Ground penetrating radar assessment of historical buildings: the study of the roofs, columns and ground of Santa Maria del Mar, in Barcelona / GPR assessment of the basilica Santa Maria del Mar

Santa Maria del Mar is a magnificent gothic church built between 1329 and 1383 in a neighbourhood outside the city walls, over the remains of a more ancient church. The inhabitants of this district (merchants, downloaders of the port, ship-owners artisans and craftsmen) contributed and took part in the construction of this building. Nowadays it is one of the most representative gothic buildings of Barcelona. The structure was completely studied with GPR in order to obtain useful information for a further restoration. Some of the most interesting results were obtained during the evaluation of the vaults and roofs of the building. Radar images demonstrate that the inner structure was designed in order to diminish the load on the arches and walls. Hollow elements were used to support partly the roof in some areas. Moreover, walls, floors and columns were also assessed, and also the ground outside the building. A large number of graves were located under the church floor, but also some of the radar images suggest the existence of large underground walls. The GPR study of the columns and walls was completed with a seismic survey that demonstrates the existence of zones of non-consolidated materials and defined the joints of the ashlars.Postprint (author's final draft

Application of particle motion technique to structural modal identification of heritage buildings

Determining the behavior of a structure estimated by means of finite elements analysis requires not only an in-depth knowledge of its geometry and dynamic properties but also an experimental validation to corroborate the adequacy of the characteristics of the structure. Most of the current structural identification techniques are based on linear methods that call for many measurement points and/or a relative simple structure. Complex structures are somewhat still an unexplored field due to the difficulties with the finite element method and the experimental corroboration of its results. This study presents the use of particle motion computation applied to each structural vibration mode to improve the identification of its dynamic properties, and its application to the Gothic Cathedral of Palma de Majorca (Spain).Postprint (author’s final draft

Integrated GPR and laser vibration surveys to preserve prehistorical painted caves: Cueva Pintada case study

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of Architectural Heritage on 2019, available online at: http://www.tandfonline.com/10.1080/15583058.2019.1643947The study of structural safety when it is covered by important paintings requires a careful analysis without affecting the paintings. Therefore, non-destructive surveys are the only feasible method to obtain data about its state. In Cueva Pintada case, the problem requires a detailed but noninvasive analysis because this cave was dug in volcanic tuff. The tuff presents poor consolidation. This geological material is very sensitive to vibration. Furthermore, the proximity to the city downtown increases vibrations due to traffic. Recently, a small rockfall produces damage and alerted of the cave state of conservation. The painting walls constraint many of the NDT surveys. Two methodologies have been applied: ground-penetrating radar (GPR) and passive seismic. GPR analysis allowed determining the inner structure of the tuff cave, and results were used to determine the zones that required a wider and dense vibration study. Radar images show important anomalies at depths of about 0.2 m to 0.8 m and from 1.5 m to the top of the roof, almost horizontal. Amplification factor measured by passive seismic survey ranges from 0.03 to 93, with near half of the ceil with amplifications higher than 5 and about 10% with amplifications over 50 times.This research was partially funded by the Ministry of Economy and Competitiveness (MINECO) of the Spanish Government and by the European Regional Development Fund (FEDER) of the European Union (UE) through the project referenced as CGL2015-65913-P (MINECO/ FEDER, UE).Peer ReviewedPostprint (author's final draft

Matrices de probabilidad de daño para la catedral de Mallorca, España

Se presenta la obtención de la vulnerabilidad sísmica para una catedral Gótica de grandes dimensiones mediante la aplicación del Método del Espectro de Capacidad, y la obtención de las probabilidades de daño asociadas.Peer ReviewedPostprint (published version

Detection of damage using temporal variation in natural frequencies and principal component analysis

This is an Accepted Manuscript of an article published by Taylor & Francis Group in International Journal of Architectural Heritage on 2020, available online at: http://www.tandfonline.com/10.1080/15583058.2020.1831101.Detection of structural damage is an important issue. Some techniques require knowledge of the undamaged state or in-depth knowledge of the construction materials used. The application of principal component analysis to the temporal variation in natural frequencies is a promising technique. With an undamaged structure a single principal component will suffice to explain the change in modal frequencies with weather variables, whereas more components are needed in the case of damaged structures. Like all other detection techniques, it has advantages and drawbacks. The main advantages are the ability to work without knowledge of the previous state of the structure, the relatively short monitoring time required (about 10 days), low cost, and low number of instrumentations. The main drawback is the need for more studies to correlate degree of damage with the number of principal components. This paper presents the results obtained for six structures: Mallorca Cathedral, four university buildings in Barcelona, and a reduced model structure in a laboratory. We also propose a semiautomatic algorithm to track modal frequencies over time and add a discussion of operational modal analysis in real buildings.This research was partially funded by the Ministry of Economy and Competitiveness (MINECO) of the Spanish Government and by the European Regional Development Fund of the European Union through the project referenced as CGL2015-65913-P (MINECO/FEDER, UE). We also want to acknowledge the management and maintenance services of the UPC schools of Industrial Engineering (ETSEIB) and Architecture (ETSAB) for their readiness and help, and the Department of Quantum Physics and Astrophysics of the University of Barcelona for the meteorological data.Peer ReviewedPostprint (author's final draft

