₦airaland Forum

jattshaf:
I thought na slap I see that make me to open the tread o........... which one come be slab

slab na ogogoro wey danfo conductor drink,,, hmmmmmmm wey con DE make am misbehave for soldiers front. Which kon land him Better Akpuraka SLAP for face....... I believe u don sabi wetin b slab nao.

Just passing though. However, these things are not new here in Nigeria. So funny most people missed all this beautiful details on most public building (academic buildings, libraries, city halls etc) built between 1960 and 1990. So it's not a new thing here.

Like most people said, it's designed to reduce load.

For me, it's only suitable for specific areas. I will want to use something like this on a flat roof and areas where point load is not going to happen.

talk2riel:
It increases the head room in floor by eliminating drop beams in slabs.


modified one of the site am currently working on.

Good one but what are the disadvantages.

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HOLAROCKDAY:
To the civil Engineers, Builders in the forum.
Base on my pictures below, A friend of mine sent me this pic asking me what type of slab it is. And where can it be use, the reason of putting the waffles ball in between the reinforcement. To cut the story short, an explanation on the slab. I believe you will help me out with these.

Less I forget..... Wow first time my post featuring in front page

HOLAROCKDAY:
To the civil Engineers, Builders in the forum.
Base on my pictures below, A friend of mine sent me this pic asking me what type of slab it is. And where can it be use, the reason of putting the waffles ball in between the reinforcement. To cut the story short, an explanation on the slab. I believe you will help me out with these.

Less I forget..... Wow first time my post featuring in front page..... I blive say u go DE yarn that wetin DE worry diz one nao

My fellow engineers don talk am all,this type of slab is similar to waffle slab as my co engineer said earlier and this type of slab is mostly used in construction of tall buildings and sky scrapper in other to reduce the weight of dead load on the building. Thats where you can get this type of slab.Proudly civil Engineer.

abdulwastecx:
All method of slab construction requires close supervision and clear mathematical calculations.
Waffle slab is as straight forward as one - way solid slab or two - way solid slab, I think flat slab is more technical than even this waffle slab.

For all type of slab you need the right steel strength and concrete strength.
A one way slab behave like a continuous beam where the span is sagging ( bottom Fibre is in tension) while the continuous support is in hogging (top Fibre at the support is tenaion).

A two way slab behavior is dependent on the end conditions and for this type of slab we have about 9 different end Conditions, namely
1. Interior panel
2. All edges discontinuous
3. One short edge discontinuous
4. One long edges discontinuous
5. Two short edges discontinuous
6. Two long edges discontinuous
7. Adjacent edges discontinuous
8. One short edge continuous
9. One long edge continuous.

For these two way slab design code is use to determine both the positive and negative moment for design purpose.

For ribbed and waffle slab.
Ribbed slab is like a one way slab where the solid concrete section is replaced with series of ribbed parallel to one another at a reasonable space based on the life load, span of slab and the type or former to be use. It is made up of topping, rib beam and former which can either be temporary or permanent. The analysis of the rib is carried out like that of one way slab where the span and support moment and shear is gotten through beam analysis or using appropriate formulas from bs codes.

Waffle slab is like two way slab where the rib beam is in both directions. The ribbed intersect each other to form a box that is either filled using polystyrene, clay block or sancrete block.

This is so explanatory, I wish you were my lecturer in school, well the best Engineers do not always end up in the classroom.

To me those flat slabs require more attention during construction because of the punching stress those columns will be exerting on the slab without beams. I read somewhere that if the slab is not having column head, part of the column and the slab should be casted monolithically.

