Successes and failures in fighting landslides : Some experiences from Italy and elsewhere

When is an action taken to cope with a hazardous mass movement considered a success? When is it necessary to admit failure? This paper attempts to give an answer to these questions by examining the three main aspects of a landslide risk management programme: prediction, prevention (or mitigation) and emergency planning. Examples of successes and failures are given with reference to some of the best known case histories that have occurred, more or less recently, in Italy and elsewhere in the world. The recent developments of scientific research regarding the different aspects of landslide risk management are briefly outlined. As far as the prediction phase is concerned, the state - of - the - art on landslide risk assessment and the basic differences between spatial and temporal prediction are briefly summarized and discussed. The GIS database of the Emilia - Romagna region, containing over 30000 individual landslide, is presented as a successful example of a spatial prediction containing elements for temporal forecasting. The exceptional 1996 Versilia rainstorm that triggered more than 1450 debris flows, causing 13 casualties, is described as a representative case of an unpredictable event. A general framework for the main strategies and techniques employed for landslide risk prevention is proposed. A successful case history, the urban transformation accomplished in the second half on the 19th century on the San Miniato hill of Florence is presented: the architectonic transformation, of high artistic and landscape value, was combined with an effective stabilization of the hill, the instability of which was documented in a number of historic documents starting form the 11th century. The 1998 Sarno disaster is illustrated as an example of prevention failure: a series of debris flows caused 161 casualties in the suburbs of Sarno and Quindici, where uncontrolled urban development took place on areas historically exposed to high hazard. The basic requirements of a successful emergency plan are therefore discussed, such as monitoring and warning system and simulation techniques for risk scenario analyses. The emergency plan devised and implemented after the occurrence of the 1993 La Josefina landslide in Ecuador is presented as a success: the landslide produced a dam on the Rio Paute and the successive emergency measures managed to reduce the losses caused by the dam breaching and overtopping to a minimum. Finally, the well - known 1963 Vaiont disaster is proposed as a representative example of unsuccessful emergency planning: more than 1700 casualties were caused by the catastrophic flood wave generated by the sudden failure of a huge mass of rock into a reservoir. (AU)

Italian and European guidelines for seismic design of isolated bridges

In the past few years official guidelines have been issued in Europe and in Italy to regulate the design of (passively) isolated bridges. Explicity covered is the use of elastomeric and elato-plastic elements. The design philosophy aims at ensuring adequate protection with respect to two Limit-States or Perfomance Levels: the first one being the limit of fully elastic response, the second one being a state where the structure is still undamaged while the isolating elements are close to their ultimate deformation. Capcity design measures are adopted to ensure the protection of the structural parts even for larger-than-anticipated seismic events. Detailed requirements on the behaviour of the isolating elements so that they can reliably fulfil their protective role are given. Modelling, methods of analysis and verification criteria complete the content of the Guidelines. Aspects requiring improved definition are discusses in the conclusions of the paper.(AU)

Seismic vulnerability evaluation and damage scenarios

Some conceptual aspects of vulnerability evaluation are firstly examined. The need for experiments, either real or virtual, is recognized as a key for understanding and classifying the various methods. The discussion on damage scenarios is restricted to damage to constructions, leaving apart damage to contents, casualties and economic losses, whose assessment is at an earlier stage.(AU)

Seismic evaluation and rehabilitation of masonry buildings

Considerations on seismic assessment and retrofit of unreinforced masonry buildings are presented with special reference to the recent reasearch activity coordinated by the Italian National Group for the Defense from earthquakes (GNDT).The role of experimental testing is briefly discussed, summarizing issues which are meaningful for design and assessment applications.Needs for future research are pointed out in the course of the paper.(AU)

Actuality and modeling of historical masonry

The following presentation deals with the masonry hauses in historical towns, regarding them with the aim to understand their constructive actuality and to point our the most suitable way of mechanical modeling. The research is not at its conclusion and only the main steps of its development can be illustrated toghether with some partial results, nevertheless both the approach to the constructive analysis and the modeling proposal are worth, in our opinion, to be presented and discussed, The first of them, as it will be illustrated, shows the peculiar feature of the masonry work present in historical tows in Italy and in large part of western area. From such peculiarity the second item derives a consequent way to model, from a mechanical point of view, such masonry walls (AU)

Rehabilitation of URM building in Italy

The problem concernig the rehabilitation of unreinforced masonry buildings in Italy is presented in its general dimension, a problem which deals with the definition of seismic hazard, the vision of seismic risk for the whole population of buildings present on the territory, the related concept of seismic vulnerability, the basic problem of how to reduce the risk on the whole population and on the single buildings, the particular questions which arise for historical and monumental buildings, and for strategic buildings, and finally the problems regarding applications: technical codes, specific laws and spreading of knowledge (AU)

Some aspects of seismic hazard assessment when comparing different approaches

The Cornell and Gumbel approaches to probabilistic seismic hazard assessment have been applied in northeastern Italy to test the influence of various input parameters. Problems related to earthquake source geometry, seismicity descriptions, an d attenuation of two ground-motion parameters of engineering interest (peak ground acceleration and macroseismic intensity) have been analyzed. The results seem to be very sensitive to this last variable (attenuation), while different methodologies can lead to very similar evaluations, if properly applied. Properly applied means that all the input parameters are prepared to satisfy the conditions of the chosen approach. In addition, the seismotectonic knowledge of the study region conditions the choice of approach to be applied.(AU)