Application of regularization methods to damage detection in large scale plane frame structures using incomplete noisy modal data

This paper presents an approach for detecting local damage in large scale frame structures by utilizing regularization methods for ill-posed problems. A direct relationship between the change in stiffness caused by local damage and the measured modal data for the damaged structure is developed, based on the perturbation method for structural dynamic systems. Thus, the measured incomplete modal data can be directly adopted in damage identification without requiring model reduction techniques, and common regularization methods could be effectively employed to solve the developed equations. Damage indicators are appropriately chosen to reflect both the location and severity of local damage in individual components of frame structures such as in brace members and at beam-column joints. The Truncated Singular Value Decomposition solution incorporating the Generalized Cross Validation method is introduced to evaluate the damage indicators for the cases when realistic errors exist in modal data measurements. Results for a 16-story building model structure show that structural damage can be correctly identified at detailed level using only limited information on the measured noisy modal data for the damaged structure.

A volume of fluid numerical model for wave impacts at coastal structures

The first stages in the development of a new design tool, to be used by coastal engineers to improve the efficiency, analysis, design, management and operation of a wide range of coastal and harbour structures, are described. The tool is based on a two-dimensional numerical model, NEWMOTICS-2D, using the volume of fluid (VOF) method, which permits the rapid calculation of wave hydrodynamics at impermeable natural and man-made structures. The critical hydrodynamic flow processes and forces are identified together with the equations that describe these key processes. The different possible numerical approaches for the solution of these equations, and the types of numerical models currently available, are examined and assessed. Preliminary tests of the model, using comparisons with results from a series of hydraulic model test cases, are described. The results of these tests demonstrate that the VOF approach is particularly appropriate for the simulation of the dynamics of waves at coastal structures because of its flexibility in representing the complex free surfaces encountered during wave impact and breaking. The further programme of work, required to develop the existing model into a tool for use in routine engineering design, is outlined.

Two fluid approach to high speed impact interaction amongst solid structures

The issues surrounding collision of projectiles with structures has gained a high profile since the events of 11th September 2001. In such collision problems, the projectile penetrates the stucture so that tracking the interface between one material and another becomes very complex, especially if the projectile is essentially a vessel containing a fluid, e.g. fuel load. The subsequent combustion, heat transfer and melting and re-solidification process in the structure render this a very challenging computational modelling problem. The conventional approaches to the analysis of collision processes involves a Lagrangian-Lagrangian contact driven methodology. This approach suffers from a number of disadvantages in its implementation, most of which are associated with the challenges of the contact analysis component of the calculations. This paper describes a 'two fluid' approach to high speed impact between solid structures, where the objective is to overcome the problems of penetration and re-meshing. The work has been carried out using the finite volume, unstructured mesh multi-physics code PHYSICA+, where the three dimensional fluid flow, free surface, heat transfer, combustion, melting and re-solidification algorithms are approximated using cell-centred finite volume, unstructured mesh techniques on a collocated mesh. The basic procedure is illustrated for two cases of Newtonian and non-Newtonian flow to test various of its component capabilities in the analysis of problems of industrial interest.

Fire safety engineering and ship design using advanced fire and evacuation simulation

When designing a new passenger ship or modifying an existing design, how do we ensure that the proposed design and crew emergency procedures are safe from an evacuation resulting from fire or other incident? In the wake of major maritime disasters such as the Scandinavian Star, Herald of Free Enterprise, Estonia and in light of the growth in the number of high density, high-speed ferries and large capacity cruise ships, issues concerning the evacuation of passengers and crew at sea are receiving renewed interest. Fire and evacuation models with features such as the ability to realistically simulate the spread of heat and smoke and the human response to fire as well as the capability to model human performance in heeled orientations linked to a virtual reality environment that produces realistic visualisations of the modelled scenarios are now available and can be used to aid the engineer in assessing ship design and procedures. This paper describes the maritimeEXODUS ship evacuation and the SMARTFIRE fire simulation model and provides an example application demonstrating the use of the models in performing fire and evacuation analysis for a large passenger ship partially based on the requirements of MSC circular 1033

Computational methodology for analysis of historic composite structures

This paper details the computational methodology for analysis of the structural behaviour of historic composite structures. The modelling approach is based on finite element analysis and has been developed to aid the efficient and inexpensive computational mechanics of complex composite structures. The discussion is primarily focussed on the modelling methodology and analysis of structural designs that comprise of structural beam components acting as stiffeners to a wider shell part of the structure. A computational strategy for analysis of this type of composite structures that exploits their representation through smeared shell models is detailed in the paper.

