The application of reliability methods in the design of tophat stiffened composite panels under in-plane loading

Composite materials have been widely used in modern engineering fields such as aircraft, space and marine structures due to their high strength-to-weight and stiffness-to-weight ratios. However, structural efficiency gained through the adoption of composite materials can only be guaranteed by understanding the influence of production upon as-designed performance. In particular, topologies that are challenging to production including panels stiffened with pi or tophat stiffeners dominate many engineering applications and often observe complex loading. The design of stiffened composite panels against buckling is a key point of composite structures. While a growing number of studies are related to the reliability analysis of composites few of these relate to the local analysis of more complicated structures. Furthermore for the assessment of these structures in a design environment it is important to have models that allow the rapid assessment of the reliability of these local structures. This paper explores the use of a stochastic approach to the design of stiffened composite panels for which typical applications can be found in composite ship structures. A parametric study is conducted using Navier grillage theory and First-order Reliability Methods to investigate any detectable trend in the safety index with various design parameters. Finally, recommendations are made to provide guidance on applications

Acceptable risk criteria for infrastructure protection

This paper reviews risk-based approaches to assessing the risk acceptability and cost-effectiveness of protective measures for infrastructure. The paper describes three risk acceptance criteria based on fatality risks, failure probabilities and net benefit assessment. These criteria can be applied to any item of infrastructure such as buildings, bridges, dams, offshore platforms, etc. and also applies to any manmade or natural hazard such as earthquakes, cyclones, terrorism, floods and so on. The decision support framework accompanying these risk acceptance criteria considers hazard and threat probabilities, value of human life, physical and indirect damages, risk reduction and protective measure costs. This has specific utility for the safety and economical design and assessment of new and existing protective structures against shock and impact loading. Risk assessments are conducted for a bridge over an inland waterway where the hazard is ship impact and a building subject to terrorist attack. The illustrative examples showed under what combination of risk reduction, and fatality and damage costs the fatality and failure risks would be acceptable, and when protective measures would be cost-effective