FOSTERING THE RESILIENCE OF HERITAGE BUILDINGS IN NEW ZEALAND: POTENTIALITIES OF DECISION SUPPORT SYSTEMS

Sonia GIOVINAZZI1, Shannon ABELING2, Francisco GALVEZ2, Stacy VALLIS23, Tatiana GODED4, Nick HORSPOOL5, Elena CALANDRA6, Jason INGHAM7

ABSTRACT

The 2010-2011 Canterbury earthquake sequence (CES) in New Zealand, and further recent earthquake events worldwide, has shown the invaluable loss that earthquakes can cause to architectural heritage. This paper explores the potentiality and the extent to which Decision Support Systems (DSSs) might have on informing the decision- making processes towards thriving the resilience of heritage buildings to natural hazards, with special focus on earthquakes. In particular, in the paper, reference is made to RiskScape, the New Zealand DSS platform for assessing the risks from natural hazards, where the possibility to assess the seismic vulnerability of heritage buildings and to prove the effectiveness of different mitigation options, at territorial scale, has been already embedded, as far as churches are concerned. The idea would be to include further add-ins to RiskScape to contribute towards an ambitious initiative aiming to enhance the seismic resilience of heritage buildings in New Zealand. In this paper, the idea to include in RiskScape, as a first step, a database to foster the awareness of stakeholders and communities on their Cultural Heritage at risk, is firstly discuss. The already embedded RiskScape add-in that allows performing scenario analysis at territorial scale to assess direct and indirect impacts is then illustrated. Finally, a further add-in that enables the analysis at single building level to identify the most likely collapse mechanisms is illustrated. This could support the identification of effective mitigation strategies pre-event and of emergency management and repair/reconstruction strategies, post-event.

Keywords: Cultural Heritage; Resilience; Decision Support Systems; Seismic Vulnerability; Retrofitting Strategies.

1. INTRODUCTION

There is a unanimous agreement on the criticality and urgency to collaboratively work to foster the resilience of cultural heritage, including tangible and intangible, moveable and immovable items, since they are increasingly affected by both natural and human-made threats and since the conservation of cultural heritage, is critical for sustainable and stable development of societies. Cultural heritage supports, among others, cultural identity and wellbeing of communities as well as local economy and economic growth; also, the cultural diversity that cultural heritage embodies, contributes to the resilience of social systems as it is the result of centuries of slow adaptation to the hazards that affect local environments. Unfortunately, in all regions of the world and for all types of cultural heritage there is, at the time being, a very low level of awareness and preparedness in regard to disaster risks that might potentially affect cultural heritage, and an almost total lack of inclusion of cultural heritage in general

1Senior Research Fellow, Geospatial Research Institute, University of Canterbury, , New Zealand, [email protected] 2 PhD candidate, Department of Civil and Environmental Engineering, University of Auckland, 1023 Auckland. 3 PhD candidate, School of Architecture and Planning, University of Auckland, 1010 Auckland 4Seismic Hazard Modeller, GNS Science, Avalon, New Zealand, [email protected] 5Risk Specialist, GNS Science, Avalon, New Zealand, [email protected] 6Director, Istituto Centrale per l'Archeologia - MiBACT, Rome, Italy 7Professor, Department of Civil and Environmental Engineering, University of Auckland, Auckland, New Zealand, [email protected]

disaster risk management strategies and plans8 The 2010-2011 Canterbury earthquake sequence (CES) in New Zealand and further recent earthquake events worldwide have shown the invaluable loss that earthquakes can cause to architectural heritage. In particular, the CES resulted in the loss of invaluable local architectural heritage, as a number of unreinforced masonry buildings, having significant historic, architectural, and social importance, and recognized as “historic places” by (2018) were demolished instead of undergoing repair (Figure 1). In the aftermath of the CES9 BlueShield released a statement reminding that “In addition to the tragic loss of human lives and the country’s prevailing state of shock, the loss of significant aspects of Christchurch’s heritage will have profound and lasting consequences on the self-conception and the collective memory of its inhabitants. The intangible values of a people’s cultural heritage can support the processes to regenerate normality and help people to move forward. Cultural heritage is a fundamental aspect in the rebuilding of community identity and dignity, as well as in keeping up hope after such a catastrophe. The Blue Shield trusts that the emergency authorities will take appropriate measures to ensure the preservation of heritage features of the city in the aftermath of the disaster’’.

