Accident happen during concreting of slab

[Chetan Yadav]

I have seen the accident which happened during concreting of slab due to failure of formwork supporting system.
Below is the video.

Do anyone can tell why this accident was happened.

What are the thing should be checked in formwork shuttering work before concreting of slab to ensure no such failure.

 

[man singh]

Span between two front coloums very long

 

[natarajan.balu]

Let us list out the reasons for failure in shuttering for slabs and beams :
1) Whenever the floor height is more than 3 metre, we have to go for staging compulsorily with bracings (horizontal ties).
2) We should calculate the weight of concrete including the shuttering the materials and based on that we have to calculate the loading pattern on each and every support. If the load/thickness ofslab/beam is more then we have to go for M.S. Props/acrowspans instead of wooden supports.
3) Even in case of wooden supports we must and should tie each and every support with bracings(horizontal ties).
4) We all have a negligient attitude towards shuttering. Many of the Enginners feel once shuttering and barbending and tying is done as per drawing major work is done. Unfortunately, many of then does not know the importance of proper supports in shuttering.
5) Nowadays, everything is available on internet. Pls get into the types of props/acrowspans in google and the load bearing capacity of these supporting systems.
Based on this you can calculate no.of props required for each acrowspans.
6) Eventhough we have lot of checking methods like checklists/pour card etc., unless Engineers feel the seriousness of proper shuttering we have to face such
accidents every now and then.

 

[amd007]

My observations for this failure:

THE FIRST MAJOR MISTAKE IS THAT THIS STRUCTURE IS DESIGNED BY A MORON. Reason: only 2 columns on extreme portions and not a single column to take the load of the slab in the central portion. So this structure was doomed to fail no rocket science here.

However, if the columns were provided then the slab would also have anyways failed due to the following reasons:

1 the front portion which collapsed is double height as compared to the back portion which was single height pour.
2. props in the interior portion were arranged in two layers which are very dangerous.
3. the structure seems to be in the rural area hence they have definitely not done the shuttering design and have followed ideas of some local shuttering mistri.
4. they have started the concreting in longer direction instead of shorter direction( despite this action it would have failed as supporting system itself was wrong.
5. the concrete itself is of very high water content which is evident by the reflection of water at top of the concrete surface.
6. If you see clearly the hoist for transportation of concrete is on left and delivery point is at the double height portion, this causes jerks when the landing platform reaches the slab level, these jerks also could have triggered the displacement of the already ill designed propping.

As regards shuttering checks there are various checklists on this forum which one can go through.......

However, some of the things not mentioned in the checklists are :

1. Always verify the diameter of the props is as per the shuttering design.
2. Sometimes engineers tend to overlook the thickness of the prop diameter which is very crucial both in wooden and metal props, however, more care is required in metal props as they tend to corrode from the inside reducing the thickness of the pipe resulting in failures.
3. For all double height, slabs use of cup locks shuttering or H frames are advisable as compulsory bracing is provided in such shuttering resulting in sound shuttering ( here again the thickness of the pipes should always be ensured by loading tests on the props)
4.If at all wooden props are used then carefully design the spacing and the thickness of the props along with bracing in both directions considering the slenderness ratio of both wooden as well as metal props ( this is basically overlooked by most of the engineers)
5.If metal props are not available for double heights and only wooden props are available then staging to be done with ISMB or ISMC which should be anchored to the columns with secondary supporting also of ISLB or ISLC and once this metal staging is done props can be arranged as per the shuttering design so here even wooden props will work.
6. Bracing of each and every prop is compulsory as in case of any lateral movements the props will be kept in place.

Shuttering itself is a vast subject so based on some of the experiences which I have studied where slab failures have occurred have tried to incorporate some here.

Extremely sorry for some rough words, but you feel really frustrated when people instead of hiring experts result to some mestri, kadiya etc for advice. Just like in case of a disease we go to the doctor and that too to the right doctor similarly CIVIL ENGINEERING is by itself complex SUBJECT and hence the advice of a CORRECT CIVIL ENGINEER IS A NEED OF THE HOUR IN INDIA...... THINK ABOUT IT......

 

[Jayant Joshi]

As per my information this is some where on out skirt of Surat.(Canal road)
The camera is at opposite side petrol pump.

I agree,
This is total negligence of shuttering arrangement.
The failure started from temporary concrete lift side.
Props are not properly tied, as well as very poor propping done.
For such span, metal staging with H frame should be erected.
All metal or wooden props must have firm base, several time if floor below slab is only soil then props penetrate in soil, as well as water continuously running near mixer helps subsoil to soften, this leads base of all props to settle in ground.

Here in this case all technical discussion is useless as not a single rule of double staging shuttering is followed.

Even design is also doubtful, only two columns at front side span seems more then 50 feet.

Really horrible,

OK, but let us learn from this event and request to all contractors, site engineers, consultants, builders, designers that please give equal importance to shuttering activity also.

 

[natarajan.balu]

This is unfortunate to say that CIVIL ENGINEERING is taken for granted. Since a very long time, certain things were getting into my mind which I want to share with you. In all Engineerings things cannot be taken for granted. For example in Electrical Engg., wires and connections cannot be changed as you wish. In computer Engg., unless the programmes are perfect you will not get the final result. But only in case of Civil Engg., that too in India things are taken for granted .Anyone can design shuttering/concreting. Anyone can decide anything and that too Developers/owners of houses never ever worry about Civil Engineering but they are much worried about reducing the cost by hook or crook method. Unless and until these things are resolved these types of accidents are bound to happen. Hope Senior Technical Experts from Civil Engineering will put force on Government and Public not to involve this type of arrogance towards Civil Engineering aspects and thereby reduce accidents.