Mechanical characterisation of masonry in existing structures by means of laboratory and in-situ experimental techniques

Tesi en modalitat de compendi de publicacions(English) Masonry structures are among the most abundant construction typologies in the world, having been commonly built until the second half of the 20th century. The determination of the mechanical properties of these structures entails significant difficulties given the intrinsic complexity of masonry as a composite material. For this reason, the accurate evaluation of masonry buildings against vertical and horizontal actions requires the development and improvement of techniques for the characterisation of the mechanical properties of existing masonry and their components. This thesis presents an extensive experimental program on the characterisation of solid fired clay bricks, including the case of both handmade bricks and mechanically extruded ones. The research has also comprised extensive campaigns on the mechanical characterisation of bricks and mortar in existing historic buildings in Barcelona (Spain), using minor destructive tests (MDT). The main objective of the in-situ experimental campaigns was the calibration and validation of the MDT techniques by comparison with results obtained through destructive tests (DT) applied in the laboratory. The laboratory experimental campaigns involved the study and improvement of existing techniques and the development of new ones for the mechanical characterisation of masonry components. The research has focused on the measurement of mechanical parameters of solid clay bricks, such as the compressive strength and the modulus of elasticity. Currently, there is a lack of unanimity in the scientific literature and also among the standards on how to evaluate the compressive strength, which in any case requires of a large number of specimens and the use of various tools and techniques. Also, there are no reference standards on the determination of the modulus of elasticity and, therefore, new proposals on standardizable methodologies are needed. In spite of the challenges encountered in the experimental characterization of bricks, different methodod have been proposed in this research in order to allow their mechanical characterization. The proposed approaches and method have shown their suitability and practical applicability. Finally, a test methodology is recommended for each of the parameters studied in the research, whose final objective is the correlation between the MDT values and the DT values.(Español) Las estructuras de obra de fábrica de ladrillo se hayan entre los tipos constructivos más abundantes a escala mundial, habiendo sido comúnmente construidas hasta la segunda mitad del siglo XX. La determinación de las propiedades mecánicas de estas estructuras conlleva dificultades significativas dada la intrínseca complejidad de la mampostería como material compuesto. Por este motivo, la evaluación estructural precisa de los edificios de obra de fábrica ante acciones verticales y horizontales requiere el desarrollo de técnicas para la caracterización de las propiedades mecánicas de la obra de fábrica y de sus componentes. Esta tesis presenta un extenso programa experimental relativo a la caracterización de ladrillos macizos de arcilla cocida, incluyendo tanto el caso de ladrillos fabricados a mano como de ladrillos fabricados por extrusión. La tesis también ha comprendido extensas campañas relativas a la caracterización de ladrillos y mortero en edificios históricos existentes de la ciudad de Barcelona (España) mediante ensayos moderadamente destructivos (MDT). El objetivo principal de las campañas experimentales desarrolladas in-situ ha sido la comparación, validación y calibración de las técnicas MDT con resultados de los ensayos destructivos (DT) obtenidos en laboratorio. Las campañas experimentales conllevaron el estudio y mejora de técnicas existentes y el desarrollo de nuevas técnicas para la caracterización mecánico-resistente de los materiales componentes de la obra de fábrica. La investigación se ha centrado en la medida de parámetros mecánicos de ladrillos macizos, tales como la resistencia a compresión y el módulo de elasticidad. El estado del conocimiento muestra falta de unanimidad entre las propuestas de la comunidad científica y entre las diferentes normativas vigentes en relación a cómo medir la resistencia a compresión, lo cual en cualquier caso requiere un gran número de probetas y la utilización de diversas herramientas y técnicas. El estado del conocimiento también muestra la inexistencia de estándares de referencia para la determinación del módulo de elasticidad, siendo necesaria la propuesta de una metodología estandarizable para esta finalidad. A pesar de los retos hallados en la caracterización experimental de ladrillos, la presente investigación ha propuesto distintos métodos propuestos para su caracterización mecánica.(Italiano) Le strutture in muratura costruite in mattoni sono tra le tipologie costruttive più numerose al mondo, essendo state comunemente costruitefino alla seconda metà del XX secolo. La determinazione delle proprietà meccaniche di queste strutture comporta notevoli difficoltà, data la complessità intrinseca della muratura come materiale composito. Per questo motivo, la valutazione precisa degli edifici in muratura nei confronti delle azioni verticali e orizzontali richiede lo sviluppo e il miglioramento delle tecniche per la caratterizzazione delle propietà meccaniche delle murature esistenti e dei loro componenti. Questa tesi di dottorato presenta un ampio programma sperimentale relativo alla caratterizzazione di mattoni pieni in argilla cotta, sia realizzati a mano che realizzati per estrusione. La ricerca ha considerato anche ampie campagne sulla caratterizzazione meccanica di mattoni e malte di edifici storici esistenti nella città di Barcellona (Spagna), utilizzando prove moderatamente distruttive (MDT). L’obiettivo principale delle campagne sperimentali in situ è stato la calibrazione e la validazione delle tecniche MDT rispetto ai risultati delle prove distruttive (DT) ottenute in laboratorio. Le campagne sperimentali di laboratorio hanno riguardato lo studio e il miglioramento delle tecniche esistenti e lo sviluppo di nuove per la caratterizzazione meccanico-resistente dei componenti dell’opera muraria. La ricerca si è concentrata sulla misura di parametri meccanici di mattoni pieni, quali la resistenza a compressione e il modulo di elasticità. Attualmente non vi è unanimità nella letteratura scientifica e nemmeno sulle norme su come valutare la resistenza a compressione, che comunque richiede un numero elevato di campioni e l’utilizzo di vari strumenti e tecniche. Inoltre, non esistono norme di riferimento sulla determinazione del modulo di elasticità e, pertanto, sono necessarie nuove proposte su metodologie standardizzabili. Nonostante le difficoltà incontrate nella caratterizzazione sperimentale dei mattoni, in questa ricerca sono stati proposti diversi metodi per eseguire la loro caracterizzazione meccanica. Gli approcci ed il metodo proposti hanno dimostrato la loro idoneità e applicabilità pratica. Infine, si raccomanda una metodologia di prova per ciascuno dei parametri studiati nella ricerca, il cui obiettivo finale è la correlazione tra i valori MDT ei valori DT.Enginyeria de la construcci

