Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 32-33). Also available on the World Wide Web.

Columns are critical elements of any structure and their failure can lead to the catastrophic consequences of progressive failure. In structural design, procedures to design structures to resist conventional loads are well established. But design for accidental loading conditions is increasingly requested by clients and occupants in modern engineering designs. Among many accidental causes that induce column failure, impact (e.g. vehicular impact, ship impact, crane impact, impact by flying debris after an explosion) has rarely been considered in the modern engineering designs of civil engineering structures such as buildings and bridges. Therefore, most of the design requirements for structural members under vehicle impact as suggested by the current standards and codes such as Eurocode 1 are based on simple equations or procedures that make gross assumptions and they may be highly inaccurate. This research aims to develop more accurate methods of assessing steel column behaviour under vehicle impact.The first main objective of this study is to numerically simulate the dynamic impact response of axially loaded steel columns under vehicle impact, including the prediction of failure modes, using the finite element method. To achieve this goal, a numerical model has been proposed and validated to simulate the behaviour and failure modes of axially loaded steel columns under rigid body impact using the commercial finite element code ABAQUS/Explicit. Afterwards, an extensive parametric study was conducted to provide a comprehensive database of results covering different impact masses, impact velocities and impact locations in addition to different column boundary conditions, axial load ratios and section sizes. The parametric study results show that global buckling is the predominant failure mode of axially unrestrained compressed steel columns under transverse impact. The parametric study results have also revealed that column failure was mainly dependent on the value of the kinetic energy of impact. The parametric study has also shown that strain rate has a minor effect on the behaviour and failure of steel columns under low to medium velocity impact. The parametric study results have been used to develop an understanding of the detailed behaviour of steel columns under transverse impact in order to inform the assumptions of the proposed analytical method.To account for the effect of vehicle impact on the behaviour of steel columns, a simplified numerical vehicle model was developed and validated in this study using a spring mass system. In this spring mass system, the spring represents the stiffness characteristics of the vehicle. The vehicle stiffness characteristics can be assumed to be bilinear, with the first part representing the vehicle deformation behaviour up to the engine box and the second part representing the stiffness of the engine box, which is almost rigid. The second main objective of this research is to develop a simplified analytical approach that can be used to predict the critical velocity of impact on steel columns. The proposed method utilizes the energy balance principle with a quasi-static approximation of the steel column response and assumes global plastic buckling as the main failure mode of the impacted column. The validation results show very good agreement between the analytical method results and the ABAQUS simulation results with the analytical results tending to be on the safe side. A detailed assessment of the design requirements suggested by Eurocode 1, regarding the design of steel columns to resist vehicle impact, has shown that the equivalent static design force approach can be used in the design of moderately sized columns that are typically used in low multi-storey buildings (less than 10 storeys). For bigger columns, it is unsafe to use the Eurocode 1 equivalent static forces. It is acceptable to use a dynamic impulse in a dynamic analysis to represent the dynamic action of vehicle impact on columns, but it is important that both the column and vehicle stiffness values should be included when calculating the equivalent impulse force – time relationship. It is also necessary to consider the two stage behaviour of the impacting vehicle, before and after the column is in contact with the vehicle engine. A method has been developed to implement these changes.

"As jurisdictions throughout the world progress toward performance based building codes, it is important that the proper tools be made available to the engineering profession in order that they may take full advantage of these new codes. There is currently a large body of work written on the subject of performance based or engineered structural fire safety. Unfortunately, most of this information is scattered throughout technical journals from different countries and organizations, and not easily accessible to the practicing engineer. Under the current prescriptive code regime there is generally no requirement to undertake an engineering approach to structural fire safety, since the required fire resistance ratings are prescribed and the fire resistance ratings of materials/assemblies are determined through standard tests. However, these methods have been shown to be both unnecessary and expensive in some cases. A method will be developed that can be used to determine required fire resistance ratings for fire exposed structural steel based on a realistic engineering approach. A procedure is summarized for calculating time-temperature curves from a real fire in a typical compartment. With this time-temperature relationship a realistic time to failure for structural steel members can be determined. The method is summarized. Comments regarding important considerations and a worked example are provided to demonstrate the utility of the method."

