LR 20 :How unsafe it is to do construction without structural strength testing

 This is an alert for those who want to resume construction work in a project where work remained stopped for 3-4 or more years.

I am using the word ALERT because I have seen the case of Vivekanand flyover in Kolkata in which the under- construction flyover suddenly fell down and all traffic plying under it got crushed under impact of massive load. It happened at 10 AM on 31-3-2016 when the road was full with traffic.The reason was simple

 

The work started about 7 years back came to halt due to some dispute . The iron structure which was to support the road slab was ready.The work of slab started after a gap of  5 years.During this period ,the underlying iron structure ,had got its nuts -bolts, rusted.

When new concrete slab was cast after 5 years, the rusted nut-bolts failed and the iron structure tilted under heavy slab load. 

While this incident was already doing rounds in my mind, I recently happened to attend a training course on structural stability of buildings and structures.The course faculties were from CBRI,Roorkee. During question session I asked the head faculty, Sir , in Greater Noida, the construction work in many stalled projects are being resumed. What type of test should they conduct to ensure that the structure has not deteriorated under prolonged action of sun rail and frost over 6 to 10 years.

The faculty told me that I have asked a very good question and it can save the life of many people. They told that the main problem in such exposed structures is corrosion of steel rods which are placed inside RCC members such as beam, column and slab. Since plaster is not present, the water from rain and corbon dioxide from atmosphere makes carbonic acid H2CO3 which provides acidic environment which causes corrosion of steel through electrolysis. They told that even if 1 percent of steel is corroded, the loss of its load bearing capacity is as high as 50%.

Most of us would be surprised to know that 1% corrosion of steel rod causes 50% loss of strength in RCC. I was also surprised and asked, why? They told that the bonding between steel and concrete is through firm grip between outer layer of rod and concrete mass surrounding it. If outer layer of steel rod is rusted, it will peel off and there will be either gap or loose grip between the steel and the concrete mass. Once the grip is lost, there is no use of steel in an RCC because transfer of tensile stress from concrete to steel takes place only through this bonding.

After this explanation, the CBRI faculty suggested various types of non- destructive tests NDTs , core cutter tests and load test to be conducted on an old structure if further work is being resumed after a long gap.

In fact NBCC is doing all these tests in all buildings which are given to them. But our tower-wise people are no bothering about this important aspect at all.

Is there really the same kind of threat in La residentia buildings?

The answer lies at site. Just go and see what amount of rain water, stagnant blackish water and continuously flowing leakage water is constantly damaging our structure for the past 6 -10 years.If you are not in a position to go to the site, just have a look on these pictures of Tower 30

  

 

You would definitely agree that at least  1% of steel layer must have been lost in corrosion with this kind of exposure. If it is so, the member where such corrosion has occurred needs to be dismantled and re casrt with new reinforcement bars. I am most concerned about the balcony slabs. The main attraction of La Residentia are the balcony slabs where Builder was telling, wind will cone from 3 sides. If you don’t remember, see the brochure

 

 

What will happen if reinforcement in balcony slabs is corroded and its strength become 50%?The day 3 or more people stand on this balcony, it will collapse. It will fall on another balcony 2 floors below it and the chain will go on.

It is a serious threat to life of buyers. Those who are doing new construction without checking the strength of old construction are playing with their own life and life of other innocent persons.

So dear Tower wise buyers ger ALERT . You may be held accountable if any accident occurred because you are a part of this decision. The builder is already facing several cases and is having enough money to fight all cases. How about you ?

If you want to save your life and career, please leave the lust of hurriedly constructing the towers as per builder’s will and ignoring all safety aspects. Please join our association and fight in the supreme court. When our flats will be built under court receiver’s supervision by NBCC, such technical points would not be ignored.