OVERVIEW OF THE VESUVIUS CASE STUDY … · FINAL CONFERENCE. Naples, ... Giornata Inaugurale del...

COST Action C26

Urban Habitat Constructions under Catastrophic Events

FINAL CONFERENCE. Naples, 16th- 18th September 2010

M. Indirli, ENEA, Bologna, Italy

VESUVIUS SPECIAL SESSION

OVERVIEW OF THE VESUVIUS CASE STUDY ACTIVITY

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The VESUVIUS case study in the framework of the EU COST Action C26 activity

In the Delft meeting (November 17 - 18, 2006), the goal of WG4 has been devoted to any natural hazard except earthquake

“Resistance to Infrequent Loading Conditions”

as flood, landslide, extreme wind and snow, avalanche, tsunami and storm surge, coastal erosion, volcanic eruption, etc.

The focus has been pointed on:

- identification, characterization and modeling of natural disasters (and their interrelations/scenarios);

- construction response and possible relevant consequences of combined extreme loadings in the built environment.

Since the beginning, the work seemed too huge without a robust “Ariadne's thread” to follow.

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Therefore, three directions have been identified for the research:

a) the investigation on each single catastrophic infrequent event; b) the set up of a multi-hazard approach, together with the development

of a common methodology for risk assessment; c) the identification of a pilot study enough general to join several disciplines

in a transversal approach.

Delft meeting, November 17 - 18, 2006; Prague Workshop, March 30-31, 2006; Naples, June 8-9, 2007.

In Naples, the discussion was related to the organization of WG4, deciding to modify its scope and name, which changed in:

“Risk Assessment for Catastrophic Scenarios in Urban Areas”

The Vesuvius extreme dangerousness induced the WG4 to introduce the ‘Vesuvius case study’ within its research activities,

with particular regard to the effects on the constructions produced by a possible eruption.

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After a general discussion (Timisoara, October 26-27, 2007), a specific enlarged WG4 meeting was organized (Trieste, January 17-18, 2008), where the Vesuvius case study has been focused.

Not addressed to the issue of evacuation, the study has been restricted to the modelling of loads acting on structures and the corresponding construction response.

The work on Vesuvius continued in the following Action meetings, with the main result to find some paradigmatic sets of structures, to be investigated in the surrounding area of the

Neapolitan volcano.

(Vilnius, April 11-12, 2008; Naples, 19 May 2008;

Madeira, June 5-6, 2008; Malta Workshop, October 23-25, 2008;

Naples, January 23, 2009; Southampton, March 27-28, 2009;

Rome, June 22-24, 2009; Skiathos, September 4-5, 2009; Aveiro, November 27-28, 2009;

Nicosia, March 19-20, 2010).

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The work involved several experts of different disciplines and created an enlarged platform

for a free and productive discussion.

VESUVIUS 2000Project objectives

Flavio Dobran

GVES, Napoli, Italy

www.westnet.com/~dobran

Urban Habitat Constructions Under Catastrophic Events

Trieste, 17 January 2008

Earthquake scenarios for the Earthquake scenarios for the

determination of the seismic load on determination of the seismic load on

the structures surrounding Vesuvius.the structures surrounding Vesuvius.

Giuliano F. PanzaGiuliano F. Panza

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Trieste, 17-18 January 2008

COST C26 ACTIONCOST C26 ACTION

““URBAN HABITAT CONSTRUCTIONS UNDER URBAN HABITAT CONSTRUCTIONS UNDER

CATASTROPHIC EVENTSCATASTROPHIC EVENTS””

1717--18 JANUARY 200718 JANUARY 2007

TRIESTE, ITALYTRIESTE, ITALY

UNIVERSITY OF NAPLES UNIVERSITY OF NAPLES ““FEDERICO IIFEDERICO II””

Department of Structural EngineeringDepartment of Structural Engineering

PROF.PROF. Federico M. MAZZOLANIFederico M. MAZZOLANI

Dr. Beatrice FAGGIANODr. Beatrice FAGGIANO

ENG. Daniela DE GREGORIOENG. Daniela DE GREGORIO

VESUVIUS CASEVESUVIUS CASE

Università degli Studi di Napoli “ Federico II”

