Modelling of rammed earth under shear loading

The intensive use of earth as a building material since ancient times resulted in an important and significant earthen built heritage currently existing worldwide spread. The rammed earth technique has a significant presence in this heritage, where it served to build from simple dwell-ings to fortresses. However, the high vulnerability of rammed earth constructions to decay agents and to seismic events puts in risk their further existence and the lives of millions of peo-ple. With respect to the seismic behaviour of rammed earth walls, the understanding and mod-elling of their shear behaviour are topics underdeveloped in the bibliography. Nevertheless, these topics are of extreme importance in the preservation and strengthening of rammed earth constructions. Therefore, this paper presents a numerical work aiming at modelling the non-linear behaviour of unstabilised rammed earth under shear loading, resorting to the finite ele-ments method (FEM). The models were used to simulate the behaviour of a set of rammed earth wallets tested under diagonal compression. Both macro- and micro-modelling approach-es were considered, where the objective of this last approach was to evaluate the influence of apparent weakness of the interfaces between layers on the shear behaviour. The total strain ro-tating crack model (TSCRM) 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 be-tween layers. Furthermore, uncertainties related to the definition of the input parameters re-quired performing a sensitivity analysis. The numerical models achieved good agreement with the experimental results and 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.Fundação para a Ciência e a Tecnologia (FC

Modelling the structural behaviour of rammed earth components

Proceedings of the Twelfth International Conference on Computational Structures Technology, B.H.V. Topping and P. Iványi, (Editors), Civil-Comp Press, Stirlingshire, Scotland.The rammed earth technique has a significant presence in the earthen built heritage, where was used to build from simple dwellings to fortresses. However, the high vulnerability of rammed earth construction to decay agents and to seismic events puts at risk their further existence and the lives of millions of people. With respect to the seismic behaviour of rammed earth walls, the understanding and modelling of their shear behaviour are topics rarely approached in literature. Nevertheless, these topics are of significant importance in the preservation and strengthening of rammed earth constructions. This paper presents experimental and numerical work where the shear behaviour of unstabilised rammed earth is analysed. The experimental program consisted in the testing of several unstabilised rammed earth wallets subject to diagonal compression, which allowed a better understanding of the shear behaviour of unstabilised rammed earth. The numerical work consists of the modelling, of the previous tests, using the finite element method and by considering both the macroand micro-modelling approaches. In general, the numerical models showed a good agreement with the experimental results.The authors would like to thank gratefully the funding provided by the Portuguese Science and Technology Foundation through project FCOMP-01-0124-FEDER-028864 (FCT-PTDC/ECM-EST/2396/2012). Furthermore, the authors wish to express their gratitude to Júlio Machado for his valuable help in the experimental program.info:eu-repo/semantics/publishedVersio

Semi-automated creation of accurate FEM meshes of heritage masonry walls from point cloud data

The structural analysis of buildings requires accurate spatial models. Additionally, pathologies such as settlement-induced damages are paramount in the assessment of heritage assets. This spatial information is used as a basis for Finite Element Method (FEM) meshes to evaluate the stability of the structure. Traditional data acquisition approaches rely on manual measurements which are labor intensive and error prone. Therefore, major simplifications are made to document structures efficiently. The goal of this research is to provide faster and more accurate procedures to capture the spatial information required by a FEM. This paper presents a semi-automated approach to create accurate models of complex heritage buildings for the purpose of structural analysis. By employing non-destructive techniques such as terrestrial laser scanning and photogrammetry, a complex mesh of the structure is created. Also, a methodology is proposed to capture crack information. A stepwise approach is elaborated to illustrate how the spatial information is adapted towards a FEM mesh. The results show a significant difference between the geometry our model and a traditional wire- frame model. Not only does accurate modelling result in deviating loads, it also affects the behavior of the object. Through the proposed approach, experts can develop highly accurate FEM meshes to assess the stability of the structure up to as-built conditionsPostprint (published version

Effectiveness of the repair of unstabilised rammed earth with injection of mud grouts

The presence of cracks debilitates the structural performance of rammed earth. Grout injection is a repair solution put forward recently, where compatibility issues demand using mud grouts. Little is known on this topic, whereby an experimental program on the mechanical effectiveness of grout injection for repairing cracks in rammed earth was performed. Specimens tested under bending and diagonal compression were retested after repair with injection of mud grouts. Mud grouts incorporating the original soil of the rammed earth are shown to perform better and their injection achieves satisfactory shear strength recovery, but is less effective in recovering initial shear stiffness.This work was partly financed by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of projects POCI-01-0145-FEDER-007633 and POCI-01-0145-FEDER-016737 (PTDC/ECM-EST/2777/2014). The first author would also like to acknowledge FCT for the Post-doc grant SFRH/BPD/97082/2013

Sequential design of computer experiments for the estimation of a probability of failure

This paper deals with the problem of estimating the volume of the excursion set of a function $f:\mathbb{R}^d \to \mathbb{R}$ above a given threshold, under a probability measure on $\mathbb{R}^d$ that is assumed to be known. In the industrial world, this corresponds to the problem of estimating a probability of failure of a system. When only an expensive-to-simulate model of the system is available, the budget for simulations is usually severely limited and therefore classical Monte Carlo methods ought to be avoided. One of the main contributions of this article is to derive SUR (stepwise uncertainty reduction) strategies from a Bayesian-theoretic formulation of the problem of estimating a probability of failure. These sequential strategies use a Gaussian process model of $f$ and aim at performing evaluations of $f$ as efficiently as possible to infer the value of the probability of failure. We compare these strategies to other strategies also based on a Gaussian process model for estimating a probability of failure.Comment: This is an author-generated postprint version. The published version is available at http://www.springerlink.co

Skanowanie laserem dla dokumentacji dziedzictwa kulturowego

W ciągu ostatnich kilku lat wielu naukowców próbowało wykorzystać skanowanie laserowe, używając tej techniki w szerokim zakresie zastosowań i stale rzucając wyzwanie jej możliwościom. Zwłaszcza w dziedzinie dziedzictwa kulturowego skanowanie laserowe stało się ważnym narzędziem dla tworzenia rzeczywistych, wynikających z budowli, danych dla cyfrowego archiwizowania, monitoringu lub restaurowania ważnych elementów naszego ojczystego dziedzictwa kulturowego. Jednym z wyzwań, nadal stojącym przed nami, jest użycie skanowania laserowego dla monitoringu odkształceń. Ten artykuł stawia pytanie, czy skanowanie laserowe może zapewnić wystarczająco dokładne pomiary, żeby mogło zostać użyte dla monitoringu odkształceń historycznych konstrukcji.Over the last few years many researchers have tried to exploit the benefits of laser scanning by using the technique in a broad range of applications and constantly challenging its possibilities. Especially in the field of cultural heritage, laser scanning has become an important tool for the creation of as-built data for digital archiving, monitoring or restoration of important elements of our cultural heritage patrimonial. One of the challenges, still remaining, is the use of laser scanning for deformation monitoring. This article addresses the question whether laser scanning can produce sufficiently accurate measurements so that it can be used for deformation monitoring of historical structures

Welding of cold-rolled steel tubes : sensitivity of FEA input parameters

In this contribution, an overview of material inputparameters necessary for the adequate simulation of welding processes is given. The importance of a good knowledge of the emissivity (important for the temperature field) and the thermal expansion coefficient (the driving force behind the origin of residual stresses) are discussed by performing a sensitivity analysis using finite element analysis (FEA)