Thursday, 3 January 2019

Co-operation in cooperation

Hello everyone!

As you know, thanks to INFRASTAR we can travel to the partner institutions and work there with fellow Early Stage Researchers. Now at EPFL we have a visitor from France - Antoine. He's working on crack opening measurements using distributed fibre optics strain gauges. He got some nice results with ordinary concrete, thus we have decided to put them into my beams.

We've started the preparation of common experiment in September, when he came to Lausanne to glue some of his fibres on rebars, and to cast the beams with me. I must admit, that we have prepared a massive amount of sensors for some of the beams ;)


Then, when he came to EPFL for his secondment, we've glued some more fibres onto the surface of the beams.



Some of the beams prepared in this way will be tested in static, while the others in fatigue.

Thanks to that, he'll check if his method works with UHPFRC, and I'll get more interesting data on my specimens.

So, it's a WIN-WIN situation - that's how the cooperation should look like!


Sunday, 2 December 2018

Fatigue does exist!

Hello everyone,
today just a short post as lately I am very busy in the lab.

The first proper fatigue test is running. I am still amazed with the capabilities of our machines - in the current test I load and unload my beam 5 times per second with equivalent of 16 tonnes! Still, almost 3 weeks is needed to get 10 millions of cycles. You can see the beam during the test below.



In the meantime I have proven that the fatigue does exist (do you remember this?). Here is one of the bolts from my testing rig.



After strengthening of the connection the test continued.

That's it for now, I will keep you up to date!



Sunday, 11 November 2018

Experimental campaign... finally!

Hello everyone!

Long time no hear, as I am stuck in the lab. After casting, it is time to break some beams!

So far, I have tested three beams statically. I did it to get their resistance, which will help in calibration of my fatigue tests. One of the tested R-UHPFRC beams below, with visible huge force-redistribution steel beam on top of it.



I've got one unexpected shear failure... Which opened a whole new research branch on influence of vibrations during casting on the fibre orientation in beam! The project is ongoing.


And, when I say I BREAK the beams, I really mean it. The one below is broken for sure ;)

Thanks to its fibres, the UHPFRC is very ductile. Here, you can see a time-lapse video of the post-peak load. This means, that the beam has already reached its maximum resistance and now can be considered as damaged, but there is still a lot of capability of deflection and load support. 
Just imagine, that you can see through the beam while there is still a load of around 25 tonnes on it! (so, weight of 15 cars...) 



Stay tuned to see more pictures from another tests! Coming when I'll only find some time to upload them...






Thursday, 9 August 2018

Casting campaign

Hello everyone!

In the last post I was informing you about preparation of the casting campaign.
Now, my own small factory is fully operational, including:


Mixing,


casting... with use of external vibrators!


curing for 7 days in formworks,



demoulding, labeling,


...and finally moving to the storage area.

In July I have reached efficiency of  3 beams per week, which is a good result.

Unfortunately, I am not that good in taking videos with my cell phone... or maybe this post was just optimised for your mobiles? ;)

Now, the beams are awaiting for my test setup to be ready. This should happen within a week or two.
So, stay tuned!

Saturday, 2 June 2018

Step by step towards experimental campaign

Hello everyone!

One important part of my PhD research within INFRASTAR is an experimental campaign on R-UHPFRC beams (Reinforced Ultra High Performance Fibre Reinforced Cementitious composite).

This complex name stands for combination of UHPFRC and reinforcement bars, as known from reinforced concrete. I will not spoil the fun and reveal all the details for now - wait for it ;)

Currently I am getting step by step closer to the experiments themselves. But, there is a long way behind me already.

The origin of campaign takes back to the end of last year, when I was getting ready for my candidacy exam (read here) and I had to come up with ideas. I have decided to look at the problem of steel reinforcement and UHPFRC long term behaviour. This topic is relevant, as more and more structures are built every year, and it largely still hasn't been explored.

Since the beginning of 2018, fight for materials started. Finally, UHPFRC and reinforcement arrived to EPFL around May.





