Combined footings are provided only when it is absolutely necessary, as 1. When two columns are close together, causing overlap of adjacent isolated footings 2. Where soil bearing capacity is low, causing overlap of adjacent isolated footings 3.
- Individual Footing or Isolated Footing. Individual footing or an isolated footing is the most common type of foundation used for building construction.
- Combined Footing.
- Spread footings or Strip footings and Wall footings.
- Raft or Mat Foundations.
- Pile Foundations.
- Drilled Shafts or Caisson Foundation.
A Strip Footing is a relatively small strip of concrete placed into a trench and reinforced with steel. The footing supports the load of the exterior walls and any interior wall that is load bearing or supports a slab such as for a bathroom. Strip footings can be used for both traditional timber and concrete floors.
The foundation is general expression for structural element that support the superstructure as well as the supported soil, while the footing is represent the shallow structural element that support the superstructure.
Column Footing is also famous as independent footing. An independent footing is one which is provided under a column or either similar member for distributing concentrated load in the form of uniformly loads on the soil below. column footings may be circular, rectangular or square in plan.
A raft foundation, also called a mat foundation, is essentially a continuous slab resting on the soil that extends over the entire footprint of the building, thereby supporting the building and transferring its weight to the ground. A raft foundation is also very good for basements.
Rectangular footingThe rectangular combined footings are part of combined footings. They have rectangular shapes. They are supporting two or more columns. These are used when having a rectangular shape and have a carry equal loads.
3. which of the following, is a type of shallow footing? Explanation: The shallow foundations are of the following types: spread footing (or simple footing), strap footing, combined footing, and mat footing or raft footing. 4.
These may be square, rectangular or circular in plan. This type of footing is preferred when only single column is appearing in the foundation plan of a particular project. Combined footing: Combined footing supports two or more column loads. These may be continuous with rectangular or trapezoidal in plan.
Design of rectangular footings
- Determine footing depth for punching shear and direct shear in the longitudinal direction.
- Determine footing reinforcement for longitudinal direction.
- Determine footing reinforcement for transverse direction.
- Determine column dowel to transfer column load.
A spread footing foundation, which is common in residential buildings, has a wider bottom portion than the load-bearing foundation walls it supports. This wider part "spreads" the weight of the structure over more area for greater stability.
Rectangular FootingThe purpose of the footing. The footing provides a stable flat supportive base that distributes the weight of the load of the structure into the surrounding soil. The weight distribution is spread out through the soil as the distance increases from the footing.
It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings. A strap footing is often used in conjunction with columns that are located along a building's property or lot line.
Isolated footings are provided where the soil bearing capacity is generally high and it comprises of a thick slab which may be flat or stepped or sloped. This type of footings are most economical when compared with the other kind of footings. Economical when columns are placed at longer distances.
Depth: Footings should extend to a minimum depth of 12 inches below previously undisturbed soil. Footings also must extend at least 12 inches below the frost line (the depth to which the ground freezes in winter) or must be frost-protected. Width: Footings should have a minimum width of 12 inches.
The foundation or foundation walls your home rests on is determined by building codes and the location of the home. Other conditions such as the frost line, the soil composition, water levels and drainage can play into the type of foundation your home is built upon.
Example – Calculation Using Trapezoidal Footing Formula
- A1= A x B = 1.5 x 1.5 = 2.25m.
- A2 = a x b = 0.8 x 0.8m = . 64m.
- ht = 0.3m.
There are five main foundation types and a handful of important variations.
- Basement Foundation.
- Crawlspace Stem Walls.
- Concrete Slab Foundations.
- Wood Foundations.
- Pier and Beam Foundations.
Stepped foundations can also be used to transition from deep foundations to shallow foundations, and at corners and intersections. Regularly stepping foundations also avoids abrupt and excessive changes in level that could cause a weakness resulting in movement.
