M.Tech. / Soccer is the most widely played sport in the world and, of all the skills required to participate, the instep soccer kick is considered to be the primary offensive action within the game of soccer. Biomechanical analysis of the instep soccer kick has revealed that the action of kicking is characterised by a proximal to distal series of multi-articular movements with distal segmental movements being predetermined by more proximal ones (Kellis and Katis, 2007). According to Smith, Gilleard, Hammond and Brooks (2006), the lower spine and pelvis play a pivotal role in determining the placement and actions of distal segmental motion during the action of the instep soccer kick. The aim of this study was to determine the effectiveness of chiropractic adjustments in soccer players with lumbar facet and sacroiliac joint dysfunctions by assessing the resultant speed of a soccer ball once kicked with an instep soccer kick. By correcting the lumbar facet and sacroiliac joint dysfunction of the affected soccer players, it was postulated that with restoration of joint motion and reduction of pain, the speed of the soccer ball, when kicked, would improve. When kicked the resultant ball speed is indicative of biomechanical kicking success. Thirty male professional soccer players from the Jomo Cosmos football establishment who met the study’s selection criteria were selected and randomly divided into one of two groups. The study group received chiropractic adjustments of dysfunctional lumbar facets and sacroiliac joints and the control group received a placebo treatment in form of a de-tuned stationary ultra-sound head over the effected facets joints for five minutes. Treatment for both groups occurred over a two week period with treatment being administered twice a week, totalling of four treatments per participant. Data capture was collected 3 times over the 2-week period; 1st reading done before the 1st treatment, the 2nd reading before the 3rd treatment and the final reading taken after the 4th and final treatment. Data capture consisted of both subjective and objective readings. The subjective data consisted of the measurements of pain experienced by the participants in the form of a Numerical Pain Rating Scale. Objective data involved the measurement of ball speed once kicked, with the use of a radar speed gun as well as lumbar spine range of motion measurements by means of a Digital Inclinometer. In executing the group comparisons, it was found that both groups would present with contrasting results. The group undergoing the chiropractic adjustments would show an improvement in their ball speed, reduction in their overall pain and increased lumbar spine extension and rotation ROM; where as the group undergoing the placebo treatment experienced a decrease in their ball speed, an increase in their overall pain and decreased lumbar spine ROM. The results obtained from the study demonstrated that the majority of the data was not statistically significant in either of the groups however, from a clinical perspective there was a definite effect on the lumbar spine range of motion, ball speed and pain reduction as a result of the Chiropractic adjustments that would warrant further investigation. There is a definite link with the negative effects that lumbar facet and sacroiliac joint dysfunctions have on the proximal to distal sequence of events that take place during the instep soccer kick. Therefore, treating the lumbar facet and sacroiliac joint dysfunction with chiropractic adjustments allows for better transfer of energy between segments and for greater resultant ball speed. In conclusion, the study demonstrated that chiropractic adjustment of lumbar facet and Sacroiliac joint dysfunctions showed good improvement in the resultant ball speed, reduction in lower back pain and improved lumbar spine extension and rotation ROM. From these results, it would be prudent to incorporate more chiropractic treatment into mainstream soccer and encourage further research into the advantages that chiropractic treatment has in better understanding the biomechanics involved in the instep soccer kick.

M.Ing. (Mechanical Engineering) / The use of longitudinally welded tube are limited in certain sectors of industry due to the belief that seamless tubes are superior. The main objective of this study was to try and prove that sufficient resistance to internal pressure could be achieved by longitudinally welded type 304L stainless steel tubes, while subjected to various external forces. A knowledge of plasticity theory and failure criteria provides the basis of the different mechanisms of tube failure. Four different tests were performed using different external forces, while internal pressure was increased until failure occurred. It was found that test specimens failed after reaching acceptable pressures, irrespective of the external loading conditions.

