A load bearing wall can be defined as the structural component that resists the weight of all the structural elements resting on it by transferring the weight to the foundation below.
In other words, a load-bearing wall can be defined as the wall that is constructed to provide support to the slab above it and also other vertical loads. It is regarded as the active structural element of the building.
It has been used since ancient times and is one of the earliest forms of civil engineering constructions.
The earliest known example of the load-bearing wall is the Notre Dame Cathedral with the flying buttresses.
The primary objective of the load-bearing wall is to provide the separation between the internal spaces of the structure and to transfer the loads from the structural elements to the foundation below.
2. Features of Load Bearing Wall
The important features of a load bearing wall can be listed as follows:
1. It carries the weight of the entire structure particularly the building weight from the roof and the floors.
2. It transfers the imposed load down to the foundation or other appropriate frame members.
3. It provides support to the structural members of the building such as beams, slabs, and other walls.
4. It is capable of carrying its weight.
5. The consecutive load-bearing walls are laid one over another on each floor.
6. It can be constructed as both interior wall and exterior wall.
7. It is constructed perpendicular to the floor ridge or the joists.
3. Types of Load Bearing Wall
The different types of load bearing walls can be listed as follows:
a. Pre-Cast Concrete Wall
It is the type of load bearing wall that is mostly constructed by casting concrete in a reusable wall mold or form which is then cured in a controlled environment, transported to the construction site, lifted, and placed in position.
The primary objective of constructing such precast walls is to accelerate the speed of the construction.
The precast wall must be capable of opposing the parallel loads bestowed on it due to the self-weight, wind loads, and earthquake loads.
Before the construction, the plan and the specifications must be prepared and thoroughly analyzed. This is done so that during the erection of the precast walls, no undesirable burdens are enforced on the wall.
The undesirable loads can greatly affect the transportation and the lifting of the precast walls and thus it must be analyzed during the design phase itself.
The joints between the pre-cast concrete walls must be wide enough to withstand the expansion due to high temperature and seasonal variations.
i. Features of Pre-Cast Concrete Wall
Some of the distinct features of the precast concrete walls are as follows:
1. Thermal Resistance:
The precast concrete wall offers significant resistance to thermal changes.
This is usually achieved due to the protection that is set in the depression or inside the reinforcement divider, which is a metal stud divider.
2. Moisture Protection:
The moisture protection is obtained using sealants particularly the pigmented sealants.
3. Fire Safety:
The pre-cast concrete wall has very high fire-resistant properties. This is because these walls are mostly manufactured using concrete with good fire resisting characteristics.
The precast concrete wall offers good insulation to sound.
For preventing the transmission of sound from the outside to the inside of the building, a precast wall with a veneer is constructed.
Like the concrete, the pre-cast concrete wall is also durable.
The durability of the precast wall is dependent on the type of connections made with the structural member.
The precast concrete wall does not require any maintenance.
However, the connection, sealants, anchorages, and accessories used in the precast wall need regular maintenance.
ii. Advantages of Pre-Cast Concrete Wall
Some of the advantages of the Pre-Cast concrete wall can be listed as follows:
a. It offers the benefit of acting as thermal storage thereby reducing the peak thermal loads.
b. The construction of such a wall helps to minimize the time and cost by eliminating the need for separate stud framing and drywall costs.
c. The precast concrete wall can be used as a load-bearing structure.
d. The precast concrete wall can be reused for future building expansions if designed accordingly.
e. This wall offers a high degree of durability even in extreme weather conditions.
f. The precast concrete wall permits great flexibility in terms of finishing. The finishing can be achieved through the use of various aggregates, cement, pigments, and finishing techniques.
g. The precast concrete wall can be produced in several designs with different textures such as linear shapes, artwork, lettering, etc.
h. The precast concrete wall can also be provided with the electrical boxes.
b. Retaining Wall
The retaining wall is the load bearing wall that is specially designed and constructed to resist the lateral pressure of the overburdened soil i.e. to hold back the soil.
The lateral pressure may be exerted by the earthen fills, liquid pressure, sand, and other similar materials.
Every retaining wall should be capable of supporting a wedge of the soil. The wedge of soil can be calculated after the soil friction angle is known or computed.
