With the ever increasing need for MSE walls, the study of the interaction between soil and geosynthetics has become increasingly relevant. New concepts are constantly being researched, including the use of industrial byproducts as alternative backfill materials. The idea that byproduct material could somehow be a suitable fill for these MSE walls may spark new opportunities. One such byproduct being researched is dredged material. The suitability of dredged material as a backfill would not only contribute to lower construction costs, but would also benefit local confined disposal facilities looking to reduce their already overflowing dredged material accumulation. This thesis further considers the use of dredged material by evaluating its interface shear strength with uniaxial geogrids. A series of laboratory pullout tests were conducted using two types of uniaxial geogrids (UX1400 and UX1700) embedded in three different soil types (Monterey Sand and two different dredged materials). The laboratory results are used to examine the effect on the coefficient of interaction of the various parameters governing the pullout resistance. The results of this study show that: (1) the presence of adhesion to characterize the soil-reinforcement interface shear strength causes a decrease in the coefficient of interaction with increasing normal stress, (2) the reinforcement length of the geogrid was found not to affect the coefficient of interaction; provided that boundary effects are minimized, (3) the dredged material, tested wet of optimum, showed a response consistent with an undrained behavior, which produced pullout resistances significantly lower than that of the Monterey Sand, (4) the coefficient of interaction for the UX1700 was comparatively higher than that for the UX1400; however the differences obtained when testing Monterey Sand were similar to those obtained when testing the dredged materials. / text

A hybrid material design has been developed to improve creep performance in pressurized metallic pipes subjected to high temperatures. Metallic pipes were reinforced with various arrangements of external wires which have substantially greater creep resistance than the pipe material. This research was conducted to explore the field of reinforcement of piping for creep reduction, exploit the creep strength of refractory metals, and investigate structure-property relationships in architectured materials. Two basic wire reinforcement architectures were tested, simple helical windings and braided sleeves. By adjusting the architecture of the reinforcement, apparent tangential (hoop) and longitudinal stresses on the pipe are altered, thereby allowing multiaxial creep strains to be controlled. The utilization of a reinforcement layer in a hybrid layup, where it is not bonded or embedded in a matrix is a relatively unexplored field. Hybridization allows the most desirable properties to be extracted from each component and have them work together in parallel. The use of braided refractory reinforcement is also a particularly novel concept, with refractory materials for reinforcement purposes traditionally being utilized in particle, whisker and discontinuous fibre form. Rather than testing in a uniaxial stress state, the present approach to creep testing pressurized pipes at high temperature remains largely underutilized, and is especially relevant to industry applications where creep takes place in the complex, multiaxial stress state of a pressurized pipe. In a low-temperature reinforcement architecture optimization study of a brass-stainless steel system, designed for ease of fabrication and to negate oxidation issues, pipes were pressurized and creep rupture tested at 400°C. Even in an unoptimized state, braided reinforcement was observed to out-perform a simple iv helical wrap by at least 22%, giving a 10-times life extension without rupture, and a reduction in creep rate in excess of 45-times for reinforcement oriented at a 50°. A simple analytical model from reinforced pressure vessel theory predicts a neutral angle (θN) of 54.7°, at which point the reinforcement is oriented to act proportionally to the applied pressure stresses. An empirical model of effective creep rate with varying reinforcement angle was derived in the present study, and used to find that a braid angle of approximately 54.7±1.5° is optimal to minimize the effective multiaxial creep rate of a hybrid pipe under internal pressure, reducing it to the point of being negligible. The braided reinforcement was observed to be constantly shifting towards the equilibrium point of θN, but only for initial angles below θN. This concept of braid reorientation is generally associated with rapid elastic deformation or static reinforcement of systems at room temperature, and the gradual shift towards θN facilitated by creep deformation has not been reported previously. A relationship for -θ (i.e. creep rate for a given reinforcement angle) was derived, including the reduction in as θ tends to θN. Findings of this optimization study were applied to a high temperature system which served as an acceleration of reformer furnace operating conditions: 253MA pipes were reinforced with tungsten wire and creep rupture tested at 1030-1040°C. Using braided reinforcement oriented at 52.6±1.4° a life extension in excess of 700x was observed, with no signs of bulk deformation after a 309x life extension. These high temperature results were considered in light of the intended industry application, with a balance of life extension, weight reduction and increased operating temperature preferred over outright life extension for the reformer furnace application.

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Glass Fibre Reinforced Polymer (GFRP) bars have been developed as an alternative to steel reinforcement for various structural concrete applications. Due to their non-corrossive nature, they are particularly suited for harsh environments where steel reinforcement is prone to corrosion. The purpose of this research is to determine the feasibility of GFRP reinforcing bars as concrete bridge deck reinforcement for locations, such as coastal New Zealand, where the non-corrosive benefits of GFRP may offer an alternative to traditional mild steel reinforcement. GFRP use as structural reinforcement may offer life-cycle cost benefits for certain structures as maintenance to repair corroded reinforcement is not necessary. The use of GFRP reinforcement in a New Zealand design context was investigated to directly compare the structural performance of this alternative reinforcing product. Mateen-bar, manufactured by Pultron Composites Ltd, is the GFRP reinforcing bar used in the experimental tests. Experimental investigation of tensile properties of GFRP bar samples was carried out to understand the mechanical behaviour of GFRP reinforcement and validate the manufacturer’s specifications. This series of tests highlighted the complexities of carrying out tensile testing of FRP products, due to the inability to grip the GFRP directly in a testing machine without crushing the specimen. Two phases of full-scale tests were carried out to compare the performance of bridge deck slabs reinforced with typical mild steel and GFRP reinforcing bar. This experimental testing was different to most existing research on GFRP reinforced slab performance as it did not compare the performance of a GFRP reinforcing bar area equivalent to steel, but was designed in such a way as to dependably give the same moment capacity of the steel reinforced slab design. This incorporated the recommended limit of 20% of design stress given by the manufacturer which led to an apparent over-reinforced section for the GFRP slab design. The aim of the experiments was to investigate the comparative performance of a typical New Zealand bridge deck design and a GFRP reinforced equivalent designed in such a way as is currently recommended by the manufacturer. The over-reinforcement lead to differences in conclusions drawn by other authors who have studied GFRP reinforced slab behaviour. Both flexural and concentrated loading (simulating vehicle loading) tests were carried out on both the steel and GFRP reinforced slab designs. Due to over-reinforcement the GFRP slab was considerably stiffer and stronger than the steel design, indicating that serviceability issues are unlikely to be as much of a design issue as existing literature would suggest. Deflection prediction models generally underestimate the strength of over-reinforced sections. All slabs failed in punching shear under concentrated loads, indicating that punching shear may be a critical failure mechanism for GFRP reinforced slabs Based on the findings from the extensive experimental phases, a set of design recommendations were made to further improve the potential for GFRP to be used for bridge deck design in a New Zealand context.

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