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Eingeladener Vortrag
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Structural performances of earthen building materials. A comparison between different typologies
(2011)
UHPC-AAC/CLC composite panels with self-cleaning properties. Materials and production technology
(2016)
The aim of this study is to show the development of a façade composite panel combining either an autoclaved aerated concrete or a cellular lightweight concrete insulation layer with a box-type external ultra-high performance concrete (UHPC) supporting layer. The paper presents the materials characteristics of the different components and the production technology of the panel. The efficiency of surface modifications of the materials forming the external shell of the panel is reported. The activation of self-cleaning properties is described. The test results showed that the most efficient way to use the water-repellent agent is its application on the substrate before the concrete cast.
Concerning the production technology, the preliminary studies showed more advantages of a two-step manufacturing procedure of the UHPC boxes than a one-step procedure.
The goal of the present study is to assess the feasibility to develop a first reliable database of materials parameters for Earth Block Masonry (EBM). The database is crucial when defining the materials safety factors. In the first part an experimental campaign of compressive tests were carried out on two types of earth block and two types of earth mortar. The results showed that the mean variation of the compressive strength was remarkably less than expected. This low variation is related to a production with high quality standards of the materials employed. In the second part a partial safety factor for EBM under uniaxial compression was determined through the reliability method. The results proved the reliability of a common calculation method for EBM based on partial safety factors following the current standards.
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.
The aim of this study was to develop a lightweight composite façade element for refurbishment of existing façades. It was crucial to minimize the thermal bridges and to undercut the thermal requirement of the system existing façade new element. The awareness of the environmental impact of the building sector is increasing. 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, optimized use of building area due to thinner elements and minimized maintenance due to the absence of reinforcement or use of non-corrosive reinforcing materials such as carbon fibers. In this framework, composite elements have been developed combining an autoclaved aerated concrete insulation layer with an external UHPC supporting layer. The results show that the lightweight composite element has a good performance in term of thermal transmittance and minimization of thermal bridges.
The paper presents a comparison between different numerical modelling ap-proaches aiming to simulate the in-plain behaviour of three types of earthen materials, name-ly adobe masonry, rammed earth and cob. For this purpose, uniaxial and diagonal compression tests were carried out, which allowed determining important mechanical param-eters, such as compressive strength, Young’s modulus, Poisson’s ratio, shear strength and shear modulus. Furthermore, the tests 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 for the calibration of numerical models (based on the finite element method) for simulating the non-linear behaviour of the earth materials under in-plane shear loading. Both macro- and micro-modelling approaches were considered for this purpose. The procedures adopted for model calibration established the reliability of various modelling strategies for the different loading conditions. The simplified approach based on macro-modelling shows a satisfactory accuracy and low computational costs. The results reproduc-ing the uniaxial compression are in good correspondence with the post-elastic behaviour ob-served in the experimental campaign. The micro-modelling approach adopted to reproduce the shear behaviour, even with higher computational cost, represents a suitable tool to pre-dict the adobe masonry and rammed earth collapse mechanisms
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.
The paper investigates the dynamic characterisation along with the numerical model tuning and the seismic risk assessment of a monumental masonry tower in Italy namely the Santa Maria a Vico bell tower. Full-scale ambient vibration tests were performed under the impact of environmental loads. The technique of modal extraction in the frequency domain was applied. In-situ investigation survey was used in calibrating the refined 3D finite element model. The FEM tuning was 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 paper shows that the modal identification is a reliable technique that can be used in-situ for assessing the dynamic behaviour of monumental buildings. The tuned FEM model of the tower was usefully employed to determine the theoretical fundamental frequencies, which accurately fit the experiment data. Finally, the seismic performance of the bell tower was assessed using a non-linear static procedure based on the multi-modal pushover analysis and the capacity spectrum method. The results confirm that seismic events of moderate intensity can produce heavy damage to the masonry tower presented in this study.
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 compressive strength, Young’s modulus, Poisson’s ratio, shear strength and shear modulus. Furthermore, the tests 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 for the calibration of numerical models (based on the finite element method) for simulating the non-linear behaviour of the earth materials under in-plane shear loading. Both macro- and micro-modelling approaches were considered for this purpose. The procedures adopted for model calibration established the reliability of various modelling strategies for the different loading conditions. The simplified Approach based on macromodelling 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 higher computational cost, represents a suitable tool to predict the adobe masonry and rammed earth collapse mechanisms.