It is mandatory for any building to have the necessary support and stability to withstand loads, without causing any damage to the structure. If the structure requires additional support to carry the loads, providing permanent support or reinforcement can be costly. That’s where the box crib plays a crucial role. The strategic installation of box cribbing can provide temporary support to the structure at an economical cost and is versatile for different purposes. This blog explores box cribs and its versatility in various applications.
What is a Box Crib?
Box crib or cribbing in construction refers to the process of providing a temporary wooden structure that is specially designed to support structures. It helps withstand heavy loads and uniform distribution of loads. It prevents a structure from shifting, tilting or collapsing during construction and enhances its durability.
Components of a Box Crib
Cribbing Blocks
Wooden cribbling that is made of timber, oak, hardwood or engineered wood is the primary component of a box crib. These cribs are boxy in shape with the number of members in each layer varying from 4×4, 6×6, or 8×8 based on the load-bearing requirements. These blocks are stacked in a crossing pattern to form a stable structure.
Wedges
Cribbing wedges are used to adjust the height of the box crib, and level the surface to provide adequate support to the load-bearing structure.
Interlocks
Interlocks are the pattern in which the blocks are arranged in each layer, to increase the stability and load distribution. There are two common types of interlocking patterns in box cribs— straight crib (linear pattern), and angled crib (45-degree angle).
Shims
It is a thin piece of wood, metal, or plastic that is typically placed between the layers of blocks to adjust the height of the cribbing structure, to prevent shifting and enhance stability.
Applications of Box Cribs in Construction
- Box cribs are most commonly used for stabilising heavy machinery, such as cranes, excavators or loaders, to provide necessary support and prevent shifting during operation or maintenance.
- It provides necessary temporary support to structures, especially while undergoing maintenance works such as repairs, innovations, and modifications.
- They are also used in stabilising vehicles when they are caught in accidents and emergencies to stop further rollovers or movements, especially in slopy areas.
- It is also used in the trench shoring process to prevent the collapsing of soil and improve worker safety.
- They are used as bridging components during construction and maintenance to ensure stability and safety.
- They are used in marine construction projects to stabilise docks, piers and offshore platforms to resist the forces of water and waves.
- They are crucial in mining and excavation operations to provide adequate support for tunnels and underground structures.
Types of Box Cribs
Vertical Cribbing
Vertical cribbing is the process of stacking box cribs vertically to create a stable structure to withstand heavy loads and provide structural stability.
Horizontal Cribbing
As the name suggests, the cribbing blocks are arranged in a horizontal pattern, parallel to each other and help in the uniform distribution of loads.
Box Cribbing
Box cribbing is the process of arranging cribbing blocks in a box-like structure to provide high stability and load-bearing capacity.
Pyramid Cribbing
Pyramid cribbing involves arranging the blocks in the shape of pyramids to provide stable support to the load-bearing structure and help in distributing the loads efficiently.
How to Construct a Box Crib?
- The first step in constructing a box crib is selecting a suitable area for installing – this area must be strong enough to withstand load without causing shifting.
- The chosen area should be completely clean to ensure a secure and stable foundation.
- Start laying the first course of blocks on the ground horizontally in a straight line, and closer to each block.
- Level the blocks using shims or wedges, to adjust the height of the blocks.
- After installing the first layer, lay the second layer of blocks in a crisscross pattern (perpendicular pattern), by closely interlocking the blocks.
- Use shims or wedges, wherever necessary to adjust the blocks, and complete placing the blocks, until they achieve the desired height.
- After laying, place the object or structure to be supported onto the cribbing structure and monitor whether the loads are distributed evenly.
Advantages and Disadvantages of Box Cribs
Advantages
- They provide adequate support and stability and prevent the structure from potential accidents, collapsing and structural failures.
- They have versatile usages in the construction industry and can be customised based on the application process.
- Using box cribbing is a cost-effective solution when compared to other permanent structural modifications or reinforcements.
- Box cribs are used for temporary applications and can be removed or modified based on the needs.
Disadvantages
- Cribbing requires skilled and experienced professionals, as assessing the loads, soil conditions and other factors that influence the efficiency of cribs is crucial.
- Box cribs require proper load distribution to avoid overloading and ensure uniform weight distribution.
- Structures that use cribbing should be regularly monitored to ensure that they are free from potential risks such as deterioration, shifting, or settlement.
Safety Considerations of Using Box Cribs
Professional Assessment
Installation and maintenance of box cribbing should be taken under the guidance of experienced professionals, as assessing the loads, soil conditions and other affecting factors is crucial.
Load Distribution
The area chosen for the installation of cribbing should be strong enough to withstand loads, in order to avoid overloading or uneven distribution of loads.
Regular Inspection
Regular monitoring of cribbing structures is essential to check signs of deterioration, shifting, or settlement, at the earlier stages, to prevent further damage.
Proper Clearance
The cribbing should provide enough clearance to help labourers and equipment to operate safely, without causing any hindrance.
Conclusion
In summary, cribbing is an efficient technique in construction that provides necessary strength, support, and stability in various construction activities. They provide temporary support to the structure and are more economical than other permanent reinforcements. Although they are efficient, they require regular maintenance and skilled labourers for installation.