Adobe is a traditional masonry made of sundried earthen bricks and mud mortar. Despite a millennial history of buildings of architectural value, adobe still connotes a so called ‘not engineered’ construction type. Namely, the material and structural properties of adobe are still not entirely addressed, resulting in an equally uncertain normative framework for adobe buildings design. However, over the last ten years, a large research program has been conducted in the Netherlands to qualify the material and structural properties of this sustainable building technology. In this paper, a critical analysis of the current normative body for the material characterization of adobe is addressed. Guidelines, prescriptions and requirements related to test methods, materials selection and properties contained in the available building codes for adobe around the world are assessed. A critical normative review is performed using the most recent literature produced on adobe, with particular regards to the results of experimental tests and numerical simulations performed by the authors. On the basis of these findings, some issues have been identified in relation to the knowledge currently condensed in the norms for adobe. A series of programmatic guidelines is aimed at orienting future research on adobe as well as fostering the process of updating its current normative body.

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This paper presents the results of an experimental research aimed at assessing the material performance of adobe bricks in compression for a wide range of induced strain rates, from statics to high velocity impact. Adobe connotes a traditional masonry whose bricks are made of sundried soil mixtures possibly reinforced with natural fibres and joined together using mud mortar. The inclusion of fibre and the presence of water in the mixture have a dominant effect on the mechanical performance of adobe bricks and masonry. Their influence on the dynamic behaviour of this material is quantified and interpreted in this study at high strain rates also with data produced through Hopkinson bar testing. Appropriate dynamic increase factors and constitutive equations for adobe materials in dynamics are also investigated. The paper presents the experimental campaign, shows the main results and offers qualitative and quantitative interpretations for the principal damage patterns observed.@en

Buildings and structures in many cities have recently been exposed to an increased number of highly dynamic hazards. These include not only floods and earthquakes but also man made threats such as ballistic impacts and blasts. Thus, the assessment of the dynamic performance of structures made of quasi-brittle materials must account also for high strain rate loadings. In engineering software, numerical simulations of dynamic failure processes are often carried out in a framework of damage mechanics, in which failure is interpreted as a degradation of the elastic material capacity. However, for many damage models, the link between the implemented numerical functions representing the corresponding physical mechanisms aimed is still a controversial issue. This is also the case because damage models suffer from a numerical pathology which prevents the objective evaluation of failure for different spatial discretization. To solve this issue, non local regularization algorithms are often used to solve mesh dependence, often at the expenses of complex identification procedures and non- trivial code implementation. Instead, a locally regularized rate dependent model has been developed by the authors for the static assessment of unbaked masonry materials made of clay sand and silt [1]. It adapts damage delay functions originally proposed in [2] in a local damage model developed for cementitious materials [3] based on the decomposition of the Dirichlet boundary conditions solved with an implicit solver. The regularization properties of the model were shown in [1] in statics. The regularization properties of the algorithm are analysed in this contribution for the dynamic problem of a bar uniaxially compressed at high velocity deformation rates. Furthermore, the physical background of the delay formulation is interpreted in light of the main failure processes commonly depicted for quasi-brittle materials in dynamic tests. In particular, the material parameters of the delay function in [1] are linked in this study to the bridging processes of micro-cracks starting from initial flaws inside the material and the resulting macro-crack development up to failure. Considering the physics shown in literature for quasi-brittle materials under multi-strain rate tests, the constant parameters in [1] are made functions of internal and environmental factors, namely material mineralogical properties and applied loading rates in this study. The resulting delay formulation produces an improvement in the capability of the model both to address the complete stress-strain curve of the response of traditional masonry materials subjected to a dynamic load and the rate of enhancement of the main mechanical parameters typical for these rate sensitive materials when subjected to multi-strain rates tests. This is shown in this paper by means of theoretical tests and practical applications with regards to the results of an experimental campaign performed by the authors on adobe specimens subjected to dynamic tests at three different strain rates, ranging from statics to Split Hopkinson bar tests.@en

