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Compression tests on cob: (a) crack pattern of a wallet; (b) compression stress-axial strain curves and respective envelope.
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The paper presents a comparison between different numerical modelling approaches aiming to simulate the in-plain behaviour of three types of earthen materials, namely adobe masonry, rammed earth and cob. For this purpose, uniaxial and diagonal compression tests were carried out, which allowed determining important mechanical parameters, such as com...
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Context 1
... of rammed under uniaxial compression, which starts from low stress levels. It should be noted that fc showed relatively low scattering and varied between 3.3 and 3.9 N/mm 2 , while E presented relatively high scattering and varied between 2844 and 5048 N/mm 2 . A typical crack pattern at the failure of one of the cob wallets tested is shown in Fig. 3a. Fig. 3b reports the compression tests results in terms of axial stress-strain curves and the re- spective envelope. These curves draw attention to the non-linear behaviour of cob under com- pression. The values of fc showed relatively low scattering and varied in the range of 1.55- 1.63 N/mm 2 . Also E presented relatively low ...
Context 2
... under uniaxial compression, which starts from low stress levels. It should be noted that fc showed relatively low scattering and varied between 3.3 and 3.9 N/mm 2 , while E presented relatively high scattering and varied between 2844 and 5048 N/mm 2 . A typical crack pattern at the failure of one of the cob wallets tested is shown in Fig. 3a. Fig. 3b reports the compression tests results in terms of axial stress-strain curves and the re- spective envelope. These curves draw attention to the non-linear behaviour of cob under com- pression. The values of fc showed relatively low scattering and varied in the range of 1.55- 1.63 N/mm 2 . Also E presented relatively low scattering and ...
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Scaled masonry model testing has been performed for many decades, with earlier researchers establishing that it is possible to model masonry behaviour at reduced scale, but that strength and stiffness are affected and with many studies suggesting that masonry is anisotropic. The effects of scale on clay brick masonry compressive strength, Young's M...
Citations
... The values obtained from the different studies are widely scattered and not fully comparable, ranging from 1 to 2.5 MPa (Avila et al. 2021) for unstabilised rammed earth. Many factors influence the results, namely type and shape of the specimen (cylindrical or cubic) or dimensions of the wallet or full-scale element tested; slenderness, moisture content; density, particle size distribution (soil composition and grading), additives if any, manufacturing and testing procedures, etc.… Furthermore, several studies have been conducted on the seismic performance of different earthen vernacular constructions, developing numerical models and carrying out tests at different scales and with different strengthening techniques (Yamín et al. 2007;Bui et al. 2016;Miccoli et al. 2016;Arslan et al. 2017;Miccoli et al. 2017;El-Nabouch et al. 2017;Silva et al. 2017;Bui et al. 2018;Ortega et al. 2018;Reyes et al. 2018;Allahvirdizadeh et al. 2019;Ramezanpour et al. 2021). ...
... The values obtained from the different studies are widely scattered and not fully comparable, ranging from 1 to 2.5 MPa (Avila et al. 2021) for unstabilised rammed earth. Many factors influence the results, namely type and shape of the specimen (cylindrical or cubic) or dimensions of the wallet or full-scale element tested; slenderness, moisture content; density, particle size distribution (soil composition and grading), additives if any, manufacturing and testing procedures, etc.… Furthermore, several studies have been conducted on the seismic performance of different earthen vernacular constructions, developing numerical models and carrying out tests at different scales and with different strengthening techniques (Yamín et al. 2007;Bui et al. 2016;Miccoli et al. 2016;Arslan et al. 2017;Miccoli et al. 2017;El-Nabouch et al. 2017;Silva et al. 2017;Bui et al. 2018;Ortega et al. 2018;Reyes et al. 2018;Allahvirdizadeh et al. 2019;Ramezanpour et al. 2021). ...
This study is aligned with United Nations, Sustainable Development Goal 11, concerned about making cities and human settlements inclusive, safe, resilient and sustainable, in particular, in line with resilience to disasters, and protecting the world’s cultural heritage targets. Focused on a small sample of rammed earth residential dwellings in the city of Mula, one of the areas of highest seismic hazard in Spain, the seismic vulnerability has been assessed adapting the Vulnerability Index Method (Risk-UE) to tackle the specificities of earthen residential buildings. The majority of this humble earthen heritage, despite being an essential part of the Spanish Culture, suffers from the effects of abandonment and insufficient maintenance. As a consequence, these genuine buildings will be seriously damaged in the event of an earthquake of intensities from VII to VIII, with heritage losses representing 17% to 43% of the built area. These research outcomes can be used to define repair and strengthening priorities among the buildings in the sample when financial resources are limited. The proposed indices and coefficients can be applied to similar earthen structures, widely built in the Iberian Peninsula and the Mediterranean region.
