South Africa's national power utility, Eskom, initiated a Demand Side Management (DSM) drive to help alleviate the electricity supply shortage experienced in South Africa. The focus of this study is on a load-shifting intervention applied in the mining environment. Load shifting is an appealing way of reducing peak demand. The mining sector is one of the largest consumers of electricity in South Africa. The application of DSM in this sector has the potential of yielding significant electrical load shifting. Firstly, this helps Eskom because they are struggling to keep up their supply. Secondly, the mines also benefit because electrical load is shifted to less expensive off-peak times. Electricity cost as a percentage of the total cost of mining output is bound to increase considerably the next few years. An investigation was conducted into the potential ofperforming load shifting on complex underground rock winders the mining sector. This involved a thorough study on existing load-shifting applications on rock winder systems. Simulations were performed on rock winder systems in their different configurations at deep-level gold mines. The simulation results indicated that there was potential for the application ofload shifting. Tau Tona was selected as a case study. This decision was based on simulations to establish which of the initially identified mines would be the best candidate for load shifting. Tau Tona has a complex underground rock winder system. Multiple rock winders feeding each other are used in a cascaded configuration. A potential load shifting target of 3' MW in the evening peak period was determined by means of simulation. The rock winder system was sequentially automated. An average evening peak demand load shift of 1 MW (or 4,2 MWh) was achieved. This translates to an average annual cost saving of R 240 000. If the load-shifting target of 3 MW could be obtained, the annual cost savings would increase by 30% to R 343 000. A study was also conducted on the feasibility of implementing maximum demand monitoring and control. Rock winders could be used in future to prevent the mines from exceeding their maximum demand. This is because rock winders consume very large amounts of electricity and can be stopped and restarted very quickly. Huge financial obligations can be prevented by making sure that the mines do not exceed their negotiated maximum demand. The necessary - and costly infrastructure to do this could not be procured during this study. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010.

To evaluate the impact of reduced truck tire pressure on strain response of low volume spring-restricted roads, research was conducted on two instrumented pavement sections in Manitoba, Canada. Tire pressure control systems tests were carried out at the sections in spring and fall 2009. Measured maximum tensile strain at the bottom of asphalt layer decreased by 15-20% when tire pressure was reduced by 50%. Measured strain at the bottom of asphalt layer in fall is about 50% less than in spring. The effects of gauge orientation, truck speed, and tire offset from the strain gauge were also analyzed. A finite element model with static load was developed and verified. The bearing capacity is lower in spring than in normal condition for flexible pavements subject to deep frost action. Reduced tire pressure is effective to reduce bottom up failure of the pavement, and is less effective to prevent rutting.

Eskom is currently facing an energy crisis due to the limited operational electricity generating capacity in South Africa. The historically low electricity price, the rapid growth in economy and the energy intensive nature of South African industries are the most common reasons for the peak supply problem. Various supply and demand technologies have been identified to address this energy crisis. Due to the lengthy process of building new peaking load power stations, Eskom has initiated the Demand-side Management (DSM) programme as a solution to the short-term supply problem. The National Energy Regulator (NER) has set targets to Eskom DSM to reduce the evening peak demand by 153 MW per annum and 4 255 MW over a 20-year planning horizon. Due to the energy intensive nature of the mining industry, it has been targeted for DSM savings. To date there have been a number of DSM projects implemented on the clear-water pumping systems of various mines, with a large potential for DSM savings identified on future projects still unrealised. The generation benefit of DSM load-shifting projects is twofold; firstly Eskom's evening load capacity increases due to the reduction in demand during these periods and secondly, the mine receives electricity cost savings due to load management practices. Because Eskom DSM is dependent on the client consumer to accept and roll-out the DSM programme, client satisfaction is of paramount importance. Due to the fact that load-shifting efforts require from the mine to change their normal operating schedules, there is uncertainty on the impact and knock-on effects of DSM projects on a mine. Therefore, the purpose of this study is to investigate and thereafter quantify the overall impact of DSM load-shifting on the clear-water pumping system of South African mines. A generic model was developed by performing case studies on existing DSM projects. This model was then applied to future DSM projects to validate the findings made throughout the research study. The case studies performed on existing DSM projects, as well as the results obtained when modelling the overall impact of DSM on future mines, proofs that DSM definitely benefits a mine. The total annual cost saving on the four future DSM projects is predicted to be in the order of R 7.64 million instead of the R 4.27 million when considering only the electricity cost savings to the mine. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.