M.Tech. (Chiropractic) / Purpose: This study aims to ascertain the extent Chiropractic manipulative therapy increases ROM beyond the joint-separation induced ROM initially experienced via the cavitation phenomenon in the absence of neck pain. Method: Sixty participants between eighteen and thirty-five years of age, thirty male and thirty female whom met the inclusion of no neck pain and perceived decreased ROM were selected for participation. There was a single group with each participant‟s pre-adjustment readings acting as a baseline. Procedure: Participants were assessed for hypomobility and joint dysfunction. Those who met the inclusion criteria underwent a detailed history, physical and cervical spine regional examination on the initial consult. A pre-adjustment objective measurement was acquired using a cervical spine range of motion (CROM) device. Once the consent form was signed participants received Chiropractic cervical spine manipulative therapy to the area/s of the cervical spine found to be restricted on motion palpation by the researcher. Post-adjustment objective measurements were taken at one, twenty, forty and sixty minutes using the CROM device. Participants were required to remain in the researcher‟s examination room for 60 minutes post-adjustment with continuation of regular day to day activity and no strenuous activity during the twenty-four hour period of the study. The participant was required to return for a single follow up visit within a time frame of twenty-four hours of the initial visit. The follow-up visit required no treatment. At twenty-four hours, the participant was objectively measured for cervical spine ROM using the CROM. The results were based on objective data in the form of cervical spine ROM measurements. Results: Clinical analysis of the percentage change in cervical spine ROM values revealed that clinically and statistically significant improvement was seen in all ranges of motion post-adjustment. General consensus showed that a peak value of improved ROM was seen post-adjustment at the one minute interval for all ranges of motion except flexion. Flexion demonstrated a peak ROM value at the twenty minute post-adjustment interval.

During propped construction the steel-concrete composite action resists dead as well as imposed loads. Conversely, the steel section alone resists the floor self-weight in unpropped beams. The major difference between propped and unpropped composite beams lies in the ductility requirements rather than in the strength requirements. Relatively few studies have been carried out to assess the rotation requirements for unpropped semi-continuous composite beams. The outstanding critical factor in the case of unpropped construction is the dead load stress that must be carried by the steel beam alone prior to hardening of the concrete. This research overcomes the difficulties involved in modelling the composite and noncomposite stages by using a numerical integration technique developed from the basic principles of structural mechanics. The method incorporates the fully non-linear material properties and requires very little assumption. The technique was initially validated using the experimental results from plain steel beam bending tests. The subsequent comparison between the model predictions and the results from the large-scale frame test carried out for this research purpose, showed that the method is capable of predicting non-elastic load vs. end rotation behaviour within a high degree of accuracy. Thus the model can be used with confidence in order to predict the connection rotation requirements for a wider range of loading configurations than is practically possible from experimental testing alone. A parametric study is carried out using the numerical integration technique developed for the semi-continuous composite beam on a total of 2160 different beam configurations, utilising different steel grades and loading conditions. In this study the influence of dead load stress on the connection rotation requirement has been thoroughly evaluated along with several other factors including span to depth ratio, location within the building frame, ratio between the support (connection) moment capacity and span (beam) moment capacity, loading type, steel grade and percentage of the beam strength utilised during design. The connection rotation capacity requirements resulting from this study are assessed to establish the scope for extending the use of composite connections to unpropped beams. The large-scale experiment that has been carried out provided an opportunity to investigate the behaviour of a modified form of composite connection detail for use at perimeter columns (single-sided composite connections) with improved rebar anchorage. Additionally, another extensive parametric study is carried out using the numerical integration technique developed for the steel beam to establish the influence of strainhardening on elastic-plastic frame instability design.

