Nathanaël Savalle- PhD - Civil Engineering
- Professor (Assistant) at University of Clermont Auvergne
Nathanaël Savalle
- PhD - Civil Engineering
- Professor (Assistant) at University of Clermont Auvergne
Assistant Professor interested in the behaviour of masonry structures, geotechnical structures and soils behaviour
About
29
Publications
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Introduction
PhD at University of Lyon, France.
Working on drystone retaining walls.
Especially interested in their seismic behaviour: analytical, experimental and numerical approaches (using UDEC (Itasca) DEM numerical model).
Current institution
Additional affiliations
March 2020 - August 2022
Position
- PostDoc Position
Description
- Experimental testing on masonry specimens. Seismic out-of-plane behaviour of masonry structures. Control systems of shaking-table, DIC software.
April 2016 - October 2019
Position
- PhD Student
Description
- Seismic behaviour of Drystone Retaining Walls, with the aim at providing recommendations for their design. Analytical (pseudo-static), Numerical (real dynamic DEM simulations) and Experimental (tilting tests and shaking-table tests) approchaes.
May 2014 - November 2014
Position
- Master's Student
Description
- Study of the hygro-mechanical properties of a clayey soil treated with lime. Geotechnical tests: Atterberg's limits, Proctor, VBS, IPI, CBR.
Education
October 2016 - October 2019
September 2015 - September 2016
September 2012 - September 2016
Publications
Publications (29)
Cultural heritage preservation requires a deeper understanding of their seismic response and imposes the use of effective strengthening methods. Fibre‐reinforced polymers (FRP) have emerged as an effective solution for strengthening masonry structural elements. The decision over the optimal configuration for a FRP‐based strengthening is a trade‐off...
Dry-stone structures are traditional constructions that are present everywhere around the world, with their stability working mostly by gravity. Contrarily to their in-plane behavior, their out-of-plane response is very brittle and is fully controlled by the geometry, as well as the contact properties, between units (stones). Two main local failure...
Masonry is one of the oldest building materials. In addition, it is widespread and highly represented all over the world. Masonry structures can be subjected to various loading, including earthquakes , floods, winds, or soil settlements. On the other hand, climate change leads to dryer summers and wetter winters which, consequently, leads to more p...
Masonry is one of the most used construction materials for structural and non-structural elements. The number of masonry constructions is still remarkable in countries where the costs of modern technology are high, as masonry solutions remain the most convenient and economical alternatives. Among these countries, unreinforced masonry is usually fou...
Many monumental masonry structures, such as aqueducts and public or military constructions, have been built using regular units neatly dressed without mortar. Detailed numerical modeling is commonly utilized to simulate the behavior of such dry-joint structures, which necessitates the proper definition of various physical and mechanical input param...
Masonry structures are highly vulnerable to climate change effects. In particular, over the last few decades, the effects of global warming have caused wetter winters and drier summers. Such phenomenon has produced variations in soil saturation that, in the long term, may trigger consolidation-induced differential settlements. Therefore, the experi...
Dry-joint masonry structures are particularly vulnerable to earthquakes and their dynamic response strongly depends on the interaction between units. Therefore, the precise characterisation of their behaviour is of paramount importance. This study performs an experimental campaign to estimate the normal interface stiffness of dry-joint masonry spec...
The accurate description of the dynamics of dry-joint masonry structures strongly relies on the characterisation of the interaction at the units’ interfaces. Several experimental techniques are available for estimating the mechanical properties of the interface (i.e. stiffness and damping), yet, their reliability remains questionable given the lack...
Dry Stone Retaining Walls are structures made of rubble stones assembled without mortar and have been present worldwide for centuries. Today, they still constitute an attractive alternative to building techniques involving higher embodied energy, such as reinforced concrete walls. This study uses a pseudo-static approach to give design recommendati...
The present work aims to expand the knowledge of the behaviour of masonry corners, which are capital to obtain an integral seismic response in masonry buildings. In particular, the influence of the seismic load orientation (from π/4 to π/2) is investigated experimentally, numerically and analytically. Both units and interfaces have been subjected t...
![Retaining wall mock-up [33], for a wall of slenderness H/B = 3.3.](publication/361384184/figure/fig2/AS:11431281431953912@1746826073457/Retaining-wall-mock-up-33-for-a-wall-of-slenderness-H-B-33_Q320.jpg)
Dry-stone retaining walls can be found worldwide and constitute critical assets of the built heritage for many sloped territories, holding cultural and economic value. Their design currently follows empirical rules, though the first steps towards a static safety assessment have recently been proposed in the scientific and engineering literature. Ho...
![Collapse mechanism observed for WD 1. (a) Experimental [22]; (b) Limit...](publication/358699621/figure/fig5/AS:11431281351911945@1743781039308/Collapse-mechanism-observed-for-WD-1-a-Experimental-22-b-Limit-Analysis_Q320.jpg)
Featured Application
Numerical modelling and seismic capacity of dry-joint masonry structures.
Abstract
Heritage masonry structures are often modelled as dry-jointed structures. On the one hand, it may correspond to the reality where the initial mortar was weak, missing, or has disappeared through time because of erosion and lixiviation. On the ot...
