validated against the results obtained from the previous experimental study. The parametric study further examined the effects of concrete strength, shear connector arrangements and asymmetry ratios of steel beam section to the load capacity of the composite beam system. The analysis and comparison provided a deeper insight into the behaviour of this type of shear connector. Through this numerical study, the structural merits of the composite beam system using demountable shear connectors were highlighted. Finally, the mid-span plastic moment of the composite beam was predicted using the direction method provided in SCI publications and compared with the moment–deflection relationship obtained from FE modelling. / The research leading to these results is part of a joint project of the University of Bradford, the University of Luxemburg, the Technology University of Delft, the Steel Construction Institute, Tata Steel, Lindab S. A., BmS and AEC3 Ltd. The authors gratefully acknowledge the funding received from the European Commission: Research Fund for Coal and Steel (RFCS-2015, RPJ, 710040). In addition, deep appreciation to Mr. Stephen Robinson for his work done in the laboratory.

Yes / This paper presents an experimental study on an innovative composite floor system that can be demounted and deconstructed. In this system, the composite slab, formed with profiled metal decking, was connected to a steel beam via demountable shear connectors. A full-scale demountable composite floor system specimen was tested to ultimate load bearing capacity and compared with a similar non-demountable composite floor system specimen using conventional welded headed stud connectors. The experimental results and observations showed that the structural behaviour and load bearing capacity of both composite floor systems are very similar. However, the composite floor system with demountable shear connectors could be deconstructed after testing and the composite slab could be easily detached from the steel beam. The comparison and analysis presented in this paper indicated that the simple design methods currently provided in the Eurocode 4 for the welded shear connections could be used to assess the ultimate moment capacity of demountable composite floor systems.

Yes / Currently, steel reuse is only a marginal practice. To facilitate deconstruction and efficient reuse of steel components, an innovative connection system was proposed. This system adopts a ‘Block Shear Connector (BSC)’ that allows beam length to be standardised and suitable for a wide range of different sizes of the supporting members within the same planning grid. This paper presents the experimental and numerical studies of a beam-to-beam connection using BSCs. The BSC used was made from a standard universal HE / UC section and was bolted to the beams by using partial depth end plates. The experimental results provided the shear resistance, momentrotation, failure behaviour, demountability and reusability of the steel components. Further numerical simulation conducted investigated the effect of some key parameters (steel strength, thickness of BSC web, thickness of BSC flange, initial bolt stress) on the behaviour of the connections. The results obtained highlighted the demountability of this innovative bolted connection system and the reusability of structural components. / European Commission: Research Fund for Coal and Steel (RFCS-2015, RPJ, 710040)

The increased amount of traffic combined with higher traffic loads leads to many existing bridges needing strengthening in the future to ensure their expected lifespan. This means the bridge owners will be focusing more on strengthening projects and smart solutions will be crucial for preserving a healthy bridge stock. When strengthening existing non-composite bridges (with steel girder and concrete deck) one potential method is to achieve composite action by installing shear connectors. The post-installed shear connectors prevent slip between the steel girders and the concrete. The composite action will reduce bending stresses and deflection of the bridge, due to the increase in moment of inertia and relocation of the neutral axis. Different types of shear connectors can be used for achieving composite action and each type of connector has its own installation method. The biggest distinction between the methods is how the connectors gain access to the steel girder for installation and what technique is used when installing them. This thesis presents the theory behind composite action, the current methods used for achieving composite action on existing bridges and to what extent a bridge can be strengthened by composite action. The thesis also provides a status of the existing road bridge stock around the world. The four case studies examined in this thesis have used different post-installed shear connectors to manage different strengthening problems like weight restriction, fatigue life of shear connectors and a unique problem on the Pitsund Bridge where loud bangs appeared from the bridge when truck passed in the morning. For the case study on the Pitsund Bridge an interview was conducted that explains the entire procedure of the project, from the noise problem to how the installation of coiled spring pins was performed. The bridge over Lule River at Akkatsfallen consists of two steel girders and a concrete deck. This bridge is chosen as a real case study to determine to what extent a bridge can increase its capacity by achieving composite action. The calculations are performed in accordance with the Eurocodes on both non- and full-composite action and the result is compared to the other case studies.