... Today, there are still three main types of traditional earthen construction techniques used for constructing single or two-story buildings: adobe, cob, and rammed earth [5,6]. Adobe is primarily used to produce earthen blocks utilized to construct walls, vaults, arches, and domes, which are difficult or even impossible to construct with rammed earth [7,8,9,10]. Earthen blocks are manufactured by compacting a mixture of wet soil and other compounds into a formwork [11]. ...
... m and must be completely dried before the next layer can be added [8,15]. Rammed earth is a technique where a mixture of moistened earth and other compounds is compacted in superposed layers within a formwork [7]. Rammed earth is primarily used to construct walls, even in humid climates where building with adobe bricks is impractical or impossible [8]. ...
One major drawback of excavation earth-based composite construction materials is the variability in excavation earth characteristics from site to site. This variability can affect certain physical properties, and, in turn, the design models used to create a structure. To solve this problem, a methodology has been developed to predict the physical properties of earth-based composites for any mix-design variation, which enables a robust structural design process. This new methodology has been tested for Shot-earth, a new class of earth-based composite material made using high rates of excavation earth, aggregates, and a low rate of stabilization if needed. Shot-earth is placed using a high-speed dry-mix process. The methodology was tested by preparing small, inexpensive specimens through a process that simulates the dry-process used to fabricate Shot-earth in the field. An adaptive technique, used in conjunction with the experimental methodology, allows for the identification of the variant of possible Shot-earth mix-designs that provides optimal physical properties for a specific project. This technique is potentially applicable to any type of earth-based composite. The proposed methodology's reliability enables a fast and cost-effective detailing of Shot-earth constructions.
... La surface peut ensuite être retaillée pour épouser au mieux la forme souhaitée. Les premières recherches ont présenté une étude plus approfondie sur la technique de la bauge, en la comparant à d'autres méthodes (Goodhew et al., 2021;Keefe, 2012;Miccoli et al., 2017;Minke, 2012;Röhlen et al., 2013 Dans l'ensemble des systèmes constructifs en terre, l'isolation n'était pas un élément majeur jusqu'au début du XX e siècle. Le système de chauffage de ces habitats était généralement concentré dans une seule pièce, la notion de confort était alors bien différente d'aujourd'hui. ...
Les enjeux économiques liés à la hausse des coûts des matériaux de construction, la raréfaction de ces derniers et les impacts environnementaux inhérents à leur fabrication et à leur utilisation conduisent les acteurs de la construction à s’orienter vers des écomatériaux. Ces dernières années, la bauge connaît une renaissance dans le nord-ouest de la France et le sud de l’Angleterre. Les connaissances techniques sur ce type de matériau de construction étant limitées, il est essentiel d’étudier les propriétés mécaniques et hygrothermiques pour des méthodes de conception modernes. Le projet CobBauge vise à développer cette technique de construction avec des matériaux innovants. Cette thèse a pour objectif le développement de la construction en terre crue avec des mélanges terre-fibres végétales. Après l’étude de plusieurs formulations, deux mélanges ont été sélectionnés pour la construction d’un bâtiment pilote : la bauge traditionnelle pour la résistance mécanique, composée de limon et de paille de lin, et la terre allégée pour l’isolation, composée d’argile et de fibres de roseau. Ce dispositif permet de satisfaire à la réglementation thermique RT 2012. Le bâtiment pilote a été construit en Normandie, dans le Parc naturel régional des Marais du Cotentin et du Bessin (Carentan). Il permet de tester de nouvelles méthodes de mise en oeuvre de bauge et de terre allégée sur le chantier, et de définir une méthode permettant la reproduction en laboratoire des caractéristiques des matériaux observées sur le chantier. Un programme expérimental a été conçu pour évaluer les propriétés des matériaux telles que la teneur en eau, la masse volumique, la porosité, la résistance à la compression et la conductivité thermique. Des échantillons de forme cylindrique (∅110 x H220 mm) et prismatique (300 x 300 x 70 mm) ont été produits sur place et en laboratoire. Un suivi régulier de la qualité des matériaux, puis des mélanges, a été mis en place sur chantier afin de suivre la cinétique de séchage, le retrait et le comportement hygrothermique du bâtiment pilote, ainsi que son environnement. Pour cela, des sondes de teneur en eau et une station météorologique ont été utilisées. Les performances hygrothermiques et de retrait ont été étudiées à l’échelle du laboratoire. Les résultats expérimentaux nous ont permis de mesurer les différents paramètres sur chantier et de reproduire les matériaux en laboratoire avec les mêmes caractéristiques, de comparer la cinétique de séchage sur les murs du bâtiment et des échantillons en laboratoire, de déterminer le retrait sur les murs du bâtiment et à l’échelle du laboratoire, et enfin d’explorer le comportement hygrothermique des matériaux.
