Renato Giannini

Out-of-plane seismic resistance of masonry walls

Seismic vulnerability of unreinforced masonry buildings is studied by means of simplified out-of-plane collapse mechanisms that take into account connections with transversal walls. According to experimental evidence, the analysis assumes that failure is reached with a rigid body motion of a part of the facade that falls down. Two classes of mechanism are examined: the overturning of the facade due either to a vertical crack at the connection or a diagonal crack on the transversal wall, both defined resorting to a simple model of masonry fabric, viewed as a regular assembly of rigid blocks and elastic plastic joints with friction but no cohesion. The use of simplified mechanisms give rise to an explicit evaluation of the seismic resistance to changes in the geometry and in the masonry fabrics, that could be used by practising engineers. This formulation is developed for both static horizontal actions and ground velocity peak, in the belief that the latter probably gives a better approximation of seismic action, while also providing, by comparison with the results of static forces, an estimate of the behaviour factor for unreinforced masonry. Eventually, the analytical forecasts are compared with numerical results obtained by means of the distinct element method.

An Efficient Approach for Seismic Fragility Assessment with Application to Old Reinforced Concrete Bridges

A procedure for seismic fragility assessment, suitable for application to non ductile RC structures is presented, which is based on the estimate of a response surface that gives the probability of failure of the structure as a function of the random variables that affect the response. The seismic fragility or risk is then evaluated through numerical integration. The method considers different sources of uncertainty: (i) in the seismic input, through the use of different accelerograms for the dynamic analysis; (ii) in the structural response, through the use of a refined nonlinear finite element model; and (iii) in the ultimate state capacity, taking into account the different modes of failure which may occur, for which a random mechanical capacity model is available. Aiming at reducing the number of simulation analyses, the uncertainties on the seismic input and on the mechanical parameters governing the response are treated according to the response surface methodology, while the limit-state randomness is treated explicitly during the simulations. Using the proposed procedure, the seismic safety of two reinforced concrete bridges from Italian highway network, with simply supported deck and either single stem or frame piers, is evaluated. The results are expressed in terms of fragility curves as function of spectral acceleration. The obtained results highlight the influence of material randomness on reliability and the relative importance of seismic input with respect to mechanical and epistemic uncertainty.

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

Seismic action can cause serious accidents to industrial plants as shown in several occasions. The actual worldwide situation of major-hazard plants against earthquakes should be considered as critical. For instance, in Italy about 30% of industrial plants with majoraccident hazards are located in areas with a high seismic risk. In addition, in case of a seismic event, the earthquake can induce the simultaneous damage of different apparatus, whose effects can be amplified because of the failure of safety systems or the simultaneous generation of multiple accidental chains. (a) (b)

Quantitative Seismic Risk Assessment of Process Plants: State of the Art Review and Directions for Future Research

Earthquakes represent a class of Natural-Technical hazards which in the past has been responsible of major accidents and significant losses in many industrial sites. However, while codes and standards have been issued to design specific structures and equipment in the civil and industrial domain, established procedures for Quantitative Seismic Risk Assessment (QSRA) of process plants are not yet available. In this paper a critical review of seismic risk assessment methods applicable to process plants is carried out. Their limitations are highlighted and areas needing further research are identified.Copyright

Seismic design and characterization of a new isolation system for high voltage circuit breakers based on wire-rope devices

This paper briefly describes the design and the characterization of a new base isolation system for the seismic protection of HV ceramics circuit breakers, in order to be qualified according to the standard CEI 62271-207. The solution adopted is based on the use of Wire Ropes. Accurate numerical analyses and experimental tests performed on a typical HV breaker upon a shaking table demonstrated the effectiveness of the proposed solution. An on-site installation in several Italian substations of this system has permitted to verify the simplicity and rapidity of the intervention necessary for the seismic upgrading of the circuit breaker.Copyright