Civil Engineering

PAD FOOTING/FOUNDATION DESIGN WITH EXCEL.

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PAD FOOTING/FOUNDATION DESIGN WITH EXCEL is a free excel program you can use to design pad footings to BS8110. It is named RCC81. It is a free excel program developed by the reinforced concrete council UK.

Pad footing/foundation design with excel
Pad footing/foundation design with excel

For us Civil/ Structural engineers, manual design can become very tasking and time consuming. However, structural analysis and design software have made the task easier but most are expensive. This one is FREE.

How to use RCC 81; Pad footing/foundation design with excel.

The excel program is very easy to understand and use. You enter data in blue cells. Part of data required include; strength of concrete and steel, bearing pressure of soil, factors of safety, proposed dimensions of pad footing and column dimensions, calculated axial loads and moments acting on the pad footing.

The program will check if pad footing dimensions chosen are suitable or not. It will even suggest pad footing dimensions that can work. You will also be able to view design status. If your design fails, it will state the reason why, so you will know which input value to adjust. When design status is valid, the program will calculate reinforcement required for the foundation footing.

You can watch video on how the program works click HERE

To download pad footing/ foundation design with excel (RCC 81), click HERE.

Basic Structural Elements of Building

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The basic structural elements of buildings will be discussed under five subheadings including; slab, beam, column, wall and roof.

Slab.

Slab is the large flat horizontal element of a building. (Pavement) and usually spans between beams or walls. Slabs can be made of wood, concrete, or interlocking blocks or bricks, although slabs made of concrete are the most common. In storey buildings, slabs are usually supported on beams or columns.

Beam.

Beams are horizontal load bearing members. In its basic form, the main function of a beam is to transfer slab and wall loads to the columns. Depending on the type of building in terms of strength and materials, beams can be made of wood, concrete, reinforced concrete or steel.

Column.

Columns are the vertical load bearing members of a building and their main function is to transmit beam, slab, wall, roof, as well as live loads safely down to the foundation of the building. Depending on strength requirements and specifications, columns can be made of wood, reinforced concrete or steel.

Wall.

Walls are usually vertical members and can be built of wood, bricks, blocks or concrete. Walls within a building would be constructed to have openings for doors and windows where appropriate. Walls can be load or non load bearing. A simple example of a load bearing wall is a situation where the wall directly supports the roof of a building.

Roof.

Roof is the upper covering of a Building. Its main function is to protect the building from rain and heat from the sun. Roofs can either be flat or pitched.

Uses of Stones in Building/Civil Engineering Construction

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Stones are naturally available building materials that have been used since early civilization. Type of stones used in civil/ building construction works are igneous, sedimentary or metamorphic in origin. Stones required for building/civil engineering construction must be strong, durable, hard, tough,  and cost effective.

Uses of stones in building/civil engineering construction

  • For construction of foundations, walls, columns and arches
  • For flooring and damp proof courses
  • Facework of buildings, paving of roads and base courses
  • Abutment and bridges, dams and retaining walls
  • Common building stones

The following are some commonly used building stones

Basalt:

An igneous rock. Colour varies from dark grey to black. Used in road construction and as aggregates for making concrete.

Granite:

An igneous rock. Crystalline in structure. Particles sizes ranges from fine to coarse grained. They are used for dams, river walls and bridge piers. Also used as coarse aggregates in concrete.

Sandstone:

Sand-stones are stratified rocks consisting of quartz and feldspar. They come in many colours including white, grey, red, yellow, brown and dark grey. Sandstone is not as strong as granite and balsalt. They are used for masonry work, dams, bridge piers and river walls.

Slates:

Slates are metamorphic rocks composed of quarz, mica and clay. Their colour varies from dark grey to black. They are used for roofing tiles, pavements etc.

Laterite:

This is also a type of metamorphic rock with porous structure. Its colour varies, i.e. brown, red, yellow, grey etc.  laterite is commonly used as filling material.

Marble.

Another type of metamorphic rock. Marble is available in different colours such as pink and white. Used for facing and ornamental works.

Cement, The Popular Binding Material in Building Construction.

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Cement is produced by burning a mixture of calcium and clay material at very high temperature then grinded to produce fine powder.

Types of cement.

Cement comes in many varieties. Some are briefly explained below.

