This PhD concerns laboratory wavemaking in shallow and intermediate water conditions. Theoretical solutions and experimental evidence are presented to advance both our understanding of the wave generation process as well as its practical success. A comparison is made between two wave generation techniques, a first based on controlling the wavemaker displacement, and a second based on controlling the wavemaker force. In deep water, a force-based approach, which includes active wave absorption, was recently shown to offer benefits in terms of wave quality. To investigate the influence of the water depth on this type of control, a range of generation scenarios is considered, including regular, bi-chromatic, focused and random waves. The work demonstrates that force-based wave generation in shallow water suffers from similar limitations as position control. This principally concerns the contamination of the testing area due to unwanted free waves, where the present focus is placed on the superharmonic range. The main advance of the work lies in the solutions it offers to overcome this free wave contamination. The nature of the nonlinear wave solution upon which force-based generation should be based depends on the type of wave case (regular, bi-chromatic, focused or random). For each of these cases, a suitable methodology is proposed and validated. The developed methodology allows for high quality wave generation, whilst maintaining the benefit of active wave absorption. The work is timely in the sense that is responds to two recent developments. First, the majority of wavemaking facilities are now computer controlled, and active absorption has become commonplace. The work presented offers solutions highly relevant to such installations. Second, developments particularly in offshore wind, have seen many new structures placed in relatively shallow-water depth. It is essential that the model testing of such structures adequately accounts for the issues and solutions presented herein.

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The reliability of bond is crucial to the performance of concrete structures strengthened with externally mounted carbon fibre reinforced polymer (CFRP) plate. This thesis investigates the behaviour of the bond interface of reinforced concrete slabs strengthened with CFRP under cyclic loading using both numerical modelling and experimental methods. The main goals of this research are:(1) To experimentally investigate the static and fatigue behaviour of the interfacial bond between CFRP plate and the concrete substrate in single shear pull-out.(2) To develop reliable numerical simulations in order to understand the post-fatigue nonlinear behaviour of the adhesive interface for CFRP –concrete bonded joints.(3) Using three dimensional finite element models, explore the nonlinear behaviour of an adhesive layer connecting CFRP to reinforced concrete one-way slabs with different levels of CFRP and different span scenarios under cyclic loading.(4) Through both experimental and numerical modelling, explore the influence of load protocol (i.e. monotonic and modified cyclic load protocol recommended by FEMA 461) on the bond performance of the two-way RC slabs with openings strengthened with CFRP plates. To achieve the above goals, both experimental tests and numerical analysis were conducted. In the experimental program, 28 single shear pull out tests were conducted with variations in CFRP plate stiffness, concrete compressive strength and loading hysteresis (static (monotonic), fatigue and fatigue following static). In all specimens, the CFRP plate was 500 mm in length and 50 mm in width. The bonded length was 300 mm. The plain concrete substrate had dimensions of 150 x 200 x 500 mm. From the tests, three failure modes were observed: (a) bond failure in the interface between the concrete and the adhesive layer, (b) CFRP composite plate rupture and (c) concrete shearing beneath the adhesive layer. The experimental16results indicate that when considering post-fatigue loading regimes, the strain required to cause debonding of the CFRP and the ultimate load capacity of the strengthening system is reduced by the previous cyclic loading. Based on the results from these tests, a relationship between the CFRP plate stiffness with the ultimate bond strength reduction and the fracture energy degradation is deduced. Further to the pull-out tests, 2 two-way RC slabs with central openings strengthened with CFRP plates were tested under cyclic loading. Results are presented in terms of deflection, ultimate load capacity, crack patterns, strains and failure mode. A detailed three Dimensional Finite Element (3D FE) model was developed using ABAQUS /standard 6.10-1and was validated against the test results for both monotonic and post-fatigue behaviour. The FE model accounted for the nonlinearity of the concrete under cyclic loading by estimating the stiffness degradation in the concrete for both compression and tension effects. The Bauschinger effect for steel reinforcement was incorporated through the application of the kinematic hardening model under cyclic loading. The ultimate bond strength reductions and fraction energy degradations deduced from the cyclic loading history of single shear tests were used as input for the interaction properties between the CFRP and the concrete slab. Using this model, a comprehensive study of the effect of variations in the bonded CFRP plate length, concrete strength and bond width ratio was conducted. The extensive numerical results have been used to assess the commonly used analytical model proposed by (Chen and Teng, 2001) and the provisions in existing design codes. The parametric study results show that the tensile strain limit is highly overestimated in both ACI and fib-1design codes and it is underestimated for the fib-2 and the CNR- DT202 codes. In contrast, the tensile strain limit proposed by TR55 and JSCE is generally acceptable; however, it is non-conservative with high CFRP plate stiffness. The simulation results have been used to develop an alternative analytical method to calculate the debonding strain and affective length for CFRP plate bond to concrete and subject to single shear. The developed numerical model was further validated by comparison against the experimental results of the two-way RC slabs strengthened with CFRP plate.

Fibre reinforced polymer (FRP) structures have been increasingly applied in construction, including in road bridges due to their advantages of lightweight, high specific strength and corrosion resistance. However, the brittle nature of FRPs leads to the need for ductile joints to improve the safety of FRP structures. To that end, Glass FRP rebar-reinforced Polymer Concrete (GFRP-RPC) joints between cellular GFRP deck units, combined with an adequate external energy dissipation device (that functions as a replaceable fuse), may fulfil this need for such decks. This PhD study focuses on the load responses of GFRP-RPC joints between cellular GFRP deck units by full-scale anchorage and joint tests, along with simplified methods for predicting the failure loads of the joints. From these studies it is concluded that the GFRP-RPC joints failed by moment-induced rebar-to-polymer concrete anchorage failure. The joints were of high efficiency and shear-strength, and exhibited impressive recovery ability after unloading from large deflections after failure. Further, friction between the polymer concrete confined within the cells of the GFRP decking and the GFRP rebars can contribute to energy dissipation during load cycling. Using rebar-to-polymer concrete shear bond stresses deduced from anchorage testing, it is shown that anchorage failure can be monitored by the third of three phases of behaviour observed during testing. Simplified methods for predicting shear and bending moment capacities of GFRP-RPC joints generally showed good correspondence to experimental data. Future work can focus on cumulative residual shear bond stresses and irreversible slip observed in the anchorage tests, and also on shear failure behaviours of GFRP-RPC joints. Further, a half plastic hinge (HPH) joint (GFRP-RPC joint combined with an adequate external energy dissipation device) between FRP components has been under development by the author. It is expected that "a ductile FRP structure" can be achieved via these HPH joints.

The soil response under cyclic loading conditions is of interest for a number of geotechnical structure such as road pavements, tank foundations and offshore structures. When a geotechnical structure is subjected to cyclic loading, permanent settlements and rotations are accumulated affecting the serviceability of the structure. In the last years, a number of modelling strategies have been proposed to quantify the strain accumulation of soils under cyclic loading; however, most of the models are valid only for limited loading and drainage conditions, and they generally employ complex constitutive formulations. In this thesis, a new constitutive model, the Memory Surface Hardening model, which accounts for the effects of cyclic loading on the soil response, is proposed. The primary aim of this research is to develop a simple set of equations which can accurately predict the cyclic mechanical response of granular soils under generalised loading and density conditions. The modelling strategy is developed in an existing critical state - bounding surface - state parameter - elasto-plastic framework. A new surface, the memory surface, is introduced to track the experienced stress history. In the experiments available in the literature, it is observed that the soil response is highly affected by the experienced loading states. The memory surface evolution responds to two rules: the yield surface is always enclosed by the memory surface; the memory surface expands or contracts following the experienced plastic strains. The last rule is the key to reproduce the typical features observed experimentally for granular soils subjected to cyclic loading. Whenever the soil experiences contractive volumetric strains, the memory surface expands; on the contrary, when the soil experiences dilative plastic volumetric strains, the memory surface contracts. The plastic soil stiffness is affected by the size of the memory surface. The evolution of the memory surface can be interpreted as a representation of the evolution of the soil fabric when the soil is subjected to cyclic loading conditions. The model is developed by maintaining the same hardening rules for any loading conditions, minimising the number of implemented rules and employing a limited number of constitutive parameters. The model is proposed for both the triaxial and the multiaxial stress space. The model has been validated for different types of granular soils under different loading conditions, drained and undrained conditions. The evolution of model surfaces for different loading conditions is presented in the simulations and the occurring mechanisms are widely described.

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