Dissertations / Theses on the topic 'Bolted steel connection'

An experimental investigation was conducted to study the behavior of extended end-plate moment connections subjected to cyclic loading. Eleven specimens were tested, representing typical connection configurations used in the metal building manufacturing industry. Four of the beams were shallow (30 in. or less), and seven were deep (60 in. or more). Two of the beams had compact webs, two had non-compact webs, and seven had slender webs. All specimens were designed according to the "thick plate" procedure contained in AISC Design Guide 16, Flush and Extended Multiple-Row Moment End-Plate Connections. A displacement-controlled history was used to load the specimens. Experimental maximum moments were compared to analytical predictions of beam and connection strength. Also, each moment versus rotation relationship was analyzed for compliance with the requirements of Ordinary, Intermediate, and Special Moment Frames, as defined by AISC in the Seismic Provisions for Structural Steel Buildings. The experimental results demonstrated that the thick plate procedure in Design Guide 16 is an accurate model for predicting the strength of the connection elements, and the procedure is recommended for designing connections subject to cyclic (seismic) loads. The connection design moment should be based on the expected plastic strength of the beam, regardless of the equations governing nominal beam strength.
Master of Science

Experimental and analytical research has been conducted to develop unified design procedures for eight extended end-plate moment connection configurations subject to cyclic/seismic loading. In addition, the suitability of extended end-plate moment connections for use in seismic force resisting moment frames was investigated. Eleven full-scale cyclic and nine monotonic extended end-plate moment connection tests were conducted. Design procedures for determining the required bolt diameter and grade, end-plate thickness, and column flange thickness were developed. The proposed design procedure utilizes a strong column, strong connection, and weak beam design philosophy. This forces the connecting beam to provide the required inelastic deformations through formation of a plastic hinge adjacent to the connection region. The proposed design procedure was used to make comparisons with ninety experimental tests conducted over the past twenty-six years. A limited finite element study was conducted to investigate the behavior of the column flange. The experimental results demonstrate that extended end-plate moment connections can be detailed and designed to be suitable for use in seismic force resisting moment frames. The proposed design procedure strength predictions correlated well with the results from ninety experimental tests. The limited finite element modeling conducted as a part of this study, correlated well with the strength predictions produced by the proposed design procedure.
Ph. D.

In cold-formed steel (CFS) construction, bolted connections without washers for either oversized or slotted holes may significantly expedite the installation process and lower the cost. However, the North American Specification (AISI S100, 2007) for the Design of Cold-Formed Steel Structural Members requires washers to be installed in bolted connections with oversized or slotted holes. A research project (Phase 1) sponsored by American Iron and Steel Institute (AISI) was recently completed at the University of North Texas (UNT) that investigated the performance and strength of bolted CFS connections with oversized and slotted holes without using washers. The research presented in this thesis is the Phase 2 project in which the bolted CFS connections were studied in a broader respect in terms of the failure mechanism, the material thickness, and the hole configurations. Single shear and double shear connections without washers using oversized holes, oversized combined with standard or slotted holes were experimentally examined. Combined with Phase 1 results, the Phase 2 gives a comprehensive evaluation of the behavior and strength of bolted CFS connections with oversized and slotted holes without using washers. Revisions to the existing AISI North American Specification requirements for bolted connections are proposed to account for the reduction in the connection strength caused by the oversized and slotted hole configurations without washers. Specific LRFD and LSD resistance factors and ASD safety factors for different hole configurations in terms of the new proposed methods were presented.

Master of Science
Department of Architectural Engineering and Construction Science
Kimberly W. Kramer
Of seismic steel lateral force resisting systems in practice today, the Moment Frame has most diverse connection types. Special Moment frames resist lateral loads through energy dissipation of the inelastic deformation of the beam members. The 1994 Northridge earthquake proved that the standard for welded beam-column connections were not sufficient to prevent damage to the connection or failure of the connection. Through numerous studies, new methods and standards for Special Moment Frame connections are presented in the Seismic Design Manual 2nd Edition to promote energy dissipation away from the beam-column connection. A common type of SMF is the Reduce Beams Section (RBS). To encourage inelastic deformation away from the beam-column connection, the beam flange’s dimensions are reduced a distance away from the beam-column connection; making the member “weaker” at that specific location dictating where the plastic hinging will occur during a seismic event. The reduction is usually taken in a semi-circular pattern. Another type of SMF connection is the Kaiser Bolted Bracket® (KBB) which consists of brackets that stiffen the beam-column connection. KBB connections are similar to RBS connections as the stiffness is higher near the connection and lower away from the connection. Instead of reducing the beam’s sectional properties, KBB uses a bracket to stiffen the connection. The building used in this parametric study is a 4-story office building. This thesis reports the results of the parametric study by comparing two SMF connections: Reduced Beam Section and Kaiser Bolted Brackets. This parametric study includes results from three Seismic Design Categories; B, C, and D, and the use of two different foundation connections; fixed and pinned. The purpose of this parametric study is to compare member sizes, member forces, and story drift. The results of Seismic Design Category D are discussed in depth in this thesis, while the results of Seismic Design Category B and C are provided in the Appendices.

Cold-formed steel purlin systems are widely used in modem building construction, for supporting the roof and floor structures. The rotational behaviour of beam-to-beam bolted connections, which are used between the sections, significantly affects the performance of purlin systems and is hard to predict. The behaviour models currently available for the connections only offer linear or multilinear predictions with low levels of accuracy. The aim of the research presented in this thesis is to develop and propose a nonlinear, more accurate behaviour model for the sleeved modified Z bolted connections, by means of experimental and numerical analysis. Finite element models are presented for the single-bolt, single-lap connection, sleeved modified Z connections in the simply supported arrangement, and a six-span purlin system. Based on the numerical results that have been validated by the experiments, a nonlinear behaviour model is proposed for the sleeved modified Z connections. In the model, the behaviour of the connections is divided into four stages, based on the dominant mechanism that provides the resistance to the rotation. Different formulas are used in different stages to determine the behaviour of the connection, boundary conditions, and magnitudes of bolt forces. The new model reflects well the true behaviour of the connections, and provides a good understanding of what happens inside the connections. The model reveals the failure pattern of the connections and enables optimization in the design of purl in systems, for improving efficiency in material usage.

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.
Att förutse skruvförbands beteende kan kräva tillämpning av diverse metoder. Metoderna används för att kalkylera den dimensionerande lastkapaciteten. I denna avhandling värderas lastkapaciteten i enlighet med den så kallade Komponentmetoden från del 1-8 i Eurokod 3. Denna dimensioneringsmetod fastslår en enhetlig procedur när det gäller modelleringen av stålförband. Varje förbandstyp bryts ner till sina baskomponenter med avseende på belastningstypen. För att beräkna den dimensionerande lastkapaciteten för dragbelastade komponenter används en förenklad substitutionsmodell en så kallad T-knut. Komponentmetoden är något komplicerad att tillämpa för alla former av skruvförband. Därmed är den huvudsakliga ambitionen med arbetet att skapa en kortfattad handbok vars syfte är att täcka de vanligaste typerna av skruvförband som Kadesjös konstruktörer använder sig av. Ämnet som kommer att studeras är relativt omfattande, således bestämdes det att i huvudsak sätta fokus på bärförmågan hos komponenter i dragzonen för HEA-profiler och därav dyka djupare i den ekvivalenta T-knutmetodiken. För att få en helhetsbild av dimensioneringsprocessen samlades allmän information om komponentmetoden genom litteraturstudier. Därefter användes dimensioneringsreglerna, presenterade i koder och standarder, för beräkning av lastkapacitet. Dessa utnyttjades för att generera en lösningsalgoritm för två skilda förband. Beräkningen genomfördes med hjälp av beräkningsprogrammet Mathcad. De erhållna resultaten, från en parametrisk analys för särskilda profiler i varje exempel, sammanfattades i form av tabeller och diagram med hjälp av Microsoft Excel.

Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Haj-Ali, Rami; Committee Co-Chair: Leon, Roberto; Committee Co-Chair: White, Donald; Committee Member: DesRoches, Reginald; Committee Member: Gentry, Russell. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Beam splices are typically located at moment contraflexure points (where M=0). Most design specifications require these splices to develop a strength either to meet design forces or a minimum value set by specifications. The design forces are typically determined through elastic analysis, which does not include flexibility of splice connections. In this research, two types of splice connections, an extended end plate splice connection and a flange and web plate bolted splice connection, were tested and analyzed to investigate the effect of the partial strength splice connections on structural response. The splices were designed to resist 40% and 34% of connecting section capacities using current steel design codes, respectively. It has been observed from the experiments and FEM analysis results that splice connections designed under capacities of connecting steel members can result in changes in design moment diagrams obtained from analyses without splice connection simulation and can also significantly decrease the rigidity of the structure endangering serviceability. The differences in design moment diagrams can go up to 50 % of elastic analysis without connection flexibility. The vertical displacements can increase to 155% of values obtained from elastic analysis with no splice connection simulation. Therefore, connection flexibility becomes very important to define in analysis.

Orientador: João Alberto Venegas Requena
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-25T11:48:05Z (GMT). No. of bitstreams: 1 Vieira_RodrigoCuberos_D.pdf: 6229131 bytes, checksum: 7e5242e6a56caebc45c513aca2e6323e (MD5) Previous issue date: 2014
Resumo: Este trabalho apresenta o estudo de um modelo de ligação inovador para emendas de perfis tubulares circulares, visando facilitar e baratear a montagem e fabricação das estruturas metálicas tubulares, além de proporcionar economia de tempo. A ligação estudada é composta por dois tubos externos submetidos à tração, conectados à um tubo interno, de diâmetro inferior aos tubos externos, por meio de parafusos alinhados que atravessam ambos os tubos externo e interno. Esta ligação pode ser utilizada como alternativa às ligações em flange, por ser mais simples e discreta. Foi realizada uma pesquisa bibliográfica sobre as prescrições de cálculo e publicações nacionais e internacionais referentes às ligações de perfis tubulares, não sendo encontrado nenhum processo de cálculo para as ligações tubulares em luva parafusada. Um modelo numérico da ligação foi desenvolvido com o programa de elementos finitos ANSYS v13.0, levando-se em consideração o contato entre os parafusos e os tubos. Esse modelo foi validado através da análise de resultados experimentais em escala real da ligação estudada. Os resultados numéricos e experimentais possibilitaram analisar o comportamento da ligação e seus modos de falha com as respectivas resistências. Com o modelo numérico validado, foi realizado um estudo paramétrico, permitindo compreender em detalhes quais os principais modos de falha da ligação, e quais os fatores que mais influenciam na sua resistência. Através desse estudo foi possível observar a necessidade de se levar em consideração no cálculo da resistência à ruptura da seção líquida, o coeficiente de redução da área líquida, Ct, para essa ligação, sendo proposto um processo para obtenção do mesmo, assim como da resistência da ligação à tração. Os resultados obtidos demonstraram o bom comportamento da ligação tubular em luva parafusada e a viabilidade de sua utilização submetida à tração, com parafusos alinhados
Abstract: This paper presents a study of an innovative connection model to splice circular hollow sections, which can be used for an easier and cheaper assembly and manufacture of tubular steel structures, besides providing time-saving. The proposed connection consists of two external tubes under tension, connected to an internal tube with smaller diameter than the external ones, and bolts passing by both tubes. This connection can be used as an alternative to flange connections, because it is simple and discreet. A bibliographic research on national and international codes and papers of tubular connections was carried out, and no design process for tubular bolted sleeve connections was found. A numerical model of the connection was developed with the finite element program ANSYS v13.0, considering the tubes and bolts contact. The numerical model was evaluated against experimental analyses results of the connection. The numerical and experimental results allowed the behavior analysis of this connection and its possible failure modes with their respective resistances. With the evaluated numerical model, a parametric study was carried out, allowing to understand the connection main failure modes, and what factors most influence their strength. With this study it was clear the need of the reduction coefficient, Ct, calculation for this connection, being proposed a process to determine the reduction coefficient and the tension strength for this connection. The results demonstrated the good behavior and feasibility of the tubular sleeve connection under tension, with bolts in line
Doutorado
Estruturas
Doutor em Engenharia Civil

Cette thèse a pour objectifs de développer une modélisation aussi fine que possible des structures aciers et mixtes acier-béton sous sollicitations cycliques avec prise en compte d'une part du comportement des assemblages et d'autre part des non-linéarités géométriques et du contact à l'interface acier-béton. Notre attention porte en particulier sur l'assemblage de type poutre acier/mixte sur poteau métallique par platine d'extrémité boulonnée. L'objectif étant de proposer un modèle «élément fini» d'assemblage qui reproduit aussi fidèlement que possible le comportement cyclique de ce dernier pour ensuite l'assembler à un élément fini de poutre non-linéaire acier ou mixte avec prise en compte, pour ce dernier, du soulèvement à l'interface. Le travail se compose de 3 parties distinctes. Un premier modèle qui se base sur la méthode des composantes a été développé ayant pour objectif de suivre la déformation de chaque composante au cours des cycles et de prendre en compte les non-linéarités induites par la séparation entre la platine d'extrémité et la semelle du poteau auquel elle est boulonnée. Ce modèle type composantes, a été développé pour une rangée de boulons. Dans le cas le plus fréquent, de deux rangées de boulons, une résistance de groupe (en plus des résistances individuelles de chacune des rangées) est susceptible de se développer. Pour rendre compte de ce phénomène, nous avons implanté le modèle proposé par Cerfontaine qui repose sur la définition d'une surface de charge et une règle d'écoulement associée pour déterminer les allongements des ressorts équivalents. Seul le cas de plasticité parfaite est considéré. Il est mis en évidence que l'influence de l'effet de groupe s'avère non négligeable sur le comportement post-élastique de l'assemblage et donc de la structure. Dans une seconde phase, nous proposons un modèle de poutre métallique classique en grands déplacements (approche co-rotationnelle) avec rotules généralisées aux extrémités. Nous faisons l'hypothèse que les déformations plastiques sont concentrées aux rotules dont le comportement plastique est contrôlé par une surface de charge asymétrique (anisotrope) qui peut prendre différentes formes selon la valeur donnée à un facteur q dit « facteur de forme». Chacune de ces rotules plastiques comprend un ressort longitudinal pour l'effort normal Net un ressort spiral pour le moment fléchissant M. L'interaction (M-N) entre ces deux efforts dans le domaine plastique est régie par le critère de plasticité. Le modèle de rotule plastique généralisé proposé permet de rendre compte de l'adoucissement cyclique, de la ductilité et du « pinching effect ».Nous montrons aux travers de plusieurs exemples la pertinence mais également les limites d'une telle approche. Dans une troisième partie, nous proposons un nouvel élément fini de poutre mixte (à 6 ddl par nœud) en petits déplacements avec prise en compte de la non-linéarité matérielle de la poutre ainsi que du contact entre l'acier et le béton. Une stratégie efficace de type nœud mobile (Flying Node) est proposée pour déterminer l'étendue de la surface de contact au sein d'un élément fini et d'adapter le maillage de l'élément poutre/poteau. Pour la résolution du problème de contact, la technique du Lagrangien Augmenté a été retenue. On montre que dans certaines situations, le soulèvement modifie la redistribution des efforts
The goal of this thesis is to develop computational tools for the nonlinear analysis of steel and composite steel-concrete structures under cyclic loading taking into account the actual behaviour of joint, material and geometry non-linearities and contact conditions at the steel-to-concrete interface. In particular, our efforts focuses on typical bolted end-plate connection between steel or composite beam and steel column. The objective is to develop a new «joint finite element" able to reproduce accurately the cyclic behavior of the beam-to-column connection. Next this model is combined with a non-linear steel/composite beam element considering slip and possible uplift at the interface. The thesis consists of three major parts. The first part deals with the behavior of a steel beam-to-column bolted end-plate connection under arbitrarily cyclic loading. The proposed model is based on an improved component method that closely follows the deformation of each component taking into account non-linearities induced by possible gap between the column flange and the end-plate. This model has been developed for a single row connection. In the case of multiple row bolted connection group effects may develop. Possible group effect between two bolt-rows has been implemented considering the model proposed by Cerfontaine based on the definition of the multi-surface yield criterion and the associated flow rule that govern deformation of equivalent springs. Only the case of perfect plasticity is considered. It is shown that the influence of the group effect is not negligible on the nonlinear response of the joint. In the second part, we have developed a flexible co-rotational two-noded beam with generalized elasto-plastic hinges at the beam ends. It is assumed that plastic deformations concentrate at these hinges. These hinges have the ability to elongate/shorten along the beam axis and to rotate. A family of asymmetric and convex yield surfaces of super-elliptic shape is considered for the plastic behavior of the hinges. By varying the roundness factor, an infinite nun1ber of yield surface are obtained. It is shown that the nonlinear response of bolted connections subjected to both bending and tension are conveniently modeled with such a yield surface. It was observed that cyclic loading produces pinching effect, cyclic softening and ductile behavior. Advantages and limitations of the approach are discussed. Finally, the third part is dedicated to the problem of contact at the interface of steel-concrete composite beams. A "new" finite element for composite steelconcrete beam is proposed. The beam element has 6 degrees of freedom per node. The concrete beam is allowed to separate from the steel beam. An efficient contact algorithm is proposed. The Flying node concept is introduced and used to determine the extent of the contact area within a single element and modify the mesh of the beam structure. The contact problem is solve using the Augmented Lagrangian Method. The influence of contact on the loading capacity of the beam and its influence on some design variables are highlighted