This article proposes a new approach towards the design and planning of social housing destined to residents living in informal settlements of Brazil. It is aimed at restoring the proximity between the labor and domestic functions within the spatial domain of the house. This need emerges from a field research aimed at addressing the spatial logics emplaced by residents in Brazilian favelas. The integration proposed in the article is meant to be achieved with the combined goal of improving the living conditions of the residents, sustaining also their socio-economic development, while promoting also the economy of the city. Graphic guidelines are shown to the reader after a critical analysis of the main systems of housing currently emplaced for unprivileged people. @en

Research in this thesis is aimed at comprehensively characterizing the mechanical performance of adobe components. Adobe is a traditional masonry made of sundried bricks and mortar. Bricks are made of soil mixed with fibres and joined together by mud mortar. Adobe is largely spread in areas of the world prone to seismic risk or involved in military conflicts. Its low environmental impact attracts scientific attention also for sustainable applications in current building industry. Unfortunately, the material and structural properties of adobe are still hardly assessed, as a result of centuries of progressive abandonment of this building technology in western countries after introduction of modern building materials in the market. In this doctoral research, a combined experimental and numerical approach was followed. It has been aimed at fulfilling experimental data and knowledge gaps in the study of the main properties of this material. Experimental tests have been performed on bricks and mortar characterized by different mineralogical compositions, fibre percentages and moisture content. Mechanical tests consisted of bending and compression tests. Tests in compression have been performed at different rates of deformation from statics to high velocity impact. Data derived from tests have constituted a solid dataset aimed at interpreting and modelling the mechanical performance of adobe. Experimental trends resulted in physical theories concerning the main features of the quasi brittle response of adobe. In particular, the role of fibres and water content in the mixture on the mechanical response of adobe bricks and mortar has been addressed in this study in the static and dynamic regimes of the spectrum of strain rate induced loadings. The main mechanical parameters in compression and tension for adobe have been statistically determined from the static and dynamic tests. Mechanical properties and physical theories have been framed in several models that interpret the response of adobe for different applications. Constitutive models have been derived to address the uniaxial response in compression at different strain rates of adobes of different mineralogical composition and water contents. A finite element damage model has been developed to simulate the main failure modes specifically observed in earthen bricks at different loading conditions and rates, including high velocity impacts. The numerical study has been devoted at ensuring objectivity of analysis to the results of simulations performed using different mesh refinements of the geometrical model of the tested brick. Furthermore, engineering ballistic models that address the response of adobe walls to small caliber penetrations have been developed in this doctoral research. This thesis contains the description of the performed experiments, the analysis of data, the theoretical interpretations and the models developed for the material characterization of adobe masonry. @en

A local damage model is proposed for the numerical assessment of the static performance of Adobe masonry components. The model was applied to simulate the experimental behaviour of sundried soil bricks and mud mortar tested in uniaxial compression and bending. Numerical simulations of the model are made mesh objective by means of a rate dependent regularization algorithm in statics. This is achieved using a generalization of the damage delay concept based on a decomposition of the Dirichlet boundary condition. It allows non-dimensionality of model parameters mathematically needed to prevent loss of ellipticity of the equilibrium equations of the model. The entire regularization algorithm is integrated within an implicit Newton-Raphson solver.

