The propagation of blast and shock waves in confined environments is a complex phenomenon; yet, being able to derive valid predictions of such phenomena is highly relevant, for example, when it comes to the assessment of protection of personnel in military environments. This study looks at the propagation of blast waves inside a compound survival shelter. Experimental analyses are performed on a small-scale model of the actual configuration of the shelter subjected to the detonation of an explosive charge at different locations close to its entrance. Pressure-time signals are recorded on a number of locations in the model. A numerical model is also developed to complement the experimental program, based on the explicit finite element (FE) code LS-DYNA. The recorded experimental data (e.g., pressure and impulse) are compared with the numerical predictions to validate the FE model. The authors discuss two different modelling approaches (the Lagrangian and the MM-ALE formulations) and analyse the influence of using a different number of ambient layers, the advection method, the time-step size, and level of discretisation. The proposed numerical model predicts and captures the relevant stages of the propagation of the shock wave very well, with error levels on the resulting specific impulse always lower than 19% when compared to the experimental observations. Keywords Blast wave • Shock wave • Small-scale models • Confined explosions • Experimental analysis • Numerical modelling • LS-DYNA
Dynamic behaviour of Reinforced Concrete (RC) structures can be assessed using a Single-Degree-of-Freedom (SDOF) approach. Such a method is highly dependent on the resistance curve of the structure which is generally represented by a bilinear elasto-perfectly-plastic approximation. This approximation might lead to erroneous results when it refers to the use of externally bonded Fibre Reinforced composites for flexural capacity upgrade of Reinforced Concrete (RC), mainly when the concrete-to-FRP interface failure is to be included. One-way slabs are experimentally and numerically investigated in this study in a 3-point flexural configuration. Assessment on the load-displacement behaviour of a reference specimen and its retrofitted counterpart is performed. Special attention is given to the behaviour of the structure after the concrete-to-FRP failure. Comparison is made between experimental and numerical results and a good agreement is obtained. A complementary analytical study based on the SDOF method is conducted to understand the influence of several resistance curves on the overall displacement of the same structure when subjected to different pressure-impulse combinations.
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