Mechanical characterisation of masonry in existing structures by means of laboratory and in-situ experimental techniques

Tesi en modalitat de compendi de publicacions(English) Masonry structures are among the most abundant construction typologies in the world, having been commonly built until the second half of the 20th century. The determination of the mechanical properties of these structures entails significant difficulties given the intrinsic complexity of masonry as a composite material. For this reason, the accurate evaluation of masonry buildings against vertical and horizontal actions requires the development and improvement of techniques for the characterisation of the mechanical properties of existing masonry and their components. This thesis presents an extensive experimental program on the characterisation of solid fired clay bricks, including the case of both handmade bricks and mechanically extruded ones. The research has also comprised extensive campaigns on the mechanical characterisation of bricks and mortar in existing historic buildings in Barcelona (Spain), using minor destructive tests (MDT). The main objective of the in-situ experimental campaigns was the calibration and validation of the MDT techniques by comparison with results obtained through destructive tests (DT) applied in the laboratory. The laboratory experimental campaigns involved the study and improvement of existing techniques and the development of new ones for the mechanical characterisation of masonry components. The research has focused on the measurement of mechanical parameters of solid clay bricks, such as the compressive strength and the modulus of elasticity. Currently, there is a lack of unanimity in the scientific literature and also among the standards on how to evaluate the compressive strength, which in any case requires of a large number of specimens and the use of various tools and techniques. Also, there are no reference standards on the determination of the modulus of elasticity and, therefore, new proposals on standardizable methodologies are needed. In spite of the challenges encountered in the experimental characterization of bricks, different methodod have been proposed in this research in order to allow their mechanical characterization. The proposed approaches and method have shown their suitability and practical applicability. Finally, a test methodology is recommended for each of the parameters studied in the research, whose final objective is the correlation between the MDT values and the DT values.(Español) Las estructuras de obra de fábrica de ladrillo se hayan entre los tipos constructivos más abundantes a escala mundial, habiendo sido comúnmente construidas hasta la segunda mitad del siglo XX. La determinación de las propiedades mecánicas de estas estructuras conlleva dificultades significativas dada la intrínseca complejidad de la mampostería como material compuesto. Por este motivo, la evaluación estructural precisa de los edificios de obra de fábrica ante acciones verticales y horizontales requiere el desarrollo de técnicas para la caracterización de las propiedades mecánicas de la obra de fábrica y de sus componentes. Esta tesis presenta un extenso programa experimental relativo a la caracterización de ladrillos macizos de arcilla cocida, incluyendo tanto el caso de ladrillos fabricados a mano como de ladrillos fabricados por extrusión. La tesis también ha comprendido extensas campañas relativas a la caracterización de ladrillos y mortero en edificios históricos existentes de la ciudad de Barcelona (España) mediante ensayos moderadamente destructivos (MDT). El objetivo principal de las campañas experimentales desarrolladas in-situ ha sido la comparación, validación y calibración de