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Adobe is one of the most ancient forms of masonry. Adobe bricks are sundried mixtures of clay, silt, sand and natural fibres locally available joined together using mud mortar. Adobe structures are largely spread in areas of the world prone to earthquakes or involved in military conflicts. Unfortunately, almost no literature concerns the dynamic assessment of soil-based masonry components. From earlier research, it was derived that the mechanical behaviour of adobe in statics fits in the class of quasi brittle materials. Its resemblance with cementitious materials concerns the main failure modes and the constitutive models in compression. This study deals with the experimental characterization of adobe components response in dynamics. It is aimed to study and quantify the rate sensitivity of adobe material from bricks at a wide range of strain rates, from statics up to impact conditions. In particular, the influence of fiber reinforcement in the mixture on the mechanical behaviour of the material has been addressed. Adobe bricks are commonly mixed using organic content locally available in the field, from straw to chopped wood. Fibres are added to prevent shrinkage cracks during the air drying process. In modern materials such as concrete, inclusion of artificial fibres is originally meant to enhance the mechanical performance of the material, benefiting from the selective properties of reinforcement and binder. An experimental campaign was carried out in a collaboration between Delft University of Technology, Dutch Ministry of Defence, TNO and the Joint Research Centre (JRC) of the European Commission. Two types of bricks were tested. They both had the same soil composition in terms of mineralogical family and soil elements proportions but only one was mixed using straw and wood. Cylindrical samples were subjected to compression tests at different rates of loadings in compression: low ( _ 1 = 3 104 s1), intermediate ( _ 2 = 3 s1) and high ( _ 3 = 120 s1). High strain rate tests were performed using the split Hopkinson bar of the Elsa-HopLab (JRC). For each test, high resolution videos registered the failure process and force-displacement plots were recorded. Elaboration of results revealed clear trends in the dynamic material behaviour. Adobe, as concrete, is sensitive to the loading rate. The rate effects on the main properties of the material in strength and deformation are also analytically and numerically quantified. Rate sensitivity and failure mode are significantly influenced by the inclusion of fibers in the mixture. These effects are quantified, interpreted and compared with modern SFRC. This paper presents the experimental campaign and the obtained results. Moreover, physical interpretations for the observed trends are discussed. Finally, new formulations for the assessment of the dynamic increase factor of the compressive strength of adobe are proposed.@en

A local damage model has been recently developed for the numerical simulation of the static behaviour of adobe bricks. Mesh insensitivity of the local model was obtained by generalizing the damage delay concept based on a Dirichlet boundary condition decomposition integrated in an implicit solver. The regularization properties of the model were proven before only in statics. In this study, mesh independence is demonstrated in dynamics analysing the problem of a cantilever bar uniaxially loaded at high deformation rates. Furthermore, the physical background of the delay formulation is interpreted regarding the main failure processes in compression exhibited by quasi brittle materials used in masonry. Two limitations of the model in correctly simulating the dynamic behaviour of masonry bricks have been observed. Corrections to the original damage delay formulation are proposed in this study. These enhance the capability of the model to address also distributed failure of traditional geo-materials and the inherent rate dependence also at high strain rate regimes. The improvements are demonstrated in this paper by means of numerical simulations of both theoretical tests and practical applications. These consist of experimental tests in compression recently performed by the authors at different strain rates, from statics to high velocity impact tests.

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This paper presents a constitutive relationship to describe the uniaxial response in statics of brick and mortar samples of Adobe. This defines a traditional masonry whose components are made of soil mixture reinforced with fibres. Only recently Adobe has started attracting scientific attention, primarily as a consequence of the dramatic failures these structures have suffered in regions prone to earthquakes due to dynamic loadings. Furthermore, it possesses eco-friendly material properties which are attractive features for western countries forced to reduce the environmental impact of modern building industry. Nevertheless, the mechanical properties of Adobe are still largely neglected, especially with regards to the influence of soil mixture components. The study of the structural performance of masonry starts from the assessment of the material performance of its components. Thus, an extensive characterization campaign was organized and performed by Delft University of Technology and the Military Engineering Laboratory of the Netherlands, in order to characterize the material properties of Adobe components. Three types of bricks and one type of mortar, made with different mixture components proportions, were subjected to granulometry, moisture content, density tests and uniaxial compressive and three point bending tests. Predictive formulations for compressive and tensile strength and deformation values have been proposed by the authors [1]. These relations include the dependency of mixture components and moisture contents. In this paper, constitutive laws are developed for Adobe in pure compression and tension according to the experimental results. In compression, the force-displacement curves were interpolated according to several existing constitutive laws and the model originally developed by Priestley for concrete masonry elements was finally selected as best fitting. Despite the differences in terms of mechanical parameters, the analytical assessment revealed that the experimental force-displacement graphs of all the different types of bricks could be interpolated using the same model with the same calibrating values. Furthermore, the uniaxial response in tension was derived according to an inverse approach. A numerical model recently developed and calibrated with respect to the compressive and bending tests was used to simulate uniaxial tensile tests [2]. Also in this case, a common trend among types was observed. The results of the constitutive modelling frames components of Adobe within the class of quasi brittle (geo)materials, with particular reference to concrete-like materials. This paper presents the experimental results of the tested samples and the related analytical and numerical modelling. @en

