No description available.

Call number: LD2668 .T4 1965 W122 / Master of Science

The response of steel-framed structures to applied loading depends to a large degree on the behaviour of the joints between the columns and beams. Traditionally designers have assumed that these joints act either as 'pinned', with no ability to transmit moments from beam to column, or as 'rigid', providing perfect continuity between the connected members. Advances in analysis, and developments in modem codes of practice, permit designers to account for the real behaviour of steel joints where this is known or can be predicted. Even though experimental studies of joints conducted at many research centres around the world have provided a large bank of test data, the vast number of variables in joints (beam and column sizes, plate thicknesses, bolt sizes and spacing, etc.) often means that data for a specific joint arrangement does not exist. As a result, researchers have turned their attention to ways of predicting the behaviour of such joints. One approach which has gained acceptance is based on the "Component Method" in which overall joint behaviour is assumed to be produced by the responses of its various simpler components. To date, data on the response of joints at elevated temperatures has been gathered from full-scale furnace tests on cruciform arrangements, which have concentrated exclusively on moment-rotation behaviour in the absence of axial thrusts. However, when steel-framed structures are subjected to fire, the behaviour of the joints within the overall frame response is greatly affected by the high axial forces which are created by restraint to the thermal expansion of unprotected beams. If momentrotation- thrust surfaces were to be generated this process would require prohibitive numbers of complex and expensive furnace tests for each joint configuration. The alternative, and more practical, method is to extend the Component Method to the elevated-temperature situation. The basic theme of the Component Method is to consider any joint as an assembly of individual simple components. Each of these components is simply a non-linear spring, possessing its own level of strength and stiffness in tension, compression or shear, and these will degrade as its temperature rises. The main objective of this study was to investigate experimentally and analytically the behaviour of tension and compression zones of end-plate connections at elevated temperatures. A series of experiments has been carried out and a simplified analytical model has been developed, and this has been validated against the tests and against detailed finite element simulations. The simplified model is shown to be very reliable for this very common type of joint, although similar methods will need to be developed for other configurations. The principles of the Component Method can be used directly in either simplified or finite element modelling, without attempting to predict of the overall joint behaviour in fire, to enable semi-rigid behaviour to be taken into account in the analytical fire engineering design of steel-framed and composite buildings.

Super duplex stainless steels (SDSSs) with lower nickel content are cost effective substitutes for higher alloyed austenitics and nickel alloys in demanding environments such as oil and gas production tubulars and pipelines due to their excellent corrosion resistance and high strength. The overall properties of SDSS are derived from its dual microstructure of equal ferrite and austenite, higher alloying additions of chromium, molybdenum, nitrogen and tungsten and its thermomechanical history. Higher alloying renders SDSS prone to secondary phase precipitation such as sigma phase during improper welding operations or fabrication, affecting the materials properties. Reports suggest that tungsten additions in SDSS delays sigma phase precipitation, hence the development of tungsten based SDSS such as UNS S39274. However, secondary phases cannot be entirely avoided in SDSS. Secondary phase evolution in DSS and the mechanical properties/corrosion behaviour of SDSS has been studied extensively yet their interaction is still not clear. In-service failures of SDSS components have identified gaps in the understanding of the link between secondary phase evolution and material properties, thus limiting the safe and efficient use of SDSS. The work presented in this thesis explored and quantified experimentally the role of aging on secondary phase evolution and ensuing effects on the mechanical properties, corrosion behaviour and toughness of UNS S39274 SDSS. The results revealed that chi phase precipitation occurred preferentially before the sigma phase, although chi phase was metastable in the studied alloy. Numerical modelling established that the measured concentration of the precipitated sigma phase follows the prediction by the Johnson-Mehl-Avrami kinetic model. The time-temperature -transformation was computed using experimental data, the results were compared with theoretical predictions. Results established that increase in both sigma and chi phase led to significant drop in the uniform strain and enhancement of the modulus, hardness and yield and tensile strengths. We note that the sigma phase was attacked by corrosion in comparison to other grades of 25Cr SDSS where the sigma phase remains inert to corrosion attack. Pitting corrosion resistance was influenced more by sigma phase than the chi phase composition. Chi phase was more damaging on the toughness than sigma phase. Another key finding is that the corrosion behaviour and fracture behaviour is more sensitive to lower secondary phase volume fraction than the tensile properties.

No description available.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

published_or_final_version / Business Administration / Master / Master of Business Administration

No description available.