Natural hazards pose a significant threat to historical cities which have an authentic and universal value for mankind. This study aims at codifying a multi-risk workflow for seismic and flood hazards, for site-scale applications in historical cities, which provides the Average Annual Loss for buildings within a coherent multi-exposure and multi-vulnerability framework. The proposed methodology includes a multi-risk correlation and joint probability analysis to identify the role of urban development in re-shaping risk components in historical contexts. The workflow is unified by exposure modelling which adopts the same assumptions and parameters. Seismic vulnerability is modelled through an empirical approach by assigning to each building a vulnerability value depending on the European Macroseismic Scale (EMS-98) and modifiers available in literature. Flood vulnerability is modelled by means of stage-damage curves developed for the study area and validated against ex-post damage claims. The method is applied to the city centre of Florence (Italy) listed as UNESCO World Heritage site since 1982. Direct multi-hazard, multi-vulnerability losses are modelled for four probabilistic scenarios. A multi-risk of 3.15 M€/year is estimated for the current situation. In case of adoption of local mitigation measures like floodproofing of basements and installation of steel tie rods, multi-risk reduces to 1.55 M€/yr. The analysis of multi-risk correlation and joint probability distribution shows that the historical evolution of the city centre, from the roman castrum followed by rebuilding in the Middle Ages, the late XIX century and the post WWII, has significantly affected multi-risk in the area. Three identified portions of the study area with a different multi-risk spatial probability distribution highlight that the urban development of the historical city influenced the flood hazard and the seismic vulnerability. The presented multi-risk workflow could be applied to other historical cities and further extended to other natural hazards.

PurposeThis paper aims to contribute to the discussion of the experimental campaigns on Cultural Heritage buildings. By adopting integrated procedures it is possible to limit the invasiveness of the destructive techniques leading to reliable results. The purpose is the proper definition of the structural system, which represents the starting point of the following analysis's phases, not treated in this work. A methodology based on normative references and acknowledged non-destructive and partial destructive strategies has been conceived. The latter aims to an accurate comprehension of the structural information.Design/methodology/approachAn integrated approach for the structural assessment of cultural heritage buildings is presented. The methodology defines an interdisciplinary procedure based on normative references, non-destructive and minor-destructive techniques. A funnel-shaped workflow is developed to characterize the structural system of the buildings. The non-destructive campaigns are widely extended. Then, in-depth analysis concerning partial demolitions and minor-destructive tests are performed. The dynamic identification of the building is executed to detect its global response. The final validation of the assumed mechanical values is obtained by comparing the experimental modes coming from the ambient vibrations and the analytical modes of the structural modelling.FindingsThis research belongs to the Protocol signed between the Municipality of Florence and Department of Earth's Science and Department of Architecture of the University of Florence for the seismic vulnerability assessment of relevant and strategic buildings.Research limitations/implicationsThe descripted methodology is targeted for monuments and special buildings where the use of destructive techniques is not possible or unrecommended.Social implicationsSocial implications are related to the conservation of Heritage buildings. The latter deals with: (1) risk assessment of the targeted buildings towards different hazard sources (e.g. earthquakes, floods); (2) knowledge path developed through non-invasive diagnostic campaigns oriented to the conservation of the manufact. Furthermore, the paper encourages towards the recognition of non-destructive techniques and ambient vibration tests for the achievement of higher knowledge levels.Originality/valueThis paper defines a funnel-shaped procedure defining hierarchical roles between the different available strategies. The originality of this contribution is firstly related to the methodological flowchart. It is targeted to limit the invasive tests and consequently achieving accurate levels of knowledge. Secondly, some novelty can be found in the adoption of improvement parameters from a regional database adopting a Bayesian approach.

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H-BIM paradigms are constituted by 3-D informative contents documenting the current and past state of existing structures. Although the transversal vision and the multidisciplinary interpretation have been attributed to BIM models, in the field of monumental structures, these databases can be organized in different ways depending on the adopted protocol and classifications for the required output of the work. In this manuscript, an H-BIM approach targeted at collecting and providing useful information to execute seismic vulnerability analyses of monumental structures is presented. The BIM modeling followed a protocol based on the following steps: geometrical acquisitions, scan-to-BIM modeling, and informative data collection. The methodology has been applied to the oldest part of Palazzo Vecchio in Florence (IT), an important monumental masonry structure representing the political headquarter of the city since the Middle Ages. The parametric modeling was realized classifying the information according to structural perspectives based on the cognitive steps for the investigation of the existing structures. Finally, a seismic assessment has been realized through a simplified procedure developed for cultural heritage buildings. The outcomes of the evaluation are still part of the collected information of the H-BIM model, as an example of continuous improvement of the available contents of the database.