Adobe is an ancient building technology made of sun dried bricks joined together by mud mortar. This paper deals with the physical and mechanical characterization of three different typologies of adobe bricks and one typology of mud mortar produced in Europe. They differed in terms of internal soil element proportions and amount of organic content. Physical tests consisted of granulometry, moisture content and density tests. The mechanical characterization consisted of uniaxial compressive tests and three point bending tests. Tests were performed according to modern material standards. The main mechanical properties both in tension and compression were determined at different curing conditions. The outcome provided in this study offers a general overview on the assessment of the mechanical performance of adobe in relation to the properties and interactions of its soil constituents. In fact, the comparison between components with the same soil mineralogical family and production process made it possible to assess both at a qualitative and quantitative level the effect of the physical properties of the mixture (such as fiber and clay percentages or moisture content) on the mechanical parameters of the resulting bricks and mortar. This paper proposes new predictive formulations of the most relevant material parameters in strength and deformation, such as compressive strength, deformation at peak stress and ultimate displacement for both adobe bricks and mortar. They quantify the influence that water content, clay percentage and fiber reinforcement produce on the mechanical performance of the tested adobe components. This was made possible by means of multivariate statistical analyses on the mechanical parameters derived from all the tested samples.

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A local damage model has been developed for interpreting the dynamic performance of Adobe, a traditional form of masonry whose components are made of sun-dried and unpressed soil possibly reinforced with fibres. This paper presents a numerical model to assess the static performance of bricks and mortar of Adobe. It has been validated with reference to the results of a characterization campaign performed in 2016 on Adobe bricks and mortar produced in Germany. Although Adobe buildings are among the oldest examples of masonry constructions, spread in all continents of the world, the properties of the material and the overall mechanical performance are still poorly understood, especially with respect to the influence of the adopted mixture on the mechanical properties. As a consequence, very few numerical models are developed for Adobe. The assessment of Adobe structures is becoming a priority task because they are often spread in areas of the world prone to a wide range of dynamic hazards, whose disastrous consequences must be prevented. As for masonry, the overall performance of Adobe structures depends on the properties of bricks and mortar. Three

types of bricks and one type of mortar with different element mixture compositions were tested in compression and bending tests and their behaviour was analysed. The interpretation of experimental results classifies Adobe as a quasi brittle material, with special reference to concrete. Moreover, it was found out that for the same mineralogical family, the amount of fibres in the mixture of Adobe controls the deformation capacity of Adobe. Overall, a numerical model for Adobe was cast within a damage concept originally defined for concrete. A modified version of the last damage model by Mazars was developed. In order to avoid the typical mesh dependency that characterizes simulations of softening materials, a local regularization algorithm was implemented, starting from the damage delay model developed by Allix. Overall, only two mechanical parameters in compression and

