The ability of bones to concentrate material where the body needs most of its strength and the ability of trees to spread roots in search of moisture rich locations are only a few amongst the many examples of nature’s way of building adaptive “structures”. Even though civil engineering structures often appear inefficient, static and cumbersome, a new era of structural design aims to alter the status quo by mimicking nature’s way. This suggested adaptation process in civil structures often takes the form of passive, active and semi- active control. Through direct comparison of these methods, semi-active control is shown to combine the benefits of both active and passive systems and can be arguably considered the next step in improving dynamic structural performance; however the applicability of this exciting and novel for the structural engineering field technology, is not all-embracing. In order to enhance the development of this promising technology and contribute on the creation of a new era of “smart & thinking” structures that encompass an unconventional form of performance based design, this study aimed to develop enabling technologies and tools that enhance the selling strengths of semi-active and smart control using tuned-mass dampers. The original contributions to knowledge in this work are divided in three aspects. Firstly, the investigation of the influence of control algorithms on smart tuned-mass damper equipped high-rise structures, for which practical limitations have been taken into account. Leading to conclusion on the conditions for which each algorithm exhibits superior performance over the other. Secondly, the development of a fail-safe novel semi-active hybrid device configuration that enables performance gains similar to the active mass damper at considerably lower actuation and power demands. Finally, the development of a simple and robust at all gains control algorithm based on the modification of one of the most widely used controller in the engineering industry, namely the proportional-integral-derivative controller.

Flooding is a serious natural disaster in urban areas. Moreover, the consequences of land use change and rainfall can affect the flood process in urbanised catchments. Fluvial flooding can be seen at downstream locations due to the high and fast discharge from sub-catchments. In addition, pluvial flooding can be seen at settlements are situated on the floodplains by river channel at downstream locations, due to the impermeable surfaces and insufficient drainage capacity. Therefore, the combined pluvial and fluvial flooding can be observed on the floodplains of urban stream basins. Although, flood risk can be severe for these places, research on combined fluvial and pluvial flooding is very rare. One of these places is Wortley Beck catchment, Leeds, UK. To observe the interaction between fluvial and pluvial flooding, the floods were modelled for different land-use scenarios and rainfall events for an urbanised and ungauged catchment. The inflow hydrographs and rainfall hyetograph were designed by using the ReFH rainfall-runoff method. 1D and 2D hydrodynamic models were used to simulate fluvial and pluvial flooding. The outcomes were peak flow values and probabilistic inundation maps with maximum water depth values. The peak flow values were used to investigate the relationship of return period between rainfall and flow by using the FEH statistical model. The effects of the land use change and rainfall on the flood risk were observed from the maps. In addition, the flood extent of combined pluvial and fluvial flooding was observed from these maps. Water depth values in the inundation area by combined flooding were computed. Hence, fluvial flooding in combination with pluvial flooding was observed to have a higher flood risk in the urban stream basins. These outcomes can be used to manage flood risk due to land use change in the future for ungauged catchments by National and Local Governments.

Discrete Element Method (DEM) and Smoothed Particles Hydrodynamics (SPH) are integrated to investigate the macroscopic dynamics of fluid-solid interaction (FSI) problems. This coupled model is originated from two different meshless methods without mesh generation, which can handle fluid-particle-structure interactions with structural deformation/failure. With SPH the fluid phase is represented by a set of SPH particle elements moving in accordance with the Navier-Stokes equations. The solid phase consists of single or multiple solid particle(s) phase and deformable structure(s) phase which are represented by DEM particle elements using a linear contact model and a linear parallel contact model to account for the interaction between particle elements, respectively. To couple the fluid phase and solid particle phase, a local volume fraction and a weighted average algorithm are proposed to reformulate the governing equations and the interaction forces. The structure phase is coupled with the fluid phase by incorporating the structure’s DEM particle elements in SPH algorithm. The interaction forces between the solid particles and the structure phases are computed using the linear contact model in DEM. The proposed model is capable of simulating simultaneously fluid-structure interaction, particleparticle interaction and fluid-particle interaction, with good agreement between complicated hybrid numerical methods and experimental results being achieved. Finally, two engineering problems in injection moulding and 3D printing process are carried out to demonstrate the capability of the integrated particle model for simulating fluid-solid interaction problems with the occurrence of structural failure.

The microbial transformation of Fe (III) to Fe (II) can be coupled to the oxidation and reduction of organic contaminants in sub-oxic to anoxic environments. A multidisciplinary approach was adopted in this study to investigate the biogeochemical influences on the degradation of toluene (a representative of the class of aromatic hydrocarbons collectively known as BTEX) using experimental analogues of subsurface soil environments under predominantly iron-reducing conditions. The removal of toluene over the period of incubation indicated the soil-water mixture supported the degradation of toluene under predominantly iron-reducing conditions. Chemical sequential extractions showed the removal of toluene in the active mesocosms induced an increase in carbonate-bound iron fractions from 196.1 ± 11.4 mg/kg to 5,252.1 ± 291.8 mg/kg and a decrease in the reducible iron fraction from 2,504.4 ± 1,445.9 mg/kg to 375.6 ± 20.8 mg/kg. Analysis of the soil-water mixture showed slight shifts in the pH of the control and active mesocosms at the start of the experiments however these shifts occurred to a lesser degree over the remainder of the incubation period. Further experiments analysed the degree of influence of differing soil matrices and extraneous sources of iron (hematite, goethite, magnetite, ferrihydrite and lepidocrocite) on toluene removal. With the exception of the lepidocrocite-amended mesocosms, all of the iron-amended mesocosms were shown to have supported toluene removal. The presence of hematite, goethite and magnetite did not produce a significant change in the pH or total iron concentrations of the soil-water mixture. However the presence of ferrihydrite in the ferrihydrite-amended mesocosms induced a decrease in pH to slightly acid values ranging between pH 6.5 at the start of the experiments and 5.2 at the end of the experiments. The lepidocrocite-amended mesocosms induced a change to slightly alkaline values ranging between pH 8.4 and 8.8 during the period of incubation. All of the soil-amended mesocosms supported the removal of toluene in the soil-water mixture. The mesocosms containing soils with a greater percentage clay fraction removed higher amounts of toluene, possibly an indication that the bulk of this removal was sorption-induced and not microbially-mediated. An experimental approach based on the standard stable carbon isotope analytical method made it possible to determine the source of carbon in the incubated mesocosm material. The application of the mixed effects model approach to analyse the repeatedly measured experimental data demonstrated the possibility of producing predictive models for toluene removal in soil.

Biofilms in drinking water distribution networks (DWDNs) are recognized as potential pathogen reservoirs. Recent experiments have found that biofilm can also act as precursors for the formation of disinfection by-products (DBPs). This project aimed to better understand the impact of the presence of biofilms and improve prediction of DBPs in DWDNs. To study the microbial significance of biofilms in water pipes, bacterial communities in biofilm and bulk water were identified in a DWDN in a tropical climate country. Drinking water and biofilms were characterised by physico-chemical parameters. Relationships between biotic, physico-chemical parameters and engineered factors (i.e., pipe age, material and diameter; and water age) were explored by the application of statistical tests. Additionally, improvement of DBP prediction in DWDNs was approached by modelling the role of biofilms as DBP precursors. Two models for predicting DBP formation potentials were developed from chlorination of cells and extracellular polymeric substances. The first model corresponded to stagnant conditions and a second more complex model was produced for transitional and turbulent flow. The models were implemented in the software COMSOL Multiphysics 5.2a and sensitivity analysis was carried out to screen the parameters influence on the response variables. Field-work assessment allowed determining that biofilms are richer habitats than bulk water. Pipe age, pipe material, water age, free chlorine, pH and temperature can be key to the composition of bacterial communities. Model simulations suggested that the important DBP exposure is related to dichloroacetronitrile, stagnant bulk, and slow flow. The microbial and chemical significance of biofilms is important in the context of climate change and developing countries because water managers can face multiple challenges under these conditions. Alterations of raw water properties, increasing occurrence of extreme weather events and poor capacity to mitigate such events may rise the chemical and microbiological risk associated to biofilms in DWDNs in tropical countries.

In this work, a robust two-dimensional model is constructed to simulate river erosion and deposition of cohesive and non-cohesive sediment. The numerical model is constructed based on the shallow water equations with sediment-flow interactions that incorporates a sediment transport model including, significantly, the evolution of the bed profile. The governing equations are solved explicitly using finite volume method using a Godunov type approximate Riemann solver. A spatially first order accurate and numerically robust Harten-Lax-van Leer (HLL) solver is utilised to calculate the fluxes at cell faces. A Courant-Friedrichs-Lewy (CFL) type criterion governs temporal stability of the solver. The sediment transport component of the model consists of two different elements: the first, HMD-NC, is constructed to simulate flow over a movable bed with non-cohesive materials; and the second, HMD-C, is constructed to simulate the flow over a movable bed of cohesive materials. The models are tested and validated against experimental and theoretical works from published literature. The results show good agreement with the measurements, demonstrating that the models are both capable of predicting the spatial and temporal changes of the flow and bed change effectively. In a case study is used to demonstrate the cohesive model, HMD-C, which shows the impact of employing different formulations for erosion rates of the channel bed in which significant differences are seen in resulting solutions. An intensive investigation of the model parameters on the numerical result is presented. It is found that the model is particularly sensitive to certain parameters such as erodibility, Manning’s roughness, and the critical shear stress for erosion. While others such as critical shear stress for deposition, bed porosity, and the settling velocity show very low influence on the erosion.

The problem of concrete durability in marine environments remains a major challenge for the construction industry. Chlorides and sulphates from sea water attack both the steel reinforcing bars and the concrete binder respectively. Chloride attack leads to steel corrosion, while sulphate attack leads to the formation of expansive ettringite. These challenges, combined with pressures to reduce CO2 emissions associated with conventional Portland cement production, have encouraged the increasing use of supplementary cementitious materials (SCMs). Ground granulated blast-furnace slag is one of the most widely used SCMs, since it offers the potential for the greatest replacement in cement clinker. However, the effects of chemical composition, temperature, slag loading, curing and exposure conditions, concerning changes to microstructure, mechanical strength and durability performance of slag-blended cements are yet to be fully understood. This situation is worsened in marine environments, by the limited information on the combined attack of concrete by chloride and sulphate. This is important, since these ions co-exist in real marine conditions. The present study combines different experimental techniques to investigate the above stated effects on hydration, microstructure, mechanical and transport properties, including chloride binding, to provide improved understanding to the existing literature. The relationships between hydration, microstructure and durability performance have been highlighted, along with chloride binding. Two slags of different chemical compositions (CaO/SiO2 ratios = 1.05 and 0.94), designated as slags 1 and 2, were each blended with CEM I 52.5R at 30 and 70 wt.% replacements to produce 4 blends. Paste and mortar samples were prepared at a constant w/b ratio of 0.5. Reference samples were prepared at w/c of 0.5 using CEM I 42.5R. The pastes were characterised for chemical and microstructural properties, while mortars were used for investigating mechanical and transport properties. Tests were performed under parallel temperatures of 20 and 38°C to reflect temperate and warm tropical climates. The samples were exposed to combined sodium chloride and sulphate, after curing in water for 7 or 28 days. Hydration kinetics were investigated in paste systems using isothermal conduction calorimetry. Crystalline hydration products and phase assemblages were followed by x-ray diffraction (XRD), complemented with simultaneous thermal analysis (STA), to confirm and quantify the phases formed, including chemically bound water. The degrees of slag and clinker hydration were quantified using scanning electron microscope (SEM), coupled with energy dispersive x-ray (EDX) analysis. SEM-EDX spot analysis was also used to characterise poorly crystalline, calcium silicate hydrate (C-S-H). Microstructural development was followed using SEM backscattered electron (BSE) image analysis. This was also used to quantify the paste porosity, which was then complemented with mercury intrusion porosimetry (MIP). Mechanical properties of mortar samples were investigated using compressive and flexural strengths. Transport properties were investigated using water sorptivity and gas permeability in mortar samples. Chloride penetration profiles and non-steady state diffusivity were investigated in mortar prisms, including free chloride penetration depths, using colorimetric approach. Also, chloride and sulphate penetration profiles were investigated in polished paste samples, using SEM-EDX spot analysis. This included analysis of atomic ratios to identify the phases binding chloride and sulphate, and their intermixing with the C-S-H. Chloride binding with and without the presence of sulphate, were investigated in paste samples. Length and mass change due to sulphate attack were investigated in mortar prisms and cubes respectively. Samples were exposed in combined chloride-sulphate solution by submersion or repeated wetting/drying cycles, for a period of 664 days. The results show a positive influence of elevated temperature for the slag blends, leading to a refined microstructure, improved early age strengths and improved resistance to the transport of fluids, including chloride and sulphate. The presence of the combined salt solution led to increased flexural strength. Transport properties were improved during early stages of exposure to salt solution but worsened over longer periods. The developed multiple regression models reasonably predicted changes in mechanical and transport properties, considering the effects of temperature and slag loading. Length change and mass change reduced significantly at elevated temperature. Also, chloride binding was improved at elevated temperature but decreased in the presence of sulphate. The main phases binding chloride include Friedel’s salt, Kuzel’s salt and C-S-H, while sulphate was bound in ettringite, AFm and C-S-H. Generally, within the period of this study, there was a synergy between chloride and sulphate, as sulphate expansion was reduced, while chloride diffusivity was also reduced at the same time. The greatly improved durability properties of the slag blends at 38°C is significant for their application in warm climates.

Freshly cast concrete undergoes volume changes due to thermal and shrinkage mechanisms which can be restrained both internally and externally. Externally applied restraint can be either end, edge or a combination of the two. Tensile stresses are induced as a consequence of restraint of volume changes which often result in cracking particularly during early age. These are ‘through’ cracks and are of particular concern in liquid retaining structures, nuclear containment chambers, tunnels and basements where besides being aesthetically unpleasant, such cracks can also result in water leakage, ingress / discharge of harmful chemicals and corrosion of steel reinforcement. This calls for development of a clear understanding of the mechanism of cracking and the factors involved in restraint formation so that appropriate mitigation measures at the design and construction stage can be taken. Currently available guidance is based on the end restraint cases and has been evolved from experimental and analytical investigations on axially reinforced prisms. In walls and slabs, reinforcement is present in both longitudinal and transverse directions and the influence of transverse reinforcement on cracking has not been analysed and incorporated in existing guidance. Critical review of previous research revealed that cracking behaviour of members subjected to edge restraint is very different from those under end restraint. Therefore, the need to undertake experimental investigation for determining the influence of major influencing factors like vertical steel dowels and members geometry was realized. This research investigates the restraint of imposed strains in edge restrained members and in particular, experimentally illustrates the influence of vertical steel reinforcement between the restrained (wall) and the restraining (base slab) members on the mechanism of restraint development. The investigation constructed real scale reinforced concrete walls onto reinforced concrete bases and also illustrated why previous studies, which have mostly utilized steel members to restrain the imposed strain, are inappropriate for gaining an understanding of edge restraint as they fail to reflect the heat transfer between the wall and the base. Thickness of the tested walls was also varied in the tests to ascertain the influence of relative geometries of the two members on degree of restraint. Results revealed that the restraint significantly increased in the presence of vertical steel reinforcement. They also showed that restraint increases with time due to the steel reinforcement and decreases in its absence. Moreover, in order to ascertain the significance of the transverse reinforcement, tests on reinforced concrete panels were performed. The panels were subjected to direct tension and the results indicate that when transverse reinforcement was present, the cracking load for the tested specimens decreased by 25 – 30 %, whereas the crack widths and number of cracks increased. Due to paucity of time and the resources involved in experimental investigation, finite element analysis has been utilized to study the behaviour of walls subjected to combination of end and edge restraint. Parametric study was carried out to investigate the influence of combined restraint on the number and size of cracks and crack widths. By investigating walls of different aspect ratios, the domination of end restraint in higher parts of the walls having lower aspect ratios was found. Through finite element analysis the significance of correctly incorporating the real time boundary conditions of the restraining base slab was also identified.

Sewage sludge management is one of the biggest concerns to the wastewater industry due to the increasing volumes produced and new stringent environmental regulations. Hydrothermal Treatments (HT) are a good option for converting wet biomass such as sewage sludge into high value products. However, HT are still not well developed when compared with other waste processing treatments. One of the most promising areas for developing hydrothermal processing applications is in sewage sludge treatment facilities. Sewage sludge has been identified as a potential feedstock for hydrothermal processing that could make use of existing facilities currently in place in wastewater treatment works (WWTWs). In order to look for options aimed at reducing the costs of the WWT process and digestate management by delivering a sustainable and novel approach, the aim of this project is to assess alternatives to enhance the way sewage sludge is handled in WWTWs, by focusing on the use of hydrothermal processes and the potential of recovering energy and nutrients. The potential of integrating HT Processes with AD for sewage sludge treatment was evaluated. Hydrochar yields ranged from 38 to 68% at 160°C and from 29 and 40% at 250°C for all thermal treated sewage sludge samples. The soluble fraction of organic carbon increased in primary sludge digestate (525%), secondary sludge digestate (808%) and sewage digestate sludge (675%) after thermal treatments compared with the untreated digestates. Figures from Biomethane Potential (BMP) tests showed that hydrothermal treatment enhanced methane production in all non-AD and AD sludge samples processed. Mass and energy balances were carried out from six proposed process configurations from different sewage sludge feedstocks and their digestates (primary, secondary and 1:1 Mix) in order to evaluate the waste generation, nutrients potential fate, net energy production and potential profit. The results showed the HTC at higher temperatures (250°C) seems to have more economic and environmental benefits. Scenarios that involved primary and mix sludge seemed to be the most suitable options in terms of the organic matter removal, energy harnessing and economic feasibility.

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