Horizontal System in Tower Based Formwork
The horizontal system is made of secondary and primary beams (in construction jargon: „ligers“ and „unterligers“, respectively).
The horizontal system comes in contact with the cast concrete element and transfers the load to the shoring towers.
The secondary and primary beams that exist in the market are made of wood, steel and aluminum.
The coating is, often, made of plywood or wooden boards. Yet, it can also be made of steel.
When economically assessing an overall system, the horizontal system functions as a significant factor, since it determines the distance between the shoring towers.
The more strength the secondary beams and joists hold (for bending, cutting and sinking), the better and more efficient it will become when using the towers.
It is crucial that the components of the horizontal system will have a low weight, so their assembly will be carried out without any devices for lifting, and that the workers’ manual assembly will require a low work inputs.
A horizontal system made of aluminum and wood is considered as light, especially in comparison to the one made of steel, and can be assembled without any auxiliary devices for lifting.
Advantages of using aluminum components over wood and steel components:
Aluminum is a relatively new material, therefore, its use is not as common as wood and steel. Nevertheless, over the past several years, its use gradually grows due to its distinct advantages, such as: Low weight, a strength-weight ratio that is 3 times higher than that of steel, resistance against corrosion, low maintenance costs, as well as fast and simple assembly of the horizontal system’s components above the towers.
Aluminum or steel primary beams and joists hold a higher bending strength than that of a wooden beam. As a consequence, they are able to bridge over large openings and reduce the required number of towers, along with the additional advantages that arise.
To be on the safe side, be sure to follow the next points:
- High concentrated load above the tower’s post requires a considerable precision of proper load distribution over the bearing surface (either a concrete floor or a tight platform).
- When concentrated loads are being transferred to it by the towers’ posts, check if there is a need for the support of the bearing surface.
- When the tower is higher than 6 m’, bridging the large openings via primary beams and joists becomes a possibility, as it increases the load which the tower’s posts carry. It happens due to diagonal reinforcement that reduces the buckling length of the towers’ posts.