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

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

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 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.

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

The RCC 71 is an excel software developed by the Reinforced concrete council for the design of staircase. It designs to BS 8110: 1997. It can be used to design stairs, flight and landing.Upon starting the program you might see a macros warning. Enable macros if possible.

All blue text data are editable. Data which you will be required to enter include, dimensions of the staircase, concrete parameters and loading.

You do not need to do any previous major calculation before using RCC 71.

In the Flight tab of RCC 71, there are 4 input sections. They are the;

Project Name Title 

Materials

Dimensions

and Loading sections.

In the Project title section you can input the name of the project and so on

In the materials  section you can enter parameters such as strength of concrete, strength of steel, diameter of reinforcement and so on

The dimension section is where you enter the staircase dimensions such as length of thread, riser, thickness of waist..etc. 

In the loading section, you input the imposed loading and any other additional dead loads.

The design is longitudinal so the main bars are along the length of the stairs.

The software is a free to use version. A public release version.

To download RCC 71 and other structural design excel programs 

CLICK HERE 

What is bamboo scaffolding? 

Bamboo scaffolding is simply scaffolding using bamboo stems. It is a cheaper alternative to the conventional scaffolding that uses hollow steel columns and struts.

How is bamboo scaffolding constructed?

The bamboo stems are connected together using big five inches long nails and binding wire. The column bamboo stems must be braced. The column stems are usually spaced 1.5m apart..For added strength and rigidity, bamboo struts that support the platform on which workmen will stand are bored into the wall.

 How reusable is bamboo scaffolding?

Bamboo is still reusable a few times. You can also dismantle bamboo scaffolding and erect in another section of the building if you don’t have enough scaffolding to go round the whole building.

How much bamboo stems is need for a typical building?

The number of bamboo stems a building will need depends on the perimeter of the building and its height. A typical story building that is about 6m high will need about 120 bamboo stems to construct scaffolding for it at once.

How to construct bamboo scaffolding based on its properties.

Bamboo stems are very strong in compression and rigidity. Bamboo stems good for scaffolding should be at least 6cm and above.Use bamboo stems with higher diameter for struts, beams and bracings.