Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Higher grade steels are being rolled in South Africa by suppliers and results in structural members having an increased axial and bending moment capacity due to an increased yield stress. Structural elements used in designs are stronger and therefore lighter sections with sufficient axial and bending moment capacity are used. Displacements of structural elements are calculated using the stiffness and Young’s modulus of a profile. These values are not affected by the increased yield stress in higher steel grades and therefore have a negative effect on the displacements of the structure. The potential of these higher grade structural elements are not utilized through serviceability limit state criteria, since the displacement determination does not account for the increased capacities of higher grade steels, but only stiffness and elasticity of the members. Structural analysis of portal frames does not account for the real behaviour of steel connections and column bases. It is assumed that connections and bases are either fully rigid or perfectly pinned. This assumption is used in the analysis and design of the structure. Although it is assumed that connections and bases are either rigid or pinned, the real behaviour is in between these two extremes. Rigid connections exhibit a certain flexibility under loading whereas pinned bases provide a certain restraint under loading. The real behaviour of connections and bases are referred to as the moment-rotation behaviour of the connection. For a certain applied moment to the connection or base, the connection exhibits a certain rotation. The focus of this study is placed on the accuracy and feasibility of modelling the real behaviour of connections and bases in a structural analysis of a portal frame. A connection stiffness is determined from the connection’s moment-rotation behaviour, and is assigned to a rotational spring of zero length in a structural analysis. An experimental investigation was conducted to obtain the real displacement data of a portal frame subject to loads for two different support conditions, i.e. a perfect hinge and grouted-support. A perfect hinge support was used to isolate the moment-rotation response of the ridge and eaves connection. The experimental results were used to compared to the results obtained from a structural analysis to determine the accuracy of the numerical results. A real design case was investigated with load combinations imposed on the frame in accordance with SANS 10160:2011. Three methods of modelling connections and bases in an analysis were considered. Firstly modelling connections as rigid and bases as pinned, secondly modelling connections as linear rotational springs and bases as pinned. Lastly was to model connections as linear rotational springs and bases as non-linear rotational springs. The outcome of the research was that more accurate displacements of a portal frame could be obtained by modelling the real behaviour of rigid connections as rotational springs, but this is not the case with grouted column bases. It is thus not feasible to model the real behaviour of connections and bases in a structural analysis as the current method of modelling connections as rigid and bases as pinned provides reliable and accurate displacement results. / AFRIKAANSE OPSOMMING: Hoë graad staal word tans in Suid Afrika gerol deur verskaffers en lei daartoe dat strukturele elemente oor ’n groter aksiale- en buigmomentkapasiteit het as gevolg van ’n groter vloeispanning. Strukturele elemente in ontwerpe is sterker en gevolglik het ligter elemente die benodigde aksiale- en buigmoment-kapasiteit. Verplasings van strukturele elemente word bepaal vanaf die styfheid en Young modulus van die element. Hierdie waardes word nie beïnvloed deur die groter vloeispanning van hoë graad staal nie, en het dus ’n negatiewe uitwerking op die verplasings van die struktuur. Die potensiaal van die gebruik van hoë graad staal word nie benut in die geval van voldoening aan diensbaarheids kriterium nie, aangesien verplasings bepaal word vanaf die styfheid en elastisiteit van die elemente, en nie vloeispanning nie. Strukturele analise van portaalrame neem nie die ware gedrag van konneksies en kolomvoetstukke in ag nie. Die aanname word gemaak in analises en ontwerpe dat konneksies en voetstukke óf rigied óf geskarnierd is. Hierdie is slegs ’n aanname en in die werklikheid lê die ware gedrag van konneksies en voetstukke tussen hierdie grense. Rigiede