A three-dimensional finite element model is developed, validated and used in the parametric study to investigate the influence of shear stud's position and profiled sheeting thickness on the strength, ductility and failure modes of the headed shear stud welded to the modern profiled sheeting. A total of 240 push tests were analysed with different sheeting thicknesses, positions of the shear stud in the trough, concrete strengths and transverse spacings. The results showed that the sheeting thickness influenced the shear connector resistance of studs placed in the unfavourable position more than studs placed in favourable and central positions. The strength of the shear connector placed in the unfavourable position increased by as much as 30% when the sheeting thickness was increased. The shear connector resistance of the unfavourable stud was found to be primarily a function of the strength and the thickness of the profiled sheeting rather than the concrete strength. The strength prediction equations for unfavourable and central studs were also proposed. The results suggested that the strength of the shear connector increased as the distance of the shear stud increased from the mid-height of the deck rib in the load bearing direction of the stud. The load¿slip behaviour of the studs in the unfavourable position was more ductile than the studs in the favourable position, with slip of 2-4 times higher. It was found that the increase in sheeting thickness and transverse spacing improved the ductility of the stud in unfavourable position, but had no effect on the stud in the favourable position. The failure modes suggested that the favourable and central studs failed by concrete cone failure and unfavourable studs failed by rib punching together with crushing of the narrow strip of the concrete in front of the stud.

Many of the existing steel-concrete bridges may need to be strengthened, as heavier vehicles areallowed on the Swedish roads. These bridges could possibly be strengthened by post-installingshear connectors. The shear connectors may enhance the load-bearing capacity through a higherdegree of composite action between the steel and concrete interface.For post-installing of shear connectors, it is advantageous to use a method that allows forinstallation from underneath the bridge as it avoids disrupting the traffic flow. The authors havehence focused on a shear connector called coiled spring pin (CSP); a sheet of metal rolled intoa coil. It’s inserted by hydraulic jacking into a pre-drilled hole and maintained in position dueto radial spring force, avoiding the need for welding.Information and data are collected from beam tests performed at Luleå technical university, theEurocodes and literature.This study investigates and identifies the behaviour and characteristics of a partial compositegirder reinforced with CSPs. The study compares the results obtained from the laboratory testsand the FEM-simulations. Furthermore, this research examines the factors that contribute to theaccuracy of the FEM models and investigates the influence of the CSP placement on the overallload-bearing capacity.Both the FEM simulations and laboratory tests indicate that the girders exhibit strength benefitsfrom applying CSPs. An optimal position for the connectors could not be determined, as theresults presented in the simulations was not proved by the laboratory tests. The simulationsindicate benefits with central placed CSPs, in contrast to the laboratory test where no differencesfrom the placement were shown, although only two test setups were used.

For bridges to cope with increased requirements such as increased loads, strengthening work can be carried out. In cases where older steel-concrete bridges do not have a composite action, an alternative is to create composite-action to achieve a higher flexural strength. It is introduced by post-installing shear connectors. There are many different alternatives of shear connectors that can be used, hence a number that can be installed from below the bridge to minimize the impact on the traffic. Coiled Spring Pins are of the interference fit type connector and are put in place from below the bridge by first drilling a hole upward through the upper steel flange and then into the concrete slab. Then, the spiral bolt is pushed up into the drilled hole by means of a hydraulic hammer. Using data from push-out tests and non-linear material models for steel and concrete, a non-linear finite element analysis was created using the commercial finite element software Abaqus. The analysis is based on dimensions and load cases that will mimic a planned full-scale beam test that will be carried out later in 2019. To verify that the material and the model behave in a realistic manner, an analysis was initially performed on a beam without composite-action, and a full-composite action beam with infinitely rigid connectors. These were then compared with hand calculations according to Eurocode. When the material models were verified, it is seen that the materials steel and concrete work for themselves in the analysis without composite-action and together in the analysis with full composite-action. The data for the spiral bolts is than defined instead of infinitely rigid connectors and new analyzes were performed to see the effect of the coiled spring pins properties. The results show that a significant increase in the point load in the middle of the beam can take place before failure occurs after installation of this type of shear connector. Already at a low number of connectors and a low shear connection-ratio, a significant increase in the flexural strength is seen in the beam. By using partial-composite action, with a lower number of spiral bolts, a significant higher flexural strength can be achieved in an economical way. / När kraven på att broar ska klara av ökade laster, kan förstärkningsarbeten utföras. I de fall där äldre stål-betongbroar saknar samverkanseffekt, är det ett alternativ att inför samverkan för att uppnå en högre böj-hållfastighet. Det införs genom att man installerar skjuvförbindare i efterhand. Det finns många olika alternativ av skjuvförbindare som kan användas, därav ett antal som går att installera underifrån bron för att minimera påverkan på trafiken. Spiralbultar (Coiled Spring Pins) är av typen presspassnings-förbindare och sätts på plats underifrån bron genom att det först borras ett hål uppåt genom övre stålflänsen och sedan upp i betongplattan. Därefter pressas spiralbulten upp i det borrade hålet med hjälp av en hydraulisk hammare. Med hjälp av data ifrån push-out-tester samt icke-linjära material modeller för stål och betong, skapades en icke-linjär analys i det finita element metods programmet Abaqus. Analysen är uppbyggd med dimensioner och lastfall som ska efterlikna ett planerat full-skaligt balktest som kommer utföras under 2019. För att verifiera att materialet och modellen beter sig realistiskt, utförs en analys på en balk utan samverkan, samt en full-samverkans balk med oändligt styva förbindare. Dessa jämförs sedan med handberäkningar enligt Eurokod. När materialmodellerna var verifierade sågs det att materialen stål och betong arbetar för sig själva i analysen utan samverkan och tillsammans i analysen med full-samverkan. Data för spiralbultarna lades sedan in istället för oändligt styva förbindare och nya analyser utförs för att se påverkan av spiralbultarnas egenskaper. Resultaten visade att en betydande ökning av punklasten i mitten av balken kan ske innan brott uppstår vid installation i efterhand av denna typen skjuvförbindare. Redan vid ett lågt antal förbindare och ett lågt skjuv-förhållande ses en betydande ökning av böj-hållfastigheten i balken. Genom att använda delvis-samverkan med ett lägre antal spiralbultar kan man på ett ekonomiskt sätt uppnå en betydligt högre böj-hållfasthet.

