Earthquake damage to Christian basilica churches: the application of an expert system for the preliminary in-plane design of stone masonry piers

Abstract

This paper summarizes observations and conclusions from a series of investigations on the seismic performance of stone masonry Christian basilica churches. A considerable number of these churches develops structural damage to the masonry walls-piers that arises from the amplitude of the gravitational and seismic actions combined with the deformability of the foundation. This traditional "old-type" construction for Christian churches still exists in several regions of the Mediterranean Basin, apart from Greece, despite the considerable seismic hazard that these regions are exposed to. An expert system was developed, which utilizes the basic geometric and material characteristics of a given masonry pier together with the in-plane stress resultant demands in a cross section, such as the axial force (Ny) the bending moment (M y ) and the shear force (Q y ), in order to check the performance of such a pier. This is done by comparing the demands posed by these stress resultants with the corresponding capacities as they are predicted by the provisions of Euro-code 6 or from relevant empirical formulae. This is done by considering either the in-plane flexural or the in-plane shear capacity. This expert system is applied to typical basilica churches damaged by the recent 2014 Kefalonia earthquake in order to demonstrate its usefulness in the evaluation process of either the expected or the observed earthquake performance of this type of heritage structure.

Evaluation of the Performance of Unreinforced Stone Masonry Greek “Basilica” Churches When Subjected to Seismic Forces and Foundation Settlement

“…As was shown in this study by Manos et al [29] the above linear-elastic approach is a reasonable approximation of the actual behaviour and of predicting regions of structural damage, being both less complex and time consuming than the corresponding non-linear approach. Manos et al [30,31] developed a relevant expert system for assessing the various resisting capacities of vertical masonry structural elements. Figure 3a-c), damaged by foundation settlement are presented here.…”

“…In the previous sections, typical damage sustained by stone masonry "Greek Basilica" churches was presented together with the underlying causes due to natural hazards. Some of these churches span a period of over 800 years [1,9,12,13,29,30] with the majority of them being approximately 300 years old. One significant factor is the variability of the severity of the natural hazards that are linked with the structural response of the foundation and/or the superstructure.…”

Unreinforced Stone Masonry Churces in Greece Under Gravitational and Earthquake Actions

“…In this way, the validity the relevant dynamic system, formed in this way, can be checked and properly adjusted. d) Critical structural elements with stress concentration regions can be identified ( [20], [23]). e) Using parametric studies the influence of various parameters, either regarding the actions or the structural formation (e.g.…”

“…More detailed description of such failure criteria are presented by Manos et al ([20], [21], [23]). Despite the above stated advantages, the results from such an elastic numerical representation must be considered with sufficient skepticism bearing in mind that the validity of assuming elastic properties as well as assuming full interconnection of the various structural elements is an approximation with serious limitations (figure 1).…”

Unreinforced Stone Masonry Under in-Plane State of Stress From Gravitational and Seismic Actions. Measured and Predicted Behaviour

“…Some of these events, not necessarily the most intense, occurred near urban areas (Manos [7] and [14]). One of the most demanding tasks for counteracting the consequences of all these seismic events was the effort to ensure the structural integrity of old masonry construction, which in many cases they sustained considerable damage as can be seen in figure 1a (Manos et al [5], [6], [7], [8], [10], [12], [13], [14]). In many cases the observed damage to the stone masonry is amplified by the foundation deformability depicted in figure 1b (Manos et al [9], [11]).…”