Analysis of the Seismic Risk of Major-Hazard Industrial Plants and Applicability of Innovative Seismic Protection Systems

In this paper the main results obtained within different research projects, developed about the applicability of seismic passive control of major-hazard industrial installations are shown. The work concerns the main components of a refinery that have been classified and collected into a limited number of classes on the basis of the geometrical and mechanical characteristics. For each class, the main damages caused by past earthquakes have been described and the most vulnerable component have been identified. Finally, a synthesis of the effects of earthquakes on the different typology of process components has been carried out and the most suitable innovative seismic protection systems, in particular of passive type, have been recognized. Finally an example of using dissipative coupling between a distillation column and an adjacent service frame is illustrated

On the cyclic behaviour of new pier-to-deck connections for short-medium span composite I-girder bridges

Short-medium span steel–concrete composite I-girder bridges are becoming more and more popular, because of the reduced construction time and costs. The light weight renders them particularly suitable also is seismic areas, even though this advantage has not been yet adequately investigated. In fact, in case of seismic loading, significant tensile forces might be exhibited at the bottom flange of the steel girder, especially when monolithic connection between deck and pier is adopted, and the connection, conceived for sustaining prevailing hogging bending moments, could experience an excessive damage. With this aim, the cyclic behaviour of new pier-to-deck joints involving the use of concrete cross-beams (CCB) has been recently analysed within the European project (SEQBRI). This paper deals with the results of a wide experimental investigation of these new joints, performed with the aim of characterizing their hysteretic behaviour. Three different typologies were tested: one designed according to the German standard DIN-FB-104, generally utilized for gravity loads only, and other two types proposed for bridges located in low (VAR-1) and medium (VAR-2) seismicity. A series of displacement-imposed cyclic tests highlighted a good seismic behaviour of all the tested solutions. In particular, the DIN-FB-104 VAR C and VAR-2 displayed a similar global behaviour in terms of maximum force and displacement, but with a more pronounced crack development and buckling of steel girders of the first solution. The VAR-2 also avoids possible pull-out phenomena in the CCB thanks to the beneficial action of pre-stressing bars.A damage analysis of the proposed connections was finally performed in view of the application of the performance-based earthquake engineering methodology and the quantification the seismic performance of this bridge typology, which was among the aims of SEQBRI project. Keywords: Steel–concrete bridges, Concrete cross-beam, Cyclic behaviour, Experimental test, Damage analysi

Performance-based Earthquake Evaluation of a Full-Scale Petrochemical Piping System

Assessment of seismic vulnerability of industrial petrochemical and oil & gas piping systems can be performed, beyond analytical tools, through experimental testing as well. Along this line, this paper describes an experimental test campaign carried out on a full-scale piping system in order to assess its seismic behaviour. In particular, a typical industrial piping system, containing several critical components, such as elbows, a bolted flange joint and a Tee joint, was tested under different levels of realistic earthquake loading. They corresponded to serviceability and ultimate limit states for support structures as suggested by modern performance-based earthquake engineering standards. The so called hybrid simulation techniques namely, pseudo-dynamic and real time testing with dynamic substructuring, were adopted to perform seismic tests. Experimental results displayed a favorable performance of the piping system and its components; they remained below their yielding, allowable stress and allowable strain limits without any leakage even at the Near Collapse limit state condition for the support structure. Moreover, the favourable comparison between experimental and numerical results, proved the validity of the proposed hybrid techniques alternative to shaking table tests

Seismic vulnerability of above-ground storage tanks with unanchored support conditions for Na-tech risks based on Gaussian process regression

AbstractThis paper aims to investigate the seismic vulnerability of an existing unanchored steel storage tank ideally installed in a refinery in Sicily (Italy), along the lines of performance-based earthquake engineering. Tank performance is estimated by means of component-level fragility curves for specific limit states. The assessment is based on a framework that relies on a three-dimensional finite element (3D FE) model and a low-fidelity demand model based on Gaussian process regression, which allows for cheaper simulations. Moreover, to approximate the system response corresponding to the random variation of both peak ground acceleration and liquid filling level, a second-order design of experiments method is adopted. Hence, a parametric investigation is conducted on a specific existing unanchored steel storage tank. The relevant 3D FE model is validated with an experimental campaign carried out on a shaking table test. Special attention is paid to the base uplift due to significant inelastic deformations that occur at the baseplate close to the welded baseplate-to-wall connection, offering extensive information on both capacity and demand. As a result, the tank performance is estimated by means of component-level fragility curves for the aforementioned limit state which are derived through Monte Carlo simulations. The flexibility of the proposed framework allows fragility curves to be derived considering both deterministic and random filling levels. The comparison of the seismic vulnerability of the tank obtained with probabilistic and deterministic mechanical models demonstrates the conservatism of the latter. The same trend is also exhibited in terms of risk assessment