tension are required to calibrate the loading evolution laws of the model. In fact, the initial damage strains and elastic moduli in tension and compression were derived directly from the mean values experimentally associated
to each mixture. For each type of mixture, numerical simulations on resulting bricks were performed in statics for uniaxial compression and three point bending tests using the strength and strain values experimentally derived. The mechanical parameters of the model were calibrated in order to match the experimental force displacement curves. The Adobe delta damage model proves to constitute a suitable tool to predict the material performance of Adobe. This paper resumes the experimental campaign, presents the algorithmic details of the model and the comparisons with respect to experimental data and mesh dependence.
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This article presents the knowledge gaps and the methodological steps inherent the process of standardization of the terrorist threat in urban environments for the structural design and rehabilitation of buildings for civilian use. The necessity for a revision of the current technical codes for building constructions which shall include also the terrorist threat, appears as cogent in light of the progression in number and harshness, of the terrorist attacks recently involving soft targets inserted in highly urbanized environments of European cities, with the aim of provoking the highest number of civilian victims within their everyday life. The normative integration of the terrorist threat in the design process of civil constructions implies performing a number of delicate methodological steps. In fact, the physical-mechanical nature of impact waves referred to explosions or hyper-velocity impacts is different from the ones associated to dynamic loadings already known and properly treated within design codes for civilian buildings, such as earthquakes (or wind). The peculiarity of the threat is reflected in the different behavior which the different types of dynamic loadings provoke on the same structure, requiring an update not simply to the validations currently employed within the structural design, but also including the approach itself inherent the anti-seismic philosophy of design when dealing with terrorism. The unique phenomenology of the terrorist threat with reference to the involved target, primarily lies on the social function of the spatial distributions and relative interactions of the urban fabric of the city in which the target is inserted, that the terrorist attack is primarily aimed to disaggregate. This unique feature requires also the comprehension and subsequent quali-quantitative assessment of the social function of the target and of the social dimension of the attacker (the carrier of the terrorist threat), within the standardization process of the terrorist input. However, this source of vulnerability to man-made threat, intrinsic to most of the buildings and constructions in Europe, potentially rises as promoter of the recovery of an urban harmony often neglected within the Architecture of the contemporary city, toward a philosophy of design of the single building which includes the humanistic function of the architectural and urbanistic elements in which it is inserted. http://www.sicurezzaterrorismosocieta.it/fascicolo-8-2018/@en

In this paper, a dataset collecting the results of in-plane cyclic tests on unreinforced masonry piers, carried out within different research projects, is presented. The dataset includes brick and block walls with different materials, bed-and head-joint typologies, dimensions, boundary conditions and vertical applied loads. The development of such dataset aims at providing a tool for the improvement of the understanding and the evaluation of the main parameters that may influence and govern the lateral response of the URM piers under seismic excitation. A preliminary investigation on the in-plane lateral strength and displacement capacity, being two of the most significant parameters used in seismic analyses for the design and assessment of masonry buildings, has been proposed. The dataset, that already groups several specimens, is freely shared and might be continuously updated. This source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules within the scientific and technical community, in particular for the improvement of codified criteria, analytical and numerical models and testing procedures.

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This paper presents a constitutive relationship to describe the uniaxial response in statics of brick and mortar samples of Adobe, a traditional masonry whose components are made of sundried soil mixture reinforced with fibres. Only recently Adobe has been attracting scientific attention, primarily as a consequence of the dramatic failures these structures have suffered in regions prone to earthquakes. Furthermore, it possesses eco-friendly material properties which are attractive features for western countries forced to reduce the environmental impact of modern building industry. Nevertheless, the mechanical properties of Adobe are still largely neglected, especially with regards to the influence of soil mixture components. The study of the structural performance of masonry starts from the assessment of the material performance of its components. Thus, an extensive characterization campaign was performed by Delft University of Technology and the Military Engineering Laboratory of the Netherlands. Three types of bricks and one type of mortar with different mixture components proportions, were subjected to granulometry, moisture content, density tests and uniaxial compressive and three point bending tests. Predictive formulations for compressive and tensile strength and deformation values have been proposed by the authors. These relations include the dependency of mixture components and moisture content. In this paper, constitutive laws are developed for Adobe in pure compression and tension validated by experimental results. In compression, the force-displacement curves were interpolated according to several existing constitutive laws and the model originally developed by Priestley for concrete masonry elements was finally selected as best fitting. Despite the differences in terms of mechanical parameters, the analytical assessment revealed that the experimental force-displacement graphs of all the different types of bricks could be interpolated using the same model with the same calibrating values. Furthermore, the uniaxial response in tension was derived according to an inverse approach. A numerical model recently developed by the authors and calibrated with respect to the compressive and bending tests was used to simulate uniaxial tensile tests. Also in tension, a common trend among types was observed. The results of the constitutive modelling frames components of Adobe within the class of quasi brittle (geo)materials, with particular reference to concrete. This paper presents the experimental results of the tested samples and the related analytical and numerical modelling.

