GUWAHATI, May 5 � Renowned expert in earthquake engineering Dr Sarada Kanta Sarma has underscored the need of post-earthquake field studies to know the reasons behind the failures of the structures.
Dr Sarma, presently an Emeritus Reader of Engineering Seismology and Senior Research Investigator at Imperial College, London, who has developed a method of seismic slope stability analysis, named Sarma method, maintained that since earthquakes are beyond the control of the humanity, �efforts should be made to make our areas safe from future earthquakes.�
The only way to do this is to build structures, which are designed to seismic codes and to follow the codes also at the time of building them. �The Indian Seismic Design Code is very good. At the same time, we have to learn from structural failures in earthquakes too,� he said.
Dr Sarma told this correspondent that if a seismically designed structure fails in an earthquake, we have to know why. �We are to ascertain whether it is the shortcoming of the seismic code; the fault in construction (for not following the design correctly) or pure negligence during construction.�
The negligence comes from not understanding why the provisions of the seismic codes are there, he said. He also maintained that the codes should not only say what should be done but also what should not be done. �The second part is not there in any code in any country,� he said.
He informed that once he saw a Coca-Cola can in the concrete after an earthquake. �The can was probably thrown into the concrete while pouring, not realising that this had made the concrete weak at that point and an earthquake finds such weak points in the structures and makes them fail. To check such developments, we have to educate the builders as well as the construction workers,� he maintained.
�There are instances where reinforcing rods are exposed after the pouring of the concrete and the builder simply covers it up with plasters after the frames are removed. These become weak points in the structure,� he said.
The stirrups (the hoops that go around the vertical reinforcements) in the concrete columns are not tied down properly and while pouring, they all slip down to the bottom, making the column weak for seismic loads. These are not design faults, but construction faults and it happens because the builder is unaware of the importance of the stirrups, asserted Sarma.
Again, proper geotechnical investigation is very important prior to designing the structures and building them. A structural failure may happen not because of the shortcomings of the structure but because of the soil underneath, he said.
On structures built on the marshlands, etc., he said, �I am not sure about the structures built in landfill areas (old marshlands, etc.), whether proper geotechnical investigations are done or not. These are very vulnerable areas against earthquakes.�
He maintained that in the case of massive earthquakes with epicentres close to the cities, massive damage and tragedies are feared. We can only hope that the structures are built to standards. As one said, earthquakes do not kill but failing structures (including geotechnical failures) do, he said.
On the important buildings, old or new, he said these should be checked thoroughly and if need be, these should be retrofitted. It should be done now and not postponed till later, he said.
He also maintained that in seismic regions, it is always preferable to have low dams than high dams, but even then, it is always better to be prepared. If we do not want to build dams, then we should look for alternative solutions like solar, wind power, etc., but not nuclear or fossil fuel, he said.