As vigas mistas aço-concreto têm sido bastante utilizadas na engenharia civil, tanto no Brasil como no contexto mundial. O comportamento adequado deste elemento estrutural faz-se pela interação entre ambos os materiais, a qual é garantida por conectores de cisalhamento. O presente trabalho apresenta uma visão geral do comportamento das vigas mistas aço-concreto, e, principalmente o estudo do comportamento estrutural de conectores de cisalhamento. Para tanto, faz-se uma simulação numérica dos conectores tipo pino com cabeça (stud) e perfil “U" formado a frio, por meio de uma modelagem do ensaio experimental tipo “Push-out", cujos resultados são confrontados com valores experimentais obtidos de ensaios realizados em laboratório. Para a simulação numérica utiliza-se um código de cálculo com base nos Método dos Elementos Finitos (MEF), cujas ferramentas disponibilizadas permitem análises dos modelos em regime de não-linearidade física e geométrica. Os modelos numéricos apresentam como variáveis de interesse o número de conectores na laje de concreto, a quantidade de armadura inserida no concreto, o diâmetro do conector tipo pino com cabeça (stud), a resistência do concreto, a espessura e posição de soldagem do conector tipo perfil “U" formado a frio. A variação desses parâmetros tem como finalidade a determinação da resistência última e da relação força-deslocamento dos conectores, bem como avaliar a concentração de tensão e deformação nas partes constituintes dos modelos / Composite steel-concrete beams have been used in civil engineering in Brazil as well other countries. A realistic determination of the behaviour of this structural element is estimated by considering the interaction between the two materials, which is safeguarded by providing shear connectors. The present research presents a general view of the behaviour of steel-concrete composite beams, and primarily the study of the behaviour of shear connectors. To meet this ends, a numerical analysis of stud bolt and cold formed U-channel under push-out test geometry was carried out and the results compared to experimental test results. The numerical analysis utilises a Finite Element Method (FEM) code that permits the analysis under non-linear material and geometric regimes. The main numerical variables in the study were the number of connectors used in the concrete plate, the quantity steel reinforcement, the diameter of stub bolt connector, concrete strength, the thickness and position of welding of the cold-formed U-channel. The main objective of varying these parameters was to determine the ultimate strength and the load-slip behaviour of the connectors as well as evaluate the stress and strain concentrations in certain parts that constitute the models

