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Das Wissen über die Materialeigenschaften und die Versagensmechanismen bei Lehmbaustoffen ist begrenzt und lückenhaft. Im Rahmen des EU-Projekts NIKER (www.niker.eu) wurden deshalb die mechanischen Eigenschaften von Bauteilen aus Lehm unter statischer Druck- und Schubbeanspruchung bestimmt. Ziel der Untersuchungen war es, grundlegende Daten zum Verformungs- und Versagensverhalten von Lehmbauteilen zu erhalten und dieses mit einem numerischen Modell zu beschreiben. Die Versuchsergebnisse belegten das spröde Verhalten von Lehmsteinmauerwerk bei uniaxialer Druckbelastung und zeigten, dass das Versagen von Lehmsteinmauerwerk infolge Schubbelastung nach Erstrissbildung in Mörtelfugen und Lehmsteinen durch Gleiten der Lehmsteine entlang der Mörtelfugen erfolgt. Die numerische Makromodellierung erbrachte zwar befriedigende Resultate hinsichtlich des Spannungs-Dehnungs-Verhaltens, jedoch konnte bei der simulierten Rissbildung keine Übereinstimmung mit den in den Versuchen beobachteten Rissbildern erzielt werden. Bei Lehmsteinmauerwerk ist also eine wesentlich aufwendigere Mikromodellierung notwendig, um das Versagensverhalten korrekt beschreiben zu können.--------------------------------------------------------------------------------------------------------------
Knowledge of the material properties and failure mechanisms of earthen materials is limited and scattered. Within the framework of the NIKER project (www.niker.eu) funded by EC, the mechanical properties of earthen material elements were therefore determined under static compression and shear loads. The aim was to obtain fundamental data on deformation behaviour and failure mechanisms of earthen material structural elements and to describe them by means of a numerical model. The test results confirmed the brittle behaviour of earth block masonry under monoaxial 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 block. Numerical macro modelling showed satisfying results with regard to stress-strain behaviour, but the simulated crack pattern was not consistent with experimental observations. In the case of earth block masonry, it is thus necessary to use micro modelling approaches in order to correctly predict the failure process at local level.
The paper investigates the dynamic characterisation, the numerical model tuning and the seismic risk assessment of two monumental masonry towers located in Italy: the Capua Cathedral bell tower and the Aversa Cathedral bell tower. Full-scale ambient vibration tests under environmental loads are performed. The modal identification is carried out using techniques of modal extraction in the frequency domain. The refined 3D finite element model (FEM) is calibrated using the in situ investigation survey. The FEM tuning is carried out by varying the mechanical parameters and accounting for the restraint offered by the neighbouring buildings and the role of soil–structure interaction. The assessment of the seismic performance of the bell towers is carried out through a nonlinear static procedure based on the multi-modal pushover analysis and the capacity spectrum method. Through the discussion of the case studies, the paper shows that the modal identification is a reliable technique that can be used in situ for assessing the dynamic behaviour of monumental buildings. By utilising the tuned FEM of the towers, the theoretical fundamental frequencies are determined, which coincide with the previously determined experimental frequencies. The results from seismic performance assessment through a pushover analysis confirm that the masonry towers in this study are particularly vulnerable to strong damage even when subjected to seismic events of moderate intensity.
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 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.
In this paper results of the experimental testing performed on brick masonry and earth block masonry are presented. The paper outlines the development of the testing procedures for two different types of anchors. For this purpose, two experimental campaigns of pull-out tests on masonry corner connections strengthened by metallic rod grouted were carried out. Experimental results proved that the implemented testing procedures are suitable to determine the most recurring failure modes of the anchor pins. Moreover, a procedure is proposed to estimate the capacity of grouted anchor pins based on experimental studies.
The awareness of the environmental impact of the building sector is increasing. Steel reinforced concrete is the most commonly used construction material, though with a high-embodied energy and carbon footprint. Large environmental gains may arise if an alternative to steel reinforced concrete is developed. In this context, ultra-high performance concrete (UHPC) materials are shown to be promising alternatives with advantages such as lower embodied energy and reduced environmental impact. Predictions suggest that UHPC composite elements for building envelopes could have other benefits such as an increased service life, optimised use of building area due to thinner elements and minimised maintenance due to the absence of reinforcement or use of non-corrosive reinforcing materials such as carbon fibres. In the framework of the H-HOUSE project funded by the European Commission, composite elements are developed. The aim is to create facade panels combining an autoclaved aerated concrete or cellular lightweight concrete insulation layer with an external UHPC supporting layer. To enhance occupant comfort and health, hygroscopic materials that are capable to buffer indoor air humidity shall be applied to the inside of such elements. Indoor air humidity levels are expected to be more stable, which shall subsequently improve the indoor climate and minimise potential decay to the construction.
The main aim of the research was the development of a first valid database for material parameters of earth block masonry (EBM) with particular regard to statistical characteristics. A solid database is needed for the determination of the materials partial safety factor. Therefore, compressive strength tests were carried out with two types of earth blocks and two types of prefabricated earth mortar.
The evaluation has shown that the mean variation of the compressive strength was remarkably less than expected, which indicates high quality standards of the components earth block and mortar with regard to industrial production. Using the reliability method, a partial safety factor for EBM subjected to compression was determined on the basis of these test results. The findings have shown that a common calculation method for EBM based on partial safety factors following the valid masonry construction standard is feasible.