About the RCC 51 Column Load Take Down Spreadsheet to BS 8110

Rcc 51 screenshot

In reinforced concrete pad footing design, one of the major questions asked is how to calculate the axial load and moments acting on the foundation columns.

Doing these calculations by hand can be tedious and time consuming.

You can use RCC 51, a spreadsheet program  that calculates the load from the structure that is acting on the pad footing.

It is known as column load take down. Recall that columns carry loads transferred from the slab and beams down to the pad footing foundation. RCC 51 will help you calculate the load acting on a particular pad footing as well as moments. It can also check if the column parameters you entered will lead to a short or slender column.

RCC51 designs to BS 8110 1997.

You can download RCC51 from RCC spreadsheets PAGE.

Or click the link below

https://docs.google.com/spreadsheets/d/1o4NtAAbw54RyciBhQkcO1UAPpGK_xY8A/edit?usp=drivesdk&ouid=106276104383891115503&rtpof=true&sd=true

Frame Structure Analysis ( reinforced concrete design) RCC 21.

RCC subframe analysis is a structural analysis program created with Microsoft Excel. It is used for structural analysis and design moments and shear forces of reinforced concrete framed structures. It is very effective for the calculations of design moments of columns and beams. 

It can handle up to six spans and seven supports. It gives you design beam moments as well as column moments above and below the beams.

It also considers the main 3 load cases so the design moments calculated are actually of the worst case.

Once you know what you are to fill in the input boxes ( blue texted ) you will certainly get the correct moments and shear forces values.

It is very easy to understand once you know how the structure you are designing is framed. For better understanding on how to use this software I will refer you to framed structural analysis examples in the book titled Reinforced Concrete Design by Mosley & Bungey 5th edition. Check out the worked examples on pages 30-32 & 33 – 39.

If you are a student, this software will greatly help you in your knowledge of structural analysis. It will greatly aid your what if scenarios. 

If you are a professional and you don’t have the money to purchase analysis and design software this is a great free alternative.

To download the software visit THIS PAGE

then scroll down till you see RCC 21 Subframe Analysis.xls and download.

Cement plaster/render; how its done

Cement and sand are mixed in the dry state in the adopted ratio. For plastering of walls, a cement sand ratio 1: 6 is adequate.

Water is added to achieve a workable plasticity.

Cement plaster can be applied in 2 coats or as a single coat. Plaster thickness for walls ranges from between 12mm to 20mm. Plaster thickness of between 12 and 15mm can be applied as a single coat while thickness above 15mm are applied in 2 coats.

Cement Plastering in a single coat:

Cement plaster ( single coat)

The plaster is first applied roughly at the required thickness on the wall. Wait for about 20 minutes, (After the plaster starts to set), and gradually smooth it out with a straight long rod or plank. The plastering is then finished off with a hand trowel and finally foaming. The finished work should be straight and smooth.

Cement plastering in 2 coats

Cement plaster ( double coat)

This method is necessary when the plaster thickness is above 15mm. The first coat is applied roughly on the surface of the wall. The surface of the plaster is then made zigzag to receive the second coat. The second coat can be applied when the first coat sets ( about 30mins upwards). However it should be applied by the second day at the latest.

What to Plaster a Wall? See what you will need

Plastering a wall means you want to give the wall a smooth and level finish with the use of a cementitious compound. Plaster is a protective or decorative coating for walls and ceiling.If a wall is constructed of sandcrete blocks then chances are high that it will be plastered to give a very smooth aesthetic finish.

Difference between plastering and rendering

“plaster” usually means a material used for the interiors of buildings, while “render” commonly refers to applications on external walls.

Types of plaster

Gypsum Plastering
  • Gypsum plaster: Also called plaster of Paris, it is calcium sulphate hemihydrate a white cementing material composed of gypsum, retarded and hardeners. It is applied to the wall in a plastic state. It thereafter hardens by the chemical combination of the gypsum and water. Gypsum plaster are usually supplied in bags.
Gypsum plaster bag
  • Cement plaster: This is a mixture of portland cement and sand. It is applied in the plastic state after mixing with water. It thereafter hardens after the chemical combination of the cement and water. Ready mix cement plaster is supplied in bags.
Ready mix cement plaster

Cement plaster

This is the most commonly used plaster material because it is cheaper and more versatile than the gypsum plaster.

Ready mix cement plaster is available but expensive. It is more economical to mix on site, cement, sand and water and use it to plaster / design walls.

Materials needed for cement plaster

  1. Cement: usually supplied in 50kg bags.
  2. Plaster sand. A type of fine sand that bonds very well with cement in the presence of water.
  3. Clean water of drinking quality.

Mixing of cement and sand for plaster works

Thorough mixing of cement and sand is first done in the dry state. After that water is added and mixed to a workable plastic state before application. For plastering works, the cement sand ratio is usually 1:4 or 1:6. Ratio 1:6 being the more commonly adopted ratio.

To calculate the amount of cement and sand need for wall plastering, read the article below by clicking on the link.

How to calculate the number of cement bags and quantity of sand required for plastering

Types of Retaining Walls

Retaining walls are structures designed to retain earth and hydrostatic loadings. Retaining walls should be capable of holding retained material in place without undue movement of overturning, sliding or deflection.

Types of Retaining Wall.

There are three major types namely;

  1. Gravity
  2. Counterfort
  3. Cantilever 

Gravity retaining wall

Gravity Retaining wall

These types are usually constructed of mass concrete. Reinforcement is only included in the faces to limit thermal and shrinkage cracking. Gravity retaining wall relay on its self weight to hold retained material in place.

Cantilever retaining walls

Cantilever retaining wall

These walls reinforced concrete retaining walls economically designed. They have a very large base and rely heavily on the backfilling of their base for strength.

Counterfort Retaining Walls

Counterfort retaining wall

Counterfort retaining walls are cantilever retaining walls supported by a type of bracings called counterforts. counterforts become necessary when the design of cantilever retaining wall becomes uneconomical or when the overall height of the wall is too high.

To design retaining walls you will have to consult specialized textbooks and the relevant code of practice.

How to Calculate the amount of Cement , Sand and Coarse Aggregates required for construction of Reinforced Concrete Slab

Concrete slab

In this article we will determine how much of cement , sand and coarse aggregates will be required to construct a slab of length;10m, width; 5m and thickness 0.15m(150mm)

 Reinforced concrete is in the ratio 1:2:4.

Meaning one part of cement to two parts of fine aggregates to four parts of coarse aggregates.

Volume of the slab is length x breadth x thickness.

I.e 10 x 5 x 0.15= 7.5m³.

Dividing this volume in ratio 1: 2: 4

Volume of cement is;

(1/7)x 7.5=1.07m³

The density of cement is 1500kg/m³

 density= mass/ volume

Therefore mass of cement ;

1500x 1.07= 1605kg

A bag of cement weights 50kg so dividing 1650/50= 33 bags.

Mass of sand;

Volume of sand is( 2/7 )x 7.5= 2.14m³

Density of sand is 1700kg/m³

Therefore mass of sand = density x  volume;

1700 x 2.14= 3638kg

Mass of coarse aggregates;

Volume of coarse aggregates is (4/7)× 7.5= 4.29m³

Density of coarse aggregates is 1650kg/m³

Therefore mass of coarse aggregates,

1650 x 4.29= 7078.5 kg