Made available in DSpace on 2014-07-29T15:03:37Z (GMT). No. of bitstreams: 1 dissertacao paulo menezes.pdf: 3080026 bytes, checksum: 27fc4469f9413ad9117d4813295e9db7 (MD5) Previous issue date: 2006-09-14 / In a composite system, a steel beam (laminated, welded or cold formed) is associated with a concrete slab, forming a composite beam. The interaction between concrete and steel can be mechanical, by friction or, in some cases, only by adherence. One of the major advantages of the composite beams is the increase in strength and stiffness due to association of steel and concrete that makes possible the reduction of the height of the structural elements, implicating in material economy. The present research has the purpose to present a general vision of the structural behavior of the composite steel-concrete beams and to proceed to a more detailed study of the behavior of the shear connectors made from cold formed steel. A modeling study of the push-out test is accomplished with the intention to find the factors that influences the resistance and rigidity of the connection. The numerical study consists in the elaboration of a three-dimensional numerical model to simulate the push-out test from which is obtained the force-displacement curve, ultimate load, deformations and tensions along the connector. The numeric results are compared with obtained experimental values of rehearsals accomplished at laboratory for validation of the same ones. For the accomplishment of the numeric modeling the computational program ANSYS® 6.1 was used, which uses non-linear material and geometric Finite Element Method models. The numeric models present as variables of interest the thickness, the height of the shear connectors made of cold formed steel and the resistance of the concrete used in the premolded slab with reinforced concrete lattice joist. Results showed that the thickness of the connector is the most important variable in the connection strength, however the height of the connector also has influence in the resistance and, mainly, in the rigidity of the connection. / Denomina-se sistema misto aço-concreto aquele no qual um perfil de aço (laminado, dobrado ou soldado) trabalha em conjunto com uma laje de concreto, formando uma viga mista. A interação entre o concreto e o perfil de aço pode se dar por meios mecânicos, por atrito, ou, em alguns casos, por simples aderência. Uma das vantagens da utilização de vigas mistas em sistemas de pisos é o acréscimo de resistência e de rigidez propiciados pela associação dos elementos de aço e de concreto, o que possibilita a redução da altura dos elementos estruturais, implicando em economia de material. O presente trabalho tem por finalidade apresentar uma visão geral do comportamento estrutural das vigas mistas aço-concreto e proceder a um estudo mais detalhado do comportamento da ligação com conectores de cisalhamento tipo U em perfil formado a frio. É realizada a modelagem computacional do ensaio de cisalhamento direto (push-out test) com o intuito de determinar os fatores que mais influenciam na resistência e rigidez da ligação A modelagem computacional consiste na elaboração de um modelo numérico tridimensional para simular o ensaio de cisalhamento direto, do qual se obtém a curva força-deslocamento, a força última e as deformações e tensões ao longo do conector. Os resultados numéricos são confrontados com valores experimentais obtidos de ensaios realizados em laboratório para validação dos mesmos. Para a realização da modelagem computacional, foi utilizado o programa comercial ANSYS® 6.1, elaborado com base no Método dos Elementos Finitos, cujas ferramentas disponibilizadas permitem análises em regime de não-linearidade física e geométrica. Os modelos computacionais apresentam como variáveis de interesse a espessura e a altura do conector tipo perfil U formado a frio e a resistência do concreto utilizado na confecção das lajes treliçadas. Os resultados obtidos mostram que a espessura do conector é a variável que mais influência a resistência da ligação, porém a altura do conector também tem influência na resistência e, principalmente, na rigidez da ligação.

As vigas mistas aço-concreto têm sido bastante utilizadas na engenharia civil, tanto no Brasil como no contexto mundial. O comportamento adequado deste elemento estrutural faz-se pela interação entre ambos os materiais, a qual é garantida por conectores de cisalhamento. O presente trabalho apresenta uma visão geral do comportamento das vigas mistas aço-concreto, e, principalmente o estudo do comportamento estrutural de conectores de cisalhamento. Para tanto, faz-se uma simulação numérica dos conectores tipo pino com cabeça (stud) e perfil “U” formado a frio, por meio de uma modelagem do ensaio experimental tipo “Push-out”, cujos resultados são confrontados com valores experimentais obtidos de ensaios realizados em laboratório. Para a simulação numérica utiliza-se um código de cálculo com base nos Método dos Elementos Finitos (MEF), cujas ferramentas disponibilizadas permitem análises dos modelos em regime de não-linearidade física e geométrica. Os modelos numéricos apresentam como variáveis de interesse o número de conectores na laje de concreto, a quantidade de armadura inserida no concreto, o diâmetro do conector tipo pino com cabeça (stud), a resistência do concreto, a espessura e posição de soldagem do conector tipo perfil “U” formado a frio. A variação desses parâmetros tem como finalidade a determinação da resistência última e da relação força-deslocamento dos conectores, bem como avaliar a concentração de tensão e deformação nas partes constituintes dos modelos / Composite steel-concrete beams have been used in civil engineering in Brazil as well other countries. A realistic determination of the behaviour of this structural element is estimated by considering the interaction between the two materials, which is safeguarded by providing shear connectors. The present research presents a general view of the behaviour of steel-concrete composite beams, and primarily the study of the behaviour of shear connectors. To meet this ends, a numerical analysis of stud bolt and cold formed U-channel under push-out test geometry was carried out and the results compared to experimental test results. The numerical analysis utilises a Finite Element Method (FEM) code that permits the analysis under non-linear material and geometric regimes. The main numerical variables in the study were the number of connectors used in the concrete plate, the quantity steel reinforcement, the diameter of stub bolt connector, concrete strength, the thickness and position of welding of the cold-formed U-channel. The main objective of varying these parameters was to determine the ultimate strength and the load-slip behaviour of the connectors as well as evaluate the stress and strain concentrations in certain parts that constitute the models