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- Diagonal compression test (5)
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- Earth block masonry (2)
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- Einpressmörtel (2)
Organisationseinheit der BAM
The therapy of eye tumors with fast protons is an excellent tool giving very high local control rates. At the Helmholtz-Zentrum Berlin (HZB) almost 1800 patients were treated since 1998. A 2 MV Tandetron was installed as injector for the k = 132 HZB cyclotron. Using the standard 358 duoplasmatron ion source with direct extraction of negative hydrogen ions an extremely stable proton beam can be delivered, both on the short-term and the long-term scale. The hair-needle filaments made from thoriated tungsten wires have safe operation times of more than 1000 h.
Schätzungen zufolge leben und arbeiten zurzeit 30 bis 40 % der Weltbevölkerung in Gebäuden aus Lehm. Darunter befindet sich auch eine nicht unerhebliche Anzahl an Baudenkmälern, davon viele in einem gefährdeten Zustand. Bauwerke aus Lehm erfordern einen hohen Unterhaltungsaufwand, da sie anfällig sind für Erosion bei Regen sowie Abplatzungen und Querschnittsschwächung, wenn Salze kapillar transportiert werden und auskristallisieren. Außerdem sind sie empfindlich gegenüber mechanischen Beanspruchungen. So führen bereits relativ niedrige Zug- oder Druckspannungen zu Schädigungen durch Rissbildung. Einige Lehmbauweisen werden heute nicht mehr ausgeführt und das Wissen über sie ist zumindest teilweise verloren gegangen. Die verschiedenen Lehmbauweisen unterscheiden sich deutlich in Bezug auf die Zusammensetzung des Materials und die Bautechniken.
Industrial byproducts and natural pozzolanas are increasingly being used as supplementary cementitious materials. In the group of natural pozzolanas volcanic ashes are the most prominent. Despite the fact that volcanic pozzolanas were used since Roman times, not much is known about their role in influencing the long term durability of concrete. The paper presents results of the volcanic pozzolana ‘Rhenish trass’, which is quarried in western Germany and its role during an alkali silica reaction (ASR). Field data and laboratory experiments indicate that trass releases alkalis into the pore solution but also changes cement paste chemistry and alkali binding behavior. There seems to be a sensitive balance between alkali release and increase of alkali binding capacity, both mechanisms crucial for the course of an ASR in concrete.
Overview of different strengthening techniques applied on walls used in historical structures
(2012)
Characterisation of earthen elements. A comparison between earth block masonry, rammed earth and cob
(2012)
Am Ende des 19. und zu Beginn des 20. Jahrhunderts wurden auch in Berlin vermehrt Bauwerke mit einer Fassadenverblendung aus Eifeler Tuffsteinen errichtet. Die Eifeler Tuffsteine zeichnen sich aufgrund ihrer hohen Porosität einerseits durch eine gute Verarbeitbarkeit aus. Andererseits sind sie nur schwach gebunden und besitzen deshalb eine geringe Verwitterungsbeständigkeit.
The purpose of this paper is to numerically simulate the in-plane behaviour of rammed earth walls under cyclic shear-compression tests. The experimental testing allowed obtaining the maximum horizontal loads, the displacement capacity and the level of non-linear behaviour of the respective loaddisplacement relationships as well as the failure modes. The calibration of the numerical model (finite element method) was carried out based on the experimental results. Within this framework, a micromodelling approach was considered. The behaviour of the rammed earth material was simulated using a total strain rotating crack model. A Mohr-Coulomb failure criterion was used to reproduce the behaviour of the interfaces between the layers.
Although the numerical results achieved a satisfactory agreement with the experimental results a sensitivity analysis of the parameters involved was performed. The sensitivity analysis aimed at determining which parameters of the model have a significant impact in the model’s results. As expected the sensitivity analysis pointed out that the sliding failure occurrence is mainly influenced by two parameters of the interface elements: the interface tensile strength fit and the friction angle u. Moreover the cohesion c and the layers thickness showed a limited effect on the shear behaviour. It should be noted that the results mentioned above are related to the cases where a significant level of vertical compressive stress r is employed.
The study presents the results from the development of a grouting material based on hydrated lime with addition of pozzolana, which is referred to as hydraulic lime, suitable for the repair of cracks in a variety of earthen building techniques. The goal was to develop a material also compatible with earthen structures exposed to dynamic loads. The grouting mortar was designed to be adaptable in strength properties and at the same time to have sufficient robustness for preparation and use on the construction site.
