Projects World

Although Britain is relatively rich in natural aggregate reserves, planning approvals to develop new quarries are running at about half the rate of aggregate extraction. The use of secondary materials, such as recycled aggregate, might not create a major course of aggregate but if secondary material were used in less demanding situations, the quantity of natural aggregate required by the construction industry would be reduced.

This dissertation reports mainly on laboratory tests conducted on crushed concrete and demolition debris to examine the potential use of these materials in new construction. Standard aggregate tests were conducted on the materials to check their compliance with the Specification for Highway Works (1986), particularly for use as aggregate in road sub-base layers.

A more detailed examination of the aggregates was conducted with regard to CBR, shear strength and frost susceptibility where the influences of moisture content, density and particle packing on these properties were investigated. One part of the study involved examining the use of recycled aggregate as the coarse aggregate fraction in new concrete.

An analysis of the shear strength data was conducted using the dilatancy index defined by Bolton (1986). From the frost susceptibility results, it was concluded that further work would be required in this area to determine the main factors which influence the frost heave of recycled aggregates. The recycled aggregate concrete compared well with the natural aggregate concrete and appeared to be of superior quality than that produced in other research.

During the study, it became evident that the recycled aggregates could perform as well as limestone in most cases and therefore could be considered for many potential uses. Some recommendations are presented at the end of this dissertation for the development of a standard on recycled materials which would help to promote the use of recycled aggregates in the construction industry in Britain.

This study examines the dynamic instability known as flutter using a two-degree-of-freedom airfoil section model in both quasi-steady and unsteady flow. It explains the fundamental forces and moments involved in the bending-torsion flutter of an airfoil section, and demonstrates a solution method for determining the critical flutter frequency and speed for both flow cases.

Additionally, through the use of a programmed Mathcad 11 worksheet, it evaluates the flutter characteristics of six example sections, illustrating the effects of the elastic, inertial and aerodynamic properties of an airfoil section.

For each section, a parametric study of the effect of the section Center of Gravity position along the section chord is performed. The flutter frequency and speed are calculated using both quasi-steady and unsteady aerodynamic forces and moments, and the results compared. Software used was MathSoft Mathcad 11, Microsoft Word and Intergraph Smart Sketch LE.

This thesis is carried out with the aim of identifying if, and how, low-cost airline services have their effects on planning issues. Low-cost airlines have set new trends in the travel market and induced air travel demands without competition with established airlines: creating new travel networks with new entry points in countries in Europe.

The development of this network is apparently grounded in the expansion of the European Union and its policies. This was also obviously present in the development of the case studies. These case studies illustrated that low-cost airlines have created a complementary system in the region which enhances theoretical network ideas.

Furthermore, it becomes more than clear that low-cost services attract passengers from larger distances and therewith have a more spread out effect to the greater region instead of what is often expected to be to the benefit for the locality. That is also why the perceptions between the adjacent town and the region differ, as respectively opportunity and support.

The conclusion of the thesis is in the end that low-cost airlines do have an effect on planning issues, though it is indirectly with more reaction from the locality but rather more meaning to the region. The implications for planning are presented and a few directions are discussed on how to handle the phenomenon and what the future might hold for this concept.

The aim of this thesis was to study the load bearing capacity of anchor plates, used for anchorage to concrete located at nuclear facilities. Two different type of anchor plates were examined, which together constitute the majority of the anchor plates used at Forsmark nuclear facility in Sweden.The first is a cast-in-place anchor plate with headed studs and the second is a post-installed anchor plate which uses sleevetype expansion anchors. Hence, anchors with both a mechanical or a frictional interlock to the concrete were examined.

The main analysis tool was the finite element method, through the use of the two commercially available software packages ABAQUS and ADINA and their non-linear material models for concrete and steel.As a first step, the numerical methods were verified against experimental results from the literature. However, these only concern single anchors. The results from the verifications were then used to build the finite element models of the anchor plates. These were then subjected to different load combinations with the purpose to find the ultimate load capacity. Failure loads from the finite element analyses were then compared to the corresponding loads calculated according to the new European technical specification SIS-CEN/TS.

Most of the failure loads from the numerical analyses were higher than the loads obtained from the technical specification, although in some cases the numerical results were lower than the technical specification value. However, many conservative assumptions regarding the finite element models were made, hence there might still be an overcapacity present.All analyses that underestimate the failure load were limited to large and slender anchor plates, which exhibit an extensive bending of the steel plate. The bending of the steel plate induce shear forces on the anchors, which leads to a lower tensile capacity.

In design codes, which assume rigid steel plates, this phenomenon is neglected. The failure loads from all different load combinations analysed were then used to develop failure envelopes as a demonstration of a useful technique, which can be utilised in the design process of complex load cases.

Shallow offshore foundations, which achieve their stability through the foundation bearing on the seabed, can in most applications be idealised as large rigid circular footings subjected to vertical, horizontal and moment loading.A small strain linear-elastic perfectly-plastic three- dimensional finite element program was developed to analyse this combined loading problem.

The selection of a suitable three-dimensional finite element for accurate and computationally efficient analysis was based on the element’s ability to model incompressible soil conditions, using exact numerical integration. A new approach for evaluating element suitability is developed and is quantified in terms of the parameter free degrees-of-freedom (equal to the degrees-of-freedom minus the incompressibility constraints).

The tetrahedron family of three- dimensional elements is found to be in general more suitable and computationally efficient than the Serendipity and Lagrangian cube families. The 20-node quadratic strain tetrahedron is adopted for all analyses presented in this thesis.

For combined loading, most of the available elastic numerical analyses also examine the effect of footings embedment from three cases of embedment geometry. This demonstrates that the increase in footing stiffness (reduction in displacement) due to embedment for horizontal and moment loading is developed at shallower depths, and has a greater magnitude, than for vertical loading.

The stability of a rough rigid circular footing placed on the surface of an undrained clay is examined. Zero thickness interface elements, despite experiencing some numerical instability problems, were found to model the footing-soil interaction better than conventional continuum elements. However, application of interface elements to footings which can lose contact with the soil, under moment loading conditions, resulted in numerical instability of the solution. A simpler model was therefore used to define the shape of the three-dimensional failure envelope at high vertical load. Comparisons with the semi-empirical inclination factors of bearing capacity solutions are included.