Several efforts were taken to preserve the heritage features of the city as envisaged by the BlueShield; but, unfortunately, the lack of prevention and, the idea that repair and reconstruction was not feasible, not-economically viable, and that in any case could not bring some unreinforced masonry (URM) buildings to an acceptable safety standard level were, among others, the reasons that supported the demolitions of some heritage buildings (Heritage New Zealand, 2018). Christchurch City Cathedral, iconic symbol of Christchurch City, only recently escaped the same fate, thanks also to the strong opposition of community groups that fought against the demolition decision originally took by the owner of the Cathedral and supported by the Government10.

c) a)

b)

Figure 1. Examples of cultural Heritage lost after the CES (pictures courtesy of Heritage New Zealand 2018): a) building”, Category 1 historic place- Demolished 2011; b) Cranmer Court (former Normal School), Category 1 historic place - Demolished 2012; c) (former Christchurch Girls High School), Category 1 historic place - Demolished 2011, Architecturally it was significant as a fine example of Victorian school architecture in a Venetian Gothic style. Historically it was identified with the development of women's education in New Zealand as housed, for over 100 years, the first public girls' school in Christchurch.

To increase the awareness of the risk affecting cultural heritage and on the dutiful need and possibility to protect the cultural heritage pre-event and/or to undertake repair and reconstruction actions the national and international scientific community joined forces and promoted several initiatives in New- Zealand. In particular, the same authors collaborated on the project “Vulnerability Analysis of Unreinforced Masonry Churches” funded by the New Zealand Earthquake Commission EQC, which moved the first step towards the seismic protection and preservation of historical buildings in New

8 https://www.unisdr.org/archive/53456 9 https://www.icomos.org/110303_ICBS_Statement_Christchurch_EN.pdf 10 http://restorechristchurchcathedral.co.nz/ 2

Zealand (Godet et al. 2016). Extending upon that earlier project, the authors worked on the project “An- operational framework to determine the seismic resilience of New Zealand churches” funded by QuakeCoRE, the New Zealand Centre for Earthquake Resilience.

Building on the aforementioned work, this paper would like to explore the possibility to create in New Zealand a Decision Support System (DSS) that could inform and support the decision-making process for understanding disaster risk and mitigating impacts on heritage buildings, therefore enhancing their resilience. DSSs include a wide range of computer-based tools that have specific simulation and prediction capabilities and are usually developed to support decision analysis and participatory processes. DSSs are also used as a vehicle of communication, training and experimentation, as DSSs facilitate dialogue and exchange of information thus providing insights to non-experts and supporting them in the exploration of policy options. In particular, DSSs and platforms for the prediction of risks and losses from natural hazards consist of different databases, coupled with hazard prediction/monitor capabilities, and ad-hoc modules for the exposure and vulnerability assessment, along with modules for socio-economic impact assessment; DSSs are, usually, provided with a dedicated interface in order to be directly and more easily accessible by policy and decision makers, stakeholders, the wider community, etc.. There are several already existing DSSs that aim to support the assessment of risks from a multi-hazard perspective and to inform and support decision-making processes for mitigation, recovery rehabilitation and reconstruction (an overview of available open-source DSSs for assessing multi-hazard risks is provided by the Global Forum for Disaster Risk Reduction, GFDRR11). However, as far as the knowledge of the authors is concerned, not many, if none of such DSSs, have included heritage buildings as part of the assets under analysis. This paper, in accordance with the priorities identified by the Sendai Framework for Disaster Risk Reduction, 2015-203012, aims to explore the potentialities of using DDSs for enhancing the resilience of heritage buildings. In particular, reference is made to an existing DSS, i.e. RiskScape (King and Bell, 2009) that, in New Zealand, supports the assessment of the risks induced by natural hazards, potentially threatening the built environment. A short overview on RiskScape is provided in Section 2. In Section 3, some proposed add-ins for costumising RiskScape so that it can be used for risk assessment and resilience enhancement of cultural heritage are briefly presented, namely: a database to foster the awareness of stakeholders and communities on their Cultural Heritage at risk; an add-in for supporting scenario analysis at territorial scale to assess direct and indirect impacts; a further add-in that enables the analysis at single building level to identify the most likely collapse mechanisms.

