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integrated survey to seismic risk anaLysis, resiLience reduction and pLanning G. Cascini, B. Murgante, M. VonaScuola di Ingegneria, Università della Basilicata, Potenza, Italy

Introduction. To mitigate the seismic risk and to reduce the economic direct and indirect losses, a synergic work based on the best practice is need using rational criteria by all those involved. Moreover, to improve the resilience of the cities, the seismic risk mitigation must be considered as a fundamental phase in mitigation strategies (Tilio et al., 2012). Due to the large amount of buildings that require seismic retrofitting and the limited available resources, the correct spatial and temporal resources distribution should be based on objective distribution strategies. In order to implement retrofitting strategies of the buildings, firstly each decision maker must be able to identify the main characteristics of the buildings. The morphological, geometrical, and structural information about town, her streets, buildings and their aggregation play a fundamental role.

The work would like to provide tools able to define direct the fundamental information for seismic risk mitigation, based on scientifically accurate assessments of geometric characteristics of the buildings. Moreover, the other part of the work is define the first survey of damage status of buildings after buildings, overcoming the use of tools based on expert and empirical evaluation. Particularly, the existing tools and methods are unable to provide a correct assessment the characteristics of the buildings and their interaction between seismic risk mitigation necessity and urban planning.

In the paper, the results of survey of a damaged historic centre have been reported. The survey has been carried out using an integrated approach between different survey methodologies and tools.

The case study.case study. study. In Italy, there is a significant number of historical centre that became ghost town. Generally, several natural events could be started the relocation of the villages. In this work, a typological characterization of a damaged historical centre is reported. The case study is the historical centre of Romagnano al Monte (Salerno, south of Italy).

The types of buildings seems almost similar with some differences for more recent buildings the more recent part of the village. The buildings in the historical centre are small size (up to 2-3 storeys) and typically have a rubble masonry structure, with poor construction quality, and were frequently connected in heterogeneous structural aggregates. In the more recent zones, structural types had somewhat heterogeneous characteristics: rubble, concrete block, and brick masonry were present, often variously combined in the same structure with several types of floor. Moreover, some framed RC buildings built after the 1960’s were present. After November 23, 1980, (MW=6.8 (CPTI15, Italian Parametric Earthquake Catalogue 2015), for Romagnano al Monte the macroseismic intensity was characterised by value of IMCS = VIII-IX, the village has been strongly damaged but not destroyed like other nearby towns.

A few months after the 1980 Irpinia earthquake, on the basis of high damage levels and mainly for mostly existing socio-economic problems, the Romagnano al Monte was forsaken (Vona et al., 2016). The relocalisation was therefore decided also and the historical centre became a ghost town. Then Romagnano al Monte is “frozen” in the 1980 post - earthquake condition. For these reason, Romagnano al Monte has been selected in order to apply and validate same techniques and procedures to survey types of buildings and the first survey of post earthquake damage.

Survey methodologies. The knowledge of vulnerability of the buildings is a key step to mitigate the seismic risk. Several studies have been carried out to assess the vulnerability of the buildings based different approaches as the observed damage and its correlation with typologies characteristics.

In order to apply these different approaches, a fundamental role is played from the quality

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and completeness of information available for the buildings. Classically, this information have been linked to the territorial scale of the investigated area. Consequently, a lot of economic resources have always been required. For all methods, the parameters are almost: construction age, structural type, height, surface, materials.

Then, the usual survey methods (Masi et al., 2014) should be overcome in order to investigate about several other aspects and other important questions. Several parameters are needed in order to investigate about the seismic vulnerability as:

- type and organization of the resisting system,- quality of the resisting system, - conventional capacity based on dimensional and strength of structural elements,- topographic and morphological conditions that are more important for historical

buildings,- types, stiffness, and connection with masonry walls of floor and roof,- configuration in-plan and in elevation,- non-structural elements,- retrofitting and maintenance level.Moreover, several additional information are need in order to carried out a wide, complete,

and complex analysis based on the concept of resilience.In this work, the novel methods are reported as alternative of existing methods. In particular,

in order to studies the buildings typologies and the failure modes, the survey has been carried out on damaged historical centre. Then, the results of the study could provide useful indications in order more reliable and fast survey of the historical centres in the post-earthquakes emergency management and in set up of the mitigation strategies pre earthquakes.