konneksies toon ’n sekere buigbaarheid tydens belasting en geskarnierde voetstukke toon ’n sekere beperking teen rotasies. Die ware gedrag van konneksies en voetstukke word gedefinieer as moment-rotasie gedrag. Vir ’n spesifieke aangewende moment, ondergaan die konneksie of voetstuk ’n sekere rotasie. Hierdie studie fokus op die akkuraatheid en uitvoerbaarheid van die modellering van die ware gedrag van konneksies en voetstukke in ’n strukturele analise van portaalrame. Die styfheid van ’n konneksie word bepaal vanaf sy unieke moment-rotasie gedrag, en word ingevoer as ’n styfheid van ’n rotasieveer in ’n strukturele analise. ’n Eksperimentele ondersoek was gedoen om verplasingswaardes van ’n portaalraam onder belastings te bepaal. Twee ondersteunings is ondersoek in die eksperimentele program, naamlik ’n geskarnierde ondersteuning asook ’n breivul ondersteuning. Die gebruik van die geskarnierde ondersteuning isoleer die moment-rotasie gedrag van die nok en dakrand konneksies. Die eksperimentele resultate was gebruik om die akkuraatheid van die resultate vanaf die strukturele analise te ondersoek. Laastens was ’n ontwerpsprobleem ondersoek deur laskombinasies, soos bepaal volgens die riglyne van SANS 10160:2011, op ’n portaalraam aan te wend. Drie gevalle van modellering van konneksies in ’n strukturele analise is ondersoek. Eerstens om konneksies as rigied en voetstukke as geskarnierd te beskou. Tweedens was die konneksies as linieêre rotasievere gemodelleer en voetstukke as geskarnierd te beskou. Laastens was om konneksies as linieêre rotasievere te modeleer en voetstukke as nie-linieêre rotasievere. Die navorsing het getoon dat meer akkurate verplasings van portaalrame bepaal kan word deur rigiede konneksies te modelleer as rotasievere, maar dit is nie die geval met breivul ondersteunings nie. Die gevolg is dat die uitvoerbaarheid van die modellering van konneksies en voetstukke as rotasievere nie effektief is nie, aangesien die huidige metode van die modellering van konneksies as rigied en voetstukke as geskarnierd akkurate en betroubare resultate lewer.

鋼鐵産業是象徵國家經濟情況的重要基礎産業，也是代表社會發展程度、經濟實力的重要標誌。因此鋼鐵產業常被認為是具有代表國力強弱的指標性意義，不論是先進國家或發展中國家，皆長期的、積極的振興鋼鐵產業。 現今臺灣的鋼鐵業者在面對上、下游皆瘦而中游獨大的特殊產業環境之下，許多企業為了達到產業規模經濟與拓展銷售市場，紛紛前往海外另闢戰場。傳統的國際化理論認為國際化過程的演變是大型企業為了因應產品生命週期的演進而選擇在海外市場發揮其資源優勢的行為，然而從網絡連結觀點我們可以把國際化看成是企業試圖和國外網絡連結建立關係的作為。通常非大型企業並不具備獨自建立國外相關網絡的資源深度，然而透過網絡關係的合作卻可以快速取得當地市場知識並藉由現有通路進入國際市場。這對於具有高進入障礙、高度資本密集、高度技術密集且企業難以獨自擁有足夠生產資源等特性的鋼鐵產業而言，網絡關係連結相當重要。 在這個全球化的時代，大多數企業遲早都會在國際上競爭。因此，專注於國內市場交易的在地企業會被迫具有國際競爭力並參與國際商業活動。所有管理國內企業或跨國集團的經理人都必須意識到這個潮流的影響力。全球化經濟現在已經充斥在世界的各個角落，而且國際化現在所影響的不僅是大型企業集團連許多的非大型企業也是。本次研究針對鋼鐵產業使用多點個案研究法，調查網絡連結對企業國際化進程的影響。來自六家鋼鐵業者的研究證據顯示可以印證在企業的國際化過程中，網絡連結會觸發並驅動企業的國際化、影響企業的海外市場選擇決策與進入模式決策、幫助企業獲得起始信用、接近新網絡關係與現成通路、也協助降低成本與風險，並且影響企業的國際化步調。 / The iron-and-steel industry is an important basic industry to symbolize national economics, and a main indicator which represents social development level and economics power. Because the iron-and-steel industry is usually considered as an index of national strength, no wander many developed and developing nations all have prospering iron-and-steel industries. Now iron-and-steel firms in Taiwan are facing a unique industrial environment, and many are expanding new overseas markets to exploit economies of scale. Traditional internationalization theory posited that the internationalization process is a behavior of giant enterprises to adapt to the product life cycle evolvement and exploit the resource advantage abroad. However, we can view internationalization as a behavior of SMEs to establish relationships with foreign networks from the network perspective. Usually small firms can’t afford enough resources to build up international networks by themselves, but by only cooperating through network connections they can obtain foreign market knowledge soon and penetrate international markets via existing channels. The iron-and-steel industry has high entry barriers, high capital requirement and technology intensity, for SMEs difficult to have all kinds of production resources, the network relationship connections are quite crucial to succeed in international markets. In this era of globalization, most firms will sooner or later have to compete in the international market. Therefore, local firms that focus their business on the domestic market are forced to be internationally competitive and to participate in international business. All managers must be aware of this trend when managing a domestic firm or a multinational