Filtern
Dokumenttyp
Sprache
- Englisch (7)
- Deutsch (2)
- Mehrsprachig (1)
Schlagworte
- Cultural heritage (2)
- Earth masonry (2)
- Material test (2)
- Rammed earth (2)
- Archaeology (1)
- Baustoffe (1)
- Bemessung (1)
- Cob (1)
- Compressive strength (1)
- Druckfestigkeit (1)
- Druckversuche (1)
- Earth block (1)
- Earth block masonry (1)
- Earth block masonry (EBM) (1)
- Earthen architecture (1)
- F.E.M. Modellierung (1)
- Feuchteabhängige Festigkeit (1)
- Historical earthen building (1)
- Lehmbau (1)
- Lehmmauerwerk (1)
- Lehmstein (1)
- Lehmstein Mauerwerk (1)
- Materials characterization (1)
- Mauerwerk (1)
- Mechanical behavior (1)
- Mechanical properties (1)
- Mechanische Eigenschaften (1)
- Normung (1)
- Partial safety factor (1)
- Prüfverfahren (1)
- Reliability (1)
- Schubversuche (1)
- Seismic resistance (1)
- Stampflehm (1)
- Static monitoring (1)
- Teilsicherheitsbeiwert (1)
- Wellerlehm (1)
- Zuverlässigkeit (1)
- earth block masonry (1)
- historical earthen building (1)
- material characterisation (1)
- partial safety factors (1)
- rammed earth (1)
- static monitoring (1)
- uniaxial compression test (1)
This study assesses the structural vulnerability of part of a later medieval earthen building at
Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military
Orders. An inspection of its morphology and materials coupled with the results of an extensive
campaign of static monitoring reveals marked structural inhomogeneities, the product of more
than a thousand years of construction, failure, and repair from the 10th century to the present
day. Building materials are inappropriately juxtaposed, there are discontinuities between construction
phases and fundamental concerns remain over the long-term stability of the structure.
The current condition of the structure is mainly influenced by structural discontinuities introduced
at the time of construction, the unintended consequences of repair and modification and the
material decay that has affected the base of the rammed earth walls. The overall findings of the
static monitoring show that there is no related damage, variations in crack widths are related to
the building seasonal cycle. While static analysis is an essential prerequisite before a suitable
maintenance program can be fully defined, this study argues that no evaluation of the structural
behavior of any historic building can afford to ignore its archaeological “biography” of modification
and repair.
This study presents diagnostic techniques to assess the structural vulnerability of earthen buildings. Medieval structures at Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military Orders, provide a useful case study. After more than a thousand years of construction, failure and repair from the 10th century to the present day, Ambel preceptory today is characterised by marked inhomogeneities: construction materials and structural typologies are juxtaposed, with structural discontinuities at the interfaces between construction phases. This paper argues that, while static analysis is an essential prerequisite before a suitable maintenance program can be defined, no evaluation of the structural behaviour of any historic building can ignore an understanding of the building’s history.
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.
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 has been developed in the framework of a larger EC‐research program called NIKER, in which BAM and other seventeen research partners from the Mediterrean area are jointly involved. It aims to develop and validate innovative materials and technologies for the systemic improvement of the seismic behavior of Cultural Heritage assets. The death tolls brought about by recent catastrophes in
developing countries where many inhabitants lived in earthen dwellings (Gujarat, India 2001, Bam, Iran 2003 and Concepción, Chile 2010 Earthquakes, Tamil Nadu 2004 Tsunami) have brought about research studies aimed at improving earth construction in terms of strength, seismic resistance and speed of construction.
In comparison to the recent advances in research on stone and brick masonry, knowledge on the material properties and failure mechanisms of earthen Building construction is limited and scattered.
The research presented here by aims making a comparison of mechanical behaviour between different earth masonry material typologies, consisting of earth block masonry, rammed earth and cob.
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.
Both in developed and developing countries, modern building materials tend to be preferred to traditional earthen construction. Reasons include low durability, inadequate performance under seismic loading and, in developing countries, a wish to replace what is perceived as 'poor' with what is perceived as 'rich'. In an age when building permissions and construction standards are a must, particularly in seismic areas, even when an owner is willing to build in earth, construction approval needs to be granted: we rely on values and standards to build, but the necessary data on material properties and structural performance of earthen building techniques is scarce if compared to the abundance of data for other materials (clay brick masonry, concrete, steel) available to the engineer. At the same time, traditional builders' skills, knowledge and confidence in earthen building techniques are decreasing if not disappearing. A wallette testing campaign was thus carried out with the aim of filling this knowledge gap. Prior to the wallette campaign, material properties, including composition and physical-mechanical parameters, were determined. Compression and diagonal compression (shear) tests were then performed, and a basic analysis of the mechanical behaviour of structural elements built in cob is provided in relation to earth block (adobe) masonry and rammed earth elements. Cob, shown to have low compressive resistance, has a relatively ductile post-peak behaviour if compared to earth block masonry specimens which, as expected, show a marked brittle behaviour. In terms of shear strength, cob performs relatively well in view of its low compressive strength. The study is part of our work within the framework of the ongoing project NIKER funded by the European Commission dealing with improving the structural performance of Cultural Heritage assets in order to limit earthquake hazards.
Structural performances of earthen building materials. A comparison between different typologies
(2011)
Traditional construction techniques utilizing earthen materials are often seen as inferior compared to modern ways of building. Structural earthen elements are perceived as vulnerable towards environmental influences (moisture, frost) and in particular towards the load scenarios during earthquakes. In comparison to the recent advances in research on stone and brick masonry, knowledge on the structural performance of earthen building construction is limited and scattered. Consequently the confidence in the performance of these earthen buildings constructed in the traditional techniques during earthquakes is fairly low. The research presented here aims to make a comparison of mechanical behavior between different earth masonry material typologies, consisting of earth block masonry, rammed earth and cob. The paper has been developed in the framework of a larger research program called NIKER. BAM and other seventeen research partners from the Mediterrean area are jointly involved to develop and validate innovative materials and technologies for the systemic improvement of the seismic behavior of Cultural Heritage assets
Ziel der vorliegenden Untersuchung war es zu überprüfen, inwiefern eine Bemessungsvorschrift auf Basis von Teilsicherheitsbeiwerten im Lehmmauerwerksbau möglich ist. Bemessungsvorschriften im konventionellen Mauerwerksbau und im Lehmmauerwerksbau waren aufgrund des prinzipiell gleichen Tragverhaltens stets eng miteinander verknüpft. Die im Rahmen dieser Arbeit durchgeführten Druckversuche an Lehmmauermörtel, Lehmsteinen und Lehmmauerwerk konnten zeigen, dass die Streuungen der Festigkeiten von Lehmbaustoffen aufgrund der industriellen Herstellung sehr gering sind. Es konnte festgestellt werden, dass eine Bemessung auf Grundlage des semiprobabilistischen Bemessungskonzeptes in Anlehnung an den konventionellen Mauerwerksbau möglich ist. Neben einem ersten Vorschlag des Teilsicherheitsbeiwertes für den Lastzustand Druck werden Vorschläge für Prüfvorschriften im Lehmbau beziehungsweise deren Modifikation unterbreitet und künftige Forschungsschwerpunkte herausgearbeitet.