2. OVERVIEW ON RISK-SCAPE: A DSS THAT SUPPORTS ASSESSMENT AND MITIGATION OF NATURAL HAZARDS IN NEW ZEALAND

RiskScape is a multi-hazard loss modelling tool developed in New Zealand by two leading research institutions, namely GNS Science and NIWA, with the aim of informing and supporting decision makers and stakeholders to plan for pre-disaster mitigation and post-disaster intervention strategies (King & Bell, 2009). RiskScape works using a modular framework. The input module combines hazard, asset and vulnerability information. Users have available built-in hazard models and asset inventories (RiskScape’s building inventory is currently the most comprehensive available in New Zealand according to Lin et. al, 2016) or have the option to define their own hazard models and asset inventories. After the hazard and asset data is input, RiskScape assigns each asset to a vulnerability class and each vulnerability class to the corresponding fragility function. RiskScape includes built-in fragility functions for typical building types. The fragility functions are used to determine the building damage state for each asset, given the hazard intensity. At the time of writing, user-defined vulnerability modules could not be installed into RiskScape without the help of developers. However, developers plan to include a vulnerability module builder in an upcoming version of RiskScape. RiskScape uses the building damage state to estimate casualties and economic losses. To estimate casualties, RiskScape assigns each occupant of a building to a casualty state (i.e., no injury or light injury, moderate injury, serious injury,

11 https://www.gfdrr.org/sites/gfdrr/files/publication/UR-Software_Review-Web_Version-rev-1.1.pdf 12 https://www.unisdr.org/we/coordinate/sendai-framework 3

critical injury, and death) using probability models that have been calibrated on worldwide casualty databases. Direct economic losses can be estimated in terms of building replacement value, contents value, and downtime. Examples of studies that utilize RiskScape to estimate damage and casualties in large New Zealand cities, such as Wellington and Auckland, are reported by Cousin (2013) and Cousins et. al (2014) respectively. The possibility to further extent RiskScape potentialities so that it could support consequence-based decision-making processes, and to speed-up its development by joining effort with international and open source initiatives such as the ERGO Multi-Hazard Assessment, Response, and Planning Consortium was discussed in Giovinazzi et al (2013) and in Lin et al. (2012).

3. PROPOSED ADD-INS FOR RISKSCAPE FOR ENHANCING AWARENESS AND ASSESSING THE RISK FOR CULTURAL HERITAGE

The safeguarding of cultural heritage is among the major objectives of the SENDAI Framework for Disaster Risk Reduction 2015-2030, referred hereafter as SFDRR. SFDRR identifies four priorities for actions, namely: Priority 1: Understanding disaster risk; Priority 2: Strengthening disaster risk governance to manage disaster risk; Priority 3: Investing in disaster risk reduction for resilience; Priority 4: Enhancing disaster preparedness for effective response and to “Build Back Better” in recovery, rehabilitation and reconstruction. DSSs have a great potentiality to support all the four-aforementioned priority for actions. In particular, as far as the resilience of cultural heritage to natural hazards is concerned and in the light of the Canterbury Earthquake experiences, some possible add-ins for RiskScape are herein envisaged, summarized in Table 1, to support directly SFDRR’s Priorities 1 and 4, and indirectly SFDRR’s Priorities 2 and 3.