conglomerate. The global economy now has reached every corner of the world, and internationalization now involves not just the giant corporations but also many SME enterprises. This research use case research method to examine the influence of network connections on the internationalization process of SME iron-and-steel firms in Taiwan. The evidence from the cases of six iron-and-steel firms shows that the firms’ internationalization process was triggered and motivated by network connections which also affected their foreign market-selection decisions and mode-of-entry decisions, helped them obtain initial credibility and access to other relationships and established channels, helped in lowering cost and risk, and influenced their internationalization pace.

Embora o Brasil tenha uma das maiores reservas de minério de ferro do mundo, estimada em 170 bilhões de toneladas, e também possua siderúrgicas próximas às minas de ferro, como a Usiminas, por exemplo, o Brasil exporta minério de ferro e importa produtos semi-acabados de aço de outros países, como o Japão e a China. O objetivo desta pesquisa é modelar a cadeia de valor global de ferro e aço e analisar sua dinâmica estrutural para verificar se esse modelo é capaz de determinar os fatores que impulsionam a geração de valor e que levaram alguns países a ter maior impacto sobre seu desenvolvimento econômico do que outros. A modelagem da cadeia de valor usa a técnica padrão de análise de entrada-saída de balanço de massa (método de modelagem estrutural ampliado de Leontief), detalhado na revisão da literatura. Para obter esses resultados, foi necessário coletar e consolidar diferentes bancos de dados utilizando ferramentas capazes de conciliar, tratar e analisar o grande volume de dados presentes nesses diferentes bancos de dados, em diferentes unidades e níveis de agregação. A análise da dinâmica estrutural revelou uma série de aspectos fundamentais para entender a guerra comercial entre os EUA e a China. A China passou de 10% da produção mundial de aço bruto para 50% em 20 anos, reduzindo a relevância de outros países no contexto da cadeia de ferro e aço. Além disso, a análise revelou que o Brasil exporta quase exclusivamente minério de ferro bruto. A Austrália, por exemplo, conseguiu agregar mais valor do que o Brasil. Isso revela, portanto, que a análise da dinâmica estrutural modelada por hipergrafos pode gerar informações semânticas relevantes sobre o contexto, atores e interesses envolvidos e pode servir como um mapa para orientar decisões e políticas voltadas para uma melhor inserção e atuação de um país em uma cadeia global de produção / Although Brazil has one of the largest reserves of iron ore in the world, estimated at 170 billion tons, and also steel mills near the iron mines, such as Usiminas, e.g., Brazil exports iron ore and imports (semi-)finished steel products from other countries, such as Japan and China. The objective of this research is to model the global value chain of iron and steel and to analyse its structural dynamics to verify if this model is able to determine the factors that drive the generation of value and that have led some countries to have greater impact on their economic development than others. Value chain modelling uses the standard mass balance input-output analysis technique (Leontief\'s extended structural modelling method), detailed in the literature review. To obtain these results, it was necessary to collect and consolidate different databases using tools able to reconcile, treat and analyse the large volume of data present in these different databases, in different units and levels of aggregation. The analysis of the structural dynamics revealed a series of fundamental aspects to understand the commercial war between the USA and China. China has shifted from 10% of the world\'s crude steel production to 50% in 20 years, reducing the relevance of other countries in the context of the iron and steel chain. In addition, the analysis revealed that Brazil exports almost exclusively crude iron ore. Australia, for example, was able to add more value than Brazil. This reveals, therefore, that the analysis of the structural dynamics modelled by hyper-graphs can generate relevant semantic information about the context, actors and interests involved and can serve as a map to guide decisions and policies aimed at a better insertion and performance of a country in a global value chain