The Master’s thesis concerns a design of load bearing multi-storey steel construction of scientific institution in Brno. This thesis contains three different solutions of a draft proposal and for the elected solution is processed technical report, structural analysis, material list and drawings.

Este trabalho realiza estudo teórico e experimental de ligações parafusadas em chapas finas onduladas, com aço de alta resistência, submetidas a esforços de tração em situação de cisalhamento simples. A aplicação deste tipo de ligação ocorre em paredes de silos cilíndricos metálicos. Também foi avaliada a utilização de montagem com chapas duplas, utilizadas na prática para aumentar a espessura total da parede, devido a demanda por silos cada vez maiores. O programa experimental compreendeu 137 ensaios, nos quais foram variados parâmetros de interesse com aplicações práticas, resultando em dois modos de falha distintos, ruptura da chapa na seção líquida e esmagamento do aço na parede do furo. Foram propostas novas equações para o cálculo da resistência deste tipo de ligação. Os resultados experimentais obtidos mostraram que em ligações com falha por ruptura na seção líquida, reduzir a área líquida à uma área efetiva por meio de um coeficiente redutor resulta em valores conservadores para a resistência deste tipo de ligação. As ligações com chapas duplas apresentaram resistência elevada, superior à condição de chapa simples.
This work presents a theoretical and experimental study of bolted connections with thin, corrugated, high strength steel sheets, subjected to tension in simple shear condition. This type of connection is applicable in walls of cylindrical steel silos. It also was evaluated the case of double sheet assemblage, that is used in practice to increase the total wall thickness, due to the demand for bigger silos. The experimental program comprised 137 tests, in which it were varied chosen parameters of practical interest, providing failure by net section tension rupture and bearing of the sheet. New equations were proposed for the strength calculation of this type of connection. The experimental results indicated that in connections subject net section rupture, to reduce the net section area to an effective area through a reduction coefficient returns conservative values of resistance for this type of connection. The connections with double sheet exhibited high values of resistance, which resulted bigger than for simple sheet cases.

The subject of this diploma thesis is design and check the steel construction of the office building in Valašské Meziříčí. Floor plan dimensions of building are 55,0 x 30,0 m. The length of building gradually increases with each floor. The building has eight floors. Overall height is 33,6 m. The building ceilings made of composite steel and concrete structure. The construction in both directions is stabilized by vertical bracings. The building adjoins a smaller building with shops. Floor plan dimensions of that building are 31,5 x 21,0 m and building height to the top of the truss girder including cladding is 17,5 m.

The use of stainless steel in construction is steadily growing, with applications designed to exploit its structural properties, durability, appearance and fire resistance. The mechanical behaviour of stainless steel is fundamentally different from that of carbon steel. The stress-strain curve of stainless steel is rounded without a well-defined yield stress and exhibits significant strain hardening at relatively small strains. Nevertheless, design provisions for bolted connections between stainless steel structural members in current international standards are essentially based on the rules for carbon steel with some very limited modifications. As the connections form an essential part of all structural assemblages, a comprehensive understanding of their behaviour is vital for efficient design and consequently better performance of structures. For this reason, an investigation into the behaviour of stainless steel bolted connections has been carried out so as to better understand the response of these structural components. Suitable available test data have been reviewed and replicated using numerical models in order to study the behaviour of lap bolted connections and gusset plate connections in stainless steel under static tensile load. Strain-based criteria were defined to identify three failure modes: net section rupture, bolt shear and bearing failure. The developed FE models were successfully validated against the test results, after which they were employed to meticulously investigate the behaviour of bearing and net section rupture of lap bolted connections, as well as the net section failure of single angles connected to gusset plates. The results demonstrated that the response of stainless steel connections has some different aspects from that of carbon steel. The findings have been used to revise the design rules for net section and bearing capacities in Eurocode 3 Part 1.4. These proposed rules take into account the particular mechanical characteristics of stainless steel and therefore offer an improvement to those currently available.

The structural behaviour of single shear bolted connections, double shear bolted connections and single shear screwed connections of thin sheet steels at elevated temperatures has been investigated in this study. The current design rules on bolted and screwed connections of thin sheet steels for cold-formed steel structures are applicable for ambient temperature condition only. These design rules may not be applicable for elevated temperature conditions. Therefore, design guidelines should be prepared for bolted and screwed connections of cold-formed steel structures at elevated temperatures. A total of 30 tensile coupon tests were conducted to investigate the material deterioration of the thin sheet steels at elevated temperatures, and also to determine the critical temperatures for connection tests. A total of 510 tests on single shear bolted connections, double shear bolted connections and single shear screwed connections of thin sheet steels at elevated temperatures was performed in the temperature ranged from 22 to 900?C using both steady state and transient state test methods. The test results were compared with the predicted values calculated from the North American, Australian/New Zealand and European specifications for coldformed steel structures. In calculating the nominal strengths of the connections, the reduced material properties of the thin sheet steels were used due to the deterioration of material at elevated temperatures. It is shown that the design strengths predicted by these specifications are generally conservative at elevated temperatures. Finite element models for single shear bolted connections, double shear bolted connections and single shear screwed connections were developed and verified against the experimental results. Explicit dynamic analysis technique was used in the numerical analyses. Extensive parametric studies that included 490 finite element specimens were carried out using the verified finite element models to evaluate the bearing strengths of bolted connections as well as the tilting and bearing strengths of screwed connections of thin sheet steels at elevated temperatures. Design equations for bearing strengths of bolted connections as well as design equations for tilting and bearing strengths of screwed connections were proposed based on both the experimental and the numerical results in the temperature ranged from 22 to 900?C. The bearing strengths of bolted connections as well as the tilting and bearing strengths of screwed connections obtained from the test specimens and the finite element analyses were compared with the predicted strengths calculated using the proposed design equations and also compared with the design strengths calculated using the current North American, Australian/New Zealand and European specifications with consideration of the reduced material properties at elevated temperatures. It is shown that the proposed design equations are generally more accurate and reliable in predicting the bearing strengths of bolted connections as well as the tilting and bearing strengths of screwed connections of thin sheet steels at elevated temperatures than the current design rules. The reliability of the current and proposed design rules was evaluated using reliability analysis. The proposed design equations are suitable for bolted and screwed connections assembled using thin sheet steels of thickness ranged from 0.35 to 3.20mm.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

