What Is Slip Formwork?
Formwork is a temporary moulid that is used for the pouring of concrete. The Traditional formwork is made from timber, steel, glass fiber, and some other types of materials.
Slip Formwork is a special type of formwork and it is one of the advanced techniques which is carried out rapid construction of megastructures such as the construction of chimneys, towers, silos, road construction as well as Bridge construction.
The word ‘Slip formwork’ itself indicates the meaning that it is formwork that moves from its position for the construction of the structures.
Slip Form is an advanced construction Technique in which the formwork continuously rises in the vertical direction for the construction process.
Slip Formwork used for the vertical construction of the RCC structures. The Slip Formwork is an economical method that required very less labor because all the process in this technique mostly runs automatically.
Slip Forming is an economical, fast, and accurate form of construction Technique that is used for the construction of various types of high-rise structures.
History of Slip Formwork
The Slip Formwork Technique was discovered in the year 1910 by America for the construction of elevators, cooling towers chimneys, etc. The Slip formwork was firstly used in the construction of the Skylon tower near Niagara Falls, Ontario in the year 1965.
The Sheraton Waikiki Hotel in Hawaii was also constructed from the Slip formwork Technique in the year 1969. The United States of Kingdom adopted the technique of the slip formwork for the construction of roadways, curbs, and bridges, etc.
The Slip Formwork Technique also used for the construction of the paving of airports and runways.
Components of Slip Formwork
Various parts of the slip formwork are as follows
- Slip Form Ribs
- Working platform or Deck
- Suspended scaffolding
- Lifting jacks
The Yokes in the slip forms are used to attach and support wales at regular intervals with the legs. The Yokes are capable of transmitting the lifting forces from the jacks that are used during the removal of the formwork.
It also plays the function of resisting the lateral force of the plastic concrete within the formwork. The Lifting jacks are mounted on the jack rods that are used to lift the slip form.
Types of Slip Form System
The Slip form system is categorized into different types that are as follows
1. Cantilever Jump Form Method
In the cantilever jump Form method, the work of the lifting devices to lift and expand the formwork is done with the help of the electric motors.
This method minimizes the use of the cranes as it is attached to the large area of the formwork concerning the story height.
2. Vertical Slip Form System
In the vertical slip form system, the concrete form is surrounded by the platform which is used by the workers to stand and work safely. The concrete form and working platform are raised with the help of hydraulic jacks.
There are different types of hydraulic lifters are available that are used to efficiently lift the formwork for the whole horizontal projection.
3. Egg Shape Slip Form Method
The egg shape slip form method is based on the principle of the jump form that can be adapted to any geometric shape.
In this method the circumference gets changes and the cantilever plate on the periphery is removed or get extended. The adjustment of the curvature can be done in this method by just simply adjusting the circumferential slope and the axis.
4. Horizontal Slip Forming
In case of the horizontal slip forming for the construction of the pavement and traffic separation walls are laid down. The vibration and proper compaction are done and then the slip slowly moves ahead. This method is mostly used and suitable for the construction of Highways.
5. Conical Slip Formwork Method
The conical formwork system consists of the formwork having conical shapes that are made from the cantilever plates as well as the overlapping plates. These plates are attached through the steel yoke frames.
The Cantilever and the overlapping plates have the mechanism of automatic adjustment of the geometry. It is one of the special types of the slip formwork method which is used for the construction of the varying thickness walls.
Slip Form Technique
- In the Slip Formwork Technique, the slip forms raised and lifted in the upward direction at a rate of about 300 mm per hour.
- It supports itself on the core and does not require any kind of external support.
- The Slip Formwork mainly consists of three platforms is Top, middle, and bottom.
- The Topmost part of the slip formwork acts as a storage and distribution area, the middle platform of the slip formwork is located at the top of the area from which the concrete is poured.
- The Bottom platform of the slip form is used for the finishing work of the structure.
- It provides an Integrated scaffolding platform which consists of horizontal work platforms that provide safe working space to the workers as well as engineers and supervisors.
Slip Form Construction
- The Slip Formwork construction Technique is carried out for the construction of structures having a height of more than 16m.
- The slip form consists of the wall-shaped form which is approximately 1m to 2m high at the base of the structure.
- The slip formwork has a belt of forms in which the one for each surface. The slip forms rest on the internal as well as external surfaces of the walls.
- The Slip form construction helps to achieve the rate of construction of about 2m to 7.2m per day which is not possible with the help of the traditional method of formwork.
Advantages of Slip Form Construction
There are various benefits of Slip Form construction that are as follows
- The Slip form construction is the economical method for the construction of high-rise structures.
- It requires less labor for its construction which ultimately saves the labor costs.
- Better finished surface achieved and does not require plastering.
- The Slip Formwork does not require a crane to move it in the upward direction.
- Slip formwork helps to achieve high production rates.
- It provides more safety to the workers and proper working space so that the labor can work efficiently.
Disadvantages of Slip Form Construction
There are also some disadvantages of slip formwork that are as follows
- It takes a little more time for the arrangement of the various components.
- For the operation of the slip formwork, Expert supervision is needed.
- The stocking of the materials on the construction site is difficult.
- The Slip form requires more initial investment as compared to the traditional formwork.
- The operation must be continued under any weather conditions.
- The labors were required to train for a certain period with the advanced equipment and types of machinery before executing the work.
- Good coordination is required among the site organization for the rapid construction.
- There will be more flexibility in the construction of the tapering structures
- The slip formwork allows the high speed of erection due to which there is faster completion of the construction project.
- The uniformity of the wall sections and the smooth, even surface can be achieved.
- It allows construction companies to increase the rate of construction and also work productivity and complete the project within the stipulated time.
Applications of Slip form construction
Slip form is used for the construction of various types of structures that are as follows.
- Construction of chimneys
- Construction of silos
- Construction of shaft linings and surge shafts.
- Construction of the long-span bridges.
- It is also used in the construction of the lifts and stair shafts
- The slip forms are also used in the construction of the roads.
Safety Features of Slip form Construction
The Safety features of the slip formwork are as follows
- The working platforms, ladders, guard rails, and windshields should be built into the completed system.
- The complete assembly of the slip formwork should be strong and should sustain the load of the persons working on it.
- There should be lateral support of forms provided.
- The care should be taken that all parts of the formwork should be move at a uniform rate.
- It is necessary to check and ensure that whether there is any jam in the jack.
- The site engineers should have knowledge and skills in the health and safety management of these job sites.
Economical Consideration of Slip form Construction
Here are some of the points that should be considered for the economic construction of the structures.
- The slip formwork is only economical for the construction of structures having a height of more than 16m.
- The thickness of the wall that is constructed should be of minimum 15 cm.
- The slip form system is only suitable for the construction of the structures such as cooling towers, chimneys, piers and tall buildings, etc.
Conclusion of Slip form Construction
The slip Form construction method is one of the innovative methods that is used for the construction of megastructures and it also helps to improve the productivity of the work as well as saves time required for the construction.
It helps the construction businesses to deliver quality construction within the stipulated time of the project. This method ensures the quality control and homogeneity of the structure.
The slip-form method ensures quality construction, economical construction, and speedier construction.