Implementation of a condition monitoring strategy for the Monastery of Salzedas, Portugal: challenges and optimisation

The implementation of condition monitoring for damage identification and the generation of a reliable digital twin are essential elements of preventive conservation. The application of this promising approach to Cultural Heritage (CH) sites is deemed truly beneficial, constituting a minimally invasive mitigation strategy and a cost-effective decision-making tool. In this light, the present work focuses on establishing an informative virtual model as a platform for the conservation of the monastery of Santa Maria de Salzedas, a CH building located in the north of Portugal. The platform is the first step towards the generation of the digital twin and is populated with existing documentation as well as new information collected within the scope of an inspection and diagnosis programme. At this stage, the virtual model encompasses the main cloister, whose structural condition and safety raised concerns in the past and required the implementation of urgent remedial measures. In the definition of a vibration-based condition monitoring strategy for the south wing of the cloister, five modes were identified by carrying out an extensive dynamic identification. Nonetheless, significant challenges emerged due to the low amplitude of the ambient-induced vibrations and the intrusiveness of the activities. To this end, a data-driven Optimal Sensor Placement (OSP) approach was followed, testing and comparing five heuristic methods to define a good trade-off between the number of sensors and the quality of the collected information. The results showed that these algorithms for OSP allow the selection of sensor locations with good signal strength.This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020, and under the Associate Laboratory Advanced Production and Intelligent Systems ARISE, under reference LA/P/0112/2020

First hypothesis for optimized monitoring strategy through ambient vibrations in historic buildings

Dynamic identification strategies and, in particular, Operational Modal Analysis (OMA) approaches demonstrated to be a significant source of information about the condition of an investigated building, as well as, repeated data acquisitions and processing methods, developed in the field of Structural Health Monitoring (SHM), have been successfully used to track the evolution of this condition over time. Nonetheless, planning a cost-effective ambient vibration monitoring campaign is still an open challenge as several uncertainties must be considered to ensure a beneficial trade-off between number of sensors or set-ups and quality of the information collected. This is particularly important when dealing with historical masonry buildings. The present work discusses the preliminary results of a project, currently under development, whose aim is the definition of optimised protocols for data acquisition and processing for built cultural heritage dynamic identification and monitoring, with specific focus on the Venetian palace typology.FCT - Fundação para a Ciência e a Tecnologia(UIDB/04029/2020

Experimental analysis of unreinforced masonry buildings through the quasi-static test: a half-scale two-story modern masonry building

Masonry is one of the most used construction materials for structural and non-structural elements. Thenumber of masonry constructions is still remarkable in countries where the costs of modern technology arehigh, as masonry solutions remain the most convenient and economical alternatives. Among these countries,unreinforced masonry is usually found in low- and mid-rise buildings, both residential and commercial. De-veloped countries, however, have favored alternative construction materials like reinforced concrete andsteel, while masonry is regarded as an aesthetic and non-structural feature. Most objections to masonry con-struction are based on its lack of seismic performance. However, a substantial number of well- preservedmasonry structures demonstrate that when they are built properly, they can withstand any form of loading,such as wind or seismic loads. Thus, masonry buildings’ seismic performance is underrated and experimen-tal research is necessary to gain insight into their response. The studies available in the literature mainlyfocus on shake table testing of masonry buildings, while they have not been extensively studied in a quasi-static regimen. In this context, a half-scale two-story unreinforced masonry building with plan irregularityhas been tested at the Laboratory of the Structures at the University of Minho. The experimental campaigninvolves cyclic quasi-static testing with a mode proportional unidirectional loading. Dynamic identificationand digital image correlation techniques have been employed to monitor the damage progression. The testhas resulted in a rocking response under lateral loading, with a wall detachment from the foundation and slabin the first and second levels, respectively. This paper presents and discusses the experimental procedureand the main outcomes of the study.This work is financed by national funds through FCT - Foundation for Science and Technology, under grant agreement SFRH/BD/143949/2019 attributed to the 1st author. Additionally, this work is financed by national funds through FCT - National Foundation for Science and Technology, in the scope of the research project “Experimental and Numerical Pushover Analysis of Masonry Buildings (PUMA)” (PTDC/ECIEGC/29010/2017)