las técnicas MDT con resultados de los ensayos destructivos (DT) obtenidos en laboratorio. Las campañas experimentales conllevaron el estudio y mejora de técnicas existentes y el desarrollo de nuevas técnicas para la caracterización mecánico-resistente de los materiales componentes de la obra de fábrica. La investigación se ha centrado en la medida de parámetros mecánicos de ladrillos macizos, tales como la resistencia a compresión y el módulo de elasticidad. El estado del conocimiento muestra falta de unanimidad entre las propuestas de la comunidad científica y entre las diferentes normativas vigentes en relación a cómo medir la resistencia a compresión, lo cual en cualquier caso requiere un gran número de probetas y la utilización de diversas herramientas y técnicas. El estado del conocimiento también muestra la inexistencia de estándares de referencia para la determinación del módulo de elasticidad, siendo necesaria la propuesta de una metodología estandarizable para esta finalidad. A pesar de los retos hallados en la caracterización experimental de ladrillos, la presente investigación ha propuesto distintos métodos propuestos para su caracterización mecánica.(Italiano) Le strutture in muratura costruite in mattoni sono tra le tipologie costruttive più numerose al mondo, essendo state comunemente costruitefino alla seconda metà del XX secolo. La determinazione delle proprietà meccaniche di queste strutture comporta notevoli difficoltà, data la complessità intrinseca della muratura come materiale composito. Per questo motivo, la valutazione precisa degli edifici in muratura nei confronti delle azioni verticali e orizzontali richiede lo sviluppo e il miglioramento delle tecniche per la caratterizzazione delle propietà meccaniche delle murature esistenti e dei loro componenti. Questa tesi di dottorato presenta un ampio programma sperimentale relativo alla caratterizzazione di mattoni pieni in argilla cotta, sia realizzati a mano che realizzati per estrusione. La ricerca ha considerato anche ampie campagne sulla caratterizzazione meccanica di mattoni e malte di edifici storici esistenti nella città di Barcellona (Spagna), utilizzando prove moderatamente distruttive (MDT). L’obiettivo principale delle campagne sperimentali in situ è stato la calibrazione e la validazione delle tecniche MDT rispetto ai risultati delle prove distruttive (DT) ottenute in laboratorio. Le campagne sperimentali di laboratorio hanno riguardato lo studio e il miglioramento delle tecniche esistenti e lo sviluppo di nuove per la caratterizzazione meccanico-resistente dei componenti dell’opera muraria. La ricerca si è concentrata sulla misura di parametri meccanici di mattoni pieni, quali la resistenza a compressione e il modulo di elasticità. Attualmente non vi è unanimità nella letteratura scientifica e nemmeno sulle norme su come valutare la resistenza a compressione, che comunque richiede un numero elevato di campioni e l’utilizzo di vari strumenti e tecniche. Inoltre, non esistono norme di riferimento sulla determinazione del modulo di elasticità e, pertanto, sono necessarie nuove proposte su metodologie standardizzabili. Nonostante le difficoltà incontrate nella caratterizzazione sperimentale dei mattoni, in questa ricerca sono stati proposti diversi metodi per eseguire la loro caracterizzazione meccanica. Gli approcci ed il metodo proposti hanno dimostrato la loro idoneità e applicabilità pratica. Infine, si raccomanda una metodologia di prova per ciascuno dei parametri studiati nella ricerca, il cui obiettivo finale è la correlazione tra i valori MDT ei valori DT.Postprint (published version

Effect of cross section aspect ratio and bearing surfaces treatment on the compressive strength of solid fired clay brick specimens

