A new apparatus for large scale dynamic tests on materials

The development of an innovative apparatus, based on Hopkinson bar techniques, for performing large scale dynamic tests is presented and discussed. The activity is centered at the recently upgraded HOPLAB facility, which is basically a split Hopkinson bar with a total length of approximately 200 m, with bar diameters of 72 mm and where force pulses up to 2 MN and 40 ms duration can be generated and strain rates up to 50 s −1 can be achieved. Several modifications in the basic configuration have been introduced: twin incident and transmitter bars have been installed with strong steel plates at their ends where large specimens can be placed. A series of calibration and quantification tests has been conducted in order to prove the reliability of the experimental technique proposed. Moreover, real tests on concrete cylindrical samples of 200 mm diameter and of up to 400 mm length have been performed. Analyses of recorded signals indicate proper Hopkinson bar testing conditions and reliable functioning of the facility.JRC.G.4 - European laboratory for structural assessmen

e-BLAST simulator: final design, setup improvements and demonstration tests

The Electrical Blast Simulator (e-BLAST) activity involves the development of an apparatus capable of reproducing the effects of a blast pressure wave on large-scale structural components (such as columns, walls, etc.) without the use of explosives but through the action of impacting masses. The work relates to the PROTECT project which deals with the protection and resilience of the built environment (critical buildings, transportation and energy infrastructure etc.) under catastrophic events such as blast and impacts. The e-BLAST facility has been conceived and designed with the expertise acquired in the previous project “Blast Simulation Technology Development”, supported through an Administrative Arrangement by DG HOME. Differently from the prototype developed in that project, the e-BLAST exploits a recent technology that appears to be very promising in this particular research field. Specifically, three synchronous electrical linear motors have been adopted for accelerating the impacting masses. This choice has led to the development of a more efficient, versatile and low-cost facility. The report presents in detail the final facility design, its components and their assembly, and a series of preliminary tests carried out in the ELSA laboratory in order to assess the performance of the enhanced e-BLAST. Finally, a brief description of further developments and feasible large-scale structural tests, planned to be performed with the new apparatus, are discussed.JRC.E.4-Safety and Security of Building

Dynamic Behaviour of "Collapsible" Concrete

In this work a particular cement composite material for protection of structures and infrastructures against accidental actions, such as blast or impact, has been investigated. An experimental procedure has been developed in order to assess static and dynamic behaviour of energy absorbing cementitious composites. The granular cementitious composite has been studied focusing attention to compressive strength, high deformation and energy dissipation capacity which are important characteristics for an absorber material. An experimental characterization of the material behaviour under compressive static and dynamic loadings has been carried out. Different deformation velocities have been studied in order to define the material behaviour in a wide range of strain rates. The velocity range up to 0.1 m/s is investigated by means of a universal servo-hydraulic MTS 50 kN testing machine. Some preliminary results have been reported and discussed in the present work.JRC.G.4-European laboratory for structural assessmen

Compressive behaviour of dam concrete at higher strain rates

The mechanical behaviour of concrete when subjected to impact or blast has still many aspects requiring further study. Dam concrete is characterized by large coarse aggregates, hence large specimen sizes are needed in order to study a representative volume of the material. Exploiting an innovative equipment, based on Hopkinson bar techniques, the dynamic behaviour of concrete of 64~mm maximum aggregate size has been investigated. Direct dynamic compression tests have been performed on medium and large size cylindrical samples. Full stress-strain curves have been obtained, which have allowed the estimation of fracturing energies and of the relevant dynamic increase factor. The experimental campaign has also included a reference standard concrete in order to highlight the peculiarity of the dam concrete at high strain rates and to validate the transition of this type of testing to very large specimens.JRC.G.4-European laboratory for structural assessmen

Dynamic behaviour of HPFRCC: The influence of fibres dispersion

The promise of fibre-reinforced cementitious composites for dynamic loading application stems from their observed good response under static loading mainly due to fibre contribution. An experimental research aimed at contributing to the understanding of the behaviour of advanced fibre-reinforced cementitious composites subjected to low and high strain rates was carried out underlining the influence of fibres. The material behaviour was investigated at three strain rates (0.1, 1, and 150 s−1) and the tests results were compared with their static behaviour. Tests at intermediate strain rates (0.1–1 s −1) were carried out by means of a hydro-pneumatic machine (HPM), while high strain rates (150 s−1) were investigated by exploiting a modified Hopkinson bar (MHB). Particular attention has been placed on the influence of fibre and fibre dispersion on the dynamic behaviour of the materials: matrix, HPFRCC with random fibre distribution and aligned fibres were compared. The comparison between static and dynamic tests highlighted several relevant aspects regarding the influence of fibres on the peak strength and post-peak behaviour at high strain rate