A three-phase numerical study was undertaken to address some design issues related with special truss moment frames (STMFs). In the first phase, the design approaches for distribution of shear strength among stories were examined. Multistory STMFs sized based on elastic and inelastic behavior were evaluated from a performance point of view. A set of time history analysis was conducted to investigate performance parameters such as the interstory drift ratio and the plastic rotation at chord member ends. The results of the analysis reveal that the maximum interstory drifts are not significantly influenced by the adopted design philosophy while considerable differences are observed for plastic rotations. In the second phase, the expected shear strength at vierendeel openings was studied through three dimensional finite element modeling. The results from finite element analysis reveal that the expected shear strength formulation presented in the AISC Seismic Provisions for Structural Steel Buildings is overly conservative. Based on the analysis results, an expected shear strength formula was developed and is presented herein. In the third phase, the effects of the load share and slenderness of X-diagonals in the special segment on the performance of the system were evaluated. Lateral drift, curvature at chord member ends, axial strain at X-diagonals and base shear were the investigated parameters obtained from a set of time history analysis. The results illustrate that as the load share of X-diagonals increases, the deformations decreases. Moreover, the slenderness of X-diagonals is not significantly effective on the system performance.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 180-185). Also available in electronic format on the Internet.

Thesis (M.S.)--University of North Texas, Dec., 2008. / Title from title page display. Includes bibliographical references.

Orientadores: Francisco Borges Filho, Silvia Aparecida Mikami Gonçalves Pina / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-14T19:39:19Z (GMT). No. of bitstreams: 1 Borsato_KarenTostes_M.pdf: 36279316 bytes, checksum: 0ec83c2265143394abddde3b4095bc42 (MD5) Previous issue date: 2009 / Resumo: As soluções adotadas durante a concepção arquitetônica têm amplas repercussões em todo o processo de projeto e a falta de conhecimento dos princípios determinantes na concepção da estrutura metálica pelo arquiteto é um dos fatores que influencia a pouca utilização deste material. O domínio sobre as especificidades da produção arquitetônica em aço é imprescindível para o correto processo de projeto e garante subsídios para projetistas, que deveriam ser iniciados na formação do arquiteto. Para tanto, o objetivo dessa dissertação é entender como ocorre a integração da arquitetura no processo de projeto e evidenciar quais são os requisitos e peculiaridades da arquitetura em aço. A pesquisa aborda a integração da arquitetura e a concepção do projeto a partir de uma revisão bibliográfica com temas correlatos e um estudo de campo que contribuiu para viabilizar o projeto em aço. A partir dessa revisão, analisou-se arquitetos selecionados de acordo com o envolvimento na produção em aço de modo a demonstrar a metodologia de projeto de cada profissional, possibilitando a posterior análise e comparação de similaridades e divergências. A partir da metodologia dos casos estudados, este trabalho colaborou com o aprimoramento de idéias e descobertas por parte dos profissionais de arquitetura das características e propriedades do aço, permitindo um entendimento da condução do processo de projeto em torno das diretrizes e premissas que garantem a integração das estruturas metálicas na concepção do projeto arquitetônico. Nesse contexto, o produto desta pesquisa envolveu o aumento das inter-relações entre arquitetos e processos de projeto que incluem com sucesso o uso da estrutura metálica. / Abstract: The used solutions during the architectural conception have wide repercutions in the whole design process and the architect's lack of knowledge regarding the principles for defining the steel structure's design is one of the factors influencing the non-use of this material. The know how of steel production's peculiarities is required for a correct design process and garantees a support for architects and engineers which should be acomplished in their graduation. Thus, the purpose of this research is to understand how the design process integrates with arquitecture and also to put in evidence the steel architectures requirements and peculiarities. From this review, previously selected architects were analyzed to show the design process of each of these professionals alowing later analysis and comparison of their similarities and differences. Thus, based on studied cases' methodology this work collaborated with architects' improvement of ideas and discoveries concerning steel's characteristics and properties, allowing the understanding of design's practice in steel construction from a survey around the guidelines that ensure steel structures and architectural projects design integration. / Mestrado / Arquitetura e Construção / Mestre em Engenharia Civil