Thermo-mechanical modelling of power electronics module structures

Power electronic modules distinguish themselves from other modules by their high power operation. These modules are used extensively in high power application markets such as aerospace, automotive, industrial and traction and drives. This paper discusses typical packaging technologies for power electronics modules. It also discusses the latest results from a UK research project investigating the physics-of-failure approach to reliability analysis and predictions for power modules. An integrated design enviroment for incorporating of affects of uncertainty into the design environment was outlined.

Reliability analysis of SiP structures

This presentation discusses latest developments in SiP technology and the challenges for design in terms of manufacture and reliability. It presents results from a UK government funded project that aims to develop modelling techniques that will assess the thermo-mechanical reliability of SiP structures such as (i) stacked die, (ii) side-by-side dies and (iii) embedded die. Finite element analysis coupled with numerical optimisation and uncertainty analysis is used is used to model the reliability of a particular package design. In particular, the damage (energy density) in the lead free solder interconnects under accelerated temperature cycling is predicted and used to observe the fatigue life-time. Warpage of the structure is also investigated

Modelling of nano-imprint forming process for the production of miniaturised 3D structures

Nano-imprint forming (NIF) as manufacturing technology is ideally placed to enable high resolution, low-cost and high-throughput fabrication of three-dimensional fine structures and the packaging of heterogeneous micro-systems (S.Y. Chou and P.R. Krauss, 1997). This paper details a thermo-mechanical modelling methodology for optimising this process for different materials used in components such as mini-fluidics and bio-chemical systems, optoelectronics, photonics and health usage monitoring systems (HUMS). This work is part of a major UK Grand Challenge project - 3D-Mintegration - which is aiming to develop modelling and design technologies for the next generation of fabrication, assembly and test processes for 3D-miniaturised systems.

Scalable and efficient graph colouring in 3 dimensions using emergence engineering principles

This paper describes ways in which emergence engineering principles can be applied to the development of distributed applications. A distributed solution to the graph-colouring problem is used as a vehicle to illustrate some novel techniques. Each node acts autonomously to colour itself based only on its local view of its neighbourhood, and following a simple set of carefully tuned rules. Randomness breaks symmetry and thus enhances stability. The algorithm has been developed to enable self-configuration in wireless sensor networks, and to reflect real-world configurations the algorithm operates with 3 dimensional topologies (reflecting the propagation of radio waves and the placement of sensors in buildings, bridge structures etc.). The algorithm’s performance is evaluated and results presented. It is shown to be simultaneously highly stable and scalable whilst achieving low convergence times. The use of eavesdropping gives rise to low interaction complexity and high efficiency in terms of the communication overheads.

Reinforcement corrosion initiation and activation times in concrete structures exposed to severe marine environments

The corrosion of steel reinforcement bars in reinforced concrete structures exposed to severe marine environments usually is attributed to the aggressive nature of chloride ions. In some cases in practice corrosion has been observed to commence already within a few years of exposure even with considerable concrete cover to the reinforcement and apparently high quality concretes. However, there are a number of other cases in practice for which corrosion initiation took much longer, even in cases with quite modest concrete cover and modest concrete quality. Many of these structures show satisfactory long-term structural performance, despite having high levels of localized chloride concentrations at the reinforcement. This disparity was noted already more than 50 years ago, but appears still not fully explained. This paper presents a systematic overview of cases reported in the engineering and corrosion literature and considers possible reasons for these differences. Consistent with observations by others, the data show that concretes made from blast furnace cements have better corrosion durability properties. The data also strongly suggest that concretes made with limestone or non-reactive dolomite aggregates or sufficiently high levels of other forms of calcium carbonates have favourable reinforcement corrosion properties. Both corrosion initiation and the onset of significant damage are delayed. Some possible reasons for this are explored briefly.