This study addresses the evaluation of the confinement effect in the experimental determination of compressive strength in solid fired clay units. The experimental campaign has focused on two different types of solid fired clay bricks, namely mechanically extruded and handmade, with a total amount of 458 specimens. The research considers different standard specimens, such as whole or half brick, and 100 × 100 × 40 mm3 specimen, and nonstandard 40 × 40 × 40 mm3 specimen, subjected to different standard bearing surface treatments, i.e. grinding, capping with cement mortar or gypsum plaster, placing with birch plywood or fibreboard. Additionally, two novel bearing surface treatments are proposed, i.e. covering with gypsum powder, and placing two oiled PTFE leaves. The experimental campaign has focused on four main aspects. First, the evaluation of the compressive strength value in specimens with hardening response. Second, the influence of the cross section’s aspect ratio, defined as the ratio between the specimen’s length and width. Third, the influence of the bearing surface treatment on the determination of the compressive strength. Fourth, the evaluation of the standard compressive strength through the comparison amongst reference standards. The results highlight and quantify the different factors that influence the confinement, while detecting differences depending on the manufacturing process of the unit. In addition, the results reveal the use of oiled PTFE leaves as a promising and fast possibility of low boundary friction to obtain the strength regardless of the specimen shape.The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI) as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. Num. RTI2018-099589-B-I00). Support from MCIU through a predoctoral grant awarded to the first author is also gratefully acknowledged.Peer ReviewedPostprint (published version

Anisotropy and compressive strength evaluation of solid fired clay bricks by testing small specimens

A study is presented on the use of a non-standard 40 × 40 × 40 mm3 specimen for the experimental measurement of the compressive strength of solid fired clay bricks extracted from existing masonry buildings. The viability of such specimen has been assessed by comparison with experimental results obtained with the standard 100 × 100 × 40 mm3 specimen. The use of the non-standard 40 × 40 × 40 mm3 has two main advantages. First, it significantly reduces the volume of sampled material, which can be severely restrained in architectural heritage buildings. Second, it allows carrying out tests in the three brick dimensions (length, width and thickness), and therefore investigating the anisotropy that clay bricks can exhibit depending of their manufacturing process. The experimental campaign has focused on three different types of solid fired clay bricks, namely mechanically extruded, hydraulic press moulded, and handmade units, with a total amount of 461 specimens. Using the mentioned small cubic specimen, a detailed research on the compressive strength and the anisotropy of different solid clay brick types has been carried out by applying a statistical approach. The experimental results and the statistical processing have shown that the proposed specimen can be utilized for a reliable estimation of the compressive strengths along the three main directions of solid fired clay bricks.The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI) as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. Num. RTI2018-099589-B-I00). Support from MCIU through a pre-doctoral grant awarded to the first author is also gratefully acknowledged.Peer ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesPostprint (published version

Experimental setup and numerical evaluation of the compression test on thin tiles for masonry timbrel vaults

Compressive tests on clay tiles used in historical masonry timbrel vaults are hindered by the relatively small thickness of the specimens, resulting in buckling or confinement problems depending on the loading direction. This paper presents an experimental campaign and a numerical validation of a novel testing setup for estimating the compressive strength of thin clay tiles used in timbrel vaults. The experimental campaign focuses on two different types corresponding to historical and modern handmade tiles. Experimental and numerical results show that the proposed test setup can be used for the estimation of the compressive strength of thin clay tiles.The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI) as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. Num. RTI2018-099589-B-I00). Support from MCIU through a predoctoral grant awarded to the first author is also gratefully acknowledged.Peer ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónPostprint (published version

Experimental analysis of the size effect on the compressive behaviour of cylindrical samples core-drilled from existing brick masonry

This paper presents the results of an experimental programme about the evaluation of the size effect on the compressive behaviour of cylindrical samples of existing masonry. The study focuses on the in-situ coring and experimental testing of core specimens with 150 mm and 90 mm diameter. The 150 mm cylinder, recurrent in minor destructive evaluation of the compressive strength of existing masonry, includes four brick pieces, two mortar beds and one head joint. The 90 mm specimen includes one mortar bed and two segments of brick, and inflicts less damage on the inspected structural member due to its lower invasivity. The experimental research investigates the size effect on four different types of clay brick masonry. The first type was built in the laboratory using historical-like materials. The other three types of masonry belong to structural walls of existing historical buildings. The combination of experimental results from laboratory controlled materials and existing historical members shows that the size of the cylindrical specimen has regular effect on the compressive strength and the Young’s modulus. The consistent relationship found between the compressive strengths of the 150 mm and 90 mm core samples allows the use of the latter specimen for a more respectful inspection of existing structural masonry.Peer ReviewedPostprint (author's final draft

