Expansion joint and design

Expansion Joints

An expansion joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials. To absorb vibration, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of sidewalks, bridges, railway tracks, pipeing systems, and other structures.

Expansion joint design:

A design specification shall be prepared for each expansion joint application. Prior to writing the expansion joint design specification it is imperative that the system designer completely review the structural system layout, and other items which may affect the performance of the expansion joint. Particular attention shall be given to the following items.

The system should be reviewed to determine the location and type of expansion joint

which is most suitable for the application. Both the EJMA Standards and most reliable expansion joint manufacturers'' catalogs provide numerous examples to assist the user in this

effort. The availability of supporting structures for anchoring and guiding of the system, and the direction and magnitude of thermal movements to be absorbed must be considered when selecting the type and location of the expansion joint.

Conventional rubber expansion joint

Expansion joints are designed to provide stress relief in piping systems that are loaded by thermal movements and mechanical vibration. To deal with the various forces on the joint they require fibre reinforcement which guarantees both flexibility and strength. Conventional expansion joints are reinforced using prefabricated fibre plies. The use of these fabric plies makes it impossible to control the orientation of the fibres on complex shapes such as the bellow of an expansion joint. In both cases the inability to use the fibres in an optimal way leads to the following disadvantages:

High Material Cost:

v More fibres needed than necessary

v More rubber needed than necessary

v Additional parts such as metal reinforcement rings necessary with multiple bellows Lower Performance

v High rubber wall thickness and fibre pack make product less flexible

v Undesired radial and axial expansion under pressure.

1)  Introduction

2) Necessity

3) Advantages

4) Pre requisites

5) Types of prefabrications

Pre-fabrication means that the structure is disunited in its disunited in its members and these are precast in factor built and equipped particularly this purpose or in temporary plants establish on the site. Then the precast reinforced core members are shipped to the place where they used. Here they are hoisted set into their fix places and assembled in the form of a complete structure. The stages involved are

1)    The structure is divided into no of units.

2)    The different units are precast in permanent plants. Permanent prefabrications - plant prefabrication. Temporary plants (sheds) - Site prefabrication

3)    Transported to the site

4)    Hoisted and put into their places Prefabrications eliminates the use of scaffle.

Necessity:

Million houses in rural areas.

20 million houses in urban areas speedier construction.

Conventinal methods - time consuming

- The components are not a man power is not effectively.

Factors:

1)    Cellular concrete plant at Madras

2)    Hindustan Housing Factory at New

3)    SIPOREX, India Limited at Poona

4)    Key Jay Spirole private limited.

In New Delhi they are manufacturing -sleepers & poles.

Object or AIM :

1)    To accelerate the building construction.

2)    To increase the building activity.

To effectively utilize the man power. Pre-Requisite:

1.     Large demand of flats in a limired area

2.     Availability of adequate funds & buildings materials

3)    Prospective planning of building activities and long time orders.

4)    Standardization allowing mass production

5)    Adequate mechanization of production process.