A simple and effective element distortion factor

In this paper, the main methods employed during mesh generation to control element distortion are reviewed and some shortcomings are outlined. New distortion factors are then introduced, which are both simple to implement, and along with the aspect ratio, provide a rapid measure of an element's quality. Some meshes demonstrating their use are finally presented

A 2D combined advancing front-Delaunay mesh generation scheme

A new unstructured triangular mesh generator, DBMesh, is described, incorporating both the Delaunay and advancing front methods. The domain boundary comprising the initial front is discretised by adding nodes based on pre-specified element densities. Internal optimal nodes are then computed from the front such that the latter are each located inside the circumscribed Delaunay circle, and an optimum equiangular triangle is created. The mesh is finally optimised. Advantages of the new method are also outlined. Examples of generated meshes are described, with element quality factors used to generate quadrilaterals if a hybrid, or purely quadrilateral element mesh is required

A-posteriori error estimation in axisymmetric geotechnical analyses

In this paper, an a-posteriori error estimator suitable for use in axisymmetric geotechnical analyses has been developed. The consolidation superconvergent patch recovery with equilibrium and boundaries (CSPREB) method, developed for plane-strain coupledconsolidation problems, is extended to axisymmetric analyses. The use of pore pressures in the error estimator was found to improve results when predicting consolidation. Collapse loads under undrained soil conditions are known to be over-predicted due to “locking”, especially in axial symmetry where there are further displacement constraints. The proposed solution technique reduced locking slightly, but could not eliminate it, as it is inherent in the displacement formulation for lower order elements

The practicalities of transferring data between project collaboration systems used by the construction industry

As part of an industry-lead initiative, standards have been developed to enable bulk exchange of project data between project collaboration systems used by the construction industry. Through the work of developing exchange standards to the practical implementation of data transfer, this paper examines the issues that need to be addressed by both solution providers and their clients when considering moving a project’s data between two different instances of collaborative software. It highlights the practical difficulties of keeping the consistency of the data during the transfer process and gives solutions that can help to overcome these and other problems. The paper draws on experience gained through the development of vendor-neutral standards and real-life project migrations to put forward procedures which should be adopted by vendors, and gives insight into the underlying process for clients. The paper will form a vital framework for clients to determine if the benefits of moving projects between suppliers outweigh the difficulties associated with the move, and to help vendors put processes in place to best facilitate the transfer

Cost-effective parabolic trough foundations for concentrated solar power plants

As part of the continuing requirement for a broad sustainable energy mix, substantial investment is being currently made into renewable energy, including concentrated solar power (CSP). To improve the financial viability of this under-developed technology, research into optimising design is underway in order to reduce the large capital costs associated with CSP plants. At present around 30 % of capital costs of a 50 MW farm are in the solar field (Vallentine et al., 2009), due to the large number of solar collector assemblies (SCAs) required, and therefore there is a large potential to reduce the overall cost by optimising the design of the SCAs and their foundations. The challenge arises in reducing material and weight, and in simplifying manufacture and assembly, while maintaining the structural rigidity, as the efficiency of the collectors is highly dependent on the optical accuracy. This can be potentially compromised by the wind loading, which is predicted to be the most significant source of optical error (Kolb and Diver, 2008), particularly for flexible systems. A literature review has highlighted that considerable effort has been put into optimising SCA design, but the foundations have been neglected. As well as this there is limited understanding of the loads experienced by the foundations of SCAs. This paper will present the current level of understanding of SCA loading and how this knowledge can be used to derive the variation in foundation design across the solar field and therefore allow optimisation of foundation design, highlighting potential capital savings that can be made in a typical 50 MW CSP plant

Wear in large diameter grouted connections for offshore wind energy converters

The paper provides a critical appraisal of the events surrounding the unexpected settlement of large-diameter monopile foundations for offshore wind energy converters, and will detail experimentation that is to be undertaken to determine the extent of the wear failure mode in such structures. The potential for wear deterioration at the grout-steel interface has been caused by the lack of axial load transfer of the grout and steel and so relative movement between the grout and steel is occurring. Hence, a better understanding of this phenomenon is of key importance to determine the long term integrity of the structure. The remedial solution currently favoured within industry consists of the installation of elastomeric bearings, which however may further exasperate the wear due to its lower stiffness than steel contact currently occurring, also because of the presence of water in the grouted connection. The aim of the testing is therefore to identify the risk to offshore foundation integrity due to grout wear under conditions typically observed during life-time operation of offshore wind turbines. The main factors influencing the wear rate of grout will be identified, and the possibility to define indicators for the integrity of the grout that could be used for offshore inspection will be also considered