Table 1. Proposed add-ins for RiskScape and actions that might support in accordance with SFDRR

Proposed add-in Priority and actions A shared and accessible database of Priority 1. Understanding Disaster Risk information regulations and best- 24(a) To promote the collection, analysis, management and use of practices relevant data and practical information and ensure its collating data and information on dissemination, taking into account the needs of different cultural heritage at risk including categories of users …; 24(f) To promote real time access to geolocation, architectural and reliable data, make use of space and in situ information, including constructive features, audio-visual geographic information systems… information, etc. A territorial scale assessment tool Priority 1. Understanding Disaster Risk for assessing vulnerabilities (as a function 24. (b) To…periodically assess disaster risks, vulnerability, of data at different level of details, capacity, exposure, hazard characteristics and their possible including basic information already sequential effects at the relevant social and spatial scale; available), for estimating risks and 24. (h) To promote and improve dialogue and cooperation among tangible and intangible impacts, and for scientific and technological communities, other relevant supporting and informing high level stakeholders and policymakers in order to facilitate a science strategies planning, etc. policy interface for effective decision-making …; A single-building-level assessment tool Priority 4: Enhancing disaster preparedness for effective for identifying needed retrofitting response and to “Build Back Better” in recovery, rehabilitation interventions pre-disaster or and reconstruction. recovery/reconstruction interventions 33 (j). To promote the incorporation of disaster risk management post-disasters. (This evaluation might into post-disaster recovery and rehabilitation processes…to require the knowledge of more detailed develop capacities that reduce disaster risk in the short, medium information, such as few geometric and and long term, including through the development of measures mechanical parameters as far as such as land-use planning, structural standards improvement and buildings are concerned). the sharing of expertise, knowledge, post-disaster reviews and lessons learned…

In the sections below focus is given to tangible immovable cultural heritage building, in particular to

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unreinforced masonry churches, when subjected to earthquakes; however, what proposed hereafter is extendable to other cultural heritage items (both collections and sites) and to other kind of natural and man-induced hazards.

3.1 A shared and accessible database of information, regulations and best-practices

A first necessary add-in for RiskScape towards understanding the risks that Cultural Heritage in New Zealand is facing would be a database, colleting all available information on cultural heritage and any existing regulations and identifies best-practices; a shared and accessible database could become a reference framework for fostering awareness among communities and stakeholders and for facilitating cooperation towards resilience enhancement among all the interested parties. After the Canterbury earthquake sequence of 2010/11 and the resulting demolition of several buildings having significant historic, architectural, and social importance, a great deal of work and research has been undertaken in New Zealand in terms of cataloguing and assessing URM buildings, and in particular churches. As far as churches are concerned, a nationwide inventory of URM churches was created for the first time (Marotta et al., 2015, Figures 2a and 2b) and the seismic vulnerability of several churches was assessed (Leite et al., 2013; Leite et al., 2014; Cattari et al., 2015; Goded et al., 2016; Marotta et al., 2017). A proposal was advanced for the typological classification of other URM complex buildings in New Zealand further than churches (Gálvez et al. 2018). The development of the nationwide inventory of URM churches, was an outstanding and time consuming effort that was achieved by merging different information sources (such as the Heritage New Zealand List13, online inventories of the different religious denominations in New Zealand, archive documentation, architectural books and reports, etc. as reported in Goded 2016) and by complementing all the collected information with Google Street View observations and with direct observations, through an in-field survey along a 10 000 km itinerary. This massive work cannot be wasted and it should be made available to both the wider public and the stakeholder aiming to increase their awareness of an existing patrimony that could be disregarded/ forgotten otherwise; furthermore, action should be taken to promote the creation of a nationwide inventory for tangible and intangible cultural heritage in New Zealand.

Figure 2. Creating databases for Cultural Heritage: a) geolocation of brick and stone masonry churches identified after the post-earthquake survey campaign (Marotta et al., 2017); b) a screenshot of Sistema Informatico Territoriale Carta del Rischio SIT-CR a reference tool for the safeguard of Italian Cultural Heritage (image sourced from Accardo et al. 2005).