Secondly, I am on a project where they use waffle slab for the decking and from what I observed on the bottom the beam width is not more than 75mm between the sandcrete blocks, what do you see to this ?

true2home:
The above explanations covered the idea for its use. I will not recommend it in Nigeria because the method requires close supervision and clear structural mathematical calculation. Less me just say there is less room for mistake when building such deck. The iron used has to be the right Fy and the concrete right Fc as well. Concrete characteristic is compression strength, while iron's is tension. Tension is experience in the bottom of a slab while compression is exact on the top section of a slab. if the bottom section does not deform excessively, then the concrete at the bottom area of a slab do not serve much engineering purpose other then composition for the iron rod. Anyways, i have to stop here before i loss non-engineering NL

Why wouldn't you recommend in Nigeria. Waffle slabs have been used in Nigeria many years before now.

akin003:
Wow! Nice one, would be a pleasure to get to relate with you I must say.
Before I get distracted, the slab you've seen are all modifications of ribbed/ waffle slabs with essentially the same background principle underlying it's design n construction.
To a lay man, what those balls,styrofoam, pots or whatever else you see do is just take up space,basically to reduce the volume of concrete used in the slab. Now the logic is simple, if I can create many supports(beams), my slab need not be solid/big / thick. This is based on the premise that the higher the design load the thicker the slab has to be, also like someone mentioned, any concrete u have below the neutral zone is a waste( study civil engineering to understand this) ie anything below the reinforcement of a slab is just cover. Its like the 'ay' you have in the word OKAY, absolutely useless.
The beams provided are spaced at less than 500mm spacing along the shorter span in a one way slab(ribbed) or in both ways (waffle slab). This reduces the dead weight significantly without affecting the serviceability and ultimate limit state design considerations. Note that the materials used to fill the voids can be removed so it's not for soundproofing or insulation, those are just added benefits if you keep the material. The primary reason we engineers design ribbed/waffle slabs is when we have long spans panels exceeding 7metres along both axis, a drop beam and slab thickness of more than 200mm becomes excessive. Another reason is if the design load is high eg a library or hospital would have a live load consideration in excess of maybe 10KN/m2 which translates into plenty loadddddddd! That's why yabatech library that someone mentioned and most other such structures have waffle slabs.
This method has been perfected by Nigerian engineers, and we would continue to tweak it as more technological advance is made.
This building is somewhere in lagos, and it has a ribbed slab that had the void material removed, it's beautiful, lovely and it's still standing.
I don talk story sha, but it's like doctors talk, u have to belong to understand.
Kudos to the other quality and well informed engineers here! NICE,NIstructE.

Im the one who mentioned yabatech structure. I belong. Im part of a thriving constrn team. Im no layman. I think u didnt read my posts or what i was replying to.

Horlawoomey:
This is so explanatory, I wish you were my lecturer in school, well the best Engineers do not always end up in the classroom.

To me those flat slabs require more attention during construction because of the punching stress those columns will be exerting on the slab without beams. I read somewhere that if the slab is not having column head, part of the column and the slab should be casted monolithically.

Secondly, I am on a project where they use waffle slab for the decking and from what I observed on the bottom the beam width is not more than 75mm between the sandcrete blocks, what do you see to this ?

Actually it is possible to have a rib beam width of 75mm if they use a single reinforcement like Y16 bottom for the rib beam without links and top reinforcement.

The size of rib beam is govern by fire resistance (cover), bar size, spacing of bar within the section.

Flat slab is the most technical among all slab type to detailed and execute. It contains lot of reinforcement as a result of punching shear along the column areas. flat slab without column head or drop down panel can also be constructed normally provided the punching shear along the critical perimeter are adequately provided for during the design and detailing of slab

n3xt:
Good one but what are the disadvantages.

It is not suitable for heavily loaded floor like that of garage, store, factory etc.

n3xt:
Good one but what are the disadvantages.

The only disadvantage is that you incur a lot more cost in painting and rendering. Also, you need a high skilled artesan to carry out the finishing works in order to produce a perfect final finish. Also, it is not advisable in areas where there will be a lot of traffic. As it isnt designed to bear such load but in places like libraries, etc. It also provides great aesthetics.

n3xt:
Just passing though. However, these things are not new here in Nigeria. So funny most people missed all this beautiful details on most public building (academic buildings, libraries, city halls etc) built between 1960 and 1990. So it's not a new thing here.

Like most people said, it's designed to reduce load.

For me, it's only suitable for specific areas. I will want to use something like this on a flat roof and areas where point load is not going to happen.