Ordinary portland cement;

The most used type of cement in general concrete construction. It is suitable when there is no danger of exposure to sulphates in the soil.

Quick setting cement;

Quick setting cement is produced by reducing the percentage of gypsum and adding a small amount of aluminium sulphate during production. This type of cement starts setting around 5 minutes and hardens within 30 minutes. Quick  setting cement is used to produce concrete for underwater construction.

White cement;

it is made from oxides of manganese,iron and chlorium. It is used for plastering, ornamental works, fixing of marbles and tiles.

Rapid hardening cement;

This type of cement gains strength earlier than ordinary Portland cement and consequently speeds up construction activity.

Coloured cement;

Coloured cement is produced by mixing pigments with ordinary Portland cement. Pigments such as colbalt produces blue colour, iron oxide produces brown, red or yellow colours.

Low heat cement;

When heat produced by hydration of cement does not get easily dispersed, it may give rise to cracks, hence in such situations it is preferable to use low heat cement.

High alumina cement;

This type of cement is produced from a mixture of lime and banxite. It is resistant to sulphate and acid attack.it is used in underwater construction.

Acid resistant cement;

This is cement made by adding acid resistant materials such as quartz, quartzite, sodium silicate or soluble glass. Acid resistant cement is commonly used in construction of chemical factories.

Common Problems of Fresh Concrete

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Common problems of fresh concrete will be discussed under 4 modes which are: inadequate workability, segregation, bleeding and harshness.

Inadequate workability:

Workability is the ease at which concrete can be placed and compacted. When inadequate, it leads to segregation and bleeding. Workability depends on quantity of water, shape of aggregates and their percentage in concrete.

Segregation:

This is the separation of coarse particles in green (fresh) concrete. It happens due to insufficient finer particles. Segregation can also be caused by throwing concrete from great heights at time of placing. Segregation causes loss of cohesiveness in concrete which results in honey combing and loss of strength.

Bleeding:

The appearance of water with cement particles on surface of freshly laid concrete. Caused by excessive quantity of water in the mix or too much compaction. Bleeding causes pores to form on concrete and renders it weak.

Harshness:

Fresh concrete is said to be harsh when it becomes difficult to obtain a smooth surface finish. It is caused by insufficient quantity of fine aggregates or insufficient quantity of water.

Plain Concrete

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Plain concrete is known as concrete without steel reinforcement. It is an intimate mixture of cement, fine aggregates, coarse aggregates and water. It can be easily molded to desired shape and size before it hardens. Plain concrete is strong in compression but weak in tension.

Major ingredients of plain concrete are;

  • Binding materials such as cement, lime, polymer.
  • Fine aggregate material such as sand.
  • Coarse aggregate materials like crushed stone, gravel, and granite.
  • Clean water.

Common cement, sand and coarse aggregate ratios are;

1:1:2, 1:2:4, 1:3:6, 1:4:8

Constituents of plain concrete.

Cement:

Cement is the binding material. It binds and hardens when water is added. Generally a concrete mix with more cement gives more strength.

Coarse aggregate:

Coarse aggregates consists of crushed stones of igneous origin. They should be clean, hard, angular and sharp. They give mass to the concrete and prevent shrinkage of cement.

Fine aggregates:

River sand is the common fine aggregate for plain concrete. Its gives mass to concrete and fills voids created by coarse aggregates.it adds density to concrete. A denser concrete is higher in strength.

Water:

Water used for making concrete should be clean. It hydrates the cement to form a plastic mass which hardens gradually. Water makes it possible to mix the concrete with ease and place it in final position. The more water the better, however, excess water reduces the strength of concrete. A water – cement ratio of 0.5-0.6 is used to achieve desired concrete strength when hand mixed.

Preparing and placing of concrete.

Batching:

Batching by volume or weight are the 2 common methods of measurement.

Mixing: 

Thorough mixing to produce good quality concrete. Cement, sand and coarse aggregates is mixed in dry condition, then in wet condition after adding water. Hand and machine mixing are 2 common methods of mixing of concrete mixing

Transport and placing:

Fresh concrete is transported on site using head pans, wheel barrow on small scale work while concreting chutes, bell conveyors or pumps are used in large scale construction.

Compaction:

Compaction of concrete is necessary to remove entrapped air during placement of concrete. Compaction can be carried out by hand or with help of  concrete vibrators