The Influence of the Geometrical Features on the Seismic Response of Historical Churches Reinforced by Different Cross Lam Roof-Solutions

Recent Italian earthquakes have shown the seismic vulnerability of many typical historical masonry churches characterized by one nave and wooden roofs. Under transverse earthquake the nave transverse response of this kind of churches can be influenced by the geometrical and material features. To increase the seismic performance, strengthening interventions aimed to pursue the global box-behavior by the realization of dissipative roof-structure represent a valid strategy especially for avoiding out-of-plane mechanisms. In this way, the roof structure must be able to represent a tool for the damped rocking of the perimeter walls. Cross-laminated timber panels (CLT) have been recently adopted as roof-diaphragm having shown valid ductile behavior in experimental tests, satisfying the conservative restoration criteria at the same time. In this paper, after a description of the numerical approach for the damped rocking mechanism for one nave configuration church, the effectiveness of different CLT based roof-diaphragms in the nave transverse response is investigated for four historical churches. The seismic responses are performed by comparative dynamic nonlinear analyses and the results are shown in terms of displacements and shear actions transferred to the façade. The influence of the geometrical features of the churches on the nave transversal response is deepened by sensitivity analyses with the aim to predict the displacements and shear variations under the same earthquake excitation.

Seismic Vulnerability Assessment for Masonry Churches: An Overview on Existing Methodologies

The present manuscript deals with the seismic vulnerability assessment of existing masonry churches, which is a fundamental process for risk and consequent prioritization analyses, as well as application of effective retrofitting strategies. In the past, different approaches with various levels of accuracy and application ranges have been developed to assess the vulnerability to damage of such structures in case of seismic events. Based on the classification provided in the Italian Guidelines for the Cultural Heritage, in this paper a review of seismic vulnerability assessment methodologies for existing masonry churches is presented. The main goal of the current study is to provide a critical comparative overview about these procedures, highlighting the main issues related to the application of each detail level. Moreover, particular attention is focused on the applications present in literature, allowing for the definition of a potential systematic procedure for smart management policy aimed at preserving cultural, architectural and historical heritage.

Overturning of the façade in single-nave churches under seismic loading

The out-of-plane collapse of the façade represents one of the major threats and the most frequent cause of damages of churches due to strong earthquakes. Due to the slenderness of the façade and the lack of adequate connections to the side walls and the wooden roof, the seismic action can trigger the overturning. A detailed assessment is therefore required to judge whether or not to intervene. This paper presents an approach for the seismic assessment of the stability of the façade, through a discrete element model based on a photographic survey, with the aim of representing the actual geometry and arrangement of the stone units and their effects on the kinematics of the overturning. The collapse mechanism is simulated with both, quasi-static pushover and dynamic pulse-based analyses and the results compared to those of conventional rigid-body kinematics. The proposed approach is then applied to seven masonry churches that suffered severe damages during the 2009 L’Aquila (Italy) earthquake and the failure mode provided by the analyses is compared to the damages caused by the earthquake. The method is able to give a reliable estimate of the expected failure mechanism, taking into account the quality of the masonry and the connections to the side walls, while also providing the seismic acceleration required to trigger the motion and the ultimate displacement beyond which collapse occurs.

EXPERT PANEL ON IN-SITU VISUAL INSPECTIONS FOR MASONRY CHURCHES MAINTENANCE STAGE

The incorporation of protocols in heritage building preservation is important for the definition of preventive conservation actions. Such integration is needed to avoid restoration actions and to promote preventive maintenance instead of corrective maintenance actions. This paper presents the application of an innovative digital management system using artificial intelligence that can quantify the suitability of a sample. This kind of application can support the maintenance management of buildings and minimise human error in data collection. The fuzzy system showed slight differences between the members of the expert panel during the in-situ visual inspection. These results indicate that, despite differences between various experts’ evaluation of a building, the proposed digital method helps minimise the uncertainty in the results. The paper highlights input variables, which present high dispersion (load state modification, fire and occupancy), and input parameters, which present low dispersion (preservation, roof design and overloads). Fuzzy systems can adequately manage the uncertainties associated with different experts’ assessment of sample that present constructive homogeneity. This study can give advantages to stakeholders during the inspection, diagnosis and evaluation stages in the improvement of mitigation policies focused on preventive maintenance programs dedicated to the resilience of heritage buildings, specifically churches emplaced in Chile.

Investigations of masonry churches seismic performance with numerical models: application to a case study

Recovering and preserving ancient churches is necessary to ensure the transmission of this cultural heritage to the future generations. To this scope, it is necessary to evaluate their performance in seismic prone areas, to design interventions capable of reducing their vulnerability ensuring also their safety use for the faithful. In this paper, investigations on seismic performance of masonry churches are illustrated by applying two different numerical methods on a case study, an existing brick masonry church. The seismic assessment is conducted by applying two simplified methods proposed by the current Italian Directive containing the Guidelines for assessment and reduction of cultural heritage seismic risk. Moreover, linear kinematic analysis is used also for investigating the influence of main parameters governing to the main façade simple overturning and narthex longitudinal response. The investigations performed highlight that the activation multiplier of macro-element response mechanism may significantly vary according to the assumptions made and that also, as narthex longitudinal response, a minimization procedure of the activation multiplier is required.

Development of parametric seismic fragility curves for historical churches

For both spiritual and cultural reasons, churches are an essential part of the historical heritage of several countries worldwide, including Europe, Americas and Australasia. The extreme damage that occurred during the 2016–2017 Central Italy seismic swarm highlighted once again the noteworthy seismic vulnerability of unreinforced masonry churches, which exhibited several collapses and caused uncountable losses to the Italian artistic heritage. The seismic performance of 158 affected buildings was analyzed in the aftermath of the main shocks. The failure modes activated by the earthquakes were identified making reference to the local mechanisms currently considered in Italy for post-seismic assessment of churches. The structural damage of the investigated buildings, related to 21 mechanisms rather than to an overall global response, was explained resorting to empirical statistical procedures taking into account ground motion intensity and structural details that can worsen or improve the seismic performance. Finally, parametric fragility curves were derived selecting those structural details that mostly influence the damage by means of the likelihood-ratio test. Developed models can be used in future territorial-scale scenario or risk analyses.

Rapid Seismic Vulnerability and Risk Assessment of Kermanshah Historic Mosques

Background: In this research a rapid vulnerability and risk assessment at a territorial level is performed. Methods: The methodology used, initially proposed for ancient masonry churches, is extended and applied to ten historic masonry mosques in Kermanshah city. The method could be considered as preliminary risk assessment approach of historic structures, refers to LV0 method, since the used methodology requires simple qualitative information. It involves the application of three distinct tools; the exposure, the seismic hazard, and the seismic vulnerability. Results: The comparisons among the obtained results, by considering also the damages suffered during the last earthquakes and war blasts, validate the methodology proposed, capable of providing a seismic risk scoring at a territorial level also for ancient masonry mosques. As known, through this kind of approach, important information is obtained in order to manage and to mitigate the seismic risk of a certain territorial asset. The results show that all ten mosques has medium earthquake vulnerability condition. Emad e Doleh mosque is the most vulnerable case with vulnerability of 34. Navab mosque is located on the most hazardous place. Furthermore, the seismic vulnerability map and seismic risk indices are presented for all the investigated mosques. Conclusion: The obtained results are useful for ranking the priorities and for preliminary defining an interventions plan to be examined in detail with additional quantitative investigations carried out with more refined approaches.