Master of Science / Department of Architectural Engineering / Kimberly W. Kramer / In structural steel connection design, simple shear connections are one of the most common connection types utilized. The industry, especially from the side of the engineer, tends to lean toward using Double Clip Angle Connections as the default standard for simple shear connections. A double clip angle connection is a connection consisting of two angles transferring the shear forces from one member to the next either through bolts or welds. The design of Double Clip Angle Connections is efficient and the connections themselves are easy to fabricate. However, benefits to utilizing other types of shear connections exist. Many of these benefits are seen in the fabrication shop or during erection and construction. This is especially true of single shear plate or shear tab connections when applied to open structure design. Shear tab connections consist of a single plate that transfers the shear forces from one member to the next with bolts or with welds. The design of shear tab connections can be a more involved process than the design of double clip angles. Sometimes the shear plate or shear tab has to be longer than is typical. This is called an extended shear plate connection. These extended shear plates can bring other variables into the design that typically don’t occur with Double Clip Angle Connections such as bending of the plate or the need for multiple bolt columns. However, with proper planning and detailing, the benefits and savings experienced in the fabrication or construction phase may outweigh what can be seen as a more laborious design task. The purpose of this report is to identify the possible benefits achieved in using each of these connections, highlight the differences in the design approach for each, and use a study model to compare the outcome of using one connection over another in the design of a typical open structure. Double clip angles are typically the most efficient approach when speed of design and simplicity of fabrication are the desired outcomes. However, shear plate or shear tab connections have the potential to provide safer erection alternatives and materials savings if used in appropriate ways and with the right applications.

The buildings that are designed according to the building codes generally perform well at severe performance objectives (like life safety) under high earthquake hazard levels. However, the building performance at low performance objectives (like immediate occupancy) under low earthquake hazards is uncertain. The motivation of this research is to modify the design and detailing rules to make the traditional systems perform better at multi-level hazards. This research introduces two new structural steel systems: hybrid Buckling Restrained Braced Frames (BRBF) and hybrid steel Moment Frames (MF). The "hybrid" term for the BRBF system comes from the use of different steel material including carbon steel (A36), high-performance steel (HPS) and low yield point (LYP) steel. The hybridity of the moment frames is related to the sequence in the plastification of the system which is provided by using weaker and stronger girder sections. Alternative moment frame connections incorporating the use of LYP steel plates are also investigated. The hybrid BRBF approach was evaluated on seventeen regular (standard) frames with different story heights, seismic design categories and building plans. By varying the steel areas and materials in the BRB cores, three hybrid BRBFs were developed for each regular (standard) frame and their behavior was compared against each other through pushover and incremental dynamic analyses. The benefits of the hybridity were presented using different damage measures such as story accelerations, interstory drifts, and residual displacements. Collapse performance evaluation was also provided. The performance of hybrid moment frames was investigated on a design space including forty-two moment frame archetypes. Two different hybrid combinations were implemented in the designs with different column sections and different strong column-weak beam (SC/WB) ratios. The efficiency of the hybrid moment frame in which only the girder sizes were changed to control the plastification was compared with regular moment frame designs with higher SC/WB ratios. As side studies, the effect of shallow and deep column sections and SC/WB ratios on the moment frame behavior were also investigated.   In order to provide adequate ductility in the reduced capacity bays with special detailing, alternative hybrid moment frame connections adapting the use of low strength steel were also studied. / PhD

Experiments were conducted on ASTM A572 50 and A992 steel over a range of intermediate strain rates in order to determine material strength properties of structural members subjected to dynamic loadings. The yield and ultimate tensile stress (UTS) of the steels were determined at increasing strain rates using a hydraulic apparatus and compared to static values obtained from ASTM E8 standardized tensile experiments. Results revealed that A572-50 steel exhibited an increase in yield stress of up to 35% and UTS of up to 20% as strain rate increased from 0.002 to 2.0 s-1. A992 steel demonstrated a similar increase in yield stress of up to 45% and UTS of up to 20%. Ratios of dynamic-to-static strengths were used to develop dynamic increase factor curves spanning the range of strain rates studied. These curves provide designers with material property values required for accurate and economical design of protective structures.