Summary
The results of an investigation of the probability of earthquake damage to nonstructural unreinforced masonry (URM) components are presented. The components include parapets, chimneys, and ...out‐of‐plane loaded facades typical of low‐rise pre‐1940 construction in Australia and New Zealand. The study is based on a street survey of component geometry, in situ data on material strength, and simplified mechanical models. Uncertainties in capacity and demand were quantified based on, respectively, stochastic and deterministic approaches. The damage probabilities were compared with relevant guidelines and empirical damage data from three earthquakes. The study established a link between the qualitative damage states reported in existing guidelines and the quantitative URM component damage states. While some median damage state thresholds correlated well with the data from the guidelines, a larger dispersion value was found in the current study due to the large variations in component properties. Comparisons with empirical data suggest that the developed fragility data provide a realistic estimate of nonstructural component damage that occurred in similar buildings, with a reasonable level of conservatism. The outcome is useful in rapid assessment of the seismic risks due to nonstructural component collapse in URM precincts.
•Integrated framework from historic building information modeling to finite element method modeling.•Application of linear modal response spectrum analysis to a complex unreinforced masonry medieval ...church case study.•Identification of local collapse mechanism via finite element method analysis.•Application of stiffness adaptation analysis to a complex unreinforced masonry medieval church case study.
A novel, integrated framework is proposed to assess the vulnerability of a case study unreinforced masonry (URM) Italian church by applying interacting modern tools including unmanned aircraft systems (UAS), “structure from motion” (SfM) photogrammetric survey equipment and software, and finite element method (FEM) analysis software in a complete heritage building information model (HBIM). The FEM model was used to perform both a modal response spectrum analysis and a validation pushover using stiffness adaptation analysis (SAA) to investigate the global behavior of the church and to identify the most critical local mechanisms for collapse potential. Once the most vulnerable components of the church were identified, macro-block analysis was used to estimate the capacity of these collapse mechanisms. Macro-block analysis is well established in the field and was proposed for use as one step in the proposed integrated framework with the aim of providing a holistic methodology that is sophisticated enough to identify the most vulnerable elements of URM churches, but also practical and efficient enough to be applied by practitioners. Traditionally, obtaining the necessary geometric information to correctly conduct the macro-block analysis of such complex buildings requires time-demanding and expensive surveying campaigns. Furthermore, accurately and precisely identifying the local failure mechanisms most influential to macro-block behavior is numerically demanding. The novelty of the current research detailed herein regards a proposed comprehensive seismic vulnerability analysis of historic URM churches with increased efficiency and accuracy of surveying and capacity modeling using modern tools in a fashion approachable by practitioners.
•Extensive material classification of unreinforced masonry Italian medieval churches (72 churches included in the research).•Extensive in-situ testing of historic unreinforced masonry using ...non-destructive testing techniques and expert judgment-based techniques (170 specimen included in the research).•Development of predictive equations to determine compressive strength, Young’s modulus, and shear modulus of historic unreinforced masonry via SonReb procedure.•Partial validation of the developed equations via destructive testing of specimens coming from relatively modern unreinforced masonry.
Medieval churches constructed of unreinforced masonry (URM) represent critical assets of Italian architectural heritage. In order to preserve these churches against earthquakes, obtaining robust information regarding their material mechanical characteristics is necessary as part of a reliable structural analysis and strengthening intervention program. Given the drawbacks of semi-destructive or destructive testing of heritage material, non-destructive testing (NDT) is the most viable approach to obtain data regarding the mechanical characteristics of the material composing the structure of the churches. However, there are several uncertainties inherent within NDT techniques based on the current state of the art. Thus, two different NDT techniques (i.e., rebound hammer testing, and pulse velocity testing) and two expert judgment-based investigation techniques (i.e., masonry quality index, and mechanical properties ranges based on the Commentary to the Italian building code) were applied to 170 specimens belonging to the walls of 72 URM Italian medieval churches to assess the quality of the URM and its components. The surveyed churches walls, although highly variable in geometry, materials, and conditions, can be classified into four URM types: a) irregular stone masonry with pebbles, erratic and irregular stone units; b) roughly cut stone with good bond; c) ashlar masonry with regular squared blocks and mortar joints; and d) solid fired clay bricks with lime mortar. Subsequently, using the SonReb technique, predictive equations that aggregate the two NDT techniques and the correlation coefficient specific for each URM type were developed to define some of the critical mechanical properties of the URM (i.e., compressive strength, Young’s modulus, and shear modulus). The mechanical properties determined via predictive equations were then plotted and compared with the predictions of the two well-established expert judgment-based investigation techniques to evaluate the accuracy of the approach. Finally, a partial validation based on NDT and destructive testing techniques of six URM prisms was performed to evaluate the accuracy of the proposed predictive equations. Ultimately, three equations to determine the compressive strength, the Young’s modulus, and the shear modulus were developed. The developed equations offer to engineering practitioners a rapid NDT technique to assess URM properties that do not solely rely on the judgment and expertise of the practitioner.
PDF