13 http://www.heritage.org.nz/the-list 5

As said, further to the collection of data and information, the database should act as a repository of any relevant best-practice and existing framework and/or should connect to any relevant initiative that was set after the experience of the Canterbury earthquake sequence and of any other international experiences found to be relevant. Just to provide few examples: i) relevant international know-how, e.g. the suit of survey forms, available in Italy, that allow to quickly acquire information on the induced damage and impacts on cultural heritage and therefore to inform emergency management and short and long-term interventions (G.U. no. 55, 2006); the Italian guidelines for the evaluation and reduction of seismic risk of cultural heritage (GU n. 24/2008); ii) local initiatives that could become a reference example internationally, e.g. Quakestudies Digital Archive14 conceived and designed to preserve the memories and experiences of Canterbury people after the CES, that included a “Virtual Heritage Project”; iii) local initiative that could become a best-practice reference nationwide, e.g. Heritage guide and process for Delivery Teams issued by “Stronger Christchurch Infrastructure Rebuilding Team”, SCIRT to manage heritage items (e.g. repairing a heritage bridge, working on a site near to heritage items, etc.)15. A virtuous example of a shared and accessible database for Cultural Heritage that could be regarded as a reference guide in New Zealand is the “Sistema Informatico Territoriale Carta del Rischio”16, referred hereafter as SIT-CR (Fig. 2b). SIT-CR was conceived and realized by the Superior Institute for Conservation and Restoration (ISCR former ICR), under the Italian Ministry for Cultural and Environmental Heritage (MIBAC), as the main reference tool for the safeguard of Italian Cultural Heritage. SIT-CR is a data repository for heritage building and cultural sites, capable of processing data and statistics for each one of the 8100 Italian municipalities. SIT-CR is available to MIBAC, local and regional bodies for developing safeguard, conservation, maintenance interventions, restoration and urban planning measures for the Cultural Heritage. The SIT-CR proved to be also a great tool for supporting post-disaster emergency management and reconstruction. After recent catastrophic earthquake events in Italy (e.g. Abruzzo 2009, Emilia 2012, Central Italy seismic sequence 2016-2017) SIT-CR was used: to identify the list of heritage building and cultural sites that might have been affected by the earthquakes; as a basis for collecting further information on the affected cultural heritage; to support planning and prioritizing of emergency and reconstruction interventions. Further initiatives that should be closely monitored as possible reference example for New Zealand, include among others the EU-funded RESCULT, “Increasing Resilience of Cultural Heritage”17 and the European Research Infrastructure on Heritage Science (E-RIHS)18. RESCULT aims to realize an integrated European Interoperable Database (EID) for Cultural Heritage that could support the sharing of: information, interoperable protocols, and best practices; RESCULT aim to provide a unique framework for Civil Protection, national Ministries of Cultural Heritage, the European Union, local authorities private investors and communities to enhance their understanding of the risks faced by cultural heritage and of the potential impacts on related economic activities and social cohesion, and to support the identification of disaster reduction strategies, according to the principles of the Sendai Framework. E-RIHS aims, instead, to supports research on cultural heritage, by providing state-of-the- art tools and services to cross-disciplinary groups of researchers, users and scientific communities working to advance knowledge about cultural heritage and to devise innovative strategies for its preservation, interpretation, documentation and management.

3.2 A territorial scale assessment tool

A further useful add-in, to be embedded within a DSS aiming to support the resilience enhancement of Cultural Heritage, would be a “scenario analysis” tool that, by sourcing the necessary information from the above-described database, could support the assessment of vulnerability and risks for cultural

14 https://quakestudies.canterbury.ac.nz/ 15 https://scirtlearninglegacy.org.nz/sites/default/files/qsr-part_338649.pdf 16 http://www.cartadelrischio.it/ 17 https://www.unisdr.org/archive/52042 18 http://www.e-rihs.eu/about/international-collaborations/

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heritage at territorial scale and in a multi-hazard perspective. As far as the seismic risk and churches are concerned, RiskScape can already assess the seismic vulnerability at territorial scale and estimate direct physical impacts and, to a certain extent, indirect impacts. Towards that RiskScape implements the so- called “macroseismic approach” that was originally defined by Giovinazzi and Lagomarsino (2004) for residential buildings. The use of the same approach for churches was proposed by Lagomarsino et al. (2004); the use of the “macroseismic approach” in New Zealand for URM churches was proposed by Cattari et al. (2015) and Goded et al., (2016) when specific vulnerability indexes were developed and calibrated based on the damage observed after the CES. The macroseismic approach, allows assessing the seismic vulnerability of buildings/churches based-on the qualitative knowledge of the building typology, its peculiar geometrical features, and some relevant structural parameters. After that it allows the estimation of the expected mean damage grade µD, for a single church or for a portfolio of churches, characterized by a Vulnerability Index V, when subjected to an earthquake having a macroseismic intensity I measured according to the European Macroseismic Scale EMS-98 (Grunthal 1998):