Results showed a satisfactory performance of the grout concerning fresh and hardened mortar properties as well as injectability.
The paper presents an experimental program aiming at assessing the mechanical performance of rammed earth walls, namely under compression and shear loading. Axial compression and diagonal compression tests were carried out for this purpose, which allowed determining important mechanical parameters, such as compressive strength, Young's modulus, Poisson's ratio, shear strength and shear modulus. Furthermore, it allowed assessing the level of non-linear behaviour of the respective stress–strain relationships as well as the failure modes. The experimental results were then used in the calibration of numerical models (finite element method) for simulating the non-linear behaviour of rammed earth under shear loading. Both macro- and micro modelling approaches were considered for this purpose. The total strain rotating crack model was used to simulate the behaviour of the rammed earth material, while the Mohr–Coulomb failure criterion was used to simulate the behaviour of interfaces between layers. In general, the numerical models achieved good agreement with the experimental results, but uncertainties related to the definition of the input parameters required to perform a sensitivity analysis. The compressive strength, the Poisson's ratio, the tensile strength and the tensile fracture energy revealed to be the most important parameters in the analyses.
Earth represents one of the oldest construction materials, which is still utilised both in developed and in developing countries. In this paper a comparison of the mechanical performance of structural elements built in three basic techniques, earth block (adobe) masonry, rammed earth and cob, is presented. In order to gain better knowledge on the structural behaviour under static loads an extensive compression and diagonal compression (shear) test campaign was performed. First compression results showed brittle mechanical behaviour in the case of earth block masonry and rammed earth elements, whereas cob exhibited a very different stress–strain pattern: cob can deform beyond the elastic range with a gradual drop in capacity. Despite its low compressive strength, cob thus presents a relatively good performance within the earthen material range as far as shear behaviour is concerned.
The data here reported represents a base for a further investigation on the dynamic behaviour of the three materials considered. The study was carried out within the framework of the project NIKER funded by the European Commission dealing with improving immovable Cultural Heritage assets against the risk of earthquakes.
The study evaluates Portland limestone cement mortars, natural hydraulic lime mortars and pozzolan-lime mortars modified with water-repellent admixtures (metal soaps and siloxanes) for their use in the maintenance of historic buildings. The chemical-physical characteristics, the durability and the resistance to artificial weathering (exposure to UV light and artificial rain) were examined. The exposure conditions used in the ageing test were chosen in order to simulate outdoor environmental conditions, in particular the processes caused by UV-light and thermal shock induced by rain water.
ln this paper a modelling approach is presented to reproduce the mechanical behaviour of sandwich panels via finite element analysis. Two types of panels were investigated in this scope of work. The first sandwich element was a textile reinforced concrete (TRC) panel with cellular lightweight concrete insulation and the second configuration was an ultra-high performances concrete (UHPC) panel with aerated autoclaved concrete insulation. The goal was to obtain a reliable numerical strategy that represents a reasonable compromise in terms of sufficient accuracy of the element characteristics and the computational costs. The results show the possibility of describing the composite action in a full sandwich panel. The achieved modelling approach will later be used for the optimization of TRC and UHPC panels in terms of minimizing the thickness, identifying the number and location of connectors, as well as evaluating varying anchorage Systems.
The current paper focuses on the determination of reliable numerical models of earth block masonry wallettes under different loading conditions. Uniaxial compression and diagonal compression tests were performed. Experimental behaviour was modelled with a non-linear model able to describe the cracking behaviour. The simplified approach based on macro-modelling shows a satisfactory accuracy and low computational costs. The results reproducing the uniaxial compression are in good correspondence with the post-elastic behaviour observed in the experimental campaign. The micro-modelling approach adopted to reproduce the shear behaviour, even with high computational cost, represents a suitable tool to predict the masonry collapse mechanism.
Water-repellent mortars were prepared using different hydrophobic compounds as admixtures. Calcium and zinc stearates, silane/siloxane products (as liquid solution and powder) were mixed into limestone cement mortars for obtaining in-bulk water-repellent mortars suitable for building protection and resistant to the degrading action of water. The influences of the admixtures on the hydration and structure of the designed mortars were investigated by SEM, TG–DSC, FT-IR, XRD, and isothermal calorimetry. The effectiveness of these agents against water action was evaluated by using techniques and methods such as mercury intrusion porosimetry, water absorption tests and contact angle measurements. Siloxane products conveyed good water-repellent effectiveness, without strongly influencing the setting and hydration of the binder, while the zinc stearates slowed down the hydration reactions.