Presentazione delle Attività del Centro Studi

P.LIN.I.V.S.(Per L’INgegneria Idrogeologica Vulcanica e Sismica)

Giulio Zuccaro

Napoli

19 Febbraio 2008

Giornata Inaugurale del

Centro Studi PLINIVSCentro di Competenza del

Dipartimento di Protezione

Civile Nazionale

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State-of-the-art on Vesuvius

Projects and papers

Timisoara, October 26-27, 2007

Trieste, January 17-18, 2008

Vilnius, April 11-12, 2008

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Principal eruptions of Vesuvius

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List

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Typologies of the principal volcanic actions by Vesuvius on the constructions

Volcanic actions of Vesuvius

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lava

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Identification of the target area

The red zone, the most dangerous area around Vesuvius

The investigated area: the Municipality of Torre del Greco

Coordinates 40°47’7’’N - 14°23’43’’E

Altitude 43m s.l.m.

Surface 30,66km2

Inhabitants 88.894 (2007)

Density 2.899,34 inhab./km2

Istat code 063084

Land register code L259

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Identification of the target buildings

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The survey team

- experts of University of Naples “Federico II”- experts COST ACTION C26- Experts of PLINIVS Centre, Naples

The support of PLINIVS Centre has been fundamenntal, for knowledge and experience

visual examination, the compilation of ad hoc forms

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The investigation methodology

1) volcanic vulnerability

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2) MEDEA: seismic damage mechanisms

3) Additional information specific for cultural heritage for the Vesuvian Villas

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The PLINIVS Study Centre developed:

computerized tool to build up the seismic impact in the volcanic areas around Vesuvius and Campi Flegrei

tools intended to evaluate a reasonable estimate of the cumulative damage impact scenario as a consequence of a Vesuvius eruption of assigned intensity

The model is integrated in a Geographic Information System (GIS) and refers to Vulnerability Functions and on cumulative damage on the buildings

The tool is intended to control the progressive impact up to the final impact scenario

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At the moment, EXPLORIS considers only three volcanic phenomena:earthquakes (EQ)ash falls (AF) pyroclastic flows (PF)

The eruptive event is studied from the first precursory seismic event up to the final pyroclastic flow, by evaluating the damage accumulated on the buildings and the distribution of damage on the territory at each step of the process.

The evaluation of the volcanic impact on the constructions is very complex and depends on the possible eruptive scenario, which has been assumed.

The combination of the three volcanic phenomena can increase the damage on buildings, in comparison with the effects of each phenomenon acting separately.

The ‘quick’ methodology for the volcanic vulnerability assessment and the survey form have been developed within the EXPLORIS European project (2002-2005)

developed by the PLINIVS Centre.

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THE VOLCANIC VUNERABILITY ASSESSMENT

The methodology is based on the assignment of specific vulnerability classes with respect to each exceptional action, in function of the structural elements typology.

AF: 5 classes Ar, Br, C1r, C2r, Drwith vulnerability decreasing in function of roof typologies.

PF: 3 classes Ap, Bp, Cp for masonry buildings3 classes Dp, Ep, Fp for the RC buildings

with vulnerability decreasing in each group in function of vertical and horizontal structures.

EQ: 4 classes As, Bs, Cs, Ds with vulnerability decreasing according to the combinations

of horizontal and vertical structures.

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Examples of building classification in the historic centre of Torre del Greco

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The volcanic vulnerability assessment: examples of results

The impact of ash-fall is strongly dependent on the wind direction during the

eruption; the model considers 16 possible ‘sectors’ of

prevalent wind.

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Mitigation actions

earthquake

Considering the high seismic vulnerability levels and the construction density in the Vesuvius area, cost-effective mitigation measures should be provided.

It is possible to choose cheap and reliable technical solutions (such as iron chains in masonry buildings, the insertion of infill panels or resistant elements in soft floors of reinforced concrete buildings), but also to adopt, in case of seismic reinforcement, specific solutions able to respond effectively also to other volcanic phenomena, such as pyroclastic flows or ash fall.

One solution is the construction of pitched roofs by overlapping light structures in CFS (Cold Formed Steel). This allows to chain vertical structures by increasing the resistance to seismic actions (box behaviour) and simultaneously prevent the deposit of ashes and the structural risks related to overloading of the roof, also in consideration of a possible earthquake following the ash fall phase.

