Corneliu Cismasiu

This paper investigates the dynamic behaviour of cable-supported glazing façades
subjected to medium-level air blast loads. Preliminary numerical studies are carried-out in
SAP2000 by means of a geometrically refined and simplified lumped-mass finite-element
numerical model, in order to assess the major effects of the design blast load in the main
façade components. As shown, both the glass panels and the cable system are able to
properly accommodate the incoming impulsive loads, typically involving extreme ...

The unique superelastic behaviour exhibited by shape memory alloys (SMAs) allows the material to recover after withstanding large deformations. This recovery takes place without any residual strains, while dissipating a considerable amount of energy. This property makes the SMAs particularly suitable for applications in vibration control devices. Numerical models, calibrated with experimental laboratory tests, are used to investigate the dynamic response of vibration control devices. These devices are built up of austenitic superelastic wires. The energy dissipation and re-centring capabilities, important features of these devices, are clearly illustrated by the numerical tests. One of these devices is tested as a seismic passive vibration control system in a simplified numerical model of a railway viaduct.

Being able to efficiently mitigate the effects of blast loads on structures, sacrificial cladding solutions are increasingly used to protect structural elements from the effects of accidental explosions and/or terrorist attacks. The present study analyses the loss of effectiveness of a deterministically designed sacrificial cladding when variability in the material properties and uncertainties in the mechanical model are considered. The results of an experimental campaign are used to validate the numerical models that allow the deterministic design of a sacrificial cladding which successfully improves the blast resistant capabilities of a given structural element. Nonetheless, it is shown that, taking into account the probabilistic variability of key parameters is of vital importance when designing sacrificial cladding solutions, since, when not properly designed for the structural element it intends to protect, adding a sacrificial cladding might negatively impact its blast resistant capabilities. Additionally, it is concluded that the deterministic approach might be against safety. In the reported case study, when comparing the admissible charge weight yielding from the deterministic and probabilistic approaches, one verifies that the former allows a higher charge weight.

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Superelasticity, a unique property of shape memory alloys (SMAs), allows the material to recover after withstanding large deformations. This recovery takes place without any residual strains, while dissipating a considerable amount of energy. This property makes SMAs particularly suitable for applications in vibration control devices. Numerical models, calibrated with experimental laboratory tests from the literature, are used to investigate the dynamic response of three vibration control devices, built up of austenitic superelastic wires. The energy dissipation and re-centering capabilities, important features of these devices, are clearly illustrated by the numerical tests. Their sensitivity to ambient temperature and strain rate is also addressed. Finally, one of these devices is tested as a seismic passive vibration control system in a simplified numerical model of a railway viaduct, subjected to different ground accelerations.

The present paper aims to examine the potential of the Applied Element Method (AEM) in simulating the blast effects in RC panels. The numerical estimates are compared with the results obtained in an experimental campaign designed to investigate the effectiveness of fibre grout for strengthening full scale RC panels by comparing the effects that a similar blast load produces in a reference and the strengthened panel. First, a numerical model of the reference specimen was created in the software Extreme Loading for Structures and calibrated to match the experimental results. With no further calibration, the fibre reinforced grout strengthening was added and the resulting numerical model subjected to the same blast load. The experimental blast effects on both reference and strengthened panels, despite the lack of high speed measurement equipment (pressure, strains and displacements sensors), compare well with the numerical estimates in terms of residual and maximum displacements, showing that, once calibrated, the AEM numerical models can be successfully used to simulate blast effects in RC panels.

The paper reports experimental and numerical simulation of ballistic impact problems on thin composite laminated plates reinforced with Kevlar 29. Ballistic impact was imparted with simulated fragments designed in accordance with STANAG-2920 on plates of different thickness. Numerical modelling was developed and used to obtain an estimate for the limit perforation velocity V50 and simulate failure modes and damage. Computations were carried out using a commercial code based on nite differences and values obtained are compared with the experimental data to evaluate the performance of the simulation. Good correlation between computational simulation and experimental results was achieved, both in terms of deformation and damage of the laminates. Future work is advanced to include the interposition of an outer ceramic layer as well as examining the influence of dry-wet and temperature cycles on the mechanical strength of the plates and their temporal evolution under accelerated ageing.

The numerical implementation of the displacement model of the hybrid-{T}refftz finite element formulation is presented. The geometry of the supporting element is not constrained a priori. Unbounded, non-convex and multiply connected elements can be used. The approximation basis is naturally hierarchical and very rich. It is constructed on polynomial solutions of the governing differential equation, and extended to include the particular terms known to model accurately important local effects, namely the singular stress patterns due to cracks or point loads. Numerical and semi-analytical methods are used to compute the finite element matrices and vectors, all of which present boundary integral expressions. Appropriate procedures to store, manipulate and solve symmetric highly sparse systems are used. The characteristics of the finite element solving system in terms of sparsity and conditioning are analysed, as well as its sensitivity to the effects of mesh distortion, incompressibility and rotation of the local reference systems. Benchmark tests are used also to illustrate the performance of the element in the estimation of displacements, stresses and stress intensity factors.