Die Instandsetzung von Lehmbauwerken ist keine einfache Aufgabe. Der Baustoff Lehm hat vergleichsweise schwache mechanische Eigenschaften. Er ist außerdem anfällig gegenüber eindringendem Wasser, wobei er sehr schnell seinen Zusammenhalt verlieren kann, wenn gewisse Feuchtegehalte überschritten werden. Instandsetzungskonzepte für Bauwerke aus solchen Materialien stellen deshalb eine Herausforderung dar. Historische Lehmbauwerke zeigen oft Schäden in Form von starker Rissbildung, die durch statische oder dynamische Lasten hervorgerufen sein kann. Häufig werden solche Risse wegen mangelnder Fachkenntnis und / oder fehlender Techniken nur ungenügend instandgesetzt. Die Rissinstandsetzung mit Einpressmörteln birgt insbesondere für Lehmbaustoffe eine Herausforderung und erfordert spezifische Anforderungen an den Einpressmörtel, wie z. B. niedriger Wassergehalt, gutes Wasserrückhaltevermögen, niedriges Schwindmaß, an das instandzusetzende Material angepasste Festigkeit und E-Modul sowie eine gute Haftung am Lehmuntergrund. Zusätzlich müssen Einpressmörtel eine ausreichende Fließfähigkeit aufweisen, um kleine Risse und Hohlräume ohne Entmischung zu füllen. Deshalb muss das rheologische Verhalten des Einpressmörtels gut untersucht und kontrolliert werden, um die gewünschte Wirkung zu erzielen. Die Rissinstandsetzung bei Lehmbauwerken erfolgt traditionell durch manuelles Stopfen mit einem Mörtel. Natürlich können auf diese Weise nur Risse mit einer großen Breite verfüllt werden. Ein weiterer Nachteil ist, dass Risse, die durch dickere Wände verlaufen, nicht vollständig mit den für das Stopfen verwendeten Werkzeugen erreicht werden können. Kalkgebundene Einpressmörtel für Lehmbaustoffe werden gewöhnlich für die Wiederbefestigung von Putzen und weniger aus statisch-konstruktiven Gründen eingesetzt.
Aufgrund der Eigenschaften von Lehm, müssen Einpressmörtel auf Basis von hydraulischem Kalk nach EN 459-1 [4] wesentliche Anforderungen an eine Reihe von Eigenschaften erfüllen, die sich auf die Verträglichkeit, die Dauerhaftigkeit und insbesondere die Injektionsfähigkeit beziehen. Das Ziel der vorgestellten Untersuchungen war einen Einpressmörtel zu herzustellen, mit dem die strukturelle Kontinuität in Lehmmauerwerk oder anderen massiven Lehmwänden (Stampf- und Wellerlehm) durch Rissverpressung wiederhergestellt werden kann. Das Material bestand aus Kalkhydrat mit Zusätzen von Puzzolanen und Kalksteinfüller.
In-plane shear behaviour of earthen materials panels strengthened with polyester fabric strips
(2016)
An experimental investigation was carried out to study the in-plane shear behaviour of earthen material Panels strengthened with polyester fabric strips. Strengthened panels were developed to exploit the strength potential of earthen materials and to solve its lack of tensile strength, significantly improving not only strength but also ductility. Three earthen materials were considered: cob, earth block masonry (EBM) and rammed earth (RE). As first approach the strengthening configuration, based on different adhesive materials, was tested only for cob panels. As part of the study the results of a big testing campaign of unstrengthened Panels were considered. Seven strengthened panels were tested in diagonal compression/shear.A unique reinforcement orientation was used. The results of these tests are presented in this paper, and include the load-displacement behaviours, crack patterns, failure modes. The results showed that the reinforcement was the most effective in EBM panels, with increase in strength and ductility observed. In RE and cob panels the reinforcement did not likely contribute significantly to the shear resistance, due to a lack of embedment length of the strips. Instead, in EBM it was likely that the vertical reinforcement acted in tension to restrain shear induced dilation and to restrain sliding.