Assessment of dynamic mechanical behaviour of reinforced concrete beams using a Blast Simulator

Critical infrastructures may become the target of terrorist bombing attacks or may have to withstand explosive loads due to accidents. The impulsive load connected to explosions is delivered to the structure in a few milliseconds forcing it to respond or fail in a peculiar mode. With reference to the above scientific framework this work presents an innovative apparatus designed and developed at the European Laboratory for Structural Assessment to reproduce a blast pressure history without using explosives. This apparatus is practically a hybrid nitrogen-spring-driven actuator that accelerates masses of up to 100 kg to a maximum velocity of about 25 m/s that impact against the tested structure. The pressure-load history applied to the structure is modulated and reshaped using appropriate layers of elastic soft materials (such as polymeric foams) placed between the specimen and the impacting masses. Specific instrumentation has extensively been utilised to investigate the blast simulator performance and to precisely measure the pressure loads applied to the specimen. A series of tests on real scale reinforced concrete beams/columns (250x250x2200 mm) has been performed to efficiently assess the performance and potentiality of the new blast simulator. Results are under evaluation. In addition to the experimental work, a series of numerical simulations by means of the explicit FEM code EUROPLEXUS have been carried out to support and improve the equipment design.JRC.G.4-European laboratory for structural assessmen

International networking in the building sector

Aiming to advance innovation in the building sector, the JRC is networking with the best research infrastructures in Europe and the world. Activities focus on resilience, risk assessment, energy efficiency, standards and data repositories. Innovation will support the competitiveness of the European construction industry in Europe and beyond.JRC.E.4-Safety and Security of Building

Review on resilience in literature and standards for critical built-infrastructure

A review of system resilience ideas found in literature and standards is conducted. Attention is particularly focused in the built-infrastructure, where both natural and man-made hazards are considered. In order to highlight the fragility of critical infrastructures and communities to hazards and the serious consequences of disruptions and failures, some examples of major disasters are presented. Various definitions for resilience are included and discussed in order to provide the necessary, basic concepts and background. An attempt is made to introduce some resilience properties and metrics in terms of functionality, recovery time etc. The interrelation of structural resilience and fragility curves is put into evidence and the need of some form of Guidelines along with the required research are indicated.JRC.G.4-European laboratory for structural assessmen

Proceedings of the 1st International Workshop on Resilience

Built environment constitutes the fundamental layer for many services and functions of our society. Many physical infrastructures are vulnerable to natural hazards (e.g. earthquakes, floods, tornados) as well as man-made hazards, and the risk of catastrophic damage due to hazardous events continues to increase worldwide. Considerable progress has been made towards risk management and mitigation, however, in particular the earthquake engineering community still faces many new challenges. Focusing principally on seismic resilience, the objectives of the workshop have centred on (i) how we use resilience-based engineering to steward our built environment and make it safer, resilient and sustainable, and (ii) how to assess and develop strategies to improve community resilience against a major disruptive event. The workshop has comprised presentations and discussion sessions. The state of knowledge regarding disaster resilience has first been examined in the light of the lessons learnt from recent major earthquakes. Then the views and approaches were solicited with contributions from Japan, Asia, Europe, North and South America on the new directions for Resilience-Based Design (RBD) in an effort towards catalysing and elaborating a comprehensive, collective and integrated approach to resilience. Currently running research projects on resilience, funded by the EU, were also presented.JRC.E.4 - Safety and Security of Building

Electrical Blast simulator (e-BLAST): design, development and first operational tests

The Electrical Blast Simulator (e-BLAST) activity involves the development of an apparatus capable of reproducing the effects of a blast pressure wave on large-scale structural components (such as columns, walls, etc.) with the objective of improving their strength in such severe loading situations. The work relates to the BUILT-CIP project which deals with the protection and resilience of the built environment (critical buildings, transportation and energy infrastructure etc.) under catastrophic events such as blast and impacts. The e-BLAST facility has been conceived and designed with the expertise acquired in the previous project “Blast Simulation Technology Development”, supported through an Administrative Arrangement by DG HOME. Differently from the prototype developed in that project, the e-BLAST exploits a recent technology that appears to be very promising in this particular research field. Specifically, three synchronous electrical linear motors have been adopted for accelerating the impacting masses. This choice has led to develop a more effective, versatile and low-cost facility. The report presents in detail the facility design, its components and their assembly, and a series of preliminary tests carried out in the ELSA laboratory in order to assess the performance of the e-BLAST. Finally, a brief description of further developments and feasible large-scale structural tests, planned to be performed with the new facility, are discussed.JRC.G.4-European laboratory for structural assessmen