Masonry structures have been observed to display a high vulnerability to failure under seismic action. This stems from the fact that their structural configurations usually lack adequate connections among the distinct elements, resulting in the formation of local mechanisms experiencing Out-Of-Plane (OOP) collapse. In this context, rocking dynamics...
Modelling masonry bond pattern is still challenging for the scientific community. Though advanced Laser Scanning methods are available and allow to extract blocks sizes and shapes of actual masonry structures, they are up to now very time-consuming and complex to set up. Therefore, modelling masonry as an ideal and regular assemblage of regular uni...
![Figure 6: Experimental set-up from Casapulla & Maione [16]](profile/Nathanael-Savalle/publication/351783943/figure/fig2/AS:1026615727366144@1621775671108/Experimental-set-up-from-Casapulla-Maione-16_Q320.jpg)
The observation of damages caused by past seismic events demonstrated the high vulnerability of masonry systems, which represent intrinsically diverse and complex structures with resistance to horizontal forces highly dependent on the capacity of ensuring a monolithic behaviour. In this framework, tilting tests represent a low-cost and effective st...
A two-step strategy for the mechanical analysis of unreinforced masonry (URM) structures, either subjected to in- and out-of-plane loading, is presented. At a first step, a semi-automatic digital tool allows the parametric modeling of the structure that, together with an Upper bound limit analysis tool and a heuristic optimization solver, enables t...
In this paper, an experimental study aiming at understanding the seismic behaviour of dry stone retaining walls is presented. Harmonic shaking table tests have been carried out on scaled-down dry-joint retaining walls involving parallelepiped bricks. It is found that a thicker wall is more resistant and that a given retaining wall is less sensitive...
This erratum is published due to vendor overlooked corrections related with Table 6 during proofing. The original article has been thus corrected with the corrected references and thus updated.
A pseudo-static study on dry-joint brick retaining walls has been carried out as part of a preliminary work aiming at designing actual dry stone retaining...
In this paper, an experimental study aiming at understanding the behaviour of dry stone retaining walls to shakings is presented. Harmonic shaking table tests have been carried out on scaled-down dry-joint retaining walls involving parallelepiped bricks. It is found that a thicker wall is more resistant and that a retaining wall is less sensitive t...
Slope Dry Stone RetainingWalls (DSRWs) are vernacular structures made of rubble stones assembled without mortar. DSRWs are present worldwide and may have been built hundreds and even thousands years ago. They have always played a key role in economic sectors like agriculture, transportation and at present tourism. However, the lack of scientific kn...
Dry stone retaining walls (DSRWs) are vernacular structures, which consist in a specific assemblage of individual rubble stones. Herein, we propose some recommendations to achieve a correct modelling of the mechanical behaviour of DSRWs towards failure with the use of the Discrete Element Method (DEM). There are two kinds of DSRWs, those that just...
A pseudo-static study on dry-joint brick retaining walls has been carried out as part of a preliminary work aiming at designing actual dry stone retaining walls located in seismic areas. First, scaled-down dry-joint brick retaining walls have been tilted towards failure and the influence of the wall geometry has been analysed. Then, numerical simul...
Dry stone retaining walls (DSRWs) are vernacular structures which can be found all over the world. Most of them have been built in the 19th century but they can be as old as two hundred years. Because of decades of neglect, many of these walls are highly damaged; however, in the absence of national rules for this peculiar heritage, any intervention...
Dry stone retaining walls (DSRWs) are vernacular structures, present worldwide, and made of rubble stones assembled with a precise know-how without any mortar. As many of them were built in the XIX th century and have not been maintained for decades, they need today some repairs or even sometimes whole reconstruction. However, the lack of national...
Questions
Questions (2)
Dear RG members,
I'm carrying dynamic analysis on retaining walls using UDEC software (DEM).
I'm asking myself what kind of damping should be used (Rayleigh damping, local damping, no damping) for my analysis.
In fact, it seems that Rayleigh damping is more appropriate for dynamic analysis. However, on an identical model, changing the damping (from no damping to rayleigh damping or from local damping to rayleigh damping) led to an decrease of the timestep from 1e-5 to 1e-7 (depending on the values (freq, damping) chosen for the rayleigh damping). This new value of timestep make the simulations hundred times longer which is not satisfactory.
Do you have any ideas to deal with this problem? Do you know why the timestep is decreasing?
I've read the UDEC manual and the described methodology to compute the timestep in dynamic analysis, but it does not match the values given by UDEC.
Thank you !
Nathanaël
Dear RG members,
I'm carrying dynamic analysis on retaining walls using UDEC.
Concerning boundary conditions (especially the input motion boundary), I would like to use a stress input motion (as described in the UDEC Manual). However, at the end of the shakings, the whole model still move, with a constant velocity.
Maybe, it's not a problem since the whole model is moving, but it seems that even during the shakings, the whole model moves (see attached picture).
Do you have any idea to deal with this problem ?
I've succeeded in using the velocity input motion but want to use the stress input in order to add quiet boundaries.
Thank you !
