What Is Pad Foundation | Failure of Pad Foundation | Pad Foundation Detail | Types of Pad Foundation | Design of the Pad Footing Depends on Several Factors
For the pad footing to be non-reinforced, the height of the footing should be bigger. This is an important pad footing detail to consider.
Usually, we design pad footings to be of uniform thickness, but sometimes the upper face may be sloped or stepped.
Pad footings also come in use to support ground beams.
The pad footing under an average load N and a moment M is assumed to have a linear distribution of stress under it.
You should use this type of footing only when you're sure that there isn't a possibility of varying settlement under the entire building.
The pad footing isn't suitable for the widespread loads. One should use only strip footings or mat footings in this case.
Since the pad footing spreads the structure's weight into the soil mass, it's preferred to be build when there is sufficient strength in the soil on which building will be made.
One more thing to take care of is that the footing should not be too deep to construct.
The pad footing (isolated footing) has an advantage of economic efficiency as this type of design of footing is generally straight and simple.
One must ensure that foundation pressure mustn't exceed allowable bearing stress. You can make it so by either reinforcing the pad or making the pad deep enough.
The pad's size must ensure that the concrete's tension gets prevented so that no cracking happens.
The depth of the pad is determined by the ability to resist the punching shear and ability to resist the bending.
Penetration through near-surface layers likely to change volume due to frost heave or shrink-swell.
A pad can be constructed with or without reinforcement as well as with or without formworks or mold.
The minimal absolute dimension for a pad is 40 x 40. But mostly, the size of a pole is 60 x 60 