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Development and study of a high performance protective solution against blast loads
Publication . Rebelo, Hugo Miguel Bento; Cismasiu, Corneliu
The increasing use of improvised explosive devices in terrorist attacks against civil targets
has challenged the scientific community to find new strengthening or protective solutions
able to mitigate the effects of the blast loads. As a response to this demand, the main
purpose of the present thesis is the development and study of a high performance protective
solution based on the concept of sacrificial claddings. Due to the high flexibility,
precision and relatively low costs, additive manufacturing has been increasingly used in
the search of new material disposition patterns that improve the mitigation capabilities
of crushable cores.
The presentwork assesses the performance of a PLA crushable core manufactured through
fused deposition modelling 3D printing. An experimental campaign is conducted to determine
the mechanical behaviour of the PLA. These results allow the selection and
calibration of an adequate numerical constitutive model, which considers the anisotropy
and compressive/tensile asymmetry exhibited in additively manufactured materials.
Once the constitutive material calibrated, the results of a second experimental campaign
resorting to an explosive driven shock tube are used to validate a numerical model that
allows the deterministic design of a sacrificial cladding which successfully improves the
blast resistant capabilities of a given structural element.
However, when verified taking into account the model’s uncertainties and the probabilistic
distribution of the structural element’s properties, the cladding solution might, for
certain blast scenarios, negatively impact the performance of the structural element it
intends to protect.
Therefore, one may conclude that the use of a probabilistic approach in the design of such
protective solutions is recommended, as the deterministic approach might yields results
against safety.
Simplified analysis of RC beam and beam-column elements under blast loading
Publication . Carvalho, Diogo Miguel Vieira Alves de; Cismasiu, Ildi; Cismasiu, Corneliu
The present work aims to provide a non-linear numerical tool capable of analysing
the structural response of reinforced concrete beam and beam-column elements
when subjected to blast loads.
The increasing frequency of explosion events, stemming from terrorist
attacks resorting to improvised explosive devices, or from accidental misuse of
hazardous substances has shined a new light on the topic of blast resistant
structural design. Recently, many studies have been conducted to better
understand how to improve the design of blast resistant solutions in newly
constructed buildings, as well as to provide retrofitting reinforcement solutions
to pre-existing ones. Columns are a key structural component in any building,
supporting its weight and transferring it to the foundations. If many of these
elements fail when subjected to a blast event, then the structure’s load bearing
capacity may be compromised, initiating its progressing collapse and endangering
the lives of the people inside.
The work featured in the present dissertation entails the development of
a simplified numerical tool that analyses structural elements subject to blast loads,
using single-degree-of-freedom systems with equivalent properties. The numerical
estimates are then compared with experimental data found in the literature to
assess the quality of the numerical predictions.
Both beam and beam-column output results differ no more than 25% from
experimental the data. The possible sources of this discrepancy are investigated
and it’s concluded that the numerical model developed herein proves to be a good
preliminary analysis tool for the estimate of the structural response of beams and
beam-columns, when subjected to blast loads.
Controlo dos estilhaços em paredes de alvenaria sujeitas a explosões
Publication . Eliseu, Francisca Pinto; Lúcio, Válter
Experimental Validation and Numerical Analysis of a High-Performance Blast Energy-Absorbing System for Building Structures
Publication . Gomes, Gabriel de Jesus; Lúcio, Valter José da Guia; Cismaşiu, Corneliu; Mingote, José Luis; CERIS - Polo NOVA; DEC - Departamento de Engenharia Civil; MDPI - Multidisciplinary Digital Publishing Institute
The paper presents a full-scale blast testing experimental campaign conducted on an energyabsorbing connector comprising thin-walled inversion tubes as kernel elements mounted in a façade protective panel. LS-DYNA finite element predictions of the global and local deformation/inversion of the panel/connectors compared reasonably well with the experimental observations. After validation, the numerical model was used to analyze the response of a simple idealized reinforced concrete structure under three blast-loading scenarios: the first two scenarios produce, approximately, the same impulse but are significantly different in terms of load duration and overpressures, and represent a far-field and a near-field scenario (1600 kg TNT at 20 m (i) and 150 kg TNT at 5 m (ii), respectively); the third scenario is more demanding, and consists in a half standoff distance of the second (150 kg TNT at 2.5 m (iii)). These numerical simulations allow to assess the effect of standoff distance and blast loading on the effectiveness of the protective system. One may conclude that the introduction of EACs strongly limits the forces imparted to the protected structure, reducing significantly the corresponding energy absorption demand. Comparing the energy absorbed by the structure in different scenarios, with and without the protective system (8 × ϕ64 × 2 mm), one can see that these reductions can reach, respectively 67%, 72% and 68% in the far-field, near-field and very near-field explosions.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/ECI-EST/31046/2017