The « Laboratoire Essais Mécaniques, Structures et Génie Civil LEMSC » (Mechanical Testing, Structures and Civil Engineering Laboratory) is involved in several researches, as direct or indirect actor.
RAILWAY RESEARCH
Since many years the LEMSC contributed by its experimental background to the following research projects, in collaboration with D2S International (Belgian company active in all fields of railway noise, vibrations, and dynamics of vehicle, track and superstructures):
- CORRUGATION (2002-2006) – FP5 European project – with the aim of developing solutions for the very expensive corrugation (=undulatory wear) problem in metro and tram networks
- TURNOUTS (2003-2007) – FP6 European project – with the aim of providing new concepts for turnouts in urban rail transit infrastructure
- URBAN TRACK (2006-2010) – FP6 European project – with the aim of providing solutions to achieve a modular urban track infrastructure (tramway, metro, RER) with new and cost effective solutions.
Moreover, a strong collaboration exists since 2013 between LEMSC and MEED research team (Professor Paul Fisette and senior researcher Nicolas Docquier) on the railway researches at UCLouvain. This collaboration made it possible to set up two more projects:
- WHOLETRACK (2015-2020) – Walloon Region project – with the aim of reducing the number of maintenance operations on the railway network (rolling stock and track).
- CRAMIC (2019-2022) – Walloon Region project – with the aim of developing a new technology for the tracks of the harbor cranes, which are moving faster and faster and carrying heavier and heavier loads.
The most impressive contribution of the LEMSC is the construction for WHOLETRACK of a railway of 21 meters long, mounted in real configuration, equipped with many captors (displacements, strain gauges, load cells, …), submitted to static loads, fatigue loads and real boggie loads.
SEISMIC RESEARCH
The collaboration and support of LEMSC to research on Earthquake Engineering started at around early-mid 2019, coinciding with the arrival of Prof. João Almeida.
The first big project was the experimental testing of two large-scale 2.8 m ´ 2.8 m reinforced concrete walls. In one, shape-memory NiTi alloy rebars were used as a replacement to steel rebars. The superelastic flag-shaped hysteretic response of the smart alloy in the wall boundary elements guaranteed a sizeable energy dissipation but most importantly a clear reduction of the residual displacements. The results open a promising avenue both for new construction and repair works in RC walls, since economic damage and repair costs due to earthquakes are critically connected with permanent residual structural displacements.
The test setup consisted of two independent steel frames fixed to the laboratory strong floor, one supporting the vertical actuators and the other serving as reaction frame for the horizontal actuator force. The two vertical actuators, each with a force capacity of 350 kN and a stroke of 250 mm, applied a total compressive load as well as a varying bending moment corresponding to a pre-defined shear span through the lever arm of these actuators. Their forces were coupled with the force on a third horizontal actuator, which applied a cyclic quasi-static displacement history to the top RC beam of each specimen.
Apart from the actuator load cell and internal displacement, several other LEMSC instrumentation was used per test: 12 strain gauges, 22 displacement transducers, 9 micrometers, 1 inclinometer, and 2 cameras for digital image correlation of the speckle pattern applied on each wall’s surface.
A time-lapse of the tests can be seen here. A complete description of the test setup and results is available in this 2020 scientific paper. The complete set of experimental data can be downloaded from the UCLouvain open data public repository Dataverse.
The project actively engaged most of the laboratory staff: for control programming and data acquisition, for all instrumentation-related aspects, for the material testing (concrete, steel, and shape-memory alloys), as well as welding and for the different aspects related with the assembly of the test setup and overall assistance.
The LEMSC is also supporting, with both equipment and instrumentation, a second ongoing test programme on eight specimens to study scaling effects in reinforced concrete specimens. The first results will be accessible as soon as possible.
TIMBER RESEARCH
In Belgium, the concrete industry is very powerful, with the consequence that 95% of the buildings are built with concrete.
We are convinced that, in a changing world where CO2 is a planetary issue, human kind has to build its cities with a maximum of timber. We have to use timber. We have to plant trees. We have to renew our past forests.
However, timber is not competitive : a precast prestressed slab (called”hourdis” in Belgium) can reach spans of about 14 meters with a thickness of 45 cm and a price of a tens of euros per square meter. At the same time, timber has already a cost of around 100 euros per cubic meter even before any transformation (cutting, gluing, etc).
The only solution to make timber competitive is thus to use it as raw as possible, but also to assemble and prepare it with robotic arms.
In collaboration with Belgian companies Imax-pro and Mobic, we have ongoing researches related to two fields :
- slabs composed of half raw truncs covered by concrete,
- reciprocal structures also composed of raw truncs.
HYDRAULICS
The involvement of the lab in the hydraulic researches driven by Professor Sandra Soares Frazao is a relatively passive involvement. The lab hosts the 4 hydraulic channels and helps in equipment maintenance. But the experimental design and the performing of tests are under the responsibility of the researchers.
TENSEGRITY STRUCTURES
Tensegrity is a structural concept defined by the interplay of compression bars that appear to float in a cloud of tensioned cables.
An experimental study campaign on a tensegrity structure was carried out at the LEMSC Laboratory, on a 1/5th scale model of a 60-metre span footbridge designed by Professor Pierre Latteur's team.)
These experiments validates the digital model, despite the fact that the construction elements, such as the bamboo, vary considerably.
Experimental validation of the prototype and the introduction of prestressing are the prerequisites for building the full-scale structure.
PILE DRIVING RESEARCH
Professor Alain Holeyman is still active in pile driving research. The latest involvement of the laboratory concerns tests for Mustafa Jafari’s research on “Numerical and experimental investigation of monopile driving resistance in carbonate rocks”. For this purpose, the FONDEOLE driving system is used in order to install model pipe piles in carbonate rocks. This original system was developed in 2015 thanks to the financial support of Walloon region. It can capture short impact events (about 2 Milliseconds). The driving resistance is calculated from the strain and acceleration records along the pile. A laser sensor tracks pipe displacement during impacts.
Major elements of the system are:
1) A two-segment steel pipe stabilized with lateral supports/seating system: a 4m-segment at the top guides strain wave generated during impact in order to install another 1m-segment at the bottom. The two pipes are assembled by a sleeve. The system allows for two different model pipe diameters: 60mm and 110mm.
2) The Loading system consists of (1) Ram mass, (2) Load frame (rope, pulley and guiding rods) and (3) cushion. Maximum drop height is about 1m. Ram mass can be increased up to 20 kg.
3) The specimen is placed at the bottom of the pipe. The 1m-segment of the pipe penetrates the specimen.
4) The instrumentation consists of standard foil strain gauges, piezoelectric accelerometers, and a laser displacement sensor. It is worth mentioning that the instrumentation system of FONDEOLE can be adapted so that Pile Driving Analyzer (PDA)™ tests can be performed.
5) An old National Instruments SCXI chassis house is use for power, and control signals conditioning modules combining whit a DAQ- acquisition card and a user interface Aquimem-Mx developed in LABVIEW at LEMSC.