Modern society is challenged by economic and environmental issues, requiring engineers to develop more efficient structures. Using cold-formed steel (CFS) frame in construction industry can lead to more sustainable design, since it requires less material to carry the same load compared with other materials. However, the application of CFS structural systems is limited to low story buildings due to the inherent weaknesses of premature buckling behaviour of members and the low ductility of connections. Consequently, current design guidelines of CFS systems are very conservative especially in the case of seismic design. Furthermore, there is no generic optimisation framework for the CFS elements, capable of taking into account both manufacturing/construction constraints and post-buckling behaviour. This study aims to better understand, to predict, and to optimise CFS elements based on their strength and post-buckling behaviour. The optimised elements can be then included in full-structure modelling to develop more efficient CFS structural connections with high ductility and energy dissipation capacity, suitable for multi-story buildings in seismic regions. The geometrical dimensions of manufacturable CFS cross-sections were optimised regarding their maximum compressive and bending strength. All the sections were considered to have a fix coil width and thickness while the optimisation was performed based on effective width method suggested in EC3. The optimised solutions were achieved using Particle Swarm Optimisation (PSO) algorithm. The accuracy of the optimisation procedure was assessed using experimentally validated nonlinear Finite Element (FE) analyses accounting for the effect of imperfections To allow for the development of a new ‘folded-flange’ beam cross-section, the effective width method in EC3 was extended to deal with the presence of multiple distortional buckling modes. Improved strength were achieved for CFS elements by using the proposed optimisation framework. A non-linear shape optimisation method was presented for the optimum design of CFS beam sections based on their post-buckling behaviour. A developed PSO algorithm was linked to the ABAQUS finite element programme for inelastic post-buckling analysis and optimisation. The results also demonstrate that the optimised sections develop larger plastic area, which is particularly important in seismic design of moment-resisting frames. An experimental programme was carried out at the University of Sheffield to investigate the design and optimisation, considering interactive buckling in cold-formed steel channels under compression and bending. Both standard and optimised sections were tested. The specimen imperfections were measured using a specially designed set-up with laser displacement. Material tests were also carried out to determine the tensile properties of the flat plate and of the cold-worked corners. A total of 36 columns with three lengths and 6 back-to-back beams were completed. The column specimens were tested under a concentrically applied load and with pin-ended boundary conditions while the beams were tested in a four-point bending configuration. Based on the tests, numerical models were proposed and calibrated and the proposed optimisation framework was verified. A numerical study on the structural behaviour of CFS bolted beam-to-column connections under cyclic loading was presented. An innovative two node element which can take into account the slippage-bearing effects was proposed and implemented using an ABAQUS user defined subroutine. The connection performance in terms of strength, ductility, energy dissipation capacity and damping coefficient were investigated. The effects of bolt configuration, cross-sectional shapes and thicknesses on the connection performance were therefore examined. It is indicated that the proposed numerical model is robust and computationally efficient to simulate the failure modes and moment-rotation response of CFS bolted moment resisting connections.

The existing design provision in North American Specification for Cold- Formed Steel Structural Member (AISI S100) for the bearing strength of bolted connections were developed from tests on bolted connected sheets which were restrained by bolt nut and head with or without washers. However, in the cold-formed assemblies, particularly in trusses, the single bolt goes through both sides of the connected sections, making the connected sheets on each side unrestrained. the warping of the unrestrained sheet may reduce the bearing strength of the bolted connection. This research investigates the behavior and strength of bearing failure in bolted connections in cold-formed steel trusses. Tensile tests were conducted on trusses connections with various material thicknesses. It was found that the AISI S100 works well for thick connections but provides unconservative predictions for thin materials. Based on the experimental results, a modified bearing strength method is proposed for calculating the bearing strength of bolted truss connections. the proposed method can be used for any cold-formed steel connections with unrestrained sheet.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À ESCOLA TÉCNICA
PROGRAMA DE EXCELENCIA ACADEMICA
Atualmente a utilização do aço inoxidável em elementos estruturais ainda é considerada por muitos engenheiros e arquitetos uma solução extravagante para os problemas da engenharia. Todavia, mudanças de atitude na construção civil e uma transição global para um desenvolvimento sustentável, e redução em impactos ambientais tem seguramente provocado um aumento no uso do aço inoxidável. A maioria das normas de projeto de aço inoxidável atuais ainda são baseadas em analogias assumidas com o comportamento de estruturas de aço carbono. Entretanto, o aço inoxidável apresenta quatro curvas tensão versus deformação específicas não lineares sem patamar de escoamento e região de encruamento claramente definidos (tração e compressão, paralela e perpendicular a direção de laminação), modificando assim seu comportamento global. Na presente investigação foram utilizados o aço inoxidável austenítico 304, duplex 2205, ferrítico 430 e o aço carbono USI 300, com tensões últimas e ductilidades distintas. Em elementos estruturais submetidos a esforços de tração usualmente a ruptura da seção líquida representa um dos estados limites últimos a serem verificados. Com o objetivo de se avaliar a resistência a tração de elementos estruturais aparafusados em aço inoxidável, esse trabalho apresenta resultados de um programa experimental envolvendo ligações aparafusadas com furos defasados sob tração. Esse estudo foi realizado em peças de aço carbono e aços inoxidáveis de forma a comparar as principais características mecânicas entre esses dois tipos de aços estruturais. Dessa forma foi possível apresentar novos resultados a respeito do comportamento a tração dessas ligações. Dentre outras variáveis que controlam os estados limites últimos foi verificada a influência significativa da espessura da placa de aplicação da carga, direção da laminação, configuração de parafusos da ligação e propriedades do aço inoxidável, como ductilidade e razão entre suas tensões de escoamento e de ruptura.
The use of stainless steel in structural engineering applications is still seen by many architects and engineers as na extravagant solution. However, modifications of designers paradigms and changes in the construction market and the natural transition to a sustainable development reducing environment impacts have boosted the use of stainless steel structures. A substantial majority of stainless steel structural design codes is still based on carbon steel analogies. Despite this fact, the stainless steel presents foun non-linear stress versus strain curves (tension and compression, parallel and perpendicular to the rolling direction) without a defined yield plateau and strain hardening zones, substantially altering its global structural response. The present investigation adopted the austenitic stainless steel grade 304, duplex stainless steel grade 2205, ferritic stainless steel grade 430 and the carbon steel USI300, all with similar yield stresses but with different yield strength stresses and ductility capacities. Structural elements subjected to tension axial forces usually presents the net section rupture as one of its controlling ultimate limit states. The present study performed an experimental programme to evaluate and investigate the tension capacity of staggered bolted members. The tests were made with carbon and stainless steels to compare and access their similarities and differences in terms of structural performance. Thus it was possible to observe significant findings in the behavior of these bolted staggered members under tension forces. The controlling ultimate limit states were significantly influenced by various parameters like: the loading plate thickness, the rolling direction, adopted bolt configuration, and stainless steel properties like: ductility capacity and the ratio between the yield and ultimate rupture stresses.