.. � = 1 + tanh (1) Q where Q is the Ductility Index assumed to be Q=3. The vulnerability index V is computed by considering how different typology of vertical structurers (e.g. for URM buildings, adobe, stone, brick structures, among others) might influence the seismic performance of a building and how further characteristics of the buildings (such as the typology of the horizontal structures, the state of maintenance; the presence of specific constructive details that might help the global response of the building, such as the presence of tie-roads) might modify it. The first contribution is summarized in term of a typological vulnerability index V∗, while the latter in terms of behaviour modifier Vmk scores:

∗ � = � + � (2)

The New Zealand specific typological vulnerability indexes V∗ (a most likely value V∗, i.e. and a possible * * range, from V - to V +) and behaviour modifier Vmk scores are summarized in Tables 2 and 3 respectively.

Table 2. Typological Vulnerability Index V∗ for New Zealand URM churches

* * * V - V V + URM churches (material non-better specified) 0,53 0,85 1,13 Brick churches 0,50 0,82 1,10 Stone churches 0,56 0,88 1,16

Table 3. Behaviour modifier Vmk scores for New Zealand stone and brick churches stone churches brick churches Behaviour Modifiers Description Vmk Vmk Presence -0.01 - Buttresses on the lateral wall Absence +0.04 Good -0.10 -0.02 State of preservation of masonry Average +0.04 +0.01 Bad and/or Cavity walls +0.06 +0.07 Presence +0.09 +0.04 Rose windows (big) Absence -0.10 -0.05 Presence +0.01 +0.01 Narthex / Atrium Absence -0.02 -0.02 Present and effective -0.06 -0.04 Tie-rods Absence or ineffective +0.04 +0.02 Absence 0.00 0.00 Vaults and/or dome Extended presence +0.04 +0.02 Presence of a big dome +0.08 +0.05

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Metal sheet -0.02 -0.01 Characteristics of the roof Thin stones or tile roof +0.02 +0.01 Heavy roof +0.06 +0.04

The vulnerability curves and indexes specific for New Zealand URM churches were calibrated based on the specific building characteristics (such as masonry quality, state of maintenance, existing building structural transformations, and structural features such as the number of naves or the height of the lateral walls, etc.,) on the specific ground motions that were sustained by the churches and the specific damage observed (Cattari et al. 2015; Goded et al. 2016). The following ad-hoc Intensity-PGA correlation was assumed for translating the peak ground acceleration, PGA [g], recorded at the church sites, into Macroseismic Intensity I (Goded et al. 2016):

� = � + � ln ��� (3) where: a1=9, a2=1.35. The implementation of the macroseismic approach within RiskScape for the assessment of the seismic risk for New Zealand churches was undertaken by Abeling et. al (2018) for the estimation of both deterministic and probabilistic scenarios (Figure 3). It is worth clarifying that: starting from the µD estimated according to Eq. 1, fragility curves were obtained assuming that the damage was distributed according to a binomial distribution (Lagomarsino and Giovinazzi 2006); the hazard provided in terms of PGA by RiskScape was translated into I using Eq. 3; specific fragility functions for New Zealand churches were only available for URM buildings, therefore RiskScape existing fragility functions for timber, RC and concrete block materials were used for these other typologies (work is on-going by the same authors to further specify vulnerability curves for the aforementioned building typologies). Using RiskScape, preliminary economic loss estimations have been obtained based on asset value data, and casualty estimations have been evaluated for each church as outlined in Abeling et. al (2018).