Evaluation of non-destructive techniques for mechanical characterisation of earth-based mortars in masonry joints

In this paper, the use of non-destructive tests for the mechanical characterisation of earth-based mortars in masonry joints is discussed. Four testing methods, namely the penetrometer, Schmidt hammer, pendulum hammer and scratch test, originally developed for other types of mortar, are reviewed. The methods are applied to the earth-based mortars at the Wupatki Pueblo archaeological site, in Arizona, US. The outcomes of the experimental programme allowed to assess the reliability of the methods and to identify their limitations. Finally, the methods are compared in terms of six qualitative indicators, namely easy-of-use, consistency of results, range and granularity of results, respect towards cultural value, depth of investigation under the visible surface and versatility in application. Overall, the penetrometer test is recommended as the preferable method to characterise the mechanical performance of earth-based mortars.FCT - Fuel Cell Technologies Program(2022.09946

Effectiveness of a TRM solution for rammed earth under in-plane cyclic loads

To evaluate the effectiveness of a TRM-strengthening solution for rammed earth walls subjected to in-plane cyclic loads, an experimental program was conducted on a strengthened mock-up previously damaged. The experimental results are discussed in comparison with the previous unstrengthened model in terms of cracking pattern, damage identification, displacements, base shear coefficient, stiffness degradation, and energy dissipation; in addition, simplified equivalent linear and bi-linear systems are inferred to assess the performance. The outcomes highlighted the effectiveness of the TRM solution in improving the in-plane shear capacity, the ductility and the dissipated energy of the mock-up.This work was partly financed by FEDER funds through the Operational Programme Competitiveness Factors (COMPETE 2020) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project SafEarth - PTDC/ECM-EST/2777/2014 (POCI-01-0145-FEDER-016737). The support from grants SFRH/BD/131006/2017 and SFRH/BPD/97082/2013 is also acknowledged. Acknowledgments are addressed to the Laboratory of Structures (LEST) of the University of Minho and to João Bernardino, Lda. and TERRACRUA - Construções Ecológicas Unipessoal, Lda for building the rammed earth model

Rethinking preventive conservation: recent examples

The past few decades have seen an increasing awareness of the potential socioeconomical and environmental impact of investment in Cultural Heritage (CH). Preserving CH is not only an obligation to sustain and transmit it to the future generation but is also a driver of sustainable growth. Here, recently concluded projects are taken in consideration for a reflective thinking on preventive conservation, as the only viable strategy towards a sustainable and cost-effective management of CH, to face unprecedented challenges posed by increasing natural and man-made threats. Here, the main open issues for a widespread implementation of preventive conservation are identified, moreover, standardised, integrated good practices, validated over significant case studies, are presented within a multi-level replicable framework.This work was financed by ERDF funds through the V Interreg Sudoe program within the framework of the project “HeritageCare - Monitoring and preventive conservation of historic and cultural heritage” (Ref. SOE1/P5/P0258). The Heritage Within research project was co-funded by the Creative Europe Programme of the European Union, under the Cross-sectorial subprogramme, Bridging culture and audiovisual content through digital action (Project 614719-CREA-1-2019-1-PT-CROSS-SECT-INNOVLAB). Moreover, this work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020

Experimental analysis of the out-of-plane behaviour of a brick masonry wall: preliminary results

Past earthquakes demonstrated that local out-of-plane collapses of brick masonry walls, particularly façades, are common even under moderate loads and a correct interpretation and assessment of their out-of-plane response is still a complex challenge. The present paper aims at contributing to the better understanding of clay brick masonry walls behaviour, through experimental analysis in laboratory environment. An extensive testing programme is carried out in the facility of the University of Minho, encompassing the characterisation of the mechanical properties of the materials through destructive and non-destructive techniques and a quasi-static test with airbag on a clay brick masonry specimen with U-shaped plan. Here, we present and discuss the preliminary results of such a thorough investigation

A proposal of classification for machine-learning vibration-based damage identification methods