... These values have been extracted based on current studies reported in the literature. Miccoli (Miccoli et al., 2017) performed uniaxial compression, pull-off, and diagonal compression tests on a laboratory model of an adobe wall. Silveira (Silveira et al., 2012), on the other hand, performed laboratory tests on material samples taken from real Portuguese adobe buildings. ...
... These values have been extracted based on current studies reported in the literature. Miccoli (Miccoli et al., 2017) performed uniaxial compression, pull-off, and diagonal compression tests on a laboratory model of an adobe wall. Silveira (Silveira et al., 2012), on the other hand, performed laboratory tests on material samples taken from real Portuguese adobe buildings. ...
Peru, in particular in the area of Cusco, is characterized by a high seismic hazard. The city of Cusco, whose historic center was recognized as UNESCO site since 1983, has a long story of telluric events and the study of the seismic vulnerability of its buildings is a duty of relevant concern for the seismic risk assessment of the whole urban area. Furthermore, protection and preservation of monumental and residential assets is an essential issue, especially for those buildings made of adobe, which are an important legacy testifying the life and the development of past civilizations. Based on these premises, this study aims to assess the seismic behavior
of a colonial adobe building located in the historic center of Cusco. This category of buildings represents the so-called “casa cusqueña”, i.e. the typical residential building realized by Spanish colonists, often characterized by architectural and structural elements coming from the ancient Inca population. Squared plan with internal courtyard, stone foundations and adobe walls are some of the main structural characteristics of this type of building. After the description of the reconnaissance campaign carried out in the considered building, the global seismic behavior of the structure is analyzed by means a finite element model implemented in ABAQUS. A step-by-step linear dynamic analysis is performed to identify cracks evolution as the ground acceleration increases.
... Accordingly, these real-time mechanical properties of concrete 3D prints have been integrated into a structural simulation in Karamba3D and other industry standard tools, providing a useful theoretical framework that may be applied to new materials [24]. Wet earth and concrete have similarities in mechanical behavior which make such tools transferable [25]. However, to date, a rigorous behavioral analysis of 3D printed earthen wall or shell structures has not been developed. ...
This paper presents a novel toolpath optimization method for formwork free 3D printing of shells. The additive fabrication of shell structures without formwork has the potential to significantly reduce material waste and construction cost, thus minimizing embodied carbon across the concrete construction industry while making an often appreciated but underused typology a feasible construction practice. Generating vault toolpaths which are stable during construction is a nontrivial challenge [1]. Here, we present a new approach to address this challenge that integrates traditional masonry strategies with advanced simulation and optimization methods. To perform multi-objective optimization of 3D printed vaults, toolpaths are (1) orientated perpendicular to principal stress lines, (2) generated relative to the supported edges of the structure, and (3) adjusted with parameterized control curves using constrained optimization with a composite objective function. This composite objective function uses a layer-by-layer mechanical simulation and minimizes both displacement during fabrication and toolpath length. The length of the toolpath is characterized by the material necessary to achieve desired strength and the print time. This model allows the designer to balance structure, environment, and form in the context of fabrication aware structural simulation.
... Other necessary material parameters were calibrated for each one of the different material constitutive models studied. Materials' parameters calibration in ANSYS was done using the design exploration module available in the software [ANSYS Inc. (2013a)] whereas that calibration for ABAQUS models was performed using the statistical software Minitab [(2013)] by adopting a central composite face centered approach (see Appendix A). (-) 0.14 Density (kg/m 3 ) 1475 a Ranges of recommended values proposed for numerical analysis purposes [Miccoli et al. (2017)]. ...
... The results obtained from the simulations are presented in the form of stress-strain graphs. The upper and lower limits of the stress-strain graphs represent the experimental envelope reported by Miccoli et al. [(2017)]. For the sake of briefness, only results correspondent to the material constitutive models deemed to be more suitable to represent cob's monotonic structural behavior are presented in detail. ...