The purpose of this dissertation is to identify the best alternative method of load shifting on clear water pumping systems in the mining industry. This can be done through a comparison analysis between manual and automated Demand Side Management (DSM) projects. The study holds benefits for Eskom and any client wishing to participate in the program. Eskom, by choosing the best method, will ensure sustainable load shifting while the client benefits financially through lower electricity costs. In order to perform this study, research was conducted on the requirements for additional electricity supply in South Africa. Research showed that there is an urgent requirement for additional electricity supply to ensure continued economical growth. DSM was identified as one of the most favourable methods that could be implemented to address the problem. A reason for this is DSM projects are economically viable and can be implemented in a relatively short time. The initiative would also decrease the need for increasing electrical generation capacity. During the research study important information regarding the computation process for load shifting and cost saving performance was gathered. Research was also conducted on the effect of DSM on labour and maintenance cost reduction, as well as economical engineering methods that can be used for alternative selection. The difference in performance between automated and manual systems was compared. The results showed that a 40% improvement of automated systems over manual systems were attainable and sustainable. This will realise a total saving of approximately 45% in electricity costs for the client. Savings in labour and maintenance costs are shown to be achievable through the automation of pumping systems. These saving results were used in the Engineering Economic alternative selection methods where applicable. Economic calculations confirmed that automated projects are the most viable control method. From the comparison study, it is shown that automated controlled systems are more advantageous than manually controlled systems. It will therefore be in the best interest of the client to automate a manually controlled pumping system, as it will result in additional load shifting and cost saving. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2009.

South Africa's national power utility, Eskom, initiated a Demand Side Management (DSM) drive to help alleviate the electricity supply shortage experienced in South Africa. The focus of this study is on a load-shifting intervention applied in the mining environment. Load shifting is an appealing way of reducing peak demand. The mining sector is one of the largest consumers of electricity in South Africa. The application of DSM in this sector has the potential of yielding significant electrical load shifting. Firstly, this helps Eskom because they are struggling to keep up their supply. Secondly, the mines also benefit because electrical load is shifted to less expensive off-peak times. Electricity cost as a percentage of the total cost of mining output is bound to increase considerably the next few years. An investigation was conducted into the potential ofperforming load shifting on complex underground rock winders the mining sector. This involved a thorough study on existing load-shifting applications on rock winder systems. Simulations were performed on rock winder systems in their different configurations at deep-level gold mines. The simulation results indicated that there was potential for the application ofload shifting. Tau Tona was selected as a case study. This decision was based on simulations to establish which of the initially identified mines would be the best candidate for load shifting. Tau Tona has a complex underground rock winder system. Multiple rock winders feeding each other are used in a cascaded configuration. A potential load shifting target of 3' MW in the evening peak period was determined by means of simulation. The rock winder system was sequentially automated. An average evening peak demand load shift of 1 MW (or 4,2 MWh) was achieved. This translates to an average annual cost saving of R 240 000. If the load-shifting target of 3 MW could be obtained, the annual cost savings would increase by 30% to R 343 000. A study was also conducted on the feasibility of implementing maximum demand monitoring and control. Rock winders could be used in future to prevent the mines from exceeding their maximum demand. This is because rock winders consume very large amounts of electricity and can be stopped and restarted very quickly. Huge financial obligations can be prevented by making sure that the mines do not exceed their negotiated maximum demand. The necessary - and costly infrastructure to do this could not be procured during this study. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2010.

No description available.

