Ongoing research projects
Ongoing research projects in iMMC (June 2023)
This a short description of research projects which are presently under progress in iMMC.
Hereunder, you may select one research direction or choose to apply another filter:
List of projects related to: Civil and environmental engineering
Researcher: Nicolas Docquier
Supervisor(s): Paul Fisette
The project aims at improving railway track lifecycle by improving its components such as the ballast, the sleeper, elastic pads, ... It consists in developing computer models coupling multi-body system dynamics (MBS) and granular modelling method (the discrete element method, DEM). Full scale experiments are conducted in parallel to validate the numerical models and assess the developed solutions.
|Optimization of tensegrity bridges based on morphological indicators|
Researcher: Jonas Feron
Supervisor(s): Pierre Latteur
Tensegrity structures are composed of struts and tendons in such way that the compression is “floating” inside a net of tension in a stable self-equilibrated state. Although tensegrity forms have inspired artists and architects for many years, there exist very few real construction projects across the world. The main reasons are, among others, the complex construction processes and the lack of design guidelines. This research, performed in collaboration with the company BESIX, aims at proving the feasibility of a first pure tensegrity bridge around the world.
When the structure is externally loaded, large displacements occur and require non-linear calculation before reaching an equilibrium. Indeed, in tensegrity structures more than in conventional ones, form and forces are intrinsically correlated. This phenomenon is due to their intern mechanism, unless appropriate pre-stressing is applied. An allowable stiffness can be possible, but at a certain material cost, which in turn justifies the relevance of the optimization of the weight.
While designing a tensegrity structure, optimization and form finding are often great challenges. Indeed, the large amount of parameters (span, height, shape, cross sections, materials, loads, pre-stress, etc) makes the search for the structure with the best performances cumbersome. A solution to this problem is to reduce the number of degrees of freedom to consider, by grouping them into dimensionless numbers, the morphological indicators.
In 2014, R.E. Skelton et al were pioneers in using a similar approach for optimizing planar tensegrity bridges uniformly loaded. In 2017, P. Latteur et al adapted the morphological indicators methodology, used so far to optimize mainly trusses and arches, to 3D non-linear and pre-stressed lattice structures such as tensegrity structures. In 2019, J. Feron et al used this methodology to investigate the performances of different 3D forms of uniformly loaded tensegrity footbridges.
This research focus on the required checks to ensure the practicality, the constructability and the economical and structural efficiency of a pure tensegrity footbridge thanks to non linear finite element analysis, experimental validation, parametric design, prestress optimization and dynamic behavior assessment
|Morphological impact of dam-flushing|
Researcher: Robin Meurice
Supervisor(s): Sandra Soares Frazao
An important number of dams worldwide face sedimentation issues, leading to a decrease in their reservoir capacity and hence, many difficulties to properly satisfy to their different functions (e.g. water distribution, flood management, hydroelectricity production). To overcome these problems, we can proceed to dam flushing operations, transporting huge amounts of sediment downstream of the dam. Nevertheless, these operations can be harmful to the environment, the living organisms and the human infrastructures if not properly handled. For that reason, this thesis aims at developing a numerical model capable of accurately predicting the sediment deposition downstream of a dam after flushing operations. In order to do so, several mathematical models shall be implemented, among which a two-phase two-layer model, and laboratory experiments shall be run. The numerical model will then be confronted with the data collected from the experiments. Finally, the model will be tested with real-case data collected in situ near Lyon, France.
|Evaluation of alternative damping approaches for nonlinear time history analysis, and their influence on the development of fragility curves used in seismic risk, for low-to-moderate seismicity regions.|
Researcher: Jose Baena Urrea
Supervisor(s): Joao Saraiva Esteves Pacheco De Almeida
One of the major sources of uncertainty in dynamic non-linear time history analysis (THA) of structures is modelling of damping as this parameter is not easy to measure and continues largely misunderstood. Damping simulates energy dissipation on structural and nonstructural elements that is not explicitly modelled. Although it is known to be frequency-independent and amplitude-dependent, these features are not typically considered by practicing engineers. The classical and most used model is Rayleigh damping, developed in the XIX century as a mathematic convenient representation of friction effects in acoustic waves transmission.