Die Instandsetzung von Lehmbauwerken ist keine einfache Aufgabe. Der Baustoff Lehm hat vergleichsweise schwache mechanische Eigenschaften. Er ist außerdem anfällig gegenüber eindringendem Wasser, wobei er sehr schnell seinen Zusammenhalt verlieren kann, wenn gewisse Feuchtegehalte überschritten werden. Instandsetzungskonzepte für Bauwerke aus solchen Materialien stellen deshalb eine Herausforderung dar. Historische Lehmbauwerke zeigen oft Schäden in Form von starker Rissbildung, die durch statische oder dynamische Lasten hervorgerufen sein kann. Häufig werden solche Risse wegen mangelnder Fachkenntnis und / oder fehlender Techniken nur ungenügend instandgesetzt. Die Rissinstandsetzung mit Einpressmörteln birgt insbesondere für Lehmbaustoffe eine Herausforderung und erfordert spezifische Anforderungen an den Einpressmörtel, wie z. B. niedriger Wassergehalt, gutes Wasserrückhaltevermögen, niedriges Schwindmaß, an das instandzusetzende Material angepasste Festigkeit und E-Modul sowie eine gute Haftung am Lehmuntergrund. Zusätzlich müssen Einpressmörtel eine ausreichende Fließfähigkeit aufweisen, um kleine Risse und Hohlräume ohne Entmischung zu füllen. Deshalb muss das rheologische Verhalten des Einpressmörtels gut untersucht und kontrolliert werden, um die gewünschte Wirkung zu erzielen.
Die Rissinstandsetzung bei Lehmbauwerken erfolgt traditionell durch manuelles Stopfen mit einem Mörtel. Natürlich können auf diese Weise nur Risse mit einer großen Breite verfüllt werden. Ein weiterer Nachteil ist, dass Risse, die durch dickere Wände verlaufen, nicht vollständig mit den für das Stopfen verwendeten Werkzeugen erreicht werden können. Kalkgebundene Einpressmörtel für Lehmbaustoffe werden gewöhnlich für die Wiederbefestigung von Putzen und weniger aus statisch-konstruktiven Gründen eingesetzt Aufgrund der Eigenschaften von Lehm, müssen Einpressmörtel auf Basis von hydraulischem Kalk nach EN 459-1 wesentliche Anforderungen an eine Reihe von Eigenschaften erfüllen, die sich auf die Verträglichkeit, die Dauerhaftigkeit und insbesondere die Injektionsfähigkeit beziehen. Das Ziel der vorgestellten Untersuchungen war einen Einpressmörtel zu herzustellen, mit dem die strukturelle Kontinuität in Lehmmauerwerk oder anderen massiven Lehmwänden (Stampf- und Wellerlehm) durch Rissverpressung wiederhergestellt werden kann. Das Material bestand aus Kalkhydrat mit Zusätzen von Puzzolanen und Kalksteinfüller.
The repair of earthen structures is not an easy task. Earth as a construction material has comparatively weak mechanical properties. It is also susceptible towards liquid water, were it can lose cohesion very quickly if certain moisture contents are exceeded. Repair concepts of structures built with such materials are therefore challenging. Historical earthen structures often exhibit damages in form of extensive cracking, which may have been caused by static or dynamic loads. Frequently these cracks are insufficiently or inappropriately repaired because of lack of knowledge and / or technology. In particular, the behaviour of crack repair by grouting poses a challenge in earthen materials and demands specific requirements for the grouting mortar, such as low water content, good water retention, low shrinkage. Grouting materials require additional specifications such as compatible strengths and Young’s modulus as well as good adhesion to the earthen substrates. In addition, grouts have to be sufficiently flowable to fill small cracks and voids without segregation or bleeding. Therefore, the rheological behaviour has to be well understood and controlled to gain the desired effects.
The repair of cracks in earthen buildings is traditionally done by stuffing manually mortar into the gap. Naturally, this method is only usable for cracks with large widths. Another disadvantage is that cracks going through thicker walls cannot be completely reached by the tools used for stuffing the mortar into the crack. Lime based grouts for earthen materials were usually used for re-attachment of plasters but less for structural reasons. Due to the nature of earthen materials grouts based on formulated or hydraulic lime (according to the definition in EN 459-1) have to meet considerable demands on a variety of properties, which are related to compatibility, durability and in particular to the ability of being injected. The goal of this study was to create a grout, which can be used to re-establish structural continuity in cracked earthen masonry or other massive earth walls (rammed earth and cob) with the focus on grouting cracks. The grout material was based on hydrated lime (calcium hydroxide) with additions of pozzolana and lime stone filler.