Should be avoided the employ of widely used reinforcement systems not satisfying the conditions of volcanic risk, such as FRP (Fiber Reinforced Polymers) Global mitigation strategies related to seismic risk in case of a volcanic event may include planning for widespread interventions, defining the areas that require priority actions.

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Mitigation actions

Pyroclastic flows

Pyroclastic flows can produce high damages to the built environment in areas near to the vent.

Although they would have a limited action range, the effects can be critical because of the combination of mechanical impact and thermal stress on the vertical surfaces of buildings.

The main damages come from the impact on openings.

Mitigation strategies mainly concern the reinforcement of infill panels in r.c. buildings and measures for the protection of openings.

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Mitigation actions

Ash fall

Ash fall is one of the eruptive phenomena with greater risk for existing buildings and infrastructure, as the expected impact involves (with different levels of intensity) a very large area, which definition is strictly linked to the direction and intensity of the wind, as well as to the type of eruption.

Mitigation strategies, beside the need to develop an operational plan for the removal of ash on roofs and transport networks, mainly concern the repairing and reinforcement of roofing systems in order to increase the load carrying capacity.

Pitched roofs with wooden or steel structure, reducing the deposits of ashes, would be at risk only in proximal areas where the surface of the cover present disconnections or missing parts. In this case, given the adequate inherent fire resistance of commonly used coating materials is enough to replace the missing elements in order to prevent the passage of hot ashes under the roof covering.

In case of flat roofs it is possible to identify two main types of intervention: the reinforcement of the roof slab in order to increase the resistance according to the expected overload, or the realization of a sloped roof over the existing one.

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Mitigation actions

Lahar

The lahars are a relevant risk factor for buildings and structures in volcanic areas.

The response of structures and buildings technical elements to the action of lateral forces produced by lahars depends mainly on construction type and materials employed, as well as specific characteristics such as size in plan and elevation, number, size and position of openings, spatial distribution and presence of protective elements around the building able to divert the flow, etc.

Structures, infill panels and ground floor openings are the technical elements most at risk in case of lahars. The reinforcement of these elements yet does not guarantee the survival of the building in case of direct impact with mudslide and debris, especially in the case of compact urban areas, where a "tunnel effect" can increase speed and height of the flow after the passage inside particularly narrow roads.

For this reason the most effective mitigation strategies are related to environmental engineering interventions, to be made in risk prone areas and designed to contain or divert lahars. Measures such as retention basins, alternative artificial canals, high-strength reinforced concrete containing structures, may be appropriate solutions to mitigate risk.

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Conclusions

The mitigation of volcanic risk on buildings and infrastructure can significantly reduce the expected damage after an eruptive event.

Even the impacts of high destructive type of eruptions, such as Sub-Plinian, can be strongly reduced by the application of one or more mitigation measures, responding to the different phenomena involved.

It is therefore necessary to start from a comprehensive knowledge of the construction types available in risk-prone areas, providing specific interventions that take into account the cumulative effects given by the expected time history of the event.

Hence, an effective design approach aims to put in relation technological features of existing buildings, parameters and data from probable scenarios, opportunities given by mixing together conventional technologies and advanced materials.

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Conclusions

Furthermore, considering the economical, political and social “weight” of the strategies for the mitigation of volcanic risk in densely populated areas, a valid evaluation method of the effectiveness of the proposed solutions can give scientific support to strategic choices and emergency plans.

Therefore, tools for assessment and comparison between different solutions and “mitigation scenarios” are needed, trying to put together the different factors involved, such as economical and social sustainability, cultural and historical value, implication on emergency plans and on post-eruption rehabilitation and reconstruction interventions.

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Conclusions

In the case of the Vesuvius “red zone”, long-term strategies capable to reduce the urban density are also strongly necessary.

It shall be very important to transfer strategic buildings, to stop the increasing of illegal constructions, to convince the people to live in places far from the volcano.

Finally, a “safety belt” around the Vesuvius belt should be re-created, in order to reduce the consequences of an eruption.

THANK YOU

FOR THE ATTENTION

OVERVIEW OF THE VESUVIUS CASE STUDY … · FINAL CONFERENCE. Naples, ... Giornata Inaugurale del...

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