Capítulo II MARCO DE REFERENCIA
2.4 Calidad de la educación
This action deals with the risk mitigation of terrorist acts involving explosives, through the development of vulnerability assessment methodologies of their effects on structures and their occupants. The rationale is that if all precau- tionary measures fail to prevent such events, it will be the physical structure itself, in terms of mechanical resistance, integrity and robustness, to bear the first consequences. If adequate provisions against abnormal loads, such as blast, explosion and impact, have been taken in the design, it is possible that catastrophic consequences will be contained and major disasters avoided. The approach followed is based mainly on computational structural mechanics and is aided by laboratory experiments.
Major 2007 achievements
Simulation techniques
Development of numerical simulation techniques for the assessment of the structural vulnerability of several construction types has been extensively pur- sued. All activities have been carried out within the code EUROPLEXUS. This is a structural analysis programme based on an explicit finite element formulation, and it is suitable for studying fast dynamic responses of structures (explosions, impacts, crashes, etc.), with special capabilities for modelling fluid-structure interaction phenomena. It has been co-developed by the JRC-IPSC and the French Commissariat à l’Énergie Atomique (CEA).
Efforts have been focused into simulating both open-air blasts, with geometries representative of urban environment, and explosions in closed spaces. The complex pressure wave propagation patterns, due to multiple reflections and tunnelling effects, have been efficiently and reliably obtained in each case. Ar- eas of high risk for the occupants, with respect to injuries potentially induced to humans due to blast wave effects and flying debris, have been identified for several explosion scenarios.
In this context, models for the debris generation and projection, based on ele- ment erosion techniques, have also been developed and implemented in the code. The efficiency of Europlexus to simulate the process of detonation of a solid TNT explosive has also been tested and validated using the Jones-Wilkins-Lee equation of state for the explosive. However, for reducing computational effort and costs, other approaches, like the compressed air-bubble and the load-time function models, have been explored and implemented in the code.
Experimental activity
Reliable structural predictions require realistic material models in the simulation codes, and the need naturally arises to characterize the construction materials under the actual conditions of their employment (higher strain-rates, tempera- ture, fatigue etc.).
In the past year the experimental activity has been focused on investigating the dynamic compression properties of concrete under lateral confinement. This least understood aspect of this widely used material is crucial for modelling the penetration of thick concrete walls by missiles and projectiles, or for contact detonations. The investigation has been successfully conducted, in collabora- tion with the Délégation Générale pour l’Armement (DGA, French Ministry of Defence).
P VA C S
Contact George Solomos tel. +39 0332 789916 e-mail: [email protected] website: http://elsa.jrc.itSimulation with Europlexus of the evolution of the pressure distribution on the interior walls for a bomb explosion inside the closed space of a small, church-like structure; a multitude of reflections is clearly seen.
Concrete behaviour for different loading conditions: the strength is almost doubled from static to dynamic loading, and it is increased many times under dynamic confined conditions.
Simulation with Europlexus of the evolution of the displacement distribution, failure and formation of projectiles (shards) for an annealed glass panel of dimensions 1m x 1.4m x 0.001m, subjected to blast due to The testing has been challenging and particularly demanding due to the very
high dynamic pulses required. It was carried out at the Large Hopkinson Bar of the JRC-IPSC, which was properly configured for this purpose. Several concrete mixes were tested, while confinement was provided by a steel jacket, inside which the specimen was fixed. The dramatic change of the compressive behav- iour of concrete due to such confinement, which reached almost 0.2GPa, was clearly observed.
The RAILPROTECT project
Its full name is “Innovative Technologies for Safer and More Secure Land Mass Transport Infrastructures under Terrorist Attacks”. The project started in late 2006 in support of the transport security policies of the Directorate General for Energy and Transport (DG TREN). It deals with the physical protection and miti- gation of the bombing attacks risk in the rail transport sector. It is expected to contribute to alleviating the vulnerability of Europe’s passenger land transport infrastructures, and it will provide assurances to the European public that the level of security and safety in the land mass transport has been upgraded (as in the air and maritime transport). Both station infrastructures and rolling stock fall within its scope.
Proceeding with the project, besides the blast analysis treatment itself, the upfront problem of the non-availability of the geometry of the structures, espe- cially of the older stations, had to be solved. In collaboration with the project partners, a field intervention at the Gare de Lyon in Paris was made in September 2007. Two areas of the station and a subway coach were successfully mapped using the 3D laser scanning technique “RECONSTRUCTOR”, developed by the JRC-IPSC. These geometric data are currently being elaborated and adapted for use in Europlexus for the numerical simulations of bomb explosion effects. A major milestone of the project has thus been accomplished.
Further activities
The objectives of PVACS include also the development of mathematical methods for the vulnerability analysis of networked critical infrastructures, whose nodes represent physical structures subject to threat and damage. Flanking this work, a new FP6 competitive project started in 2007 in this area: MANMADE “Diagnosing vulnerability, emergent phenomena, and volatility in man-made networks”. Concerning standardization, contacts with the European Committee for Stand- ardization (CEN) have been maintained through the Expert Group “Critical In- frastructure - Building and Civil Engineering Works” within CEN/BT/WG161 “Protection and Security of the Citizen”.
Challenges for the future
The major challenges lying ahead for 2008 are (a) the successful conduction and completion of the RAILPROTECT project, where an urgent, real problem and many external collaborators are involved, and (b) the upgrade of the Large Hopkinson Bar facility. Both will be critical for the future development of the activity.