100

50 % of churchesof % 0 DS1 DS2 DS3 DS4 DS5 RC Timber URM Concrete Block

14

9

4 % of churchesof %

-1

DR Median 84th Percentile

Figure 3. Estimated impacts assuming the design level earthquake for each church in the inventory: probability of churches of being in different damage state DS (from DS1 to DS5, plus the absence of damage); expected damage distribution for classes of churches (i.e Reinforced Concrete, RC; Timber; URM; Concrete block); median and 84th percentile distributions of damage ratio (DR) i.e. ratio of repair cost to replacement cost (Abeling et. al 2018)

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3.3 A single-building-level assessment tool An add-in to analyse the seismic response of URM churches, at single-building-level, and to estimate the damage pattern and collapse mechanisms that would be more likely in the event of an earthquake is proposed hereafter. This is based on the so-called “macroelement approach” that observes how the seismic response of churches can be described according to recurrent behaviour, traceable to the damage modes and collapse mechanisms of the different structural parts, called macroelements, which show an almost autonomous structural behavior (Doglioni et al. 1994). Typical examples of macroelements in a church are the façade, the bell tower, the apse and the side chapels. In Italy, the systematic implementation of such an approach has allowed the definition of a structured procedure to assess damage and to quickly acquire useful information for supporting the emergency management (G.U. no. 55, 2006). In New Zealand, as far as churches are concerned, the identified macroelements were statistically reported by Leite et al. (2013) and a methodology to perform the division of a structure into macroelement was described in Goded et al. (2016). The add-in proposed herein retrace a calculation code, based on the “macrolelement approach” that was developed by Lagomarsino et al. (1999) after the 1996 Umbria-Marche (Italy) earthquake to support the identification and design of ad-hoc repair/retrofitting interventions for damaged churches. The code proposed by Lagomarsino et al. (1999) was written in Java and allowed the verification of the various macroelements of churches in an organic and automatic way, considering all the possible collapse mechanisms. The program took into consideration churches with a rather simple typology (e.g. a single nave with a triumphal arch presbytery and apse that perfectly reflect the typologies identified in New Zealand) and allowed the assessment of the activation threshold, which is a horizontal multiplier of the loads that activate the local damage mechanism, expressed as the ratio between the acceleration, a, that trigger the activation of a certain collapse mechanism divided by the gravity acceleration: 1) in as-built conditions (αAB=aAB/g); 2) after retrofitting interventions (αRI=aRI/g). The comparison of the values assumed by the activation thresholds before and after retrofitting interventions, αAB and αRI respectively, provided a quantification of the effectiveness of the retrofitting interventions. The proposed add-in for RiskScape performs the steps described in Table 4 for the assessment of αAB, provided the availability of the input parameters summarized in the same Table.

Table 4. Vulnerability Index Modifiers for stone churches

Steps Required input parameters 1. Actions transmitted by the roof to the General dimensions of the building (e.g. dimension of the plan macro-elements constituting the church and height) characteristics of the roof

2. αAB for each macro-element Geometry of the macroelement, characteristics of the materials and presence/absence of some determining technological elements (e.g. tie-rods)

A summary table or graph of the resulting αAB for all the identified macroelements within a church, should be then made available to the end-users to inform the identification of the deficiencies for the overall building and to support the definition of an effective intervention strategy. When analyzing a portfolio of buildings, could be useful to represent in a summary way the αAB resulting for the different macroelement in all the identified churches, this to provide the end-users with a comparative overview on the most vulnerable situations that could help prioritizing interventions. As an example, Figure 4 shows the assessment of αAB for a sample of churches included in the same case-study analysed by Abeling et. al (2018). αAB have been calculated for different macroelements, i.e. apse (A) façade (F), bell-tower (T) for in-plane (IP) and out-of-plane (OOP) mechanisms, when considering the seismic action in the transversal (T) and longitudinal (L) directions, with respect to the nave of the church. The calculation of αAB were conducted using kinematic models according to Milano et al. (2009), Bernardini et al. (1988), Avorio et al. (2002) and De Felice et al. (1999). In Fig. 4 the resulting αAB are plotted for each church and each analyzed macroelement, allowing to compare the vulnerability of different churches and, within each church, to observe which specific macroelement is more vulnerable, and to what extent (i.e. by comparing the value of αAB with the expected seismic demand) also with respect to the direction of the earthquake. After that, a holistic representation of the most vulnerable collapse 9

mechanism for each analysed churches is provided in Fig. 5 to show the more vulnerable situations and which church would need more immediate intervention (highest difference between αAB and the expected seismic demand).