Laboratory and in-situ characterisation of masonry materials in a large historical industrial building in Barcelona

This paper presents an experimental campaign carried out in an historical industrial building of Barcelona from the 19th century, considering in-situ and laboratory minor destructive testing (MDT) techniques. The results obtained showed a good relationship between the in-situ MDT techniques and the tests carried out in the laboratory. The experimental results from different portions of the large-scale building allowed the discovery of different material typologies deriving from different construction phases.The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI) as well as that of the ERDF (European Regional Development Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. Num. RTI2018-099589-B-I00). Support from MCIU through a predoctoral grant awarded to the first author is also gratefully acknowledged.Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónPostprint (published version

Relationship between the static and dynamic elastic modulus of brick masonry constituents

Different brick masonry typologies have been and are still widely used in construction worldwide. Despite being a fundamental deformation property, experimentally determining the static elastic modulus in compression for brick masonry constituents remains a challenging task. Static modulus estimates usually show much larger dispersion than those involved in determining the dynamic elastic modulus. Although the static property is preferred for common structural verifications, the relationship between the two is yet to be well understood. In light of the above, this paper provides an empirical expression to estimate the static elastic modulus of brick masonry constituents from its dynamic counterpart.This research has received the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI), as well as that of the ERDF (European Regional Development Fund) through the SEVERUS project (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, Ref. num. RTI2018-099589-B-I00). The corresponding author gratefully acknowledges the AGAUR agency of the Generalitat de Catalunya, and the second author gratefully acknowledges the AEI and the European Social Found (ESF), for the financial support of their predoctoral grants.Peer ReviewedPostprint (author's final draft

The inspection by minor destructive testing in projects of adaptive reuse of historical masonry buildings and design of green rooftops in Barcelona

The mechanical characterisation of existing masonry in historical structures encounters several technical dif-ficulties due to the complexity and heterogeneity of this traditional material, as well as to the need for respectful inspec-tion activities able to preserve the cultural heritage value of the building. This paper presents and discusses different Minor Destructive Testing (MDT) techniques oriented at estimating, either in-situ or in the laboratory, the mechanical properties of masonry at the level of components, such as units, tiles, and mortar joints, and at the level of the composite material. The research addresses different issues related to the execution of laboratory tests on sampled historical mate-rials, such as selection of the size and shape of specimens, different types of treatments for the sample, testing protocols, and experimental setup. The complementary use of Finite Element Method (FEM) models represents a valuable activity to provide a good understanding of the experimental behaviour exhibited by the specimens, and especially concerning the execution of non-standard laboratory tests. The possibility of in-situ MDT is explored considering techniques based on different portable instruments, previously calibrated through ad-hoc experimental programs under controlled labora-tory conditions. The research is based on a high number of tests executed at the UPC within the context of several experimental programs linked to projects of adaptive reuse of existing masonry buildings and design of green rooftops in Barcelona.The authors gratefully acknowledge the financial support from the Ministry of Science, Innovation and Universities of the Spanish Government (MCIU), the State Agency of Research (AEI) as well as that of the ERDF (European Regional De-velopment Fund) through the project SEVERUS (Multilevel evaluation of seismic vulnerability and risk mitigation of masonry buildings in resilient historical urban centres, ref. Num. RTI2018-099589-B-I00). The first author gratefully acknowledges the owners of the historical buildings investigated, as well as people from the institutions and companies involved in the studies and projects mentioned in this work and in particular Sergio Carratalá from MataAlta. The second and third authors gratefully acknowledge the Spanish Ministry of Science, Innovation and Universities, and the AGAUR agency of the Generalitat de Catalunya, for the financial support of their predoctoral grants.Peer ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles::11.4 - Redoblar els esforços per a protegir i salvaguardar el patrimoni cultural i natural del mónObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.2 - Incorporar mesures relatives al canvi climàtic en les polítiques, les estratègies i els plans nacionalsObjectius de Desenvolupament Sostenible::13 - Acció per al Clima::13.1 - Enfortir la resiliència i la capacitat d’adaptació als riscos relacionats amb el clima i els desastres naturals a tots els païsosPostprint (author's final draft