In africa, the love people possess for buildings and construction as a whole doesnt go past the dream of proudly owning one. I can tell you from experience, how dumbfounded Ive been, having to explain cornices and skirtings to client. Then i remember my last visit to the doctors, and how I was a lay man too.

tossen:
The only disadvantage is that you incur a lot more cost in painting and rendering. Also, you need a high skilled artesan to carry out the finishing works in order to produce a perfect final finish. Also, it is not advisable in areas where there will be a lot of traffic. As it isnt designed to bear such load but in places like libraries, etc. It also provides great aesthetics.

I don't think you incure more cost from rendering ( under the decking), If any of polystyrene, clay block or concrete block is used. The rendering is plastering of the under decking after the work has been completed, similar operation is carried out on solid slab under decking.

Hall ways in build, school and hotels have life load of 3.0kN/m2, such load is can be carried continently by waffle slab.

Waffle slab without permanent former such as polystyrene or clay block cost more during finishing and requires good artisans

abdulwastecx:
I don't think you incure more cost from rendering ( under the decking), If any of polystyrene, clay block or concrete block is used. The rendering is plastering of the under decking after the work has been completed, similar operation is carried out on solid slab under decking.

Hall ways in build, school and hotels have life load of 3.0kN/m2, such load is can be carried continently by waffle slab.

Waffle slab without permanent former such as polystyrene or clay block cost more during finishing and requires good artisans

How much will the workman collect, because rendering and painting waffle pockets is more technical. The volume of paint is also twice from my last calculations. Wait why are u defining rendering? and then using the word "plaster." Oh well, final finishes of waffle slabs used more cement mortar and paint that a plain slab. It also needs more technicl knowhow, therefor it costs more money.
Wht has load carrying got to do with this. Those facts have already been established. This is about cost.

abdulwastecx:
It is not suitable for heavily loaded floor like that of garage, store, factory etc.

That's why I said I'll want to use something like that on a roof slab

n3xt:
That's why I said I'll want to use something like that on a roof slab

That would b nice if the building is in a dense area where it isnt the tallest and is not susceptible to strong winds.

HOLAROCKDAY:
slab na ogogoro wey danfo conductor drink,,, hmmmmmmm wey con DE make am misbehave for soldiers front. Which kon land him Better Akpuraka SLAP for face....... I believe u don sabi wetin b slab nao.

Lol
I don grap am bro

I did not oooo. Just from my little experience so far, some of our artisans are limited. And most comments here from clients with support my opinion. We are not underated, but some of us have not master the art of serving. I am your friend ooo; like Nigerian police

kuuljay:
with this kind knowledge you have,you still went ahead to underate us

Hi Sir, i most say you are not easy at all ooo. How you went into Structure 450 on NL is hilarious. You must be Prof. Please don't scare some people with all this static analysis. Thanks for the effort and time you expended here.

abdulwastecx:
All method of slab construction requires close supervision and clear mathematical calculations.
Waffle slab is as straight forward as one - way solid slab or two - way solid slab, I think flat slab is more technical than even this waffle slab.

For all type of slab you need the right steel strength and concrete strength.
A one way slab behave like a continuous beam where the span is sagging ( bottom Fibre is in tension) while the continuous support is in hogging (top Fibre at the support is tenaion).

A two way slab behavior is dependent on the end conditions and for this type of slab we have about 9 different end Conditions, namely
1. Interior panel
2. All edges discontinuous
3. One short edge discontinuous
4. One long edges discontinuous
5. Two short edges discontinuous
6. Two long edges discontinuous
7. Adjacent edges discontinuous
8. One short edge continuous
9. One long edge continuous.

For these two way slab design code is use to determine both the positive and negative moment for design purpose.

For ribbed and waffle slab.
Ribbed slab is like a one way slab where the solid concrete section is replaced with series of ribbed parallel to one another at a reasonable space based on the life load, span of slab and the type or former to be use. It is made up of topping, rib beam and former which can either be temporary or permanent. The analysis of the rib is carried out like that of one way slab where the span and support moment and shear is gotten through beam analysis or using appropriate formulas from bs codes.