Figure 4. Resulting αAB for three macroelements and expected seismic demand (on the left).

Figure 5. Representation of the more vulnerable macroelement at the location of each assessed church where the height of the histogram is proportional to the difference between αAB and the seismic demand.

As for the assessment of αRI the RiskScape add-ins should perform, as a first step, the re-evaluation of Step 1 in Table 4 to reflect any retrofitting interventions targeting the consolidation of the roof and/or the widespread consolidation of the masonry. Secondly, αRI should be evaluated for each macroelement and for different possible interventions, implemented in an exclusive or combined way. The resulting αRI should be then presented to the end-user in a summary table/graph to showcase the degree of safety achieved with the intervention and the improvement achieved with respect to the as-built condition. A further development of this RiskScape add-in may entail the inclusion, for different retrofitting 10

solutions, that might seems to be effective for contrasting specific collapse mechanisms, some considerations on whether or not and, in the first case to what extent, the retrofitting interventions are respectful of the conservation principles described by the ICOMOS New Zealand Charter (ICOMOS New Zealand, 2010) including, among others, minimum intervention, retention of use and heritage fixtures/fittings or contents, surviving evidence and overall compatibility with the historic building fabric. Such an approach was explored in New Zealand through a pilot study (Galvez et al., 2017), where a range of retrofit solutions were examined against established conservation criteria. Table 5 proposes a summary format, where shaded areas indicate that the retrofit interventions poorly or does not respect the specified conservation principle, whereas some considerations are included, as text, when appropriate. Table 5 demonstrates that a “perfect” solution is difficult to obtain as most of them embody advantages and disadvantages that must be taken into consideration during the decision-making process.

Table 5. Retrofitting Interventions (RI) compared to conservation principles in ICOMOS New Zealand Charter

EXAMPLES OF CONSERVATION PRINCIPLES Compatibility Retention MACROELEMENT RI with of Use and Consideration Minimal Surviving Heritage of Surviving Intervention Historic Fixtures, Evidence Building Fittings or Fabric Contents

Minimal Intrusion to fabric disturbance to is restricted to the fabric. four internal Installation corner requires connections consideration

Little/no BELL TOWER Any existing external visual fixtures impact. inside the Installation tower space avoid retained disturbance of fabric Restricted to Any existing upper portion but fixtures Some external installation may inside the and internal involve removal tower space visual impact of fabric retained

A very valuable reference for what herein proposed is the NIKER Catalogue19, realized as part of the EU-funded NIKER project (New Integrated Knowledge based Approaches to the protection of Cultural Heritage from Earthquake-Induced Risk), a structured database that links earthquake induced failure mechanisms, construction typologies and materials, interventions and assessment techniques. This aims at knowledge-based optimization of interventions and definition of main design parameters and requirements for materials and intervention techniques. Users such as architects or structural engineers are to be reminded, however, that the implementation of a specific retrofitting intervention to a specific project demands detailed examination of a particular historic site or building context, before designing or implementing a given solution. A case-by-case approach is suggested as challenges arise if generalizations are made concerning the application of retrofit solutions to many buildings, regardless of their individual history of deterioration, repair or use. Therefore, such a tool bears value in demonstrating the range of potential solutions and heritage conservation principles as an illustrative guidance only.

19 http://www.niker.eu/ 11

6. CONCLUSIONS This paper presented the possible customization of an existing DSS in New Zealand, namely RiskScape, for supporting the resilience enhancement of Cultural Heritage to natural hazards. In the light of the experience of the Canterbury Earthquake sequence, that unfortunately caused heavy damage to several heritage buildings and the consequent demolition of some of them, what proposed in this paper should be regarded as just one possible step, among several others, that should and could be moved to preserve cultural heritage by creating awareness and by joining efforts and sharing know-how nationally and internationally. This with the final goal to build capacity to mitigate the impacts from natural hazards on cultural heritage pre-disaster and to promote prompt actions, restoration and conservation of cultural heritage in post-disaster emergency management, recovery and reconstruction.

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