What is Spread Footing?
Spread Footing are typically employed to support each column of buildings, as well as the bridge piers. They are economical and affordable in the construction process. It’s ideal for any soil that has adequate capacity for load-bearing.
Specifications and codes for structural design assume a linear soil pressure distribution in designing spread footings. That makes designing spread footings an easier task.
Spread Footing can be built in various sizes and shapes like square, circular and rectangular. It can function as an inverted tilver with loads being distributed in the upward direction.
Spread Foundation
Spread foundation expands at the bottom to give individual support to the bridge abutment or the column in the case of bridges. The spread foundation can be classified under shallow foundation and has many types of subtypes.
Also Read: Tributary Area
Different types of Spread Foundation
Below are the different kinds of foundations that are classified into Spread Foundation,
1. Wall Spread Footing
Wall footing is also referred to by the name of strip footing. The wall footing strips made of continuous concrete may distribute the weight of the structure over large areas of soil. It is a shallow form of footing that could be built as simple cement concrete footing or the reinforced footing made of concrete.
Wall footings are built as pads, spreads and strip footings. They are used to support non-structural and structural walls by transferring the weight onto the soil so that the load-bearing capacity the soil is not exceeded.
The construction of Wall footing is extremely adaptable and can be accomplished with bricks, stone plain concrete, reinforced concrete in a streamlined method.
Conditions that are suitable for the construction of footings on walls is that it is constructed in an area where the it is able to transmit loads of low size and the soil layer is composed of thick sand and gravel. These conditions are ideal for smaller buildings. Hence it is possible to see smaller structures that have wall footing.
2. Column Footing or Isolated Footing
Isolated Footing often referred to as Column Footing or Pad Footing also known as isolated Spread Footing is utilized to support the load pressures imposed by the columns and spread it out evenly over the soil below. Like the wall, this can also be constructed of reinforced or unreinforced materials.
Isolated footings are affordable and easy to build they require less excavation and are very simple to build.
It has been designed with care to consider the capacity of soil and is safe against any sliding or overturning impact. It is also able to withstand soil settlement beneath the soil.
For the building industry the isolated footing is the most popular foundations that can be used to support columns where there is a large gap between two columns. It is utilized when the geotechnical characteristics of the soil don’t dramatically change in the area of the foundation. It’s also the most efficient type of foundation.
Also Read: Live Load Vs Dead Load
3. The Combined Footing
Footing that supports multiple columns and spreading the load they exert evenly to the ground below can be called combined footing. The primary function of footings is the distribution of evenly the stress of the structure to the sub-grade below.
The design based on the above-mentioned objective is designed so it is that the centre of gravity for the footing is equivalent to what the centers of gravity is of the columns, or the column footings are supported by another column.
The combined footing is typically constructed of reinforced concrete since it is thought to be a rigid structure and sits on an even soil. Soils with less load-bearing capacity , and individual footing required more space that is the best situations for the creation of combined footing.
4. Strap Footing
Strap Footing consists comprising two columns footings, strapped to each other by an concrete beam. It serves as a means for distributing the weight of extremely and eccentrically loaded columns footings adjacent footings in order to ensure stability.
The strap footing can be described as a component that connects utilized with columns placed along the plotline or property of a building. It joins the column that is eccentrically loaded with the column which is within the foundation and transmits the energy generated by the eccentricity to the column’s interior foot.
This creates the same pressure in footings that are loaded eccentrically and also one that carries transferred load. Similar to an eccentric load placed on a part of the footing that causes it to shift to one side, is held by the beam of strap.
5. Continuous Footing
Continuous footing generally includes more than two columns, where the columns’ loads transfer directly to the slab of footing or via the horizontal (longitudinal) beam that runs in parallel with the footing. When a significant load is spread across an extensive area the continuously spread footing can be employed.
Continuous footing is ideal for earthquake-prone zones in which uneven or different settlement can occur in the event of calamities. The design is to avoid any differential settlement in the structure.
Also Read: Purpose of Wall