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Bridges in the US are severely damaged or suffer collapse from fires at significant rates, even when compared to other hazards such as earthquakes. Fire-induced bridge collapses are perpetuated by the general lack of installed fire protection systems. Therefore, new materials and applications are needed to mitigate structural damage that can be caused to civil infrastructure by severe fires. Accordingly, the objective of this study is to further the development of new fire protection applications in transportation structures. Specifically, the investigation centers on the development of new applications in passive fire protection materials, within the context of shielding steel-girder bridges against severe fire effects. A steel-girder bridge has been selected for study, and a high-resolution finite element model has been formed based on the corresponding bridge structural drawings. Temperature-dependent structural material properties and thermal properties have been synthesized and incorporated into the model. Additionally, a representative fire scenario has been formed (in part) based on a recent fire incident that occurred at the selected bridge site. The fire scenario also incorporates the characteristics of a fully loaded gasoline tank truck fire, where a means of incorporating the severe fire into the finite element model (as thermal loading) has been identified and enacted. Coupled thermal-mechanical finite element analyses have been carried out using the (unprotected) steel-girder bridge model. An additional finite element simulation has been carried out, where the steel-girder bridge model has been fitted with a refractory cement material that insulates the underside of the bridge spans. Also, a finite element simulation has been carried out where the steel-girder bridge model has been fitted with intumescent coating material as insulation against fire effects. Both the refractory cement and the intumescent coating materials have been found to possess robust insulation characteristics from the simulation results. Namely, the finite element analysis results indicate that, in the event of a bridge fire, both materials are capable of preventing the buildup of damaging temperatures in underlying structural members. Accordingly, the refractory cement and intumescent coating materials have been identified as successful passive fire protection materials for the fire scenario and bridge case considered.

The construction of horizontally curved bridges with skewed supports requires careful consideration. These types of bridges exhibit three-dimensional response characteristics that are not commonly seen in straight bridges with normal supports. As a result, engineers may face difficulties during the construction, when the components of the bridge do not fit together or the final geometry of the structure does not correspond to that intended by the designer. These complications can lead to problems that compromise the serviceability aspects of the bridge and in some cases, its structural integrity. The three dimensional response that curved and skewed bridges exhibit is directly influenced by the bracing system used to configure the structure. In I-girder bridges, cross-frames are provided to integrate the structure, transforming the individual girders into a structural system that can support larger loads than when the girders work separately. In general, they facilitate the construction of the structure. However, they can also induce undesired collateral effects that can be a detriment to the performance of the system. These effects must be considered in the design of a curved and skewed bridge because, in some cases, they can modify substantially its response. This research is focused on understanding how the bracing system affects the performance of curved and skewed I-girder bridges, as well as, the ability of the approximate analysis methods to capture the structural behavior. In this research, techniques that can be implemented in the creation of 2D-grid models are developed to overcome the limitations of this analysis method. In addition, efficient cross-frame arrangements that mitigate the collateral effects of skew are developed. These mitigation schemes reduce the undesired cross-frame forces and flange lateral bending stresses associated with the transverse stiffness of the structure, while ensuring that the bracing system still performs its intended functions.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

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