In this paper an extensive research campaign aimed to define the mechanical performance of earth block masonry panels is presented. Uniaxial compression and diagonal compression tests were performed. The test results confirmed the brittle behaviour of earth block masonry under uniaxial compressive load and showed that the failure of earth block masonry under shear load occurs by sliding of the earth blocks along the mortar joints after initial cracking in mortar joints and earth blocks. For diagonal compression test results showed that building technique practice is one of the key factors affecting the structural performances. Experimental behaviour was modelled with a non-linear model capable of describing cracking behaviour. Both micro-modelling and macro-modelling implementing isotropic or orthotropic material laws were used to assess the reliability of different modelling strategies. The model calibration was carried out by sensibility analysis of the input parameters to understand the influence of unit strength on the shear behaviour of masonry.
Wild bees are important pollinators for agricultural crops and solitary species such as Osmia bicornis are particularly suitable for pollination management. Wild bees share floral resources with managed honey bees and may be exposed to emerging infectious diseases. Although studies have explored the prevalence of pathogens in solitary wild bee species, data regarding the impact of pathogens on solitary bee health are lacking.
We carried out experiments examining whether the solitary bee species O. bicornis is susceptible to infection with the emerging pathogen The results obtained indicate that N. ceranae may be able to infect O. bicornis but its impact on host fitness is negligible: survival rates did not differ between Control and inoculated bees, although male survival was marginally lower after infection. To explore the possible field-relevance of our findings, we collected wild bees near an infected and a non-infected hive and showed that N. ceranae was shared between managed and wild bees, although only the in presence of infected honey bees.
The findings of the present study show that O. bicornis is susceptible to pathogen spillover and could act as a potential reservoir host for N. ceranae in pollinator networks. Additional studies on this species incorporating sublethal effects, multiple infections and other interacting stressors are warranted.
Wild bees are important pollinators of wild plants and agricultural crops and they are threatened by several environmental stressors including emerging pathogens. Honey bees have been suggested as a potential source of pathogen spillover. One prevalent pathogen that has recently emerged as a honey bee disease is the microsporidian Nosema ceranae. While the impacts of N. ceranae in honey bees are well documented, virtually nothing is known about its effects in solitary wild bees.
The solitary mason bee Osmia bicornis is a common pollinator in orchards and amenable to Commercial management. Here, we experimentally exposed larvae of O. bicornis to food contaminated with N. ceranae and document spore presence during larval development. We measured mortality, growth parameters, and timing of pupation in a semi-field experiment. Hatched individuals were assessed for physiological state including fat body mass, wing muscle mass, and body size. We recorded higher mortality in the viable-spore-exposed group but could only detect a low number of Spores among the individuals of this treatment. Viable-spore-treated individuals with higher head capsule width had a delayed pupation start. No impact on the physiological status could be detected in hatched imagines. Although we did not find overt evidence of O. bicornis infection, our findings indicate that exposure of larvae to viable N. ceranae spores could affect bee development.
This study analyses the mechanical behaviour under pseudo-dynamic loading of structural elements built in rammed earth and strengthened with polyester fabric strips. This strengthening technique was developed to exploit the strength potential of rammed earth and to solve its lack of tensile strength. For this reason, in-plane cyclic tests were carried out to investigate the shear behaviour of unstrengthened and strengthened walls. The strengthening technique requires low-tech equipment and workmanship, uses readily available, not expensive and industrially standardised materials. The experimental results were analysed in terms of stiffness degradation, energy dissipation capacity and equivalent viscous damping. Although the unstrengthened and strengthened walls confirmed a limited ductile behaviour, the findings confirm that the strengthening contributes to limit the spread of the diagonal cracks and provide an increase of strength in terms of horizontal load and displacement capacity.
In diesem Beitrag werden numerische Analysen der mechanischen Eigenschaften von Lehmsteinmauerwerk unter Druck- und Schubbeanspruchung vorgestellt. Ergebnisse von einachsigen Druck- und Schubversuchen an Wandprüfkörpern lieferten dafür grundlegende mechanische Kennwerte im elastischen Bereich und im nichtelastischen Versagenszustand.Die Testergebnisse zeigten, dass verschiedene Vorlasten keinen wesentlichen Einfluss auf die Schubfestigkeit haben. Außerdem bestätigten die Ergebnisse das spröde Verhalten von Lehmsteinmauerwerk unter einachsiger Druckbelastung und es zeigte sich, dass das Versagen des Lehmsteinmauerwerks unter Scherbelastung entlang der Mörtelfugen erfolgt.