The purpose of this thesis has been to investigate, both analytically and experimentally, the behaviour of bolted joints in cold formed steel members. To this aim, the influences of all factors bearing a significant effect on behaviour of bolted connections in cold formed steel assemblies and structures have been investigated. Design expressions have been derived. With this information the moment capacity of bolted joints can be calculated with considerably more accuracy than the present existing expressionsin the current codeso f practice. The findings of the thesis have already influenced the design expressions for bearing strength of bolted connections in the European code of practice for design of cold formed steel sections, i. e. Eurocode No 3, Annex A. It is hoped that the conclusions drawn are further incorporated in the above mentioned code, and replace the existing guidelines in the British Standard, BS 5950 Part 5, for the design of such sections. Furthermore for the first time ever, as a result of the analyses and experiments carried out, designers are able to predict the moment-rotation relationship of such connections without having to resort to testing. It is intended to feed this information into design programmes to radically affect the elastic design of cold formed steel structures. It should then be possible to design optimum structures by specifying joints with appropriate characteristics.

The use of the cold-formed steel sheet bolted connections without washers is so significant; however, the North American Specifications for the Design of Cold Formed Steel Structural Members, NASPEC, doesn't provide provisions for such connections. The bearing failure of sheet and the shear failure of sheet were considered in this study. For the sheet shear strength, it was found that the NASPEC (2007) design provisions can be used for oversized holes in both single and double shear configurations and for the double shear connections on short slotted holes. For the sheet bearing strength, a new design method was proposed to be used for low and high ductile steel sheets. The method was compared with the NASPEC and the University of Waterloo approach. Washers were still required for single shear connections on short slotted holes. Besides, connections using ASTM A325 bolts yielded higher bearing strength than connections using ASTM A307 bolts.

The structural behaviour of single shear bolted connections and double shear bolted connections of cold-formed stainless steel at elevated temperatures and post-fire condition has been investigated in this study. The current design rules on bolted connections of cold-formed stainless steel are mainly based on those of carbon steel, and are applicable for room (ambient) temperature condition only. These design rules may not be applicable for elevated temperatures. Therefore, design guidelines should be prepared for bolted connections of cold-formed stainless steel structures at elevated temperatures. The key findings of the investigation are described in the following paragraphs. A total of 25 tensile coupon tests were conducted to investigate the material deterioration of three different grades of stainless steel at elevated temperatures. The stainless steels are austenitic stainless steel EN 1.4301 (AISI 304) and EN 1.4571 (AISI 316Ti having small amount of titanium) as well as lean duplex stainless steel EN 1.4162 (AISI S32101). Totally 434 tests on bolted connections of stainless steel were performed in the temperature ranged from 22 to 950 ºC using both steady state and transient state test methods. The test results were compared with the nominal strengths calculated from the American Specification, Australian/New Zealand Standard and European codes for stainless steel structures. In calculating the nominal strengths of the connections, the material properties at elevated temperatures were used in the design equations for room temperature. It is shown that the nominal strengths predicted by these specifications are generally conservative at elevated temperatures. A total of 78 cold-formed stainless steel single shear and double shear bolted connections were tested in post-fire condition. The test results were compared with those tested at room temperature. Generally, it is found that the bolted connection strengths in post-fire condition cooling down from 350 and 650 ºC are higher than those tested at room temperature for all three grades of stainless steel. Finite element models for single shear and double shear bolted connections were developed and verified against the experimental results. Static analysis technique was used in the numerical analyses. Extensive parametric studies that included 450 specimens were performed using the verified finite element models to evaluate the bearing resistances of bolted connections of stainless steel at elevated temperatures. Design equations for bearing resistances of cold-formed stainless steel single shear and double shear bolted connections were proposed based on both the experimental and numerical results in the temperature ranged from 22 to 950 ºC. The bearing resistances of bolted connections obtained from the tests and the finite element analyses were compared with the nominal strengths calculated using the current design rules and also compared with the predicted strengths calculated using the proposed design equations. It is shown that the proposed design equations are generally more accurate and reliable in predicting the bearing resistances of bolted connections at elevated temperatures than the current design rules. The reliability of the current and proposed design rules was evaluated using reliability analysis. The proposed design equations are recommended for bolted connections assembled using cold-formed stainless steels.
published_or_final_version
Civil Engineering
Doctoral
Doctor of Philosophy

The aim of this diploma thesis is the design of the roofing of an ice hockey stadium situated in Žďár nad Sázavou. Plan view dimensions are 55 m x 77 m. The structural height of the roof varies from 10 to 17 m. The roof itself consists of pipe truss girders with a span of 55 m, which are supported by columns on each side. The girders are suspended by a load-carrying arch with a span of 96 m and a camber of 29 m through a system of pre-stressed cables. To determine the internal forces, structural analysis software Scia Engineer was used. Individual elements were then manually designed.

The diploma thesis elaborates on the proposal of a loadbearing steel structure of a shopping centre. Four-storey building has total lenght of 88 m, width 48 m and its base structural grid is 8 x 8 m. The total height of building is 25,4 m. First three floors above ground are designed with structural height of 5,6 m whilst the 4TH floor uses height of 4,0 m. Frame structure is formed by primary beams and castellated secondary beams. Above 4TH floor, the roof structure is designed in two alternative versions, both using solid purlins and truss girder. The 3D computer animation of the building is also part of thesis. The shopping centre that is subject of the final thesis is located in Brno area.

Atualmente, a utilização do aço inoxidável em elementos estruturais é considerada uma solução cara para os problemas da engenharia estrutural. Todavia, mudanças de atitudes dentro da construção civil, uma transição global para um desenvolvimento sustentável e redução em impactos ambientais têm seguramente provocado um aumento na utilização do aço inoxidável. As normas de projeto de aço inoxidável atuais são, em grande parte, baseadas em analogias assumidas com o comportamento de estruturas desenvolvidas com aço carbono. Todavia, o aço inoxidável apresenta quatro curvas não-lineares tensão versus deformação (tensão e compressão, paralela e perpendicular a laminação do material), sem patamar de escoamento e região de encruamento claramente definidos, modificando assim, o comportamento global das estruturas que o utilizam. Em elementos estruturais submetidos a forças axiais de tração, a ruptura da seção líquida representa um dos estados limites últimos a serem verificados. Com o objetivo de se avaliar a resistência a tração de elementos estruturais aparafusados em aço inoxidável S304, este trabalho apresenta um modelo numérico baseado no método dos elementos finitos através do programa Ansys (versão 11). A não-linearidade do material foi considerada através do critério de plastificação de Von Mises e curvas tensão versus deformação verdadeira. A não-linearidade geométrica foi introduzida no modelo através da Formulação de Lagrange atualizado. O modelo numérico foi calibrado com resultados experimentais obtidos em ensaios de laboratório, a partir de ligações aparafusadas alternadas rígidas, onde não se ocorre nenhuma rotação entre os membros, transferindo nenhum momento fletor, apenas esforço normal e cisalhante.
Currently, the use of stainless steel in structural elements is considered an extravagant solution to structural engineerings problems. However, changes in attitudes within civil construction, global transition to sustainable development and environmental impacts reduction have certainly caused an increase in the use of stainless steel. Today, the codes for design of stainless steel are largely based on assumed analogies with the behavior of structures developed with carbon steel. However, stainless steel present four non-linear tension versus strain curves (tension and compression, parallel and perpendicular to the lamination material) without yielding plateau and strain hardening zones clearly defined, thus changing the overall behavior of the structures that use it. In Structural elements subjected to axial forces of tension, the net section rupture usually represents one of its controlling ultimate limit states. In order to evaluate the tensile resistance of structural components bolted stainless steel S304, this work provides a numerical model based on the finite element method using the program ANSYS (version 11). The non-linear of the material was considered by the criterion of Von Mises and stress versus strain true curves. The geometric nonlinearity was introduced into the model through the formulation of Lagrange Updated. The numerical model was calibrated based on experimental results, from rigid alternate bolted connection, which do not occur any rotation among the members, transferring any bending moment, only normal and shear internal forces.