Then, there was time for material testing,

strain gauges gluing,

formwork preparation,

and the trial casting!

It even fitted the support that our technician fabricated for me!

For now, I have casted just the trial beam. But once I know the system works, I will start an extensive casting campaign this month! And, the first tests in July.

I will let you know!

Wednesday, 4 April 2018

Art of engineering

Hello everyone,

Lately, I've been taking part in 1st INFRASTAR implementation day (more info here). It was held by BASt (Federal Highway Research Institute) near Cologne, Germany.

Once there, I took a chance to walk the city and its riverbank. They have couple of road and railway bridges over there. This brought some thoughts to my mind.

According to the European codes, the design service life of a bridge is around 100 years. During that time, the traffic and the demands that we, a society, impose on a structure can change considerably. Just think of how the road traffic changed between 1918 and now!

One of the common cases, especially in case of bridges within the city limits, is need of widening of a bridge to accommodate higher number of cars, trains etc. But, this must be done not only under economical, but also under architectural constraints.

One of ways to widen the bridge is to add new, parallel structure. This strategy was used in two cases in Cologne.

In case of the railway bridge, a new structure was built next to existing one. Same material (steel) and type of structure was used, so that it is difficult to say the difference from the distance. But, closer look, reveals the progress that happened in civil engineering during the time.



Another case is a road-pedestrian bridge. Here, two different material were used (concrete and steel) but, to keep the nice look and compatibility, the box-girders were formed in similar way.

These two cases show, that an engineer needs to think of aesthetics, as well!

Wednesday, 7 February 2018

My education at EPFL



Hello everyone,

I have just finished the last courses within the EPFL ENAC doctoral school, thus I’d like to tell you how it works in here.

During the doctoral studies, which last for four years, the candidate is obliged to obtain 12 ECTS (European Credit Transfer System) points. One ECTS is equal to 25-30 hours of work, so 12 ECTS can be understood as 8.5 working weeks - seems easy.

During the first year (so before the candidacy exam that I have passed in December) at least 4 credits need to be obtained, and one of the core courses has to be passed. The core courses are meant to be universal, applicable for researchers of various specialisations and teach how to conduct the good research, analyse the data etc.

The 4 credits per year does not seem to be much. But I have noticed, and this is my personal view, that the difficulty of obtaining the points varies from university to university. In here, it is particularly difficult. In fact, if you want to transfer the points for the courses you’ve been attending somewhere else, you obtain less credits than people in the other places! This happened to me, when for the summer school at DTU I got 5 ECTS instead of 7.5, as all my other colleagues who took it with me did. All in all, getting 12 ECTS is harder than it seems.

The first year at EPFL is sometimes treated as a preparatory year. During this time the PhD candidate should deepen the knowledge, prepare the research plan and present it during the candidacy exam. I have decided that during this preparatory year I’ll take all the necessary courses, so that I can profit from this knowledge. So far, I have passed the following:
·                     Introduction to digital signal processing using Matlab, applied to environmental sciences and civil engineering (2 ECTS) – for better analysis of signals obtained during monitoring of structures
·                     Design of experiments (4 ECTS, core course) – for optimal design of experimental campaign
·                     Fracture Mechanics and Fatigue of Structures (2 ECTS) – for better understanding of fatigue phenomena
·                     New Concretes for Structures (2 ECTS) – for better understanding of UHPFRC
·                     Uncertainty and Sensitivity Analysis of Numerical Models (Summer school at DTU, 5 ECTS according to ENAC) – for producing better models of concrete and UHPFRC in fatigue, including stochastic models
·                     Two INFRASTAR training weeks (1 ECTS each) – to get the overall view of fatigue problem. The third one is scheduled for June 2018

So, in total I have obtained 17 ECTS, more than enough during the doctoral studies. Thanks to that, and being supported by the knowledge I have gathered, for the next three years I can focus on the research only!

I will keep you updated during that time.

Stay tuned!

Co-operation in cooperation

Hello everyone! As you know, thanks to  INFRASTAR  we can travel to the partner institutions and work there with fellow Early Stage Resear...