Die experimentellen Ergebnisse wurden verwendet, um das Verhalten von Lehmsteinmauerwerk durch nichtlineare Finite-Elemente-Methoden auf der Basis von Makro- und Mikro-Modellierungsansätzen zu simulieren. Entsprechendes konstitutives Materialverhalten und Zwängungen, die in den Versuchen durch die Art der Lasteinleitung in Form von Stahlprofilen und Stahlschuhen verursacht wurden, wurde in den Modellen berücksichtigt. Es wurde zuerst ein auf der Grundlage der experimentellen Daten kalibriertes Makro-Modell entwickelt, was zu einer brauchbaren Vorhersage des Versagensverhaltens der Mauerwerksprüfkörper führte. Die simulierten Spannungs-Dehnungs-Kurven, berechnet unter einachsiger Druckbelastung, zeigten eine gute Übereinstimmung mit den Ergebnissen der geprüften Mauerwerkskörper, sowohl im elastischen als auch im nichtelastischen Bereich. Ein vereinfachter Ansatz, basierend auf der Makro-Modellierung und einem homogenisierten Prüfkörper, kann für die Untersuchung größerer Tragsysteme oder ganzer Gebäude angewendet werden, wobei eine zufriedenstellende Genauigkeit bei geringerem Rechenaufwand erreicht wird. Obwohl das globale Spannungs-Dehnungs-Verhalten zufriedenstellend wiedergegeben wurde, ist ein solches nichtlineares isotropes Kontinuumsmodell für Lehmsteinmauerwerk nicht in vollem Umfang geeignet, um das bei den Versuchen beobachtete Rissbild an den Prüfkörpern zu simulieren.
Eine detailliertere Analyse des mechanischen Verhaltensdes Mauerwerks wurde mit einem Mikro-Modellierungsansatz durchgeführt. Das Modell, in dem ein Wandabschnitt nicht mehr homogenisiert, sondern in konkrete Stein- und Fugenelemente diskretisiert wird, hat sich insbesondere für das Verhalten von Lehmsteinmauerwerk unter Schubbeanspruchung als geeignet erwiesen. Die Auswertung der Spannungsverteilungen bei der nichtlinearen Analyse lieferte Informationen über die tatsächlichen Mechanismen der Lastübertragung zwischen Steinen und Mörtelfugen. Mit dem Mikro-Modell war es möglich, das nichtlineare Verhalten von Lehmsteinmauerwerk vorherzusagen. Es stellt somit ein geeignetes Werkzeug für die Untersuchung der Versagensmechanismen von Lehmsteinmauerwerk dar. Allerdings sind aufgrund der Komplexität des Modells für die Beschreibung der Stein/Mörtel-Schnittstelle und die hohe Anzahl an erforderlichen mechanischen Parametern umfassendere Untersuchungen notwendig. Die zukünftige Forschung wird sich daher einerseits auf die Verfeinerung der numerischen Modelle und andererseits auf die Simulation komplexer Belastungssituationen und Gebäudekomponenten konzentrieren.
The aim of this paper is to implement a numerical model to reproduce the nonlinear behavior of cob walls under shear loading.
Axial compression, pull-off, and diagonal compression tests were carried out to derive the mechanical parameters. In addition, the stressstrain relationships, the nonlinear behavior, and the failure modes were defined. The experimental results were then used to calibrate a finiteelement model. The material behavior was simulated through a macromodeling approach adopting the total strain rotating crack model.
A sensitivity analysis was conducted to assess the effects of varying the parameters with higher uncertainty on the structural behavior.
The numerical model achieved good correspondence with the experimental results in terms of simulation of the shear stress–shear strain relationship and of damage pattern.
An experimental investigation was carried out to study the in-plane shear behaviour of rammed earth structural elements strengthened with polyester fabric strips. The original idea for the retrofitting with polyester fabric strips was to introduce a vertical element for walls in order to take up horizontal loads resulting in a shear response of the building element. It has to be considered that vertical slits into the walls for fixing the strips are points of weakness and have to be mitigated by the adhesive. In this case a base coat mortar was employed. Strengthened elements were tested to exploit the strength potential of earthen materials and to solve its lack of tensile strength, significantly improving not only strength but also ductility. As part of the study results of a testing campaign of unstrengthened structural elements were considered. Strengthened elements were tested in diagonal compression/shear and cyclic shear-compression. A unique reinforcement orientation was used. The results of these tests are presented in this paper and include the load-displacement behaviours, crack patterns, failure modes. The results showed that the reinforcement was the most effective under cyclic shear-compression tests, with increase in load and displacement capacity observed. Under diagonal compression the reinforcement did not likely contribute significantly to the shear resistance, due to a lack of embedment length of the strips.