The objective of the study was to examine factors that influence the strength of butt welds and gain an understanding of the process of failure. The study was divided into several sectors. The first and primary part of the programme was to determine the extent to which the pipe system's long-term strength under both internal fluctuating and constant pressure is reduced by the presence of axially misaligned butt welds. The second objective was to examine fracture initiation sites and crack propagation paths of the failed aligned and misaligned butt welded samples in relation to the melt flow zone and the weld bead in order to establish the cause of failure. Finally the project considered the influence of selected welding parameters on the fatigue performance of aligned butt fusion welds and an investigation into the influence of elevated temperature (79°C) testing technique on the basic material's properties. Fatigue and stress-rupture lifetimes were found to decrease significantly with increasing axial misalignment at the butt fusion weld in 63,90 and 125mm MDPE pipe systems at 79°C in a water environment. In the butt fusion weld having axial misalignment of 20 per cent of the wall thickness and above, the reduction in the fatigue and stress-rupture lifetime was greater than 50 per cent compared to the aligned weld. It was not clear whether there is a pipe size effect or not; there was no marked change in the fatigue performance of misaligned butt welds for the three pipe diameters examined. However, the fatigue performance of the aligned butt welds in 90 and 125mm was noticeably better compared to 63mm pipe systems. The stress rupture performance of misaligned butt welds in 90 and 125mm MDPE pipes was more than halved compared to those in 63mm pipe systems. Both the fatigue and stress rupture performance of misaligned butt welds could be explained in terms of amplified axial stress and in general, the Ory expression for evaluating the increase in axial stress due to misalignment appears to be valid. The temperature dependence of the fatigue performance of aligned and misaligned butt fusion welds in 63 and 90mm MDPE pipe systems suggests that if continuous internal fluctuating pressure under the conditions examined is maintained, then the butt fusion welds with axial misalignment of below 10 per cent of the wall thickness may well meet the design lifetime of 50 years at the service termperature. Under stress-rupture conditions, all the misaligned butt welds considered in the three pipe diameters surpassed the minimum specified requirement of 170 hours at 79°C. The fatigue was the most aggresive condition of the two for minor misalignment. Examination of the circumferential butt weld failures revealed that the crack invariably initiated from the notch located at the inner weld bead and no preferred crack propagation path was taken in relation to the melt flow zone. It was proved that the notch was responsible for the observed circumferential failure of aligned butt welds in 63mm MDPE pipes by testing these butt fusion welds where the internal weld bead was machined off. The failure site for the internal weld bead machined off sample was in the pipe remote from the weld inferring that the material in the melt flow zone does not constitute any weakness. The effect of elevated temperature (79°C) testing in 63mm HDPE pipe was found to increase the density (and crystallinity) signifying a slow annealing process in the material. However, the changes in these parameters were not of sufficient scale to strongly influence the performance. The main effect of elevated temperature testing in water environment appears to be the extraction of stabiliser from the base polymer as was indicated by the rapid decrease in oxidation induction time with the ageing times.

Fibre reinforced structural members are currently being produced using the pultrusion process. The mechanical properties of these members are fundamentally different from those of conventional metallic ones. Therefore, the approximate theories which are suitable for designing the latter elements have to be revised before they are applied to pultrusions. An important aspect of the design of building frames is that of joints. The bolting technique is considered as the most suitable method for on-site jointing. Accordingly, experimental investigations are undertaken in order to establish the behaviour of bolted joints in pultrusions. Numerical and analytical methods are used to investigate the stresses in these joints. Single and two-bolt joints were the subject of experimental investigations. It is shown that materials with high percentage of axial fibres do not develop bearing failure. However, provided the end distance is sufficient, the resulting shear failure will be ductile. The load distribution in joints with two bolts is measured and it is found that it varies with the load on the joint. The theoretical investigations compare the use of the laminated plate theory with three dimensional analyses. Because the use of the laminated plate theory is found to be reasonably accurate, an improvement for the case of a symmetrical laminate is proposed where the laminated shell theory is used to model half the plate only. This technique is based on the assumption of a bi-linear variation of the stress through the thickness of the laminate. The effect of the fastener is an important part of the behaviour of the joints. Three dimensional analyses are performed to assess its effect. To avoid the complications of performing three dimensional analyses, a two dimensional model for considering the effect of the washer on the joint is devised. In addition, a method which avoids iteration when considering the effect of friction is formulated. A finite element formulation for the non-linear and failure behaviour of uniaxial composite materials is developed to investigate the behaviour of the joints. Finally, a closed form analytical formula for calculating the tangential stress around a hole in an infinite orthotropic plate loaded on the hole is generated to simplify the design procedures.