Development and evaluation of a phase relationship for MSW

Compression is one of the most important mechanical aspects of behaviour of municipal solid waste (MSW) which concerns stability, deformation and structural performance in a landfill. Previous studies have shown that compressible particles play a significant role in MSW compression. Definition of the void ratio in classical soil mechanics theory may no longer be applicable for MSW material since high non-linearity between void ratio changes and vertical stress changes have been identified in compression tests. A new phase relationship for MSW has been developed to include the volume loss of compressible particles and this has been evaluated using onedimensional compression test data. The comparison between analytical and test results has demonstrated that the MSW phase relationship is capable of analysing the volume losses originated from inter-and intra-void ratio changes, in addition to the total volume loss of the MSW sample under different vertical stresses. Since it can isolate the volumetric change of compressible particles from the total volume loss, the MSW phase relationship is important when developing a constitutive model for MSW assuming elasto-plastic material behaviour, which couples the volumetric and shear behaviour

Towards implementing integrated building product libraries

Electronic product catalogues and brochures are gaining popularity but there is little agreement on content, format and searching methods. This limits their usability and integration with existing construction software tools. This paper examines a productmodelling approach to delivering building product information and describes a proposed multi-tier client-server environment. ISO/STEP and IAI/IFC building product models are considered to facilitate representation, exchange and sharing of product information. The proposed architecture incorporates scalability with middleware components that would provide single or few points of entry to integrated product information. This paper is part of a research project, which builds on the results of related projects including ConstructIT Strategy, PROCAT-GEN, Active Catalog, COMBINE and ARROW, towards implementing the required software components

Assessing the deflection behaviour of mechanical and insulated rail joints through finite element analysis

Rail joints constitute a weak component in the railway system. In this paper three- dimensional (3D) finite element analyses (FEA) are carried out to study the structural deflection performance of rail joints under a fatigue static test through vertical stiffness assessment. Four different types of 4-bolted joints are investigated under a dynamically enhanced static load including a glued insulated rail joint (IRJ), a dry encapsulated IRJ, a dry non-glued IRJ and a mechanical RJ. The analysis focused on the accurate simulation of the contact types between the interfaces of rail joint components, namely among the rail, fishplate faces, bolts, insulating materials and on the effect of the elastic supporting structure of the joint on the overall joint deflection. The effect of bolt pretension is included in the model. The vertical displacement of IRJs is measured experimentally both by dial gauges and Video technique both in laboratory and in field. The numerical modelling investigated the effect of different contact types on the interfaces of the rail joint components during the performance of fishplates, and of the rail in the vicinity of the RJ under a given support condition. The vertical displacement of the rail joint were presented and assessed against specified endurance tests’ limits and field measured deflection values that validate the model. Stress distribution in the fishplates was presented that could allow the calculation, through a stress-life approach, the fatigue life of the fishplates and consequently of the joints due to repeated wheel passage. A comparison of the performance of the aforementioned RJ types is included. The results indicate this FE model to be practical to be routinely applied to industry, as it was used in UK Rail industry study to allow designers to optimise life expectancy of IRJs

Architecture for implementing IFC-based online construction product libraries

Construction product information providers have responded to the demand for electronic delivery by providing online access, CD-ROMs and DVDs but these solutions have limited usability and are generally incapable of supporting prevalent and emerging industry practices. The product library implementations attempt to replicate the functionalities of the paper versions, which serve for independent specification and procurement but gives little thought to teams and tools integration through support for automated information exchange and sharing. The IFC standard provides common terminologies, technologies, syntax and semantics necessary to address present and future compatibility and integration issues, hence IFC-based implementation of product libraries have good prospect for meeting the industry requirements. This paper reviews current product information delivery methods and examines the applicability of the IFC and other standards. The requirements for IFC-based construction product libraries are identified and an architecture for realising the requirements was presented