Engineering Structures Seismic reliability of spherical containers retrofitted by means of energy dissipation devices

a b s t r a c t For the purpose of enhancing the seismic reliability of structures, external energy dissipation systems may be advantageously used. In this paper, the reliabilities of a spherical storage tank in original and updated states are assessed by means of simulation. The effect of the energy dissipation system is numerically evaluated by performing a set of nonlinear dynamic analyses on a spherical tank based on a detailed model that takes the fluid-structure interaction into account. To obtain robust estimators of the reliability, an ensemble including acceleration records with markedly different characteristics is used in the simulation study. The full reliability analysis shows that, for a typical spherical container widely used in the petrochemical industries, a reduction of the limit state probability in the order of 85% may be expected by introducing additional energy dissipation systems

Non-linear Damping and Frequency Identification in a Progressively Damaged R.C. Element

This paper describes the non-linear identification of a progressively damaged reinforced concrete beam-column node. The aims are the detection and identification of the different sources of damping and their dependence from the damage level. To this end a specially formulated non-linear identification method is proposed, based on a time-varying polynomial approximation of the system dynamics, suitable for use in the presence of excitations of any form. A minimum condition imposed to the identified dissipated energy leads to the distinction of the linear viscous component from the other damping mechanisms. The estimated values obtained from the experimental tests show a significant influence of the damage level on the linear viscous damping coefficient. This suggests that, in a non-linear dynamic time-history analysis, the use of Rayleigh damping model with proportionality to the initial stiffness is basically in contrast with experimental evidence and more refined viscous damping models are needed for prediction purpose