At the design stage, column-beam connections of steel structures are assumed as fully rigid or as hinges, and the design is completed with these assumptions. On the other hand, in practice, steel column-beam connections show neither fully rigid nor fully hinge behaviour, and the characteristic behaviour of the connections lies between these two special cases. Performing realistic calculation of these forces and knowing the behaviour of structures close to reality will decrease life and goods losses to the minimum level in a probable of earthquake to be encountered in the future. &nbsp / In this study, seismic performance of 2-D steel frames were evaluated by Capacity Spectrum Method proposed in the ATC 40 document published in 1996. A new computer program was developed in order to define all geometric and loading data and to perform nonlinear analysis of rigid and semi rigid steel frames for which the performances will be evaluated. In case studies, 3-Floor Steel Frames that have different bay numbers were investigated in various forms according to the rigid and different semi rigid connection types. In addition, the performances these frames for various seismic regions and soil conditions were compared. According to the results, it was observed that semi rigidly connected frames are under the effect of smaller ground acceleration have greater displacement values. As a consequence of this ductile and energy dissipative response, it was seen that the stresses in the members of frame become considerably small, relative to the stresses in the rigid frames&rsquo / . Furthermore, the performances of semi-rigid frames can be affected negatively beyond such a low rigidity. Consequently, the most convenient design should be made according to the seismic and soil region where the structure to be constructed by performing the necessary studies on the connection details in order to achieve desired performance, serviceability and optimum member criteria.

Shape Memory Alloys (SMAs) exhibit the ability to undergo large deformations but can recover permanent strains via heating (shape memory effect) or when stress is removed (superelastic effect). This study evaluates the comparative seismic performance of steel moment resisting frames (SMRFs) with innovative beam-to-column connections that use SMA bars as connecting elements. The performance evaluation studies are based on two types of SMA beam-to-column connections: (1) superelastic SMA connections with recentering capability; (2) martensitic SMA connections with high energy dissipation capacity. Fiber models for these SMA connections are implemented in the OpenSees finite element framework, and are verified against data from full-scale experimental tests that were performed on a prototype SMA connection in previous research at Georgia Tech. Three- and a nine-story model buildings with partially-restrained (PR) moment frames are selected from the SAC Phase II Project as case studies. Non-linear time history analyses on these model buildings, with and without SMA connections, are conducted using suites of ground acceleration records from the SAC Phase II project that represent different seismic hazard levels. Several SMA connections are designed for each structure, and their effect on peak and residual inter-story drift angles, connection rotations, and normalized dissipated hysteretic energy demands are investigated to determine the most suitable design. Finally, the seismic demands on the model buildings with conventional PR and selected SMA connections are evaluated in a probabilistic framework. The resulting seismic demand relationships are used to assess the effectiveness of the SMA connections in enhancing the building performance over a range of demand levels. The results of this performance evaluation show that the SMA connections are most effective in controlling structural response under high levels of seismic intensity leading to large deformation demands. In particular, the energy dissipating SMA connections are found to be effective in reducing maximum deformation demands, while the recentering SMA connections are more suitable for controlling residual deformations in the structure.

Two types of connection are generally considered in the design of steel structures in practice. These are classified as completely rigid (moment) and simple (shear) connections. In theory, completely rigid connections can not undergo rotation and simple connections can not transfer moment. However, in reality rigid connections have a relative flexibility which makes them to rotate and simple connections have some reserve capacity to transfer moments. In many modern design specifications, this fact is realized and another type which is called partially restrained or semi-rigid connection is introduced. These types of connections have got the transfer of some beam moment to column together with shear. However, there is a lack of information on the amount of moment transferred and rotation of connection during the action of the moment transfer. The only way to quantify the moment and rotation of the partially restrained connections is to draw momentrotation curves. Nevertheless, drawing such curves requires great amount of expenses for experiments. Taking these into account, the use of finite elements with the help of increased computational power is one way to obtain moment-rotation curves of connections. Available test results guides the finite element analysis for justifications. So these analyses can be further implemented into design functions. This thesis is intended to conduct 3-D non-linear finite element analyses to compliment with tests results for different types of semi-rigid connections with angles and compare them with mathematical models developed by different researchers.

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

The concept of semi-rigid composite connection has been widely researched in the past; however, most of the researches are limited to composite joints with metal deck ¿ooring and solid concrete slabs. Composite construction incorporating precast concrete hollowcore slabs (HCU) is a recently developed composite ¿oor system for buildings. The research on the structural behaviour of the semi-rigid composite joints with HCU is new and without any previous experimental database. In this paper, eight full-scale tests of beam-to-column semi-rigid composite joints with steel beams and precast hollowcore slabs are reported. The variables are stud spacing, degree of the shear connections, area of the longitudinal reinforcement and slab thickness. The test set-up and instrumentation is described in detail. The experimental behaviour is analysed and based on the test data the structural behaviour of these semi-rigid composite joints is discussed. Based on the experimental data, a simpli¿ed method to predict rotation and moment capacity for this type of composite connection is proposed.

The thesis deals with the analysis and standard check of structural steel connections subjected to seismic loads. Analysis is based on a software solution and standard check is performed according to standard requirements and formulas. The first part deals with the theory of seismic load. There are described the general knowledges about the earthquake and the method of determining the effects of seismic loading on buildings according to the EN 1998-1. In the second part of the thesis is made design and check seismically loaded multi-storey steel building. Design is based on recommendations of the EN 1998-1 and some recommendations of research. In the third part is the analysis, verification and check of steel joints, which are contained in the structure designed in the second part of the thesis. On the basis results of analyses of indivudual connections are defined recommendations and requirements for the use and design structural steel connections subjected to seismic loads.

As typically designed, the beam-column-brace connections of buckling-restrained braced steel frames have undesirable failure modes that compromise the integrity and performance of the frames and are costly to repair. To decrease the time and resources needed to repair the frames following an earthquake, a new connection design was developed that attempts to confine yielding to replaceable frame components. The design incorporates a gap in the beam beyond the edge of the beam-gusset weld that acts as a hinge and reduces moment forces transferred to the connection; it is bridged by splice plates that are bolted to the beam top flanges. The splice plates and buckling-restrained braces are the only frame components that are expected to yield. To investigate the performance of the proposed connection design, a prototype bay was designed and two test specimens were fabricated and tested. Each specimen represented a corner of the prototype braced bay and consisted of a beam, column, gusset plate, brace core extension assembly, splice plates, and lateral bracing angles. Both standard design procedures and newly developed criteria were used to design the connection. In preparation for testing, a method was developed for estimating the hysteretic response of a buckling-restrained brace. By using this method to program an actuator, the specimens could be tested without using actual braces, resulting in a significant reduction in testing cost. Testing was conducted using two 600 kip actuators; the first followed a static loading protocol with a maximum design drift of 6.5%, and the second replicated the prototype BRB's response. The tests yielded promising results: both specimens withstood the maximum displacements and avoided yielding in the beams, columns, and gusset plates; yielding did occur in the splice plates and BRB core extension assembly, as anticipated. Possible limitations in the design may arise under the presence of increased shear loads, concrete floor slabs, or out-of-plane loading. Additional testing is recommended.