Seismic safety assessment of historical structures using updated numerical models: the case of Mallorca cathedral in Spain

The paper presents an integrated approach aimed at assessing the seismic safety of Mallorca cathedral. This cathedral is an extraordinary historical construction dating back to the middle-ages. The experimental modal parameters of the cathedral were identified using Ambient Vibration Testing (AVT). The cathedral numerical model was updated using the identified modal parameters. This updated model was then used to study the seismic response of the cathedral using non-linear static (pushover) analysis. A sensitively analysis was carried out to reveal the dependency of the seismic capacity on the input materials properties. To assess the seismic performance and the safety of the cathedral, the N2 method was employed. It was found that the cathedral is safe when subjected to the earthquakes expected in Mallorca Island.Peer Reviewe

Evaluation of Mallorca Cathedral seismic behavior using different analysis techniques

The paper discusses the seismic assessment of Mallorca cathedral in Spain. This cathedral is an audacious Gothic structure built on the island of Mallorca during 14th-16th centuries, characterized by its large dimensions and slender structural members. For that purpose, different analysis methods were used. A 3D Finite Element (FE) model of the cathedral was created and then updated based on in-situ dynamic identification tests. Nonlinear static (pushover) analysis was firstly carried out applying the seismic loads in the longitudinal and transversal directions of the cathedral considering both positive and negative signs. The pushover results were compared with the results of the kinematic limit analysis as a way to cross check the seismic safety assessment. Although for such a large historical structure, the nonlinear time-history (dynamic) analysis requires a very high computer effort, an attempt to perform this type of advanced analysis was carried out.Peer Reviewe

Dynamic investigation of a large historical cathedral

This is the peer reviewed version of the following article: [Elyamani, A., Caselles, O., Roca, P., and Clapes, J. ( 2017) Dynamic investigation of a large historical cathedral, Struct. Control Health Monit., 24: e1885. doi: 10.1002/stc.1885. ], which has been published in final form at https://onlinelibrary.wiley.com/doi/abs/10.1002/stc.1885. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.The presented research aimed at studying the dynamic behavior of Mallorca cathedral (Mallorca Island, Spain) under ambient sources of vibration and seismic events. The cathedral is one of the greatest built masonry structures worldwide. It is characterized for its audacious dimensions and slender structural members. Because of it, the study of its dynamic behavior is a clear concern. The cathedral dynamic properties were firstly identified using ambient vibration testing. Afterwards, a dynamic monitoring system was implemented to continuously measure, record, and wirelessly transfer the acceleration records without having to set up an activating threshold. This monitoring type was implemented because of the low seismic intensity of Mallorca Island with a basic ground acceleration of only 0.04 g according to the Spanish seismic standard. The continuous monitoring allowed for capturing some seismic events and some drops in the natural frequencies were noticed because of a breathing crack effect. Using both ambient vibration testing and continuous monitoring system, global modes could be more accurately identified than more local ones. The identification of the global modes was more attainable than in the case of more local ones. The temperature was a more influential environmental parameter than humidity and wind for all of the identified modes except for one more directly depended on wind.Peer Reviewe

Integrated dynamic and thermography investigation of Mallorca cathedral

An integrated investigation of engineering archaeometry was carried out using dynamic identification, dynamic monitoring and Infra-Red (IR) thermography for the study of the dynamic behavior of Mallorca cathedral in Spain. The cathedral is a large historical masonry structure built during 14-16th c. Dynamic identification and monitoring allowed the capturing of eight natural frequencies of the cathedral. IR thermography was used as a complementary inspection technique in the context of a continuous monitoring. Usually, IR thermography is used punctually for the inspection of a part of an inspected structure. Here an alternative was tried as the IR camera was installed for two two-weeks periods in the winter and in the summer of 2011 to monitor the stone surface temperature of a large portion of the cathedral. The correlation between the cathedral natural frequencies and the stone surface temperature of some selected structural elements was investigated and compared with the correlation with the external and the internal temperatures. It was found that the correlation with stone surface temperature was lower than that with external temperature. The study allowed a better understanding of the influence of temperature changes on the structure’s dynamic behavior.Peer Reviewe

Ground penetrating radar assessment of historical buildings: the study of the roofs, columns and ground of Santa Maria del Mar, in Barcelona / GPR assessment of the basilica Santa Maria del Mar

Santa Maria del Mar is a magnificent gothic church built between 1329 and 1383 in a neighbourhood outside the city walls, over the remains of a more ancient church. The inhabitants of this district (merchants, downloaders of the port, ship-owners artisans and craftsmen) contributed and took part in the construction of this building. Nowadays it is one of the most representative gothic buildings of Barcelona. The structure was completely studied with GPR in order to obtain useful information for a further restoration. Some of the most interesting results were obtained during the evaluation of the vaults and roofs of the building. Radar images demonstrate that the inner structure was designed in order to diminish the load on the arches and walls. Hollow elements were used to support partly the roof in some areas. Moreover, walls, floors and columns were also assessed, and also the ground outside the building. A large number of graves were located under the church floor, but also some of the radar images suggest the existence of large underground walls. The GPR study of the columns and walls was completed with a seismic survey that demonstrates the existence of zones of non-consolidated materials and defined the joints of the ashlars