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Threaded connectors have been used in a variety of engineering structures for hundreds of years. Although stress analysis of threaded connectors has been performed since the early 1900's, there are still areas that are not fully understood. The way in which eccentricity affects the fatigue performance and stress distribution is one such area, and is the main area of research described in this thesis. The techniques of photoelasticity and fatigue testing were used to determine the effect of eccentricity on the stresses and fatigue performance of bolts. The results show that eccentric loading has a significant effect on the fatigue performance, but that this effect can be quantified if the local stress amplitude is considered. The photoelastic analysis results show the eccentricity slightly increases the stress intensity factors at the crack tip. A number of two-dimensional and three-dimensional finite element models were created to detennine the salient characteristics of the models. The models were validated against the resuh from the photoelastic analysis and the results agreed well. Accurate results can be obtained from a two-dimensional model, but the information obtained is limited unless many models are created. However, if a three-dimensional model is created more information can be obtained, but the nut thread run-out must be accurately modelled to obtain the correct stress distribution. The shape of cracks occurring in cyclically loaded steel bolts and the effect of crack shape on the stress distribution was also investigated. The photoelastic analysis of cracked bolts failed to predict the shapes of cracks occurring in cyclically loaded bolts. It is suggested that the inability of photoelasticity to model plasticity is the cause of this failure and this is supported by results from an elastic-plastic finite element model.

The use of dough moulding compound (DMC) as a structura~ material will be feasible as more information on mechanlcal properties becomes available. In this investigation, room temperature tensile and fatigue properties were determined prior to the testing and evaluation of simple joints in DMC. The DMC was supplied in the form of compression moulded sheets. Tensile tests were conducted to British Standards specification to obtain the mechanical properties and to identify possible sources of variability in properties. Differences in tensile strength due to sheet-to-sheet variability and specimen orientation within a sheet were significant but there was no significant variation due to the cross-head speed over the range O.05mm/min to 300mm/min. Tensile fatigue tests were conducted to British Standards specification. The scatter of fatigue lives was found to be greater than that for other reinforced plastics, but was adequately described by both the Log-Normal and Weibull distributions. In tensile and fatigue tests on larger specimens there was no size effect on tensile strength, but the fatigue strength at a given life and probability of failure was reduced ,slightly. When specimens contained bolt holes, the tensile strength decreased marginally, but the fatigue strength was not affected. Transverse compressive stresses due to a bolt load had little effect on the fatigue behaviour and changes in the cyclic-or static stress did not significantly alter the bolt load relaxation. Cyclic stress was found to cause greater bolt load relaxation than the corresponding mean stress. In tensile and fatigue tests on single shear lap joints, benditig wa~ the main cause of failure and the joint efficiency was low, 43% in tension and 51% in fatigue. By loading the specimens through the bolts at one end, bending was eliminated and the joint efficiency increased to 62% in tension and to 78% in fatigue

Recently, the use of Mechanically Fastened Fiber-Reinforced Polymer (MF-FRP) systems has emerged as a viable means for flexural strengthening of reinforced concrete members. The technique is suitable for emergency repairs where constructability and speed of installation are critical requirements. The MF-FRP system consists of pre-cured FRP laminates with enhanced longitudinal bearing strength that are attached to the concrete substrate by means of mechanical steel anchors. This research project presents an experimental investigation comprising a series of flexural tests on scaled one-way RC slabs. The test matrix includes MF-FRP strengthened specimens, a counterpart with the externally bonded (EB) FRP reinforcement, and a control specimen. The effects of fastener layout and laminate length on strength increase and failure mode were studied. It is shown that with proper selection of fastener layout the MF-FRP system results in a significant deformability and strength increase, where the latter is comparable to that attained using EB-FRP sheets. Specific gaps on the existing analytical procedures for flexural strengthening with MF-FRP systems are finally discussed.

Selection of steels for industrial purposes usually means choosing a type of steel to make a part or a product. The steel that is chosen must meet all the designer requirements. A quantitative selection procedure has been used to analyze the large amount of data involved in this selection process so that a complete and systematic evaluation can be made. The designer is responsible for the selection of steel, and this selection requires the designer to find data and information on the mechanical properties required, and also learns ways to improve these properties through different heat treatment processes. When a large number of steels and a large number of specified mechanical properties are being evaluated for selection, the weighed properties method can require a large number of tedious and time-consuming calculations. In such cases a computer program could greatly facilitate the selection process. This thesis reports the selection of steels for gears, shafts, fasteners and springs where the steps involved in the weighted properties method which is written in the form of a simple computer program to select steels from a data bank. This program also includes the digital logic method to help in determining weighing factors. The steels are ranked according to standard designation; BS, AISI, and DIN. It has been found that alloyed steels hardened and tempered at 2050C are most suitable for gears, shafts, fasteners, and springs when higher mechanical properties required, and carbon and low alloyed steels when cost is the main consideration.