Stability is not immobility Oct 18, 2018
De heer Rajarshi DAS
Earthquakes, the sudden release of energy stored below the surface of the Earth that can have disastrous consequences for humans and their environment. This trembling, rolling and vibration of the ground beneath our feet occurs almost every day and everywhere. Preventing them is impossible, so suitable safety actions should be taken. Today on ‘International Shake Out Day’ when millions of people over the world participate in the largest earthquake drill, we talk with Rajarshi Das, a Ph.D. student at UHasselt who researches safer structures that can resist earthquakes.
ALWAYS ON THE MOVE
“It takes an earthquake to remind us that we walk on the crust of an unfinished planet.” – Charles Kuralt.
The surface of our planet is continuous, yet slowly, on the move. However, the tectonic plates tend to get stuck at their edges due to friction. It is in the moment when the stress on the edge overcomes the friction that an earthquake occurs. It is estimated that there are over 500 000 detectable earthquakes each year, scattered across the globe.
Most of these are imperceptible yet the effect of some can be felt socially, environmentally and economically. One of the most common consequences of earthquakes, and the main responsible for the majority of injuries and deaths is structural damage to infrastructure. Therefore, it is of vital importance that our infrastructure possesses the ability to withstand this force of nature.
“Most of the buildings nowadays are built using strict building codes in order to ensure that they don’t immediately collapse when the earth starts to tremor. Yet there is still room for improvement. Engineers worldwide are striving to innovate and introduce novel concepts when it comes to make structures disaster-proof, and I am one of them, working in the Construction Engineering Research Group at Hasselt University.”
DEVELOPING GUIDELINES FOR A SEISMIC RESISTANT FUTURE
Structures are of vital importance to achieve community resilience because of their importance in providing emergency response, essential services and shelter, and because of the significant price tag and potential life threat associated with them being damaged or collapsing. “To ensure that our infrastructure can fulfill this role we must ensure its capability of quick restoration to full functionality after an earthquake. One novel concept is the use of coupled walls to design seismic-resistant multistoried buildings.”
Coupled walls consist of reinforced concrete walls coupled with reinforced concrete beams. More recent models include steel and concrete hybrid walls using steel or steel-concrete composite beams. These beams can be easily substituted when damaged by an earthquake.
“Recently a new system was developed that consists of a concrete shear wall coupled to steel side columns using steel links, providing higher stability and resistance to earthquakes. As these systems are quite new they have to be thoroughly investigated before we can introduce them in the real world. That is where my Ph.D. comes in. Through several models, I develop a set of guidelines for future designers.”
MAKING A DIFFERENCE
“My research mainly consists out of 4 different phases. First I made a global analysis and design of the complete structure as part of a realistic residential building plan. I do this to develop relevant design methods for industrial use. Next, I took a more detailed look at the connection between the steel links and the reinforced concrete shear wall. Currently, I am developing a novel steel link – steel column connection. The final step will be to integrate all the details of step 2 and 3 and combine them with the general model developed in the first step.”
If Rajarshi succeeds it would result in designers being able to use two steel columns, instead of a second reinforced concrete wall, and thus replace the excessive use of concrete. This while simultaneously increasing the seismic resistance of the building. Using such a structure would make way for the easy restoration of damages after heavy earthquake shocks and would, therefore, save a lot of money.
“I have always been fascinated by the various design approaches we adopt for different types of structure. On top of that my home country of India is located in a zone prone to earthquakes, so I feel like my research could really make a difference.
Rajarshi Das is affiliated with the Construction Engineering Research Group (CERG) of Hasselt University, where he prepares his Ph.D. under the supervision of Prof. Herve Degee.