Modelling the role of software in the propagation of failure across National Critical Infrastructures
Previous terrorist attacks, system failures and natural disasters have revealed the problems that many States face in preparing for national civil contingencies. The diversity of critical infrastructures and the interconnections between different systems makes it difficult for planners to ‘think of everything’. For example, the loss of power distribution networks can disrupt rail and road transportation systems. Knock-on effects can also be felt across telecommunications infrastructures as the uninterruptible power supplies (UPS’) that protect mobile phone base stations fail over time. Domestic water supplies are affected when pumping and treatment centres lose power. It is difficult to under-estimate the safety implications of these interdependencies. For example, Pironi, Spinucci and Paganelli describe how the Italian blackout of 2003 affected patients that relied on home parenteral nutrition systems [1]. These individuals used electronic pumps for the overnight infusion of nutritional solutions. The loss of power disrupted their treatment. Different devices responded in different ways as some began to generate alarms while others reverted to battery power. Patients responded in different ways as they became worried about whether or not their systems had sufficient power to complete their treatment for that night. The blackout lasted several days across many areas of Italy. This created further problems as stores of parenteral solution had to be stored in freezers. Other patients were placed at risk when the loss of power began to affect water treatment centres. It became difficult to guarantee that there was no microbiological or toxic contamination in the water supplies for dialysis patients.
Computational Support for Identifying Safety and Security Related Dependencies between National Critical Infrastructures
Previous terrorist attacks, system failures and natural disasters have revealed the problems that many States face in preparing for national civil contingencies. The diversity of critical infrastructures and the interconnections between different systems makes it difficult for planners to 'think of everything'. For example, the loss of power distribution networks can disrupt rail and road transportation systems. Knock-on effects can also be felt across telecommunications infrastructures as the uninterruptible power supplies (UPS') that protect Internet routers and mobile phone base stations fail over time. Domestic water supplies are affected when pumping and treatment centres lose power. These interconnections make it hard to anticipate the many different safety-related systems that might be affected by particular contingencies. This paper introduces a Geographic Information System that is intended to help government agencies plan for the knock-on effects that propagate between major infrastructures. The intention is to provide a flexible system, which can easily be configured and updated. This is important given that technical innovation and routine maintenance continually introduce changes across national infrastructures. (6 pages)
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.