As the setback of the wall increases, the size of the sliding wedge is reduced.
This reduction lowers the pressure on the retaining wall.
i. Types of Retaining Wall
The major types of the retaining wall are as follows:
1. Gravity Retaining Wall:
It is the retaining wall that depends upon self-weight to withstand the lateral earth pressure.
The gravity retaining wall is constructed as a huge structure. This is because such a wall requires a considerable gravity load to counteract the exerted pressure.
During the design of such a retaining wall; sliding, bearing forces as well as overturning must be given due consideration.
Various materials such as stone, concrete, masonry blocks, etc can be used for the construction of this wall.
The gravity retaining wall can be further classified into the gabion wall, crib retaining wall, and bin retaining wall.
a. Crib Retaining Wall:
It is constructed by interlocking individual boxes made from timber or pre-cast concrete and duly filling the boxes with materials such as the crushed stones or other similar materials. This is done to facilitate the drainage.
The crib retaining wall may be the reinforced precast or the timber retaining wall. It is only desirable for plane areas but not for sloped areas.
b. Gabion Retaining Wall:
It is constructed using multi-celled rectangular wire mesh boxes or similar materials.
It is used as the erosion control structure as well as for the stabilization of the steep slopes.
c. Bin Retaining Wall
It is a gravity retaining wall in which an earth mass inside the bins acts as a gravity wall with the steel members holding the earth mass intact.
2. Cantilever Retaining Wall
It is constructed using the reinforced concrete, precast concrete, or pre-stress concrete.
The cantilever retaining wall is essentially composed of stem and base slab.
It is the type of retaining wall that is most commonly used.
The cantilever wall can be constructed even with less quantity of concrete in comparison to the gravity wall. However, the cantilever retaining wall is useful and economical up to a height of 10m.
3. Counter-Fort Retaining Wall
The counter-fort retaining wall is also commonly referred to as the buttressed retaining wall.
It is similar to the cantilever retaining wall but is further strengthened with counter forts.
Usually, the height of the counter-fort retaining wall varies from 8-12m.
The counter-fort spacing is kept equal or slightly higher than half of the total height of the counter-fort.
4. Anchored Retaining Wall
The anchored retaining wall is desirable when limited space is available for the construction and loose soil is present over rocks.
As the name itself implies, the anchored retaining wall is provided with anchors or tiebacks to withstand the overturning and sliding pressure.
5. Piled Retaining Wall
Piled retaining wall is constructed by driving reinforced concrete piles adjacent to each other.
Usually, the piles are driven into the soil to a depth such that the overturning forces can be counteracted.
Piled retaining wall is suitable for both temporary and permanent works.
Sheet pile walls can also be used for height up to 6m.
6. Mechanically Stabilized Earth Retaining Wall
It is one of the most economical and commonly used types of retaining wall.
This type of wall is supported using granular materials and held together using reinforcements.
ii. Uses of Retaining Wall
a. Soil Erosion Control & Protection:
A retaining wall is used as an erosion control structure to prevent soil erosion.
It prevents the washing away of soil during heavy rainfall.
A retaining wall is also used for the stabilization of soil.
Retaining wall is sometimes used for the architectural purpose as they can be used to hold back earth thus creating an aesthetically pleasing landscape.
c. Masonry Wall
This wall is used both for architectural purposes as well as for strengthening the structure.
It is also used for thermal control and fire safety.
However, the lateral stiffness offered by the masonry wall is low.
The masonry wall can be further classified into the following types:
a. Load bearing masonry wall
b. Reinforced masonry wall
c. Hollow masonry wall
d. Composite masonry wall
d. Engineering Brick Wall
The engineering brick wall is used when it is required to enhance the structural performance of the buildings.
This wall is also used to improve the aesthetic appearance of the building.
e. Stone Wall
The stone wall is the type of load-bearing wall that is mostly used for enclosing a certain area.
f. Pre Panelized Load Bearing Metal Stud Wall
The pre-panelized load-bearing metal stud wall is used for building the exterior wall claddings.
This wall is capable of resisting gravity loads, seismic loads as well as wind loads.
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