The function of skeletal adaptation to mechanical load is to adjust the amount and distribution of bone tissue (geometry); such that stresses experienced within the bone are kept within certain physiological limits and fractures are prevented. Genetic, environmental or hormonal factors may cause heterogeneity in this adaptive response, altering geometry and consequently fragility. The purpose of this thesis was to explore the skeletal response to load in vivo, by evaluating stress at the hip under three different conditions: FRACTURE (Study 1), DIABETES (Study 2) and ESTROGEN deficiency (STUDY 3). We studied women 25 years of age or older who participated in the Canadian Multicentre Osteoporosis Study and had available Hip Structure Analysis (HSA) data from baseline dual energy x-ray absorptiometry (DXA) scans. Women were categorized according to fracture status (fracture or no fracture), diabetes status (diabetes or no diabetes) and estrogen use (current users or never users). We computed stress (megapascals=MPa) at the infero-medial margin of the femoral neck in a one-legged iii stance using a 2-D engineering beam analysis. We used linear regression to determine associations between femoral neck stress and each categorical variable. Study 1 (n=2168) demonstrated higher stresses in postmenopausal women with fractures compared to women without fractures (10.57 ± 2.19 vs. 10.30 ± 2.03 MPa; p=0.0031). Study 2 (n=3665) demonstrated higher stresses in women with Type 2 Diabetes Mellitus compared to non-diabetic women (10.98 ± 2.33 vs. 10.57 ± 2.20 MPa; p=0.0194). Study 3 (n=2447) demonstrated higher stresses in postmenopausal women not on estrogen than in premenopausal women (10.66 ± 2.14 vs. 10.09 ± 2.01 MPa; p<0.0001), but no differences in stresses between postmenopausal women on estrogen and premenopausal women (10.16 ± 2.00 vs. 10.09 ± 2.01 MPa; p=0.6102). Since stress is an indicator of underlying geometry, and geometry should be adapted to prevalent loads, higher stress indicates weaker geometry and suggests an impaired modeling response in these three conditions. Compromised modeling has important clinical implications in terms of treatment selection, as individuals with reduced load sensitivity may respond best to metabolic agents that would improve modeling responses to load stimuli.

Experimental research was conducted to investigate the influence of axial load and prestress on the shear strength of web-shear critical reinforced concrete elements. The ability of two design codes, the ACI code and the CSA code, to accurately predict the shear strength of web-shear critical reinforced concrete elements was investigated through two sets of experiments performed for this thesis, the panel tests and the beam tests. The experimental results indicated that the CSA code provided better predictions for the shear strength of web-shear critical reinforced concrete members subjected to combined axial force and shear force than the ACI code. A total of six panels, reinforced almost identically, were tested under different combinations of uni-axial stress and shear stress. In addition to the panel tests, a total of eleven I-shaped beams, with the same web thickness, were tested under different combinations of axial force and shear force. The parameters for these beams were the amount of longitudinal reinforcement, the amount of transverse reinforcement, and the thickness of the flanges. The beams were simply supported, but the loading geometry was specially designed to simulate the loading conditions in continuous beams near points of inflection. The experimental results from the panel tests and the beam tests followed a similar trend of variations. Both the inclined cracking strength and the ultimate shear strength were increased by compression and were reduced by tension. The specimens subjected to very high compression failed explosively without developing many cracks. The inclined cracking strength could be predicted with good accuracy if the influence of the co-existing compression on the cracking strength of the concrete and the non-uniform distribution of the stresses over the depth of the cross-section were considered. The strength predictions using the ACI code for these tests were neither accurate nor consistent. The ACI code was unconservative for members subjected to compression and was excessively conservative for members subjected to tension. In contrast, the strength predictions using the CSA code for these tests were generally conservative and consistent. The CSA code accurately predicted the response of specimens subjected to compression and was somewhat conservative in predicting the shear strength of specimens subjected to tension.