Waffle slab is like two way slab where the rib beam is in both directions. The ribbed intersect each other to form a box that is either filled using polystyrene, clay block or sancrete block.

msogunro:
A similar application is the use of rigid foam panels. Use of the panels help to reduce the amount of concrete needed and weight of the slab as @Ebubeslym has pointed out, among other benefits.

I've been researching it to reduce costs for my upcoming build, but it seems to be rather expensive since the panels will have to be imported.

There's an extruded polystyrene company here in Abuja.

talk2riel:
It increases the head room in floor by eliminating drop beams in slabs.


modified one of the site am currently working on.

Which kind of risk is this?

DisGuy:
surely this is anti-Nigerian engineers/contractors

ahhh you want to reduce concentrate/ cost hmm na if una building collapse now una go dey blame supervisors Oga H'add money make ur house fine well well like dasuki own

Thanks bro, you spoke my heart.

EngrOsas:
Which kind of risk is this?

How is this risky?


Civil Engineering is all about strength, durability, serviceability and optimal cost effectiveness in the construction of element.




This construction made use of fire baked bricks site, located in kaduna. Classical clay pot are sometimes use. Wonder why people are so surprised seeing this method of construction.

abdulwastecx:
All method of slab construction requires close supervision and clear mathematical calculations.
Waffle slab is as straight forward as one - way solid slab or two - way solid slab, I think flat slab is more technical than even this waffle slab.

For all type of slab you need the right steel strength and concrete strength.
A one way slab behave like a continuous beam where the span is sagging ( bottom Fibre is in tension) while the continuous support is in hogging (top Fibre at the support is tenaion).

A two way slab behavior is dependent on the end conditions and for this type of slab we have about 9 different end Conditions, namely
1. Interior panel
2. All edges discontinuous
3. One short edge discontinuous
4. One long edges discontinuous
5. Two short edges discontinuous
6. Two long edges discontinuous
7. Adjacent edges discontinuous
8. One short edge continuous
9. One long edge continuous.

For these two way slab design code is use to determine both the positive and negative moment for design purpose.

For ribbed and waffle slab.
Ribbed slab is like a one way slab where the solid concrete section is replaced with series of ribbed parallel to one another at a reasonable space based on the life load, span of slab and the type or former to be use. It is made up of topping, rib beam and former which can either be temporary or permanent. The analysis of the rib is carried out like that of one way slab where the span and support moment and shear is gotten through beam analysis or using appropriate formulas from bs codes.

Waffle slab is like two way slab where the rib beam is in both directions. The ribbed intersect each other to form a box that is either filled using polystyrene, clay block or sancrete block.

oga abdul.... I'm in deep mess. How do I learn this design of beams, slab, stairs easily... lecturers are not helping because of negligence. You see, I bought oyenuga but that book is clearly not helping.... more like for those who already know the design before hand. Even Bungey is not helping... wat do u think I do? Exam sef dey run come near me like say I carry magnet for body...

talk2riel:
It increases the head room in floor by eliminating drop beams in slabs.


modified one of the site am currently working on.

please, do u mean there will be no beams under the slab? For a framed structure? pls I would appreciate some explanations

Miscellaneous:
please, do u mean there will be no beams under the slab? For a framed structure? pls I would appreciate some explanations

There are beams impregnated in the slab(concealed beams) if you look closely at the pix, area showing concrete has beams.

true2home:
I did not oooo. Just from my little experience so far, some of our artisans are limited. And most comments here from clients with support my opinion. We are not underated, but some of us have not master the art of serving. I am your friend ooo; like Nigerian police

you are a fuvking genius and I know it from this topic,most guys that relaying what you said actually got the clue from you, get up from that comfort zone and make us proud as nigerians and the ones behind you will believe it's actually possible read about jelani aliyu That's an aboki who schooled in nigeria

Miscellaneous:
oga abdul.... I'm in deep mess. How do I learn this design of beams, slab, stairs easily... lecturers are not helping because of negligence. You see, I bought oyenuga but that book is clearly not helping.... more like for those who already know the design before hand. Even Bungey is not helping... wat do u think I do? Exam sef dey run come near me like say I carry magnet for body...