Slip-critical connections have been used in steel structures for a long time where bolted joints are subjected to cyclic load and fatigue with slotted or oversized holes. The understanding of these connections has resulted in the limitation of maximum slip coefficients (0.50 for Class B surfaces) with surface preparation. High performance surface coating (HPSC) is one possible new method to significantly enhance the strength of slip-critical connections. In this research, two kinds of mineral particles, synthetic diamond and tungsten carbide are applied on HPSC for simple shear slip tests with variation in parameters of particle size, particle density, slip rate and clamping force. Finite element simulations are conducted for sensitivity analysis of the research. The test results showed that HPSCs can give drastically enhancement in slip coefficient and provide more stable, predictable behavior than bare metal surfaces, one group of HPSCs can give slip coefficient as high as 0.52?0.01, particle grain size and particle density will affect the slip coefficient of HPSCs, slip rate and clamping force will not affect the slip coefficient of HPSCs. Simulation results showed that considering HPSCs as homogeneous and isotropic material can well predict the slip coefficient and slip load of the connection, but not suitable for the behavior after failure. Recommendations are made for continue research on HPSCs.

Single plate shear connections are designed to have sufficient strength to resist the shear force and moment transferred from the beam. The connections must also provide sufficient ductility to allow the beam end to rotate freely. In the United States the current recommended design method is found in the AISC 13th Edition Steel Construction Manual (2005b). The limited experimental work which led to the current method necessitated additional single plate shear connection investigations. This paper summarizes the results and analysis of eight full scale single plate shear connections tested at Virginia Polytechnic Institute and State University. The test setup consisted of a test beam attached to a test column with a single plate shear connection at one end and supported by a roller at the other end. The single plate was welded to the column flange and bolted to the beam web. Load was applied to the test beam at third points until failure of the connection or test beam. The current design method used in the United States was examined with respect to the connection tests performed. In particular, the ultimate shear strength and the rotational capacity were investigated. Suggestions are made regarding changes to the method and further research.
Master of Science

Este trabalho apresenta resultados teóricos e experimentais sobre o comportamento estrutural de ligações parafusadas viga-coluna com chapa de topo. São estudados dois tradicionais métodos de dimensionamento e as ligações são analisadas numericamente, via método dos estados limites. Os resultados são comparados com os obtidos através de ensaios de 35 protótipos, nos quais variou-se, alternadamente, a espessura da chapa de topo e o diâmetro dos parafusos. Discute-se, em particular, a influência destes parâmetros no comportamento momento-rotação das ligações com chapa de topo e, ao final, apresentam-se as conclusões pertinentes e recomendações para o prosseguimento dos estudos.
This work presents the theoretical and experimental results on the structural behavior of bolted end plate connections. They are designed by two traditional methods and analyzed by the finite element method. Comparisons are made between the FEM results and those obtained by an experimental analysis on 35 cruciform welded profile models, in which end plate thickness and bolt diameter was alternately varied. Special attention is paid for evaluating the influence of these parameters in the moment rotation behavior of the connections. Finally, the remarks and conclusions are presented and some topics for posterior researches are suggested.

The goal of the submitted thesis is a design and assessment of a steel load-bearing structure of a multipurpose sports hall situated in Prostějov. The floor plan measurements of the object are 38x54 m with the maximum ceiling height of 9,5 m. Final design variant was chosen on the basis of two preliminary drafts, both processed according to standard ČSN EN. The structure is designed with respect to ultimate and serviceability limit states. The construction consists of 10 cross-links spaced by 6,0 m. The spatial rigidity of the structure’s main load-bearing system is provided by spatial elliptic trussed girders, longitudinal and sway bracings. Roof cladding is carried by purlins placed on trusses. Steel columns are designed as a part of gable walls. The project was carried out in Scia Engineer 2014 software. Some particular elements were subsequently assessed by means of manual calculation. The thesis also includes assessment of joints, construction details and drawing documentation.

