Robert Davies

Wrapping legacy codes for Grid-based applications

This paper describes a process for the semi-automatic conversion of numerical and scientific routines written in the C programming language into Triana-based computational services that can be used within a distributed service-oriented architecture such as that being adopted for Grid computing. This process involves two separate but related tools, JACAW and MEDLI. JACAW is a wrapper tool based on the Java Native Interface (JNI) that can automatically generate the Java interface and related files for any C routine, or library of C routines. The MEDLI tool can then be used to assist the user in describing the mapping between the Triana and C data types involved in calling a particular routine. In this paper we describe both JACAW and MEDLI, and demonstrate how they are used in practice to convert legacy code into Grid services.

Large scale application of self-healing concrete: design, construction and testing

The work reported in this paper was carried out as part of the EPSRC funded project Materials for Life (M4L), reference EP/K026631/1 and supported with PhD studentship funding from Costain Group PLC.

Challenges of self-healing concrete scale-up and site trials

The Materials for Life (M4L) project, funded by EPSRC, is a collaboration of three UK universities investigating interdisciplinary techniques for self-healing of cementitious materials. These include the encapsulation of healing agents lead by Cambridge University, bacterial healing by Bath University, and the development of vascular flow networks and a shape memory polymer (SMP) based crack closure system for concrete by Cardiff University. These techniques have been tested in a laboratory environment on relatively small scale specimens, from which it was observed that their combined effect produced a greater strength recovery than any one of the individual selfhealing systems alone. The current work of the project is concerned with the scale-up of the techniques and their implementation and evaluation in site trials. Full-scale concrete structures, comprising wall panels incorporating different combinations of the developed self-healing systems, were built by Costain, an industrial partner of the project. These wall panels have been loaded to induce cracks and then the recovery of the structural and durability parameters of the concrete has been monitored over time. An overview of the M4L site trial setup with a particular focus on the challenges of the scale-up of the SMP system in combination with flow networks is discussed.

Micromechanical modelling of self-healing cementitious materials

A new approach is described for simulating self-healing behaviour in cementitious materials with a two phase micro-mechanical constitutive model. A Mori–Tanaka homogenisation scheme is employed for the composite along with an exterior point Eshelby solution that accounts for stress concentrations adjacent to inclusions. In addition, anisotropic micro-cracking is simulated using arrays of circular cracks. Selfhealing is incorporated into the model by using a novel solidification formulation that models healing under both null and non-zero strain conditions. The focus of the present work is on the recovery of mechanical properties of the micro-cracked material. The performance of the 3D micromechanical selfhealing model is illustrated using a series of stress-strain paths that involve damage and healing cycles. The implementation of the model in a layered beam model is also described, as are a series of model validations that employed data from a recent test series undertaken at Cardiff University as well as data from tests undertaken by others. The examples and validations show that the new micro-mechanical self-healing model is capable of representing the characteristic mechanical response of self-healing cementitious materials.