Check out the following books
1. Reinforced concrete: design theory and examples ( first and second edition) by T. J. MACGINLEY and B. S. CHOO

2. Reinforced concrete design to BS8110 - simply explained (A H ALEN)

3. Reinforced concrete designer's handbook (C E reynolds and J C Steadman.

4. Reinforced concrete design ( Bill Mosley, John Bungey and Ray Hulse).

These books were very helpful to me during my undergraduate years on reinforced concrete design.

I will also advice you to get all the BS 8110 for reinforced concrete design, steel table and structural detailing to Bs 8110. You need to also get BS 6399 loadings for building. These codes will make it easy for you to do your design.

Structural design requires lit of simple mathematics unlike structural analysis that requires advanced and vigorous maths. What you need to do is devote more time to it, understand all the steps involved and prepare your mind towards it.

During my undergraduate years, grade (gp) was secondary to me, understanding the design was more important to me. I study these things to be able to do the design, so I use lit of practical examples like working real architectural drawings instead of those simple panels giving in the classrooms.

Miscellaneous:
please, do u mean there will be no beams under the slab? For a framed structure? pls I would appreciate some explanations

There are beams but these beams are of the same depth as the rib ( the small beam of the waffle). These beams are wider than normal beams in solid slab construction ( width greater than 225mm in most cases).

tossen:
That would b nice if the building is in a dense area where it isnt the tallest and is not susceptible to strong winds.

I still disagree with your assertion. Wind load will only have effect on the building if it it produce lateral restrain to your build. When the floor is not designed to serve as a diaphragm ( a structural member that transfer lateral load to vertical resisting members)

abdulwastecx:
Check out the following books
1. Reinforced concrete: design theory and examples ( first and second edition) by T. J. MACGINLEY and B. S. CHOO

2. Reinforced concrete design to BS8110 - simply explained (A H ALEN)

3. Reinforced concrete designer's handbook (C E reynolds and J C Steadman.

4. Reinforced concrete design ( Bill Mosley, John Bungey and Ray Hulse).

These books were very helpful to me during my undergraduate years on reinforced concrete design.

I will also advice you to get all the BS 8110 for reinforced concrete design, steel table and structural detailing to Bs 8110. You need to also get BS 6399 loadings for building. These codes will make it easy for you to do your design.

Structural design requires lit of simple mathematics unlike structural analysis that requires advanced and vigorous maths. What you need to do is devote more time to it, understand all the steps involved and prepare your mind towards it.

During my undergraduate years, grade (gp) was secondary to me, understanding the design was more important to me. I study these things to be able to do the design, so I use lit of practical examples like working real architectural drawings instead of those simple panels giving in the classrooms.

thanks alot.... I'll get them today. God bless you... because of so many conditions/rules attached to design , it proved complex for starters but I'll try out those books... thanks once again

abdulwastecx:
Check out the following books
1. Reinforced concrete: design theory and examples ( first and second edition) by T. J. MACGINLEY and B. S. CHOO

2. Reinforced concrete design to BS8110 - simply explained (A H ALEN)

3. Reinforced concrete designer's handbook (C E reynolds and J C Steadman.

4. Reinforced concrete design ( Bill Mosley, John Bungey and Ray Hulse).

These books were very helpful to me during my undergraduate years on reinforced concrete design.

I will also advice you to get all the BS 8110 for reinforced concrete design, steel table and structural detailing to Bs 8110. You need to also get BS 6399 loadings for building. These codes will make it easy for you to do your design.

Structural design requires lit of simple mathematics unlike structural analysis that requires advanced and vigorous maths. What you need to do is devote more time to it, understand all the steps involved and prepare your mind towards it.

During my undergraduate years, grade (gp) was secondary to me, understanding the design was more important to me. I study these things to be able to do the design, so I use lit of practical examples like working real architectural drawings instead of those simple panels giving in the classrooms.

You know eh, when I read most of your write ups, I feel like I should get an opportunity to learn - even if it's a week - from you, I know I'll surely learn a lot. You make these stuffs easy to know. Thanks for your explanations.