In order to define an alternative approach to survey the historical centres, two topics play a fundamental role:

1. rapidity of the methods and procedures;2. reliability of the obtained data.In order to carried out a fast survey, the UAV and aero - photogrammetics tools have been

used. In order to validation of the results, several surveys with classic form and classic tools have been carried out.

Classic survey form. In this work, a first comparison has been carried out with a rapid inspection form obtained from the post-earthquake damage and safety assessment inspection AeDES form. In particular, the comparison has been carried out with the building identification data.

The survey form is able to define the position of each single building, its position in aggregate of buildings, and geometrical description of the buildings as number of storeys, average storey height, average floor area, building age, use, number of units with the respective number of occupants and percentage of utilization.

Survey from autonomous aerial robot (unmanned aerial vehicles, UAV). Considering the wide extension of survey area, the use of aerial robotic is the best solution. In fact, they are able to capture imagine to higher spatial resolutions that are sub 1-centimeter. On the basis of the fundamental topics of this work, the considered survey method seems able to define a rapid and accurate of geometrical characteristics of the buildings and urban characteristics (as dimension of the streets and so on) and damage assessment after each earthquake, in particular on historical centres that could be not quickly and easily accessible.

Significant accuracy can also be obtained on fundamental data as building size and building type. Moreover, the method is able to investigate about the facades of the buildings then about fundamental topics as windows and soft story that are not visible from satellite images.

A key role has been played from planning trajectories and motion planning methods. In this work the motion flight planning has been defined on the basis of the survey goals. In particular, the fundamental topics have been:

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- extension of survey area;- focalization and positioning of Ground Control Points (GCP) and definition of Ground

Sample Distance (GSD);- timing, data and execution of the flight.Results. The flight plan has been designed to optimize the 3D restitution of the buildings in

the urbanized areas. This result has been obtained from extraction of the point cloud of buildings. Objects (like buildings) have been extracted from non-ground points. About investigated area, the point cloud is based on 46,555,492 points as derived from DEM. It has been possible to

derive extensively height and floors number for each building within test area.

Several cases are reported in order to show the main results of the work. First, two cases of damage are reported in order to show the ability of the procedures to survey different damage cases. Obviously, the results should be considered as the first application of the procedures.

Finally, the geometrical characteristics of several building in aggregate are reported. Dimensional parameters from the image have been extracted (Fig. 3), classified and compared with classical approach.

The results show that the considered integrated method leads to results far better if compared to classical approaches. The survey has been able to define the geometrical characteristics of each single building and its aggregate. For each building, number of storeys, storey height, floor area have been accurately identified. Structural characteristics of buildings have been easily identified from direct survey, historical studies and existing technical design and literature.

Fig. 1 – The first case is the total collapse of roof.

Fig. 2 – The second case is the partial collapse of the roof.

Fig. 3 – Dimensional parameters extracted from the image.

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ReferencesMasi A., Chiauzzi L., Samela C., Tosco L. and Vona M., 2014. Survey of dwelling buildings for seismic loss assessmentSurvey of dwelling buildings for seismic loss assessment

at urban scale: the case study of 18 villages in Val d’Agri, Italy. Environmental Engineering and Management Journal. Vol. 13(2), 471-486. http://omicron.ch.tuiasi.ro/EEMJ/pdfs/vol13/no2/26_401_Masi_12.pdf

Rovida A., Locati M., Camassi R., Lolli B., Gasperini P. (eds), 2016. CPTI15, the 2015 version of the ParametricCPTI15, the 2015 version of the Parametric Catalogue of Italian Earthquakes. Istituto Nazionale di Geofisica e Vulcanologia. doi:http://doi.org/10.6092/Istituto Nazionale di Geofisica e Vulcanologia. doi:http://doi.org/10.6092/INGV.IT-CPTI15

Tilio L., Murgante B., Di Trani F., Vona M. and Masi A.; 2012: Mitigation of urban vulnerability through a spatial muulticriteria approach. Disaster Advances. Vol. 5 (3).Disaster Advances. Vol. 5 (3).

Vona M., Harabaglia P., Murgante B., 2016, Thinking about resilience cities studying Italian earthquake, Urban Design And Planning. 169 (4), pp. 185-199. http://dx.doi.org/10.1680/udap.14.00007.