Recently in the United States, there has been increasing interest in developing engineered approaches to structural fire safety of buildings as an alternative to conventional code-based prescriptive approaches. With an engineered approach, the response of a structure to fire is computed and appropriate design measures are taken to assure acceptable response. In the case of steel buildings, one of the key elements of this engineered approach is the ability to predict the elevated-temperature properties of structural steel. Although several past research studies have examined elevated-temperature properties of structural steel, there are still major gaps in the experimental database and in the available constitutive models, particularly for ASTM A992 structural steel, a commonly used grade. Accordingly, the overall objective of this dissertation is to significantly enlarge the experimental database of the elevated-temperature properties for ASTM A992 structural steel and developing improved constitutive models for application in structural-fire engineering analysis. Specific issues examined in this dissertation include the following: tensile properties at elevated temperatures; room-temperature mechanical properties after heating and cooling; and creep and relaxation properties at elevated temperatures. For the elevated-temperature studies of tension, creep and relaxation, constitutive models were developed to describe the measured experimental data. These models were compared to existing theoretical and empirical models from the literature. / text

Aluminium-silicon alloys have gained increasing market share in the automotive and aerospace industry because of increased environmental demands. These alloys have a high strength-to-weight ratio, good corrosion resistance, castability and recycling potential. However, variations in properties and limited performance at elevated temperature are restricting these alloys from use at elevated temperatures. During the last decades, researchers have investigated ways to improve the properties at elevated temperatures. However, the effect of some transition elements is not well understood. The aim of this work is to investigate the aluminium-silicon alloys with addition of cobalt and nickel for high temperature applications. Tensile testing and hardness testing were conducted on samples produced by directional solidification in a Bridgman furnace with condition generating a microstructure corresponding to that obtained in high pressure die casting, i.e. SDAS ~ 10 µm. The results show that cobalt and nickel improve the tensile properties up to 230 °C.

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