abstract / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.

No description available.

There were two main aims of the project. A surface replacement prosthesis was previously designed at the University of Durham for the metacarpo-phalangeal joint (MCPJ). Tools were required to assess the joint prosthesis pre-operatively and postoperatively. The areas of assessment which the author was involved in were joint stiffness and a self-assessment questionnaire. The Durham arthrograph had previously been used for many clinical trials to assess joint stiffness objectively. However, the computer system was not portable. Hence a new computer system was developed, in Lab VIEW, for a lap-top computer. Ten normal individuals were assessed to validate the system. A questionnaire was also developed for patients to self-assess the performance of their joints. The questionnaire assessed parameters such as range of movement, hand strength, stiffness and pain on visual analogue scales. The difficulty in performing activities of daily living were assessed on simple descriptive scales. The second part of the project was to develop a surface replacement prosthesis for the proximal interphalangeal joint (PIPJ). Since there was inadequate information in the literature on the architecture of the PEPJ bearing surfaces and phalangeal bone shafts, a detailed study was performed on the bones from 83 PIPJs. Proximal and middle phalangeal bones were dissected, modelled in bone cement, sectioned and shadowgraphed. The shadowgraphs were measured and models of the proximal phalangeal heads were produced. These models were then used to design four PIPJ surface replacement prostheses over a range of sizes which covered 97.6% of the sample population of PIPJs. It was proposed that the MCPJ and PIPJ prostheses would be made entirely from cross-linked polyethylene (XLPE). Hence wear tests on pin-on-plate apparatuses were carried out to investigate the wear characteristics of XLPE-on-XLPE compared with other biomaterial combinations. The wear of XLPE-on-XLPE was comparable with UHMWPE-on-stainless steel. XLPE-on-stainless steel wore 10 times faster than XLPE-on-XLPE, and UHMWPE-on-UHMWPE wore 100 times faster than XLPE-on- XLPE. Hence it was concluded that all XLPE joint prostheses were feasible as far as the wear considerations were concerned.

The tubular welded joints used in the construction of Offshore structures can experience millions of variable amplitude wave induced stress cycles during their operational life. Fatigue has been identified as the main cause of degradation of structural integrity in these structures. As a result, fatigue is an important consideration in their design. Jack-up legs are made from a range of high strength steels with yield strengths up to 70OMPa. These steels are thought to exhibit fatigue resistance properties which are different when compared with conventional fixed platform steels such as BS 4360 50D and BS 7191 355D. The difference in their behaviour was heightened by the discovery, in the late 80s and early 90s, of extensive cracking around the spud can regions of several Jack-ups operating in the North Sea. It was thought that these steels may be more susceptible to hydrogen cracking and embrittlement. There was the additional requirement to study their behaviour under realistic loading conditions typical of the North Sea environment. This thesis contains results of an investigation undertaken to assess the performance of a typical high strength weldable Jack-up steel under realistic loading and environmental conditions. Details of the methodology employed to develop a typical Jack-up Offshore Standard load History (JOSH) are presented. The factors which influence fatigue resistance of structural steels used in the construction of Jack-up structures are highlighted. The methods used to model the relevant factors for inclusion in JOSH are presented with particular emphasis on loading and structural response interaction. Results and details of experimental variable amplitude corrosion fatigue (VACF) tests conducted using JOSH are reported and discussed with respect to crack growth mechanisms in high strength weldable Jack-up steels. Different fracture mechanics models for VACF crack growth prediction are compared and an improved generalised methodology for fast assessment of Offshore structural welded joints is proposed.

This thesis is concerned with an experimental investigation of the behaviour of lapped joints in reinforced concrete. A review of existing literature highlights the need to establish the longitudinal strain distribution along lap joints. This has been achieved experimentally, with detailed strain measurements being taken using a technique of internally gauging the reinforcing rods. In some specimens, strain concentration gauges were installed at the tip of the lap to permit the acquisition of particularly localised information. Computer programs were developed to process the substantial amounts of data generated during the course of each test. Two series of tests were undertaken, both using axially loaded specimens, and dealing with tension and compression lap joints respectively. The laps ranged in length from 125 to 750 mm, and comprised bars of either 12 or 20 mm diameter. Transverse reinforcement was provided in two of the tension specimens. Greater emphasis was placed on the first series, with fifteen tension specimens being tested. Thirteen of these tests were each completed within a single day but, additionally, two long-term tests were undertaken. In the latter, a constant load was sustained for up to 81 days. The measurements clearly showed the changing behaviour of the specimens, first as transverse cracks developed and subsequently as failure of the lap joint was approached. The comprehensive analysis of the test results includes a comparison of the ultimate behaviour of these joints with existing design proposals and regulations. The detailed information provided by the strain measurements enables the justification of design assumptions regarding lap joint behaviour, and thus lends greater confidence to existing design regulations. The results from five compression specimens were analysed and compared with the tension tests. The significant contribution to force transfer made by the bearing of the free end of the steel against the concrete was evident. The specimens were loaded to the rig capacity without failing. Additional strain measurements were taken in one tension and one compression specimen by casting embedment gauges within the concrete. These gauges were arranged to measure the circumferential strains in the specimen, and were complemented by strain gauges mounted on the surface of the concrete. The data thus obtained permitted a comparison of the bursting forces set up inside and outside the lap joints. The work showed that some aspects of lap joint behaviour require clarification. Suggestions for further work are included.

No description available.

Thesis (MAppSc in Physiotherapy) -- University of South Australia, 1993