... Cob's mechanical properties[Miccoli et al. (2014)] &[Miccoli et al. (2017)]. ...
It has been observed by performing simple and diagonal compression tests of cob wallettes that the structural behavior of cob is highly non-linear. This paper presents the results obtained of the simulation of cob's non-linear monotonic behavior using two well-known finite element commercial packages. Pros and cons of different available constitutive material models are identified and discussed. Concrete (CONCR) and Concrete Damage Plasticity (CDP) are considered as the constitutive material models that provide the more satisfactory results reproducing cob´s non-linear monotonic behavior when using ANSYS and ABAQUS respectively.
... Thus, after a drying period of four months the pre-consolidation of the wallettes began. It was decided not to exceed the apparent yield point of cob which corresponded to approximately 30% of the computed average compressive strength of the cylinders, a similar percentage value was used and reported by Miccoli et al. [27]. The wallettes were subjected to a consolidation force of 84 kN ± 1 kN which induced a stress of roughly 0.21 MPa. ...
The flat jack test is one of the most applied investigation techniques in the field of cultural heritage conservation.
The purpose of the experimental campaign presented in this paper was to assess the feasibility
of the technique to measure the average compressive levels of stress in existing cob walls and determine
their mechanical properties. It was observed that the single flat jack test tended to overestimate the average
value of stress by a factor of two. Therefore, it is advised to apply a value of Ke = 0:51 to correct the
average compressive stress values obtained with the use of this technique.
... Testing of the rest of the wallettes .. ........................................................... 215 5.11.3 Single flat jack tests ' results summary ....................................................... 216 5.12 ....................................................................... 219 5.12.2 Testing of the rest of wallettes ................................................................... 222 5.12.3 Double flat jack tests ' results summary ..................................................... (Miccoli et al., 2014, Miccoli et al., 2017. ... 106 Chapter 5 Table 6. ...
... It can also be applied for control purposes while interventions are being carried out (Boffill et al., 2019) and the damage caused by the test can be easily repaired (Gregorczyk and Lourenço, 2000). (Briceño et al., 2018), (Tacas et al., 2019) (Lombillo, 2010), (Rufo, 2010), (Xavier, 2011), (Tacas Guillen, 2018), (Filipe, 2012), (Domingos, 2010) (Lombillo, 2010), (Lombillo et al., 2013), (Lombillo et al., 2014) * Double flat jack (Briceño et al., 2018), (Lombillo, 2010), (Tacas et al., 2019), (Manzoni et al., 2019), (Rufo, 2010), (Xavier, 2011), (Tacas Guillen, 2018), (Filipe, 2012), (Domingos, 2010), (Lombillo, 2010), (Giamello et al., 2016), (Parsekian et al., 2019), (Lombillo et al., 2013), (Lombillo et al., 2014) * Shove (Dowling et al., 2004), (Dowling et al., 2005) * * Hole drilling (Lombillo, 2010) (Lombillo, 2010), (Lombillo et al., 2013), (Lombillo et al., 2014), (Lombillo et al., 2018) * Dilatometer (Lombillo, 2010) (Lombillo, 2010), (Lombillo et al., 2013), (Lombillo et al., 2014) * Pull off test (Miccoli et al., 2017) (Shukla, 2016), (Barroso, 2017) Originally developed and applied to the field or rock mechanics, the flat jack test was adapted to be applied on historical buildings by Rossi in 1980(Rossi, 1980. Since then, it has been applied to study structures comprising of brick masonry; (Rossi, 1982a, Rossi, 1987a, Epperson and Abrams, 1990, Rossi and Vavassori, 1992, Astudillo and Garcia, 1995, de Vekey, 1995, Rossi, 1995, Binda and Tiraboschi, 1999, Gregorczyk and Lourenço, 2000, Brencich and Sabia, 2008, Carpinteri et al., 2009, Lombillo, 2010, Tecchio et al., 2012, Bartoli et al., 2013, Simões et al., 2016, Della Torre et al., 2019, Saisi et al., 2019, stone masonry; (Rossi, 1987b, Gelmi et al., 1993, Binda and Tiraboschi, 1999, Binda et al., 2003, Bosiljkov et al., 2010, Lombillo, 2010, Almeida et al., 2012, Simões et al., 2016, Della Torre et al., 2019, Fanale et al., 2019, Motisi et al., 2019, ashlar masonry; (Abdunur, 1983, Rossi and Zaldivar, 1996, de Vekey and Skandamoorthy, 1997, Binda et al., 2001, Lourenço et al., 2001, Lourenço et al., 2008, Lombillo, 2010, concrete; (Abdunur, 1983, Sumitro et al., 2003, Figueiredo et al., 2010, Chesi et al., 2019, adobe and rammed earth (see Table 2. 2). ...
