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

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

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

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 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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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