The function of skeletal adaptation to mechanical load is to adjust the amount and distribution of bone tissue (geometry); such that stresses experienced within the bone are kept within certain physiological limits and fractures are prevented. Genetic, environmental or hormonal factors may cause heterogeneity in this adaptive response, altering geometry and consequently fragility. The purpose of this thesis was to explore the skeletal response to load in vivo, by evaluating stress at the hip under three different conditions: FRACTURE (Study 1), DIABETES (Study 2) and ESTROGEN deficiency (STUDY 3). We studied women 25 years of age or older who participated in the Canadian Multicentre Osteoporosis Study and had available Hip Structure Analysis (HSA) data from baseline dual energy x-ray absorptiometry (DXA) scans. Women were categorized according to fracture status (fracture or no fracture), diabetes status (diabetes or no diabetes) and estrogen use (current users or never users). We computed stress (megapascals=MPa) at the infero-medial margin of the femoral neck in a one-legged iii stance using a 2-D engineering beam analysis. We used linear regression to determine associations between femoral neck stress and each categorical variable. Study 1 (n=2168) demonstrated higher stresses in postmenopausal women with fractures compared to women without fractures (10.57 ± 2.19 vs. 10.30 ± 2.03 MPa; p=0.0031). Study 2 (n=3665) demonstrated higher stresses in women with Type 2 Diabetes Mellitus compared to non-diabetic women (10.98 ± 2.33 vs. 10.57 ± 2.20 MPa; p=0.0194). Study 3 (n=2447) demonstrated higher stresses in postmenopausal women not on estrogen than in premenopausal women (10.66 ± 2.14 vs. 10.09 ± 2.01 MPa; p<0.0001), but no differences in stresses between postmenopausal women on estrogen and premenopausal women (10.16 ± 2.00 vs. 10.09 ± 2.01 MPa; p=0.6102). Since stress is an indicator of underlying geometry, and geometry should be adapted to prevalent loads, higher stress indicates weaker geometry and suggests an impaired modeling response in these three conditions. Compromised modeling has important clinical implications in terms of treatment selection, as individuals with reduced load sensitivity may respond best to metabolic agents that would improve modeling responses to load stimuli.

Bridge scour is the loss of soil by erosion due to water flowing around bridge supports. Scour has been the number one cause of bridge collapse in the United States with an average rate of 22 bridges collapsing each year. This dissertation addresses three topics related to bridge scour. First, three sets of databases are used to quantify the statistical parameters associated with the scatter between the predicted and measured scour depth as well as the probability that a deterministically predicted scour depth will be exceeded. The analysis results from these databases will also be used to provide the bias factors in the scour depth predictions in practice. In the second part of the dissertation, these statistical parameters are used to develop a reliability-based Load and Resistance Factor Design (LRFD) for shallow and deep foundations subjected to scour. The goal is to provide a design procedure for the bridge foundations, where the reliability of the foundation is the same with or without scour. For shallow foundations, the key of the design issue is the location of the foundation depth and the probability that the scour depth will exceed the foundation depth. Therefore, for shallow foundations, the proposed LRFD calibration is based on the probability of exceedance of the predicted scour depth. However for deep foundations, the key of the design issue is the resistance factor associated with the axial capacity of a pile. Hence, the proposed LRFD calibration for deep foundations is based on a reliability analysis using First-Order Reliability Method (FORM). The dissertation is broadened in the third part by analyzing he risk associated with bridge scour, where the risk is defined as the probability of failure times the value of the consequences. In the third part, the risk associated with bridge scour is compared to risks associated with other engineering structures as well. Target values of acceptable risk are recommended as part of the conclusions. The outcome of the research will modify the current “AASHTO LRFD Bridge Design Specifications” developed by the American Association of State Highway and Transportation Officials (AASHTO) and help the practitioners design foundations of bridges over rivers for a uniform probability of failure in the case of scour. The risk of bridge scour is also quantified in the dissertation, and compared with common societal risks and civil engineering risks. It will help engineers understand the risk level associated with bridge scour.