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In this paper, a database collecting the results of 188 in-plane cyclic tests on unreinforced masonry piers with bricks and blocks, constituted of different masonry materials, bed- and head-joint typologies, dimensions, boundary conditions, applied vertical loads and horizontal loading history, is presented. The database, which will be freely shared, is organized in eight sections regarding general information and reference, information on masonry type, units and mortar, information on masonry walls, test conditions, estimated lateral resistances, experimental results of the cyclic tests, parameters of the bilinear curves and drift capacities. A preliminary investigation on the in-plane displacement capacity of the walls is also proposed since it represents one of the main parameter to be used in the global seismic analyses for the design/assessment of masonry buildings. Particular attention has been dedicated to the evaluation of the displacement capacity at different limit states in relation with European codes. Although the database, at the present stage, already contains several specimens, it will be continuously updated since this source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules in the European context, with particular reference to the definition of specific performance limit states and related capacity models for the in-plane seismic response of structural masonry walls. Keywords: URM piers; bricks and blocks; in-plane cyclic tests; database; displacement capacity @en

The lateral resistance represents one of the most significant wall parameters to be used in the seismic analyses for the design/assessment of masonry buildings. In this article, an investigation on in-plane lateral strength of URM piers has been proposed thorough a comparison between the results from codified criteria and the outcomes of several experimental in-plane cyclic tests on masonry walls. In this context, a new database collecting the results of in-plane cyclic tests on unreinforced masonry piers, carried out within different research projects, has been devel-oped. The database consists of walls with bricks and blocks with different masonry materials (clay, lightweight aerated concrete, AAC, calcium silicate), bed-and head-joint typologies, di-mensions, boundary conditions, vertical applied loads and horizontal loading history. This source of information of consistent and reliable test results represents a necessary step into the process of definition of shared rules in the European context.@en

In this paper, a new one-dimensional phenomenological model is developed for the assessment of the ballistic performance of Adobe. Adobe is a masonry largely spread in areas of the world involved in military operations. Addressing fundamental ballistic parameters such as residual velocity or penetration depth for this building technology is necessary. The model follows the hypotheses for the ballistic response of concrete targets to high velocity impacts, provided with a dominant contribution of shear friction typical of soils. The hypotheses at the basis of the model are consistent with all experimental evidence collected by authors on Adobe. Adobe brick and mortar belong to the material class of concrete, whereas the overall mechanical parameters are determined by the internal soil mixture, including the percentage of fibre reinforcement. Despite its relative simplicity, the model is capable of well predicting ballistic test results currently available in literature for Adobe, including the data of an experimental campaign recently performed by the authors on real Adobe walls in the field.

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A significant number of published papers in the field of penetration mechanics devotes attention to the study of targets made of metal and ceramic materials for protective equipment. In recent times, the progression in harshness of urban warfare is leading western governments to investing in research focused on the ballistic response of building materials. Adobe, a traditional form of masonry made of unburnt soil bricks and mud mortar, is spread in areas of the world often involved into military conflicts. Knowledge on the material properties of the components and on the overall dynamic response of these structures is still scarce. Therefore, a ballistic campaign aimed at studying the penetration processes in Adobe was performed by TNO: residual velocity or penetration depth were measured for different small calibre projectiles impacting at different velocity Adobe walls with different composition and strength. The resulting information was collected and organized into a database. It was used as statistical basis to develop an analytical predictive model capable of correctly addressing the terminal ballistic depth, namely penetration length, in case of small calibre impacts on Adobe targets. The proposed phenomenological model, that belongs to a class of models based on Newton’s 2nd law, parametrizes the sources of energy dissipation during penetration through a linear dependent bearing resisting force model. The properties of the targets were experimentally determined during an additional experimental characterization campaign performed on Adobe components in 2016 in the Netherlands. The paper presents the experimental data, the analytical model developed and the calibration of parameters, providing the relation between the experimental and the predicted penetration lengths.@en