Theoretical assessment of progressive collapse capacity of reinforced concrete structures

The progressive collapse behaviour of reinforced concrete (RC) structures requires consideration of material and geometric non-linearity, concrete crushing and rebar fracture. Compressive arch action (CAA) and catenary action (CTA) are the main resisting mechanisms against progressive collapse following a column loss. Hence, many studies have concentrated on the development of CAA and CTA in RC beams, but without considering the effect of bar fracture and the reduction in beam effective depth due to concrete crushing. Taking these additional factors into account, an analytical model to predict the structural behaviour of RC beams under a column removal scenario was developed. The proposed model was evaluated and validated with the available experimental results. The evaluation and validation indicate that the proposed model can provide a reliable assessment of RC beam capacity against progressive collapse

The role of space in the security and defence policy of Turkey. A change in outlook: Security in space versus security from space

Space and security domains are strongly related with each other. Nowadays, space is an indispensable part of security and defence policy, and it is increasingly becoming a critical infrastructure for strategic Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance (C4ISR) systems. However, space is vulnerable itself to the new space threats. This study reviews the current and near future space role in Turkey's security and defence policy and aims to address the threats against space based capabilities. To provide security from space, space based systems shall themselves need to be secure in space to warrant the security. The concept of security from space starts with space security, in other words the security in space. This paper also highlights the emerging technological opportunities for these space threats to be secure in space in order to provide the security from space. According to the relevant taxonomy, a categorized opportunity proposal for more robust and resilient space/satellite projects' architecture is proposed for Turkey

Clearing effects on plates subjected to blast loads

Empirical prediction methods are often used in the early stages of design to quantify the blast load acting on a structure. While these methods are reasonably accurate for geometrically simple scenarios, they may not be accurate for situations where the target does not form a reflecting surface of effectively infinite lateral extent. In this case, the blast wave will diffract around the target edge, leading to the propagation of a relief wave inwards from the edge of the structure, reducing the late-time development of pressure in a process known as 'clearing'. This paper presents results from a study undertaken to determine the influence of clearing on the response of simple targets. Experiments were conducted in which deflection-time histories were recorded for target plates subjected to cleared and non-cleared blast loads. These were compared with predictions from explicit dynamic finite-element and single-degree-of-freedom models, in which the blast loading was derived by applying a simple correction to the empirical blast prediction method. The results presented show that neglecting clearing may result in highly conservative predictions of target response and that analyses using loading derived from simple corrections to the ConWep predictions match the experimentally observed results very closely.Sam E. Rigby; Andrew Tyas; Terry Bennett; James A. Warren; Stephen Fa