What is FormWork in construction?

Formwork is the mould to shape the concrete structure. Good concrete cannot be made from a poor mould; thus formwork is very important in producing good concrete. Besides that, it has to be designed to take the concrete load and the working load generated from workers and plant.

Column Forwork and support

Timber and plywood were generally used Materials in the site for in-situ concrete work. Columns Beams slabs lift walls and staircases were all constructed using Timber and plywood formwork. Steel casing formwork was used for few structures such as round columns.

The following factors were considered when doing form work;

•   Correct position
•   Line and level
•   Accuracy within permitted tolerances
•   Shape of members
•   Verticality (plumb)
•   Correct angles for batters etc.
•   Finishing heights (mark off)
•   Formwork joints flush and tight
•   No nails protruding into the concrete
•   Formwork joints sealed as required
•   Construction joints strutted and supported

All the above formwork was supported with the following false work and other materials   

• GI pipes, concrete & wire nails
• Form ties (to tie the separates and GI pipes)
• Separates (thread bar & P cone)
• Pipe supports and “T”,”U” jacks
• adjustable steel props, mould oil (diesel & grease)

Example Form work Cross section of a Column

Example Form work Cross section of a Column

  What are the accessories/tools used in Formwork

Column and Beam system in construction

This article gives a brief introduction about the column and Beam system of a typical building or structure.

Introduction

The System of Columns and Beams have been used in Construction since Ancient Egypt (Which lasted from about 3100BC until it was finally absorbed in to the Roman Empire in 30 BC) Ancient Greece and Ancient Rome. In modern day construction, Column-Beam-Slab System is been used in all superstructures with new technology, and construction materials. Generally the load of the slab is transferred to the columns or walls through the beams, down to the foundation, and then to the supporting soil beneath.

Column

Columns (Image Source Wikipedia)

Columns (Image Source Wikipedia)

A column can be defined as a vertical structural member designed to transmit a compressive load. A Column transmits the load from ceiling/roof slab and beam, including its own weight to the foundation. Hence it should be realized that the failure of a column results in the collapse of the entire structure. The design of a column should therefore receive importance.

In the modern construction industry, Columns are mostly constructed by concrete; apart from that materials such as Wood, Steel, Fibre-reinforced polymer, Cellular PVC, and Aluminium too are been used. The type of material is been decided on the scale, coast and application of the construction.

Types of Columns

Columns can be classified bases on its Shape, Slenderness ratio, type of loading and Pattern of lateral reinforcement.

Classification based on Slenderness ratio

Long Column or Slender [The length is greater than the critical buckling length and it fails by buckling.]

• Short Column [The length is less than the critical buckling length and it fails by shearing.]
• Intermediate Column

Based on shape

•  Rectangle
• Square
• Circular
• Polygon

Based on type of loading

• Axially loaded column
• Axial load and un-axial bending column
• Axial load and biaxial bending column

Based on pattern of lateral reinforcement

• Tied columns
• Spiral columns

RCC Columns (Reinforced Concrete Columns)

A reinforced concrete column can be defined as a structural member with a steel frame (reinforcement bars) composed of concrete that is been designed to carry compressive loads.


Figure Shows the Reinforcement of a Column with cross-section 500x500.

Reinforecement of Column sections

Beams

A beam is a structural member which spans horizontally between supports and carries loads which act at right angles to the length of the beam. They are small in cross-section compared with their span. The width and depth of a typical beam are "small" compared with its span. Typically, the width and depth are less than span/10.

Generally a beam is subjected to two sets of external forces and two types of internal forces. The external loads are the loads applied to the beam and reactions to the loads from the supports. The two types of internal force are bending moments and shear forces. The internal shear force and the internal bending moment can be represented as pairs of forces. The Figure below shows a Typical Beam with Internal and external forces acting on it.

Beam With Internal and external forces 

There are several types of beams

• Simply supported Beam
• Fixed Beam
• Cantilever Beam
• Continuous Beam
• Overhanging Beam

Written By : Nilantha Perrera