... Keefe (2012) Miccoli et al. (Miccoli et al., 2014, Miccoli et al., 2017 Quagliarini and Maracchini (2018) Compressive strength fc ( Minke (2000) Ziegert (2003) Akinkurolere et al. ...
Cultural heritage is increasingly threatened not only by traditional causes of decay, but also by changing social, economic and environmental conditions. The deterioration or disappearance of any cultural item constitutes a harmful impoverishment of our heritage. Besides, culture has been recognized as an enabler and driver of sustainable development, peace and economic progress, which highlights the necessity of fostering its documentation, protection, and promotion. For all these reasons, working in the conservation of our cultural heritage should not only be justified but encouraged.
The general objective of this PhD thesis is to contribute with the efforts to achieve Target 11.4 of the Sustainable Development Goals (SDG), adopted by the United Nations (UN) in 2015, by strengthening the efforts to protect and safeguard the world’s cultural and natural heritage. The aim of the research is to increase awareness regarding the importance of vernacular architecture and its intrinsic values, as identified on the International Council of Monuments and Sites (ICOMOS) Action Plan for the Future. It specifically focuses on the improvement of earthen architectural heritage conservation, as this group of structures is particularly vulnerable to environmental and anthropologic threats.
The thesis presents a summarized and concise picture of the present situation of the remaining earthen buildings in Ireland, identifies their main characteristics, the values that make such buildings important, evaluates their vulnerability as vernacular architectural style and therefore, allows to understand and better approach any future intervention on such kinds of structures.
Within the context of current conservation practice, which is based on a scientific approach and implements a cyclic method of research, diagnosis, intervention and control activities, the thesis contributes to the development of quantitative research methods. A first contribution is presented on the structural analysis of cob by evaluating the suitability of available constitutive material to model its non-linear structural behaviour using two of the most commonly used Finite Element Method (FEM) software in the market, ANSYS and ABAQUS.
A second contribution is concerned with the experimental testing of cob. A Minor Destructive Test (MDT) known as the flat jack test, has been experimentally validated by testing it in a series of cob wallettes built in the laboratory of Civil, Structural and Environmental Engineering (CSEE) at Trinity College Dublin (TCD). The purpose of the experimental campaign was to assess the feasibility of the technique to measure the average compressive levels of stress in existent cob walls and estimate their mechanical properties. The principal results show that effectively the test can be applied in cob walls but it tends to overestimate the stress values by a factor of approximately two. As conclusion, it is advised to correct the average compressive stress, fm, by using a value for the dimensionless geometrical efficiency constant, Ke, of 0.51. The use of a more realistic value would prevent the design and application of over invasive interventions that may place in danger the value of the historical fabric. The double flat jack tests allowed to estimate the mechanical parameters of the material to a good degree of certainty.
Finally, a parametric analysis of cob walls is presented with the aim of providing conservation practitioners with rule of thumb guidance to assess the safety of existent cob buildings under seismic actions. The methodology presented in this regard is not limited to the Irish context but could as well be implemented in different countries where the seismic hazard represents an actual threat for the structural safety of remaining vernacular cob buildings.
... Numerical modelling of cob has also been studied (Miccoli et al. 2017). Cob was modelled as a homogenous and continuous material using an FEM macromodelling approach. ...
Even though Irish meteorological conditions are adverse for the development of earthen con-structions, earth has been used as a construction material in Ireland for more than 4000 years. The objective of this paper is to present a summarized and concise picture of the present situation of the remaining earthen buildings in the country, identify their main characteristics, the values that make such buildings important, evaluate their vulnerability as vernacular architectural style and therefore, understand and better approach any future intervention on such kinds of structures. In particular, the paper highlights the lack of a detailed descrip-tion of traditional construction techniques and of recommended procedures for the conservation of existing earthen structures. The paper identifies the pertinent Irish texts and suggests how recent research on the me-chanical properties of cob and state-of-the-art numerical analysis techniques and constitutive models can be used to assess the strength and stability of existing historic structures.