No description available.

Master of Science / Department of Civil Engineering / Sunanda Dissanayake / Motorists generally follow the guidance provided by the pavement markings while traveling on roads. Under certain circumstances, construction joints may be necessary in concrete pavements, which are generally designed to be coincident with the pavement markings. At some locations, however, the construction joints may not exactly match the pavement markings. These situations may create confusion in the minds of drivers, which may lead them to follow joints instead of the markings. In the absence of detailed studies on this topic, an effort was made in the present study to evaluate the effects of unmatched longitudinal construction joints and pavement markings on the lateral position of vehicles. Sites having the characteristics of unmatched longitudinal construction joints and pavement markings were identified, and detailed data were collected at one of the sites. Video camera technique was used for capturing the movements of vehicles along the test site for longer durations. The video tapes were later reduced in the laboratory to extract necessary information. The distance to the right side of the vehicles from right curb of the road, the type of vehicle, presence of vehicles in the adjacent lane, weather and light conditions, and the movement of the vehicles immediately after traversing the section of the road having unmatched longitudinal construction joints and pavement markings were the main parameters observed while reducing the data. Two surveys were also conducted for gathering the opinions of some practitioners and engineers on the issue. Statistical analyses were carried out using t-tests to evaluate if there were differences. Several comparisons were made for different types of vehicles based on various conditions. The analysis results indicated that there was a statistically significant difference between the actual and expected distances to the center-line of vehicles, implying that the lateral position of vehicles may have been affected by the joints. A model was also developed to determine the lateral position of the vehicles by considering the parameters used in the analysis. Based on the survey results and analysis of field data, it was found that the lateral position of vehicles may have been affected by the unmatched joints and pavement markings.

Please read the abstract in the section front of this document / Dissertation (MEng(Metallurgical Engineering))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted

Wide cracks in land-based Ni- or Co-base superalloy turbine components are difficult to repair successfully using conventional welding or brazing techniques. This project examined the feasibility of liquid phase diffusion brazing using novel Ni- and Co-base braze alloys containing Hf or Zr as melt point depressant for the repair of wide cracks in turbine components. An optimized braze cycle was developed and the joints were evaluated using various metallographic techniques and mechanical tests (elevated temperature tensile tests, creep rupture tests and low cycle fatigue tests). Microstructural examination revealed the presence of Hf- or Zr-rich intermetallic phases (most likely Ni7Hf2 or Ni5Zr) in Ni-base braze joints. These intermetallic compounds were, however, observed to be significantly softer than the boride phases routinely found in commercially available braze alloys with boron as melt point depressant. As a result, the novel wide gap brazed joints displayed excellent mechanical properties (ranging from 80% to 100% of the base metal’s properties). The low cycle fatigue properties of wide gap braze joints performed using a combination of MarM247 superalloy powder and Ni-Cr-Hf or Ni-Cr-Zr braze filler metals were found to be superior to those of the widely used Ni-Cr-B braze filler metals. Wide gap braze repair of FSX-414 Co-base superalloy using novel MarM509/MarM509B and MarM509/Co-Hf braze alloys resulted in high temperature tensile properties equivalent to those of weld repairs in the same parent material (using Nozzalloy filler metal). The creep rupture and low cycle fatigue (LCF) properties of the braze joints were superior to those of welds performed using MarM918 filler metal. / Thesis (PhD)--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted