Roller Compacted Concrete (RCC) is a mixture of well graded aggregates, cement and water. It is placed with a high compaction asphalt type paver and compacted to high density by vibratory rollers to provide a high strength and durable pavement structure. RCC requires no formwork, surface finishing, dowelled joints or reinforcement. These characteristics make RCC simple, fast and economical. However, it also presents difficulties with high-speed applications related to surface texture and surface evenness. These difficulties have so far restricted the use of RCC to the lower layers of normal roads. A two-layer RCC pavement system is a type of composite pavement consisting of two concrete layers. The two layers are paved in either a “wet-on-wet” technique or ”wet-on-dry” technique. The bottom layer serves as the main bending-resistant component of the composite slab, while the top lift is generally constructed with higher-quality constituent materials for improved surface characteristics such as noise and skid resistance. The aim of this research is to evaluate and design two-layer RCC systems with different aggregate sizes and types and different placement conditions in order to expand the application of RCC in pavements. Mechanical properties, bond strength properties, durability characteristics, surface properties, fatigue damage, joint deterioration and pavement design are the main. A range of testing equipment, methodologies and tools have been used in this investigation. The findings of this study showed that a two-layer RCC system can achieved good strength and stiffness for each of the mixtures in the two layers. Also, the inter-layer bond was found to be strong when the two layers were placed within one hour, but weaker when the upper layer was placed three hours after the lower layer. Moreover, the durability of the two-layer RCC system was found to be acceptable, especially when the upper layer was placed within an hour of the lower layer. The surface characteristics for the upper layer of RCC showed that the minimum requirement for skid resistance and texture depth have been achieved. However, it is suggested that further investigation is needed, particularly into the evenness of RCC. The investigation into the effect of dynamic load on the two-layer RCC system demonstrated a good fatigue strength for each RCC mixture and for the two layers together, compared to conventional concrete pavements. Also, the results of load transfer stiffness and joint deterioration showed acceptable performance with regard to crack or joint width, shear stress and placement conditions. The effect of other parameters such as moisture and differential temperature requires a separate investigation and is recommended for future work. The results of the design and analysis of two-layer RCC using KENSLAB, a finite element program, indicted that RCC could perform successfully in pavements with a long service life. In conclusion, the results obtained show that the two-layer RCC are a valid alternative for pavements. On one hand, the use of a harder and more resistance aggregate at the top layer guarantees higher skid resistance and durability, while limiting for the use of high quality aggregate. On the other hand, the results show that adequate construction techniques can alleviate the problems arising from the lack bond between layers.

An extensive amount of works have been carried out to develop the current understanding in punching shear mechanism noted in reinforced concrete slabs. However, despite the increasing popularity of waffle slabs, the current understanding about punching behaviour is mainly focused on solid flat slabs, and only limited amount of works have been carried out on waffle slabs and in the presence of biaxial moment. Thus, there is a need to carry out a research in this area to aid the understanding about punching mechanism of waffle slabs in the presence of biaxial moment for the internal column and edge column connections. The experimental work carried out in this research included destructive testing of thirty-eight 1/10th scale model waffle slab specimens, which consists of fifteen internal column slabs and twenty-three edge column slabs. The main variables were, for the internal column slab, the principle angles of biaxial moment transfer, the column eccentricity, the column orientation and the size of solid sections, and for the edge column slab, the principle angles of biaxial moment transfer, the column eccentricity, the column location and the size of solid sections. From the experimental investigations, three distinct failure mechanisms were observed: the concentric punching at internal column mechanism; the eccentric punching at internal column mechanism; and the edge punching mechanism. In general, the observed punching shear failure mechanisms of waffle slabs were found identical to solid flat slabs; but the punching shear capacities reduced due to some losses in potential failure surface within the waffle section. The principle angle of biaxial moment transfer was found varying the shear surface area that was being mobilized, thus affecting the punching capacity of the slabs. An analytical study was carried out, using an upper-bound plastic model, to simulate the observed punching shear mechanisms, and hence, to predict the punching capacity of the slabs. A theoretical model was developed for each of the identified failure mechanism. In addition, three design models based on the current UK code, Eurocode 2, have been developed. In all cases, these models have achieved good agreements with the test results.

The thesis investigates ways to use internal pressure in a favourable way. It focuses on the structural effects of internal pressurisation of mechanical components. The buckling phenomenon of shell structures is analysed in depth and the conducted work confirms the long known beneficial influence of the internal pressure on buckling and suggests how to exploit this to the utmost extent. Changes in failure modes, stiffness and dynamic response due to pressurisation are also considered. Given the nature of the problem, Finite Element Analysis (FEA) is an essential part of the PhD project. The state-of-the-art FEA techniques are described and employed. Geometric imperfections are introduced in the FE models and, to this regard, a novel FEA technique ensuring high-accuracy simulations is developed. Parametric studies on thin-walled structures are carried out. The studies concern both straight and curved cylindrical shells, as well as more complex geometries. These were subjected to different combinations of loads including bending loads, compressive loads and internal pressure. Among the main findings, it is found that internal pressurisation can change the failure mechanism of the structure and, for a given geometry and material, an optimal value of internal pressure exist. This value allows to fully exploit the material capabilities and to maximise the mechanical performance of the structure. Moreover, it is found that internal pressurisation, as well as pipe curvature, modifies the stiffness and this is significant for structures wherein deflections must be kept to a minimum. Exploitation of internal pressurisation is especially attractive in applications wherein weight minimisation is a key objective. Therefore the content of the thesis is particularly relevant to the aerospace sector. A possible application consisting in the use of pressurised members within aircraft wings is here proposed. With regard to the above application, a prototype of a UAV wing with an internal pressurised structure was built. The structure is made of composite material for performance maximisation and its manufacturing process and related considerations are described. Experimental tests were performed with the aim of measuring the effects of internal pressurisation in the component stiff-ness and natural vibrational frequencies. Experimental results were compared to numerical results. Results confirms the potential of internal pressurisation to enhance mechanical properties.

Impact moling is an effective method of pile driving and percussive drilling to bore underground tunnel for various civil applications such as pipe, cable and ducts installation. An effective electro-vibroimpact system has been built on the basis of interactions between two sources of electromagnetic force. A vertical downward progression of mechanism into hard or brittle material required an increased magnitude of impact force within a compact geometry. Horizontal progression into clay is tested by combining periodic impact and static forces that produces an effective progression rate. As a consequence of this experimental work, a prototype electro-vibroimpact system is tested. Electrical circuitry consists of a timer and batteries which is a compact arrangement, functioning as waveform generator, and power supply. A cylindrical hollow aluminium tube houses the main components such as electromagnetic solenoids and oscillating bar within. This protects the main components from clay while progressing into soil and also reduces soil resistance with a minimal surface area. A mathematical model has also been numerically solved for both single and two degreeof-freedom system. Correlation has been achieved to a certain extent, and it is possible either deploy or further optimise this system.

Wind borne debris is one of the principal causes of building envelope failure during severe storms. It is often of interest in windstorm risk modelling to estimate the potential flight trajectories and impact energy of a piece of debris. This thesis presents research work aimed at the development and validation of a numerical model for the simulation of plate-type windborne debris. While a number of quasi-steady analytical models are available at present, these models are unable to account for the fluid-plate interaction in highly unstable flows. The analytical models are also limited to simple launch flow conditions and require extensive a-priori knowledge of the debris aerodynamic characteristics. In addition, the use of Euler angle parametrisations of orientation in the analytical models results in mathematical singularities when considering 3D six degree-of-freedom motion. To address these limitations, a 3D Computational Fluid Dynamics (CFD) model is sequentially coupled with a quaternion based singularity-free six degree of freedom Rigid Body Dynamics (RBD) model in order to successfully simulate the flight of plate-type windborne debris. The CFD-RBD model is applied to the numerical investigation of the flow around static, forced rotating, autorotating and free-flying plates as well as the treatment of complex launch conditions. Key insights into the phenomena of plate autorotation are highlighted including the genesis of the aerodynamic damping and acceleration torques that make autorotation possible. The CFD-RBD model is then validated against measurements of rotational speed and surface pressure obtained from recent autorotation experiments. Subsequently a general 3D spinning mode of autorotation is demonstrated and the CFD-RBD model is extended to include plate translation in order to simulate windborne debris flight. Using the CFD-RBD flight model, a parametric study of windborne debris flight is carried out and four distinct flight modes have been identified and are discussed. The flight results are contrasted against available free-flight experiments as well as predictions from existing quasi-steady analytical models and an improved quasi-steady force model based on forced rotation results is proposed. The resulting CFD-RBD model presents the most complete numerical approach to the simulation of plate-type windborne debris, directly simulating debris aerodynamics, and incorporates complex launch flow fields in the initial conditions.

This thesis describes research examining the use of computational fluid dynamics (CFD) in structural wind engineering. It looks in particular at steady and unsteady RANS simulations and Detached Eddy Simulation and their use in the calculation of structural loads on static bluff building structures. Previous research across structural wind engineering and CFD is reviewed and critically examined with respect to structural engineering. CFD simulations are performed and compared with published flow data for simple cubes. Loading studies are performed for a complex building and the results compared with wind tunnel studies used in the structural design of the building. Some important local pressure and design forces are found to be highly dependent upon simulation parameters including the spatial discretisation used. In particular, local forces and pressures in the separation and reattachment regions cannot be consistently predicted. Standard industrial CFD methods for improving simulation accuracy including mesh refinement and increasing discretisation accuracy do not necessarily improve prediction of structural loads and explanations are given for this. Results for overall structural loads are found to be sufficiently settled and repeatable for comparison with experimental values, while some local forces and pressures cannot be predicted consistently. Recommendations are made for the appropriate use of CFD in structural engineering and for the future development of CFD techniques. In particular, improved representation of multiple turbulent scales in the free stream and separation regions is required.

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. This current research work focuses on the flexural behaviour of the beam-to-column connections and their effect on the behaviour of the global precast concrete frame. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections both in full scale connection tests and smaller isolated joint tests. This has been done using the so called "component method" in which the deformation of various parts of the connection and their interfaces are summated, and compared with results from full scale sub-frame connection tests. The effects of stress redistribution, shear interaction etc. are taken of by linear transformation in the results from the full scale tests, enabling parametric equations to be formulated empirically in order to describe the semi-rigid behaviour. Eight full scale column-beam-slab assemblages were tested to determine the (hogging) moment-rotation behaviour of double (balanced loading) and single sided in-plane connections. Two of the most common types of connection were used, the welded plate and the billet type. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the joint. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The strength of the single sided connections was limited by the strength of the connection itself, and was approximately half of that for the double sided connection, even though the connection was identical. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. Measurements of the extent of damaged zones near to the connection in full scale tests showed that, unlike steel connections, semi-rigid behaviour in precast concrete does not occur at a single nodal position. In general the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. Analytical studies were carried out to determine empirical design equations for column effective length factors β in unbraced and partially braced precast concrete frames. The main variables were the relative flexural stiffness α of the frame members, and the relative linear rotational stiffness Ks of the connection to that of an encastre beam. The variation of β factors with Ks and α are presented graphically and in the form of design equations similar to those currently used in BS 8 110. The change in the response of a structure is greatest when 0< Ks <1.5 where β is found to be more sensitive to changes in Ks than α. When Ks >2 the changes in the behaviour are so small that they may be ignored within the usual levels of accuracy associated with stability analysis. This is an important finding because the experiments have found Ks to be generally less than 2 for typical sizes of beam. The results enable designers to determine β factors for situations currently not catered for in design codes of practice, in particular the upper storey of a partially braced frame. A design method is proposed to extend the concrete column design approach in BS 8110 and EC2, whereby the strength and semi-rigid stiffness of the connection enables column bending moments to be distributed to the connected beams. However, the suitability of each type of connection towards a semi-rigid design approach must be related to the stiffness and strength of the frame for which it is a part.

Although a great deal of work in investigating the possibility of using linear vibration techniques to detect damage in bridges has been carried out over the past 25 years, there are still some major concerns, such as poor sensitivity of modal parameters to damage, requirement of baseline data, need of measuring excitation force as well as environmental effects. Nonlinearity in the vibration characteristics when the structure is damaged further complicates the problem and causes doubts on the feasibility of applying these techniques on actual structures. Understanding of the nonlinear behaviour is therefore crucial. The aim of the work presented herein is to improve the current understanding of the nonlinear vibration characteristics of reinforced concrete beams and to assess its importance to the subject of structural health monitoring of bridges. These non-linear vibration characteristics were studied by conducting harmonic excitation vibration tests on reinforced concrete beams at various damage levels. In order to detect and characterise the nonlinear behaviour, both linear and nonlinear system identification techniques were used. Results indicated that the responses of the tested beams showed marked softening behaviour and that this non-linear vibration behaviour varied with increasing damage. The restoring force surface technique was applied to the test data and results suggested that cracks in reinforced concrete beams never fully closed in the vibration cycle. Existing phenomenological models suggested by other researchers were investigated and compared with the experimental results. The study confirmed that a bilinear crack model would not be sufficient to replicate the observed vibrating cracked reinforced concrete beams' behaviour. Based on these phenomenological models, an empirical model was derived. Using the empirical crack model proposed, the author suggested a means of estimating the ratio of cracked and uncracked stiffness of a vibrating cracked reinforced concrete beam. The author further suggested a possible routine for structural health monitoring for reinforced concrete beam and stressed that it could be extended for more complicated structures, like bridges. To improve understanding of the nonlinearities in the vibration characteristics, a damage mechanics model of cracked reinforced concrete beam was suggested. Based on strain softening behaviour of concrete material under tensile force, the model is capable of including damage in the form of a moment rotation relationship over the cracked region. Results from the vibration analysis of the model were compared with experimental data.

The environmental wind tunnel at Nottingham University has been extended so that realistic mean hourly atmospheric boundary layers can be generated at sufficient scale to allow aerodynamic tests of sharp edged vehicles to be undertaken. A moving model rig owned by British Rail Research was installed perpendicular to the flow near the end of the working section. As part of this project an automatic refiring mechanism was developed allowing some 2000 transits of vehicles incorporating an internal balance and data logger to be made across the working section with a realistic mean hourly atmospheric boundary layer present. The quality of the data from the moving model rig was assessed. Moving model rig tests and static model tests of a 1/50th scale lorry and 1/45th railway container vehicles have been conducted and extreme value forces and moments relevant to the gust time that overturn a vehicle were calculated. These are the first measurements to have been made using a realistic mean hourly ABL and modelling the vehicle's movement. This thesis assesses the usefulness of the normalised extreme force parameter in determining the extreme forces that a full scale moving vehicle experiences. It was found that the normalised extreme force parameter remains invariant with model time scale for the range of times considered. Further for both the moving model rig tests and the static tests the value of unity that this parameter takes for yaw angles above 30 degrees implies quasi steady behaviour without additional body induced unsteadiness. At lower yaw angles, however, some body induced unsteadiness is evident. These conclusions are compared with predictions from existing numerical models and previous experimental tests. The measured lift force from the static tests compared with the moving model rig tests at 90 degrees yaw angle, i. e. with the moving model stationary, shows a large difference. This is not understood and two concerns are expressed: the effect of the slot, through which the supports of the moving model travel, beneath the vehicle, may be altering the pressure in this region; or it could be due to a Reynolds number effect caused by the small underbody height above the ground.

The influence of the member orientation on the strength of joints formed with square hollow sections is examined. The bird beak joint system is a relatively new truss arrangement for square hollow sections, where the chord and the brace have each been rotated by 45° about their own centreline axes. Based on previous experimental testing it has been suggested that this joint system leads to a stronger joint arrangement. Finite element analysis has been used to study the strength and behaviour of such bird beak joints and to compare them to similar joints in CHS and the traditional RHS configuration to test this claim. A comprehensive study has been undertaken for bird beak X -joints and T -joints and comparisons are made with similar traditional joints in RHS and CHS as the parameters of the width ratio ß, the chord slenderness ratio 2y and the chord length ratio a are varied. Displaced shape and contoured stress plots are included to aid understanding of the failure mechanisms. The finite element work on K -joints allows comparisons of the strength and stiffness of bird beak K -joints with those formed in the traditional RHS configuration as the boundary conditions (at the ends of the members), the brace angle and loading conditions are varied. A limited amount of experimental work has been carried out in the laboratories at Nottingham University, with some assistance from the author, involving the physical testing of bird beak joints so that the finite element models can be validated. This work is reported and examined critically. The conclusions focus on the claims that the bird beak joints are stronger and how they differ from the traditional form of joints. Equations are presented to extend the design information available for a practical parameter range.