During the last decades, engineers have accepted this model in linear THA because the damping forces are relatively small compared with the other resisting forces in the structures and due to efficiency, simplicity and low computational cost. Contrary to this, when nonlinear THA are performed, several numerical pathologies appear such as spurious damping forces in the massless degrees of freedom and other issues resulting from stiffness decay during the analysis. Over the years researchers have developed damping models to overcome these challenges, but the scientific community still did not reach a generalised agreement. The most suitable model will depend, to a certain degree, on the specific structural problem. Unfortunately, one major concern with damping modelling is that the structural response can change drastically depending on the model used.
Nonlinear THA are commonly used to define fragility functions, which are statistical curves of performance relating demands (accelerations and displacements, typically) versus probability of exceedance of reaching a specific level of damage. They are used in the context of seismic risk analyses and will depend on the damping model employed.
This research focus on evaluating current models and proposing an alternative approach better matching experimental evidence of the response at the element level. Subsequently, the influence of these damping models on the development of fragility curves will be assessed. Finally, their impact on the final outcome of seismic risk assessment for low-to-moderate seismicity regions, such as Belgium, will be computed and interpreted.
|Seismic performance and residual displacements of reinforced concrete walls detailed with iron-based shape memory alloys|
Researcher: Ryan Hoult
Supervisor(s): Joao Saraiva Esteves Pacheco De Almeida
Most structures built to withstand earthquakes currently rely on reinforced concrete walls that concentrate damage in a region, typically at the base of those walls. While this can prevent collapses and save lives, it often damages the building to such an extent that it must be torn down after a quake. The EU-funded SMA-RC-Walls aims to test walls with shape-memory alloy (SMA) rebars, which offer the potential to return to their original form after seismic demands, and hence prevent damage and avoid permanent tilting of structures. The researchers will conduct experiments using iron-based SMA reinforcement in the boundary regions of concrete walls as a substitute material for the typical steel rebars. The goal is to contribute to a more robust and resilient building stock internationally, and to provide guidance for seismic design and assessment with this novel technology.
|A phase-field discrete elements model applied to granular material|
Researcher: Alexandre Sac-Morane
Supervisor(s): Hadrien Rattez
The main goal of the research project is to combine a phase-field modelization with a discrete elements modelization. This new approach is then applied to granular material to investigate the effects of the environment. A model is built and will be calibrated by experiments.
|Influence of soil saturation on earthen embankments failure by overtopping|
Researcher: Nathan Delpierre
Supervisor(s): Sandra Soares Frazao, Hadrien Rattez
In the current context of climate change and aging infrastructure, the failure of earthen dikes is becoming a
critical issue. Dikes have an essential protection role in flood defense, coastal protection or for the storage of
mining industry waste. The objective of the research is to develop and validate a simulation model to take into
account the effect of
saturation of the dike material on its stability when it is subjected to overtopping flows, which alone cause 34%
of failures (Costa, 1985). For this purpose, a complete simulation model will be developed, taking into account
the internal and external flows as well as the erosion and the consequences on the evolution of the stability of
the dam. The originality of this project lies in the multidisciplinary approach that takes into account the
evolution of the dike both from a hydraulic and hydrogeological point of view (water content, flow velocity and
surface erosion) but also from the point of view of the geomechanics and thus of the intrinsic stability of the
dike. Laboratory experiments will be carried out in order to validate the model experimentally. At this level, the
novelty brought by this project is the control of the evolution of the water content of the dike in real time with
pressure gauges and tensiometers. The acquired data will allow to calibrate the model and to confirm the key
role of the initial saturation in the dam failure.
Finally, based on the critical characteristics defined in terms of dike saturation, a study on large-scale
monitoring techniques will be carried out. In particular, the possibility of using technologies such as
photogrammetry or GPR (Ground Penetrating Radar) to determine the degree of saturation of a soil will be
investigated in the context of dike monitoring.