Understanding Traditional Anti-Seismic Strategies Beyond Their Disappearance and Distortions: Yazd Qajar Architecture Case Study

Understanding traditional seismic strategies is necessary to conduct appropriate restoration of historic buildings and city centers located in earthquake-prone areas. But, the fast disappearance of vernacular built heritage and of the associated popular knowledge and know-how, along with the spread of inappropriate maintenance works, make it very difficult. To overcome these obstacles, it is suggested to broaden the scope of observations by including both larger geographical areas and elements that do not appear as seismic features at first consideration. This paper illustrates the relevance and the limits of this approach by applying it to the case study of Yazd historic city center. Yazd is located in a moderate seismic area and is famous for its well-preserved historic city center, with a high number of Qajar adobe buildings in various conditions. The authors combined literature review, direct observation of numerous buildings and a deeper study of four Qajar houses to conduct the first part of their research. The data collected mainly relates to the geometrical features, the materials used and the interconnections between elements at different scales. Their analyses led to the elaboration of several assumptions on the seismic behaviour of the studied adobe buildings and vaults and on the distortions some features may have suffered. To validate these assumptions, two methodologies were used. Both are illustrated in this paper through the study of the insertion of baked bricks in adobe vaults. The first one is based on observation campaigns on damaged houses. The second one is based on experimental works, with tests conducted on the shear strengths of masonry made with mud mortars and adobes or baked bricks to better understand how builders benefited from mixing these materials in an adobe vault. Finally, the authors discuss the limits of the method and the extent to which restoration projects can benefit from it

Enhancement of multifiber beam elements in the case of reinforced concrete structures for taking into account the lateral confinement of concrete due to stirrup

International audienceMany researches have been conducted in the structural engineering field in order to develop efficient numerical tools able to reproduce the complex nonlinear behavior of reinforced concrete structures. In the case of slender elements, enhanced beam models have been developed to try to introduce shear effects, but in these models, the transverse steel is sometimes taken into consideration with approximated manner or often not at all. However, as shown by some experimental tests, the amount of transverse reinforcement triggers significantly the behavior of beam elements, especially under cyclic loading. The present study adresses this problem by investigating solutions for an enhanced multifiber beam element, accounting for vertical stretching of the cross-section occurring due to the presence of stirrups. A timoshenko beam element with internal degrees of freedom and higher order interpolation functions is selected. Full 3D stresses and strains are obtained and the construction of the element and sectional stiffness matrices is detailed. The element presented hereafter is suitable for an arbitrary shape cross-section made of heterogeneous materials. Numerical applications on a plain concrete cantilever beam subjected to tension and bending tests respectively are presented. Moreover, as a first application, a dilation effect is added to the concrete fibers in order to highlight the role of transversal rebars. All the numerical results are confronted to the outcomes of stantard 3D finite element computations

ENHANCEMENT OF MULTIFIBER BEAM ELEMENTS IN THE CASE OF REINFORCED CONCRETE STRUCTURES FOR TAKING INTO ACCOUNT THE LATERAL CONFINEMENT OF CONCRETE DUE TO STIRRUP

International audienceTo assess the seismic vulnerability of existing reinforced concrete structures, a large number of degrees of freedom is involved. Consequently, efficient numerical tools are required. In the case of slender elements, enhanced beam elements have been developed to try to introduce shear effects, but in these models, the transverse steel is sometimes taken into consideration with approximated manner or often not at all. However, as shown by some experimental tests, the amount of transverse reinforcement triggers significantly the behavior of beam elements, especially under cyclic loading. Thus, the main goal of this work is to investigate solutions for an enhanced multifiber beam element accounting for vertical stretching of the cross section, occurring due to the presence of transverse reinforcement. The efficiency of the proposed modeling strategies is tested with results obtained from tension and flexure tests conducted on an elastic linear material

QSPR modeling of the AmIII / EuIII separation factor How far can we predict ?

International audienceExhaustive quantitative structure-property relationship (QSPR) modeling of the separation factor logSF for 46 polyazaheterocyclic ligands extracting Am3+ and Eu3+ from nitric acid aqueous solution to the 1,1,2,2 tetrachloroethane phase has been done using different computational approaches. Modeling methods included Multiple Linear Regression, Radial Basis Function Neural Networks and Associated Neural Networks; two types of descriptors (substructural molecular fragments and molecular descriptors) and different techniques of variable selection have been employed. The developed QSPR models applied for novel t-Bu-hemi-BTP ligand resulted in logSF = 1.07-1.46; these predicted values somewhat exceed the experimental value logSF = 1.0. Several hypothetical extractants potentially possessing high logSF values are proposed. An influence of uncertainties in initial experimental data as well as the choice of the theoretical approach on the performance of QSPR models are discussed

High energy conformers of M⁺(APE)(H₂O)_0–1Ar_0–1 clusters revealed by combined IR-PD and DFT-MD anharmonic vibrational spectroscopy

International audienceIR-PD vibrational spectroscopy and DFT-based molecular dynamics simulations are combined in order to unravel the structures of M+(APE)(H2O)0–1 ionic clusters (M = Na, K), where APE (2-amino-1-phenyl ethanol) is commonly used as an analogue for the noradrenaline neurotransmitter. The strength of the synergy between experiments and simulations presented here is that DFT-MD provides anharmonic vibrational spectra that unambiguously help assign the ionic clusters structures. Depending on the interacting cation, we have found that the lowest energy conformers of K+(APE)(H2O)0–1 clusters are formed, while the lowest energy conformers of Na+(APE)(H2O)0–1 clusters can only be observed through water loss channel (i.e. without argon tagged to the clusters). Trapping of higher energy conformers is observed when the argon loss channel is recorded in the experiment. This has been rationalized by transition state energies. The dynamical anharmonic vibrational spectra unambiguously provide the prominent OH stretch due to the OH⋯NH2 H-bond, within 10 cm−1 of the experiment, hence reproducing the 240–300 cm−1 red-shift (depending on the interacting cation) from bare neutral APE. When this H-bond is not present, the dynamical anharmonic spectra provide the water O–H stretches as well as the rotational motion of the water molecule at finite temperature, as observed in the experiment

Numerical analysis on seismic resistance of a two-story timber-framed structure with stone and earth infill

International audienceDue to their seismic resistance, traditional timber-framed structures with masonry infill suffered little damage during recent earthquakes. Moreover, timber-framed structures can be built with reduced costs thanks to the use of locally available materials such as wood, stone, and earth. Based on an experimentally validated numerical simulation for a one-story house, the seismic resistance of a similar two-story house is investigated. A simplified Finite Element Model with linear and nonlinear truss elements is proposed to analyze the seismic resistance of a two-story building. Nonlinear hysteresis constitutive laws are defined only for two majorcomponents of the structure which are assumed to be representative of the global structure behavior: diagonal X-crosses (concentrating the interaction with the infill material) and steel strip connections. These kinds of structures have been overlooked due to a lack of knowledge of their potential behavior in seismic prone area and a lack of building codes and standards for their own design. To promote them, a failure criterion, that might easily be used in engineering studies, is required. This article proposes a simple criterion based on Eurocode 8 to quantify the seismic resistance of one- and two-story houses. The simulation shows that, even in case of high intensity ground motion, the two-story building should not be collapsed. This study may help at designing two-story timber-framed structures in seismic prone areas for (re)construction projects