Applied continuous modelling in the study of pyrotechnic shock propagation on Ariane 5

This paper deals with the theoretical method and the modelling problems on the analysis of the Pyrotechnic Shock Propagation in the Vehicle Equipment Bay Structure of the ARIANE 5 during the separation of the upper stage. This work has been developed under a contract with the Spanish Firm Construcciones Aeronáuticas S.A. From all the analysis and the studies it can be concluded that: 1.- The mathematical method used for the study of the pyrotechnic shock phenomena is very well suited for conducting parametric studies. 2.- A careful model of the structure should be developed taking into account the realistic stiffness and dissipation properties at the junctions. 3.- The load produced by the pyrotechnic device should be carefully calibrated to reach a good agreement between theoretical and test results. 4.- In any case with the adquired experience it can be said that with the modelling of continuous elements the order of magnitude of the accelerations can be predicted with the accuracy needed in practical applications.

Seismic modelling of bridges with semirigid connections

The need to modal semi-rigid behaviour of joints to analyze the seismic response of bridges arises when retrofitting devices such as cables or bolts are introduced in otherwise free joints or when the design takes advantage of the plastification of structural sections to impose energy dissipation though their ductile behaviour. The paper presents some preliminary results of a parametric study carried out using s1mplified computational models. Two instances where semirigid connection play a role in the seismic response of bridges have been discussed. The ongoing research from which this paper is extracted is intended to enhance understanding on the effectivness of various bridge retrofitting measures and to provide information that may be used to calibrate some ECS-2 rules. Finally, it is hoped that the development of reliable simplified techniques for nonlinear analysis will provide designers with useful tools to examine behavior and ultimately improve seismic safety in actual bridges.

Extracting energy from Vortex-Induced Vibrations: A parametric study

Here, Vortex-Induced Vibrations (VIVs) of a circular cylinder are analyzed as a potential source for energy harvesting. To this end, VIV is described by a one-degree-of-freedom model where fluid forces are introduced from experimental data from forced vibration tests. The influence of some influencing parameters, like the mass ratio m∗ or the mechanical damping ζ in the energy conversion factor is investigated. The analysis reveals that: (i) the maximum efficiency ηM is principally influenced by the mass-damping parameter m∗ζ and there is an optimum value of m∗ζ where ηM presents a maximum; (ii) the range of reduced velocities with significant efficiency is mainly governed by m∗, and (iii) it seems that encouraging high efficiency values can be achieved for high Reynolds numbers.