Grade beam are reinforced concrete members made to act as horizontal ties between footings or pile caps.
Its main function is to transmit the load from a bearing wall to a spaced foundation such as a pile cap or caisson.
These types of beams are commonly used when the bearing capacity of the soil is less than the estimated design load.
Here we learn about Grade beam, advantages & disadvantages of grade beam.
Introduction to Grade beam:
It is a beam made at grade level (earth level) that is mostly used in buildings with piles and to connect pile caps to each other.
This is not the same as wall footing, as the grade beams are designed for bending and typically extends between the pile cap and caisson, while a wall footing bears on the soil and directly transfers the weight of the wall to the foundation soil.
Also, it is not the same as strap footing because grade beams are reinforced to distribute the weight of a wall to different foundations, while using a strap beams are then reinforces the weight of a column between the footings.
It can be used in combination with a spread with moments larger than the lateral load, so as to reduce the size of each spread footing.
Grade Beams Construction Process:
The following steps are involved in the manufacturing process of grade beams as follows:
1. Preparation and excavation should be done for grade beam:
Excavation of trenches is performed for a beam depending on its level.
We can also construct these beams directly on the ground and the ground surface is leveled and framed.
2.We should install a framework for grade beam:
After the preparation and excavation is finished, it is then placed according to the dimensions of the beam.
If we built these beams on the ground, the bottom forms are pre-positioned on its edges.
The reinforcement cage is mounted on a flat soiling brick before we fix the side shuttering.
The framework of construction is similar to a conventional beams, when grade beams are constructed above the ground.
Therefore, we should place the shutter under the grade beams for both sides.
After the beams framework is finalized, designated grade beams dimensions must be supplied which should have adequate reinforcement cover.
3. Then reinforcement of grade beam should be placed:
The details of reinforcement are given in structural shapes such as size and number of longitudinal reinforcement and its required length, number, and stirrup spacing.
The number and size of top, bottom and additional reinforcements, lap length and placement, spacers, hooks, and clear reinforcement covers must be examined.
4. Finally, we pour concrete for the beam:
We can put ready mix concrete or machine-mixed concrete on site.
We can remove the side-shutter of the beam 24 hours after pouring the concrete but we can remove the bottom shutter only after getting solid gain.
Based on the time span of the beam, we can set the time period to remove the bottom shutter.
Advantages of grade beam:
1. Form easily:
These beams are manufactured in any shape and size, so grade beams are flexible in nature.
2. Excellent support for both concrete and soil:
These beams have the ability to support both soil and concrete before inserting.
3. Easy Access:
They can easily allow entry of other materials such as rebar’s, conduit, pipes or dowels.
4. Less digging required:
Its installation requires less excavation work which saves time and money.
5. Saves time and money:
Its construction required less time and low labor cost hence saving both time and money.
Disadvantages of grade beam:
1. Grade beam foundations do not work with the basement
2. Grade beam foundations require a level construction site.
Grade beams may be made either directly on the soil or above the soil spread between the piles.
In the case, when the foundation needs to be limited to the depth in the soil, a grade beam would be the right choice.