[EN] Concrete filled steel tubular columns have many advantages in terms of bearing capacity, aesthetics, execution and fire resistance, thanks to the collaborative work of both materials steel and concrete. The effort made in the last decades to rise a high understanding of their behaviour subjected to different loads and assuming multiple variations has resulted in the wide spread of its use between the designers. Nonetheless, how to solve the connection with I-beams is still a handicap and requires a specific study. One of the most common and popular solution to connect open section steel beams (I-beams) to open section steel columns are endplate connections. In the cases of columns with hollow section, special fastenings are needed, which are able to be tightened from one external side and are denominated blind-bolts. Nowadays, there are several fastener systems that allow these types of connections. The characterization of their response and their capacity to support different loads is the objective of several investigations, where the geometrical definition and the material properties are crucial parameters. Despite the promising results of these connections at room temperature regarding their capability to resist bending moments, their performance is un-known at high temperatures. Therefore, the aim of this thesis is the study of the tensile behaviour of blind-bolts in endplate connections to concrete filled tubular columns at elevated temperatures and subjected to bending moment. Primarily, the research comprises the understanding of the pure thermal transfer problem. The temperature distribution through the connection section is obtained experimental and numerically. The thermal parameters that characterize the connections response are determined through the calibration of the numerical models with the experiments. Secondly, the blind-bolt capacity under pull out and at high temperatures is under analysis. During the fire the temperature increases while connection transmits loads from the beam to the column, the objective of this dissertation is to know how the mechanical response of the pulled blind-bolts changes under these conditions. Thus, the study of the material properties dependent on the temperature and their effect on the connection response is covered by the investigation. Furthermore, the influence of the concrete and the type of fastener is a highlighted aspect through the thermal and the fire analysis. Finally, the reliability of these connections to comply with requirements of 30 minutes fire exposure before the collapse is evaluated. As a result, valuable Finite Element models able to simulate the thermal and thermo-mechanical behaviour of the connection are developed, providing useful behavioural patterns of the blind-bolts. Among the main conclusions, it is noted the temperature reduction due to concrete core in concrete filled columns compared to hollow sections, in the exposed bolt surface means 100ºC less. Conversely, a longer bolt shank of the fastener system embedded in concrete has a negligible effect on the temperature of the resistant part of the bolt. Regarding the fire capacity, the concrete core in the steel tube columns presents significant benefits in terms of fire resistance time and connection stiffness. Besides, the bolt anchorage enhances the stiffness at elevated temperatures, however, the failure of the shank next to the bolt head causes that the anchorage does not mean an improvement on the fire time resistance.
[ES] Las columnas tubulares de acero rellenas de hormigón presentan múltiples ventajas en términos de capacidad de carga, estética, ejecución y resistencia al fuego, gracias a la acción combinada de acero y hormigón. El esfuerzo realizado en las últimas décadas por conocer su comportamiento frente a diferentes cargas y bajo distintos parámetros ha dado lugar a una amplia difusión de su uso entre los diseñadores. No obstante, la forma de resolver la conexión con vigas de sección en I sigue siendo un hándicap y requiere un estudio específico. Una de las soluciones más comunes y populares para conectar las vigas de acero de sección abierta (vigas I) a columnas de acero de sección abierta es la conexión con chapa de testa, que en el caso de sección hueca requiere de tornillos especiales denominados tornillos ciegos, puesto que reciben el par de apriete desde una cara de la sección. En la actualidad existen diversos sistemas de fijación que permiten este tipo de conexiones y cuya respuesta y caracterización es objeto de numerosas investigaciones. En este sentido, la definición geométrica de la unión y las propiedades de los materiales son parámetros cruciales en el rendimiento de la conexión. La presente tesis analiza el comportamiento de los tornillos ciegos en el área traccionada de conexiones de placa de testa a columnas tubulares de acero rellenas de hormigón sometidas a momentos de flexión y a elevadas temperaturas. Las prestaciones de esta solución constructiva para la unión viga-columna tubular, junto con la ausencia de datos relacionados con su comportamiento en situación de incendio la convirtió en el objetivo del trabajo. En primer lugar, la investigación aborda el problema de transferencia de calor, analizando experimental y numéricamente la distribución de temperaturas en la sección de la conexión. En esta parte del estudio se obtienen los parámetros térmicos que caracterizan la respuesta térmica de la conexión a través de la calibración de los modelos numéricos con los datos experimentales. En segundo lugar, se realiza el estudio de la capacidad de los tornillos ciegos para soportar cargas de tracción en situación de incendio, es decir, se analiza cómo cambia el comportamiento de la conexión con sus características alteradas debido a las altas temperaturas. El estudio de las propiedades del material en función de la temperatura y su efecto sobre la respuesta de la conexión constituyen una parte importante de la investigación. Además, se evalúa la influencia del hormigón y el tipo de elemento de sujeción tanto en el comportamiento mecánico como termo-mecánico de la conexión. Por último, se estudia la capacidad de las uniones para cumplir con requerimientos de exposición al fuego de 30 minutos previamente al colapso. Como resultado de este trabajo se obtuvieron modelos de elementos finitos capaces de simular la conexión térmica y termo-mecánicamente, proporcionando patrones de comportamiento de gran utilidad en el diseño de las mismas. Entre las principales conclusiones, se observó la reducción de la temperatura en los tornillos gracias al núcleo de hormigón en columnas de hormigón lleno en comparación con secciones huecas, que ya en la superficie expuesta del tornillo se cuantificaba en 100ºC menos. Por el contrario, los elementos de fijación que presentaban mayor longitud de vástago de tornillo embebida en el hormigón, no generaban un efecto significativo sobre la temperatura de la parte resistente del perno. En cuanto a la capacidad resistente frente a fuego, el núcleo de hormigón supuso una mejora en términos de rigidez y de tiempo de resistencia al fuego. Sin embargo, el fallo de los pernos en una sección próxima a la superficie expuesta redujo el efecto esperado del anclaje del tornillo, que si bien implicaba una mayor rigidez de la conexión, no parecía mejorar el tiempo de resistencia a fuego. Finalmente se planteó la necesidad de
[CAT] Els pilars tubulars d'acer omplerts de formigó (CFT) presenten molts avantatges en termes de capacitat de carrega, estètica, execució i resistència al foc, gràcies a l'acció combinada de l'acer i el formigó. L'esforç realitzat en les darreres dècades per conèixer el seu comportament enfront a diferents càrregues i sota distints paràmetres ha donat lloc a una amplia difusió del seu ús entre el dissenyadors. No obstant això, la manera de resoldre la connexió amb bigues de secció en I, continua sent un handicap i requereix d'un estudi específic. Una de les solucions més comuns i populars per a connectar les bigues d'acer de secció oberta (bigues I) a columnes d'acer de secció oberta és la connexió amb 'chapa de testa', que en el cas de la secció buida requereix de perns especials denominats perns cecs perquè es rosquen des d'una cara de la secció. En l'actualitat existeixen diversos sistemes de fixació que permeten aquest tipus de connexions, la resposta i caracterització dels quals es l'objectiu de nombroses recerques. En aquest sentit, la definició geomètrica de la unió i les propietats dels materials son paràmetres crucials en el rendiment de la connexió. Aquesta tesi analitza el comportament dels perns cecs en l'àrea traccionada de connexions de 'chapa de testa', a pilars tubulars d'acer omplerts de formigó, sotmeses a moments de flexió i a elevades temperatures. Les prestacions d'aquesta solució constructiva per a la unió biga-pilar tubular junt amb l'absència de dades relacionades amb el comportament en situació d'incendi, la van convertir en l'objectiu d'aquest treball. En primer lloc, la recerca aborda el problema de transferència de calor, analitzant tant experimental com numèricament la distribució de temperatures en la secció de la connexió. En aquesta part de l'estudi, s'obtenen el paràmetres tèrmics que caracteritzen la resposta tèrmica de la connexió mitjançant el calibratge del models numèrics amb les dades experimentals. En segon lloc, es realitza l'estudi de la capacitat dels perns cecs per a suportar càrregues de tracció en situació d'incendi, es a dir, s'analitza com canvia el comportament de la connexió amb les seues característiques alterades degut a les altes temperatures. L'estudi de les propietats del material en funció de la temperatura i el seu efecte en la resposta de la connexió formen també part de la recerca. Un contingut important d'aquest treball consisteix en determinar l'influencia del formigó i el tipus d'element de fixació tant en el comportament mecànic com termo-mecànic de la connexió. Per últim, s'estudia la capacitat de les unions per a complir amb els requeriments d'exposició al foc de 30 minuts prèviament al col·lapse. Com a resultat d'aquest treball s'obtingueren models d'elements finits amb capacitat per a simular el comportament tèrmic i termo-mecànic de la connexió, proporcionant patrons de comportament de gran utilitat en el disseny. Entre les principals conclusions, es va observar la reducció de la temperatura en els perns gràcies al nucli de formigó en pilars omplerts de formigó en comparació amb el pilars buits, on ja en la superfície esposada del cargol es quantificava en 100 ºC menys. Pel contrari, els elements de fixació que presentaven major longitud de embeguda en el formigó, no generaven un efecte significatiu en la temperatura de la part resistent del pern. En quant a la capacitat resistent davant del foc, el nucli de formigó va suposar una millora en termes de rigidesa i de temps de resistència al foc. Tanmateix, la fallada dels perns en una secció pròxima a la superfície esposada va reduir l'efecte esperat de la fixació del pern, que si be implicava una major rigidesa de la connexió, no semblava millorar el temps de resistència al foc. Finalment, es va plantejar la necessitat de aprofundir en l'anàlisi incorporant un major rang de paràmetres.
Pascual Pastor, AM. (2015). Fire behaviour of blind-bolted connections to concrete filled tubular columns under tension [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/53240
TESIS

La procédure d'évaluation des performances des structures en génie civil soumis à des tremblements de terre implique le développement des modèles mathématiques et des procédures d'analyse dynamique non-linéaire pour estimer les réponses sismiques. Le comportement hystérétique des structures est connu pour être fortement dépendante du modèle de l'assemblage. Dans le cas de chargement cyclique, la plastification cyclique, le phénomène de fatigue oligocyclique et la détérioration du comportement dus à la dégradation de rigidité ont été jugées importantes. Cela éventuellement conduit à une grande incertitude dans les réponses d'une structure. Dans ce contexte, un modèle d'endommagement basé sur la fatigue hystérétique est développé pour évaluer la performance sismique des ossatures en acier avec des assemblages boulonnés à plaque d'extrémité. Le modèle développé est un modèle hystérétique dégradant basé sur l'indicateur de dommage par fatigue oligocyclique. Une étude expérimentale du comportement d'un assemblage boulonné à plaque d'extrémité est réalisée pour analyser les effets du comportement en fatigue oligocyclique et pour développer un modèle de prédiction de durée de vie. Les essais de fatigue ont été effectués en utilisant un pot vibrant. Les résultats des essais expérimentaux de fatigue seront utilisés pour déduire les paramètres de la fatigue qui sont nécessaires pour développer le modèle hystérétique de l'assemblage boulonné. L'analyse des dommages sismiques est l'un des problèmes les plus difficiles dans des structures grandes et complexes, particulièrement celles en ossature avec des assemblages boulonnés à plaque d'extrémité. L'existence de dommages structuraux dans une structure conduit à la modification des modes de vibration et les valeurs propres globaux sont généralement sensibles à l'ampleur des dégâts sismiques locaux dans des assemblages boulonnés. Dans ce travail, une analyse temporelle non-linéaire qui tient compte des modes et des fréquences non-linéaires a été proposée. Selon cette approche, les modes et les fréquences non-linéaires peuvent être déterminés par une procédure itérative qui repose sur la méthode de linéarisation équivalente. L'introduction de la notion des modes non-linéaires a permis d'étendre la méthode de synthèse modale linéaire aux cas non-linéaires afin d'obtenir la réponse dynamique des systèmes non-linéaires. Dans un autre contexte expérimental, cette thèse présente les résultats d'essais sur une table vibrante. L'objectif des essais expérimentaux est de comprendre le comportement inélastique des structures en acier soumis à des charges dynamiques. Par ailleurs, ces essais sont également destinés à étudier les changements dans les paramètres modaux dus au développement du comportement élasto-plastique et du dommage par fatigue oligocyclique des assemblages boulonnés. Une simulation numérique non-linéaire du système est effectuée sur la base du modèle développé et l'approche numérique proposée. Une comparaison des résultats obtenus à partir de l'analyse numérique et ceux des essais de table vibrante est présentée. Cependant, l'analyse des dommages pour les ossatures en acier sous excitations sismiques aléatoires exige l'application d'un algorithme adéquat. Un algorithme a été développé pour évaluer la performance sismique des ossatures en acier. En utilisant cet algorithme, l'influence de la fatigue oligocyclique sur le comportement des assemblages boulonnés à plaques d'extrémité peut être étudiée.