Recent advances in computing power and sensing technology led to a significant evolution of Structural Health Monitoring (SHM) techniques, transforming SHM into a “Big Data” problem. The use of data-driven approaches for damage identification purposes, specifically Machine Learning (ML) methods, has gained popularity. ML can help at various levels of the SHM process: to pre-and post-process input data, extract damage sensitive features, and operate pattern recognition in measured data and output valuable information for damage identification. In this paper, the role of ML in SHM applications is discussed together with a new scheme for classifying ML applications in SHM, especially focusing on vibration-based monitoring, given its consolidated theoretical base. Finally, the implications of the application of these methods to historic structures are discussed, with a brief account of existing case studies. The proposed classification is exemplified using the most recent studies available in the literature on cultural heritage structures.- (undefined

Performance of rammed earth subjected to in-plane cyclic displacement

Rammed earth structures are worldwide spread, both as architectural heritage and new constructions. Yet, rammed earth buildings present, in general, high seismic vulnerability. Despite the several studies conducted on the mechanical characterisation of rammed earth and on the numerical modelling of structural elements built with this material, further in-plane cyclic tests on rammed earth sub-assemblies are required to characterise their hysteretic behaviour. In this framework, an experimental program was conducted where cyclic in-plane tests were performed on a large-scale rammed earth wall. The geometry of the wall was defined to represent a sub-assembly commonly found in rammed earth dwellings from Alentejo (Southern Portugal). The wall was subjected to cyclic shear displacements with increasing amplitude, imposed in both positive and negative directions. To detect the dynamic properties of the wall and to assess the development of the structural damage, dynamic identification tests were conducted along the experimental programme. The results are analysed in terms of crack pattern, dynamic properties, displacement capacity, base shear performance and stiffness degradation. Further discussion is led on the dissipated energy, while a bi-linear and linear equivalent systems are proposed as simplified modelling approach. In conclusion, degradation of structural capacity was observed due to cyclic loads, while adequate energy dissipation and base shear coefficient were obtained.This work was partly financed by FEDER funds through the Operational Programme Competitiveness Factors (COMPETE 2020) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project SafEarth-PTDC/ECM-EST/2777/2014 (POCI-01-0145-FEDER-016737). The support from grants SFRH/BD/131006/2017 and SFRH/BPD/97082/2013 is also acknowledged. Acknowledgments are addressed to the Laboratory of Structures (LEST) of the University of Minho, Joao Bernardino, Lda, and TERRACRUA-Construcoes Ecologicas Unipessoal, Lda for building the rammed earth model

Seismic behaviour and strengthening of rammed earth constructions

The widespread use of earthen buildings can be accredited to the local availability of the raw material, sustainability of the building process, and low cost. Earthen structures suffer from high seismic vulnerability, resulting from the low strength of the material, high mass, and lack of engineering approaches in design and building. Despite the extensive use of rammed earth structures, the structural behaviour of such buildings is still not well known, particularly concerning the in-plane and out-of-plane response under cyclic loads. Moreover, proper strengthening solutions are still required to reduce seismic vulnerability. In this context, an experimental program was conducted on the in-plane and out-of-plane cyclic performance of rammed earth structural sub-assemblies. The prototypes, after being damaged, were strengthened by employing a TRM-based solution and subjected to further testing. The experimental results are reported and discussed in terms of cracking pattern and peak base shear coefficient. Finally, the effectiveness of the proposed strengthening solution was evaluated against the performance of the unstrengthened mockups. The outcomes highlighted the effectiveness of the TRM solution in improving the ductility and the in-plane shear capacity of the mockups.This work was partly financed by FEDER funds through the Operational Programme Competitiveness Factors (COMPETE 2020) and by national funds through the Foundation for Science and Technology (FCT) within the scope of project SafEarth—PTDC/ECM-EST/2777/2014 (POCI-01–0145-FEDER-016737). The support from grants SFRH/BD/131006/2017 and SFRH/BPD/97082/2013 is also acknowledged. Acknowledgments are addressed to the Laboratory of Structures (LEST) of the University of Minho, João Bernardino Lda and TERRACRUA Lda for building the rammed earth model