How to calculate unfactored dead concrete slab load

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Slab panel

A slab in terms of its dimensions consists of a thickness(depth), length and width. Understanding this concept will correctly Enable you to calculate and apply slab loading.

In reinforced concrete design, the weight of concrete is usually taken as 24kN/m³. So let’s look at an example.

A reinforced concrete slab is to be constructed having a length of 5m, width of 3m and depth of 200mm. The slab loading can be calculated as follows.

Calculating slab load in kN/m²

Note that 200mm = 0.2m..

..and weight of concrete is 24kN/m³

In most design calculations the unit of the slab load is in kN/m². In this case the slab load is calculated by multiplying 24kN/m³ by thickness (depth) of slab which is 0.2m

So 24kN/m³ × 0.2m = 4.8kN/m²

(4.8kN/m² is the unfactored dead load of the slab)

Calculating slab load in kN

To represent the slab load in kN, just multiply the unit weight concrete which is 24kN/m³ by the volume of the slab. 

Note that the volume of the slab is length x width x depth

So 24kN/m³ × 0.2m × 5m × 3m = 72kN

In practice, you will be calculating slab loading from structural plan or floor panel arrangement. A typical structural plan is shown below.

Structural plan

The slab panels are label P and a number. Let’s take a look at one of the slab panels, panel P8.

The panel’s thickness is 150mm or 0.15m. Also it is a 2 way slab. You can also easily calculate the length and width of the slab from the dimensions shown.

To calculate the unfactored dead load of the slab in kN/m², ( which is what we have been doing so far), just multiply 24kN/m³ by the slab thickness which is 0.15m;

24kN/m³ × 0.15m = 3.6kN/m²

Qualifiers From Africa for Qatar 2022 have emerged

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African World Cup Final Qualifying Matches Scores

Ghana, Senegal, Cameroon, Morocco and Tunisia will be Africa’s representatives in the forthcoming FIFA WorldCup to be held in Qatar this year.

The Nigerian Super eagles will not be in Qatar 2022. Instead it is Ghana that goes through after holding the Nigerian team to a 1-1 draw in Abuja. The Nigerians did not do enough to win, however Ghana produced a highly tactical and defensive display and they must be commended. They were able to suppress the Nigerian midfielders in the second half of the match and should have even won that game if their strikers had been ruthless.

Cameroon overturned their first leg home defeat to beat Algeria 2-1 and qualify for Qatar 2022 against all odds. Kudos to them. They were never given any chance but they did it.

After Senegal’s one nil loss to Egypt in the first leg in Egypt, Senegal qualified after beating them on penalties in the second leg. However, it was a laser marred penalty shootout as some Senegalese fans kept pointing laser pens at Egyptian players taking the penalties. That’s home advantage used to the fullest..or the organizers will be taking a good look at the issue.

Morocco’s victory over DR Congo was never in doubt after forcing them to a 1-1 draw in the first leg.. Four nil winners in the second leg at home and Morocco cruises to Qatar 2022.

Away goal rule gave Tunisia victory over Mali and qualified them for the World Cup. After forcing Mail to a 1-1 draw in Mali, Tunisia then forced them to another goalless draw at home. 

One and Two Way Slabs Simply Explained

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One Way Slab

In reinforced concrete design, a slab is said to be one way if the length of the longer side divided by the length of the shorter side is equal to or greater than 2. 

With reference to the diagram of the slab shown below, If the length of the longer side (Ly) = 5m, and the shorter side (Lx) is 2.5m then 

Ly/Lx = 5m/2.5m = 2

On structural plans, the symbol used to identify a one way slab panel is shown in the previous diagram (symbol that the arrow points at).

In a one way slab design, the main reinforcement steel spans along the shorter side of the slab, which is also the span of the slab

In a one way slab design, only the two long supporting beams along the the long side of the slab  is assumed to carry the slab load equally between them. The beams along the shorter side do not carry any slab load.

For instance with reference to this diagram of a one way slab, beam 1 carries half of the slab load and beam 2 takes the remaining half, none of the slab load is carried by beams 3&4. This makes beam 1&2 the critical beams. Beams 3&4 will not be carrying any slab load, but may carry wall load and part of roof load. 

Two Way Slab

If the length of the longer side divided by that of the shorter side is less than 2, the slab should be designed as a two way.

With reference to the diagram shown, the length of the longer side, Ly, =6, and that of the shorter side Lx = 4.75. Therefore, Ly / Lx = 6 / 4.75 = 1.26. 1.26 is less than 2 hence the slab should be designed as 2 way.

The symbol of a two way slab is as shown above (the symbol that the arrow points at);

In a 2 way slab design, the main steel reinforcement spans both directions.

All 4 supporting beams carry some part of the slab load but the beams along the longer side carry more of the slab load than the beams along the shorter side.

The loading on beams for a 2 way slab is as shown. Note that the beams 1& 2 carry more slab load than beams 3&4

African World cup Qualifiers final Round Preview

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African World cup Qualifier Final Round

The first leg of the final round of African world cup qualifiers has been played. It is looking good for Algeria, Tunisia and Morocco. They all got good first round away results.Algeria downed Cameroon 1-0, Tunisia defeated Mali 1-0, and Morocco held DR Congo to a 1-1 draw.  It will now take a very determined effort by their respective opponents to overturn the outcome in the second leg. 

Although Egypt defeated Senegal 1-0 at home, Senegal, the current African Champions, is capable of overturning that result in the second game. 

Nigeria played a 0-0 draw with the Black Stars in Ghana. While Nigeria now have a slight edge as they play the second leg, they will be given a good run for their money by the Ghanaians.

How to make Puff Puff snack

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Puff puff

Puff puff is a very popular snack and very easy to make.

What you need to make Puff Puff:

Flour

Yeast

Sugar

Warm water

Salt ( optional)

Pepper/spicing (optional)

Vegetable oil

Frying pan

Cooker.

Quantities of ingredients

3 cups of flour will need ½ cup of sugar, one tablespoon of yeast, half teaspoon of salt and also half teaspoon of spicing.

Procedure.

Put about 3 cups of flour in a bowl. Add sugar, yeast and spicing. Mix the combination with warm water until a thick paste is produced. Cover it with foil paper and you can place it in a warm oven for about 30 minutes. After 30 minutes the mixture should have risen. Put a frying pan on the cooker and let it heat up the oil. With a scoop spoon or your hand, put small lumps of the flour mixture into the frying pan. Let them fry until their colour changes to brown red. There you are, you have just made your own delicious puff puff.