The aim of diploma thesis is to design steel roof structure of minimum dimensions 45 m x 50 m and minimum height 12 m. The plan of the building design has dimensions of 52,14 m x 70, 00 m and height is 18,68 m. The roofing was design as 3D truss girders with two lower chords and one upper chord. The shape of 3D truss girder consists of three circular arcs of radius 69,88m, 12,43 m and 33,45 m. Between main girders is 3D bracing. The structure is pin-supported.

Joints are the most critical elements in a steel framed structure. In most design guides or codes, the joints are assumed to a have higher fire resistance than the connected structural members because of the lower temperatures in the joints. However, in severe fire conditions, a connected beam's temperature may be higher than its limiting temperature and the beam may develop catenary action when the beam’s axial shortening from large deflections becomes greater than the beam’s thermal expansion. This beam catenary action force could fracture the joints, increasing the risk of progressive collapse. This research focuses on the interaction between joints and the connected steel beams and columns in steel framed structures in fire, including how the behaviour of a joint-beam assembly may be efficiently analyzed and how the joints may be constructed to achieve high degrees of catenary action. Three methods of simulating the joint behaviour in fire have been developed and implemented in the commercial finite element software ABAQUS. In the first modelling method, all structural members, including the connections, were simulated using detailed solid elements to enable detailed behaviour of the structure to be faithfully represented. In the second method, the columns were represented by conventional line (beam) elements, the joints were represented using springs (Connector Elements) based on the component based method, and the beam was modelled using solid elements. In the third method, the joints were modelled using springs as in the second method and the beam and columns were simulated using line (beam) elements. As expected, the detailed simulation method was extremely time-consuming, but was able to produce detailed and accurate results. The simulation results from the second and third methods contained some inaccuracies, but depending on the simulation objective, their simulation results may be acceptable. In particular, the third simulation method was very efficient, suitable for simulating complete frame structures under very large deflections in fire. The first method (detailed finite element method) was then used to investigate how to change the joint details to increase the survivability of restrained steel beams and beam-column assemblies at high temperatures since it enables detailed behaviour of the structure to be faithfully represented. It is found that by improving joint deformation capacity, in particular, using extended endplate connection with fire resistant bolts, very high temperatures can be resisted. The frame robustness in fire was investigated using the third simulation method to save computation time. The simulation structure was three-bay by three-floor and different scenarios of fire location, fire spread and initial structural damage were considered. The simulation results show that once failure of a column occurs, progressive collapse of the structure could be easily triggered and it would be rather futile to only enhance the joint capacity. Therefore, in addition to the measures of improving joint capacities (both rotation and strength), design of the affected columns should include consideration of the additional catenary forces from the connected beams and the increased effective lengths. Furthermore, the lateral bracing system should be ensured to provide the structure with lateral restraint.

This diploma thesis deals with the design of a metalworking shed with its adjacent administrative center. Both objects are statically independent. The buildings are located in the town of Bučovice. The dimensions of the shed are 54,78x72,58 m. There is an overhead crane situated in the middle wing. The shed‘s height is +11,62 m. The administrative building has L-shaped plan. Its dimensions are 27,62x8,13 m (the wider part is 15,63 m). The design of the administrative object has two variants. Both variants have composite steel-concrete ceiling structure. The heights of the objects are +11,20 m (A variant) and +18,20 m (B variant). For the A variant, drawings were also drawn up with the design and assessment of structural details and anchoring.

Shallowly embedded column base connections with unreinforced block out concrete are a common method of connecting steel columns to their foundation. There has been little research done to accurately quantify the effects of this block out concrete on the connection strength and rigidity, and therefore there is nothing to aid the practicing engineer in accounting for this in structural analysis. Due to this lack of understanding, engineers have typically ignored the effects of shallow block out concrete in their analysis, presumably leading to a conservative design. Recent research has attempted to fill this gap in understanding. Several methods have been proposed that seek to quantify the effects of shallow block out concrete on a column base connection. Barnwell proposed a model that predicts the strength of a connection. Both Jones and Tryon used numerical modeling to predict the rotational stiffness of the connection. An experimental study was carried out to investigate the validity of these proposed models. A total of 8 test specimens were created at 2/3 scale with varying column sizes, connection details, and embedment depths. The columns were loaded laterally and cyclically at increasing displacements until the connection failed. The results show that the strength model proposed by Barnwell is reasonable and appropriate, and when applied to this series of physical tests produce predictions that have an observed/predicted ratio of between 0.95 to 1.39. The results also show that methods for estimating the rotational stiffness of the connection at the top of the block out concrete, as proposed by Jones and Tryon also produce reasonable values that had observed/predicted ratios of between 0.93 to 1.47. An alternative model for determining a design value for the rotational stiffness of a shallowly embedded column base plate is also proposed. When the embedment depth to column depth ratio is greater than 1.22, the connection is sufficiently rigid and at small deflections (less than 1% story drift) may be accurately modelled with infinite rotational stiffness (a "fixed" connection) at the base of the column.

The I-35W Bridge over the Mississippi River in Minneapolis, MN had a catastrophic failure in the main span of the deck truss in 2007. This collapse has brought significant attention on the gusset plate connections in steel truss bridges throughout the U.S. Steel truss bridge gusset plate design has not received much focus in the past 40 years, and there is a lack of consensus within the design profession on the procedures to evaluate, design, and rate these critical elements. In the short term, based on the best available information on the gusset plate design, the Federal Highway Administration (FHWA) has issued preliminary guidance. Although some experimental research has been conducted on the ultimate strength of gusset plates, much of this work has been directed toward the performance of tension members and their connections. There has been limited experimental work on the compression capacity and stability of gusset plates, but most of this work is relevant primarily to bracing connections common in building structures. This research focuses on comprehensive experimental and analytical studies on steel truss bridge gusset plate behavior. The studies include comparisons of advanced analytical models with the responses from large-scale experimental tests using discrete and innovative full-field measurements. The calibrated finite element analysis models are then utilized to study a variety of gusset plate configurations. Improved mechanistic idealizations that better capture the observed behavior in the experiments and analytical studies are proposed as the result of this work. The design checks recommended in this thesis present a comprehensive methodology for determining the ultimate gusset plate resistance. This research provides a large database of original results that will be useful for future similar studies. In addition, this research provides modeling procedures that permit the study of steel truss bridge connections and their adjacent framing members using truss bridge sub-assemblies. Based on the comprehensive analytical studies, simple and accurate design calculation procedures to assess the nominal ultimate strength of steel truss gusset plate connections are recommended for steel truss bridge gusset plate connections.