ANALYTICAL PROBABILISTIC RESILIENCE ESTIMATION FOR BRIDGES UNDER NEAR-FAULT EARTHQUAKES

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Hybrid simulation of complex structural systems based on partitioned time integration schemes

In the last two decades, the increasing complexity of engineering systems boosted the development of very efficient simulation methods based on partitioning. In view of coupling dynamic parts of hybrid systems, the finite element tearing and interconnecting approach emerged as the most promising technique. Nonetheless, there is still a lack of a comprehensive study of algorithmic performances from the experimental perspective. In this view, the present paper sheds light on the application of two well-known parallel partitioning methods for the purpose of the simulation of hybrid models. Thus, an existent reinforced concrete bridge is chosen as a benchmark case study. In order to perform hybrid simulations, a novel coupling software was devised. It allowed for combining two physical piers to the numerical model of the remaining part of the bridge. As a result, successful tests were conducted at the ELSA laboratory of the Joint Research Centre of Ispra (Italy)

Hybrid simulations of a multi-span rc viaduct with plain bars and sliding bearings

This paper deals with the seismic response assessment of an old reinforced concrete viaduct and the effectiveness of friction-based retrofitting systems. Emphasis was laid on an old bridge, not properly designed to resist seismic action, consisting of 12 portal piers that support a 13-span bay deck for each independent roadway. On the basis of an OpenSEES finite element frame pier model, calibrated in a previous experimental campaign with cyclic displacement on three 1:4 scale frame piers, a more complex experimental activity using hybrid simulation has been devised. The aim of the simulation was twofold: (i) to increase knowledge of non-linear behavior of reinforced concrete frame piers with plain steel rebars and detailing dating from the late 1950s; and (ii) to study the effectiveness of sliding bearings for seismic response mitigation. Hence, to explore the performance of the as built bridge layout and also of the viaduct retrofitted with friction-based devices, at both serviceability and ultimate limit state conditions, hybrid simulation tests were carried out. In particular, two frame piers were experimentally controlled with eight-actuator channels in the as built case while two frame piers and eight sliding bearings were controlled with 18-actuator channels in the isolated case. The remaining frame piers were part of numerical substructures and were updated offline to accurately track damage evolution

Seismic analysis and retrofitting of an existing R.C. highway bridge: investigation through pseudo-dynamic

The “Retro” TA project funded by the European commission within the Series-project aims at studying numerically and experimentally the seismic behaviour of an old existing reinforced concrete bridge with portal frame piers and the effectiveness of different isolation systems. In particular, an experimental test campaign will be performed at ELSA Laboratory of JRC (Ispra, Italy). Two piers (scale 1:2.5) will be built and tested using the PsD technique with sub-structuring; the modelling of he entire viaduct is considered along with the non-linear behaviour of each pier, due to bending, shear on the transverse beams and strain penetration effect at the column bases. The comprehensive numerical investigations have shown the high vulnerability of the sample bridge. Consequently two isolation systems (yielding-based and friction-based bearings) have been currently designed and characterized. Because the test will start after the summer 2012, in this paper the relevant issues will be here addressed and discussed.JRC.G.5-European laboratory for structural assessmen

Mortar-based systems for externally bonded strengthening of masonry

Mortar-based composite materials appear particularly promising for use as externally bonded reinforcement (EBR) systems for masonry structures. Nevertheless, their mechanical performance, which may significantly differ from that of Fibre Reinforced Polymers, is still far from being fully investigated. Furthermore, standardized and reliable testing procedures have not been defined yet. The present paper provides an insight on experimental-related issues arising from campaigns on mortar-based EBRs carried out by laboratories in Italy, Portugal and Spain. The performance of three reinforcement systems made out of steel, carbon and basalt textiles embedded in inorganic matrices has been investigated by means of uniaxial tensile coupon testing and bond tests on brick and stone substrates. The experimental results contribute to the existing knowledge regarding the structural behaviour of mortar-based EBRs against tension and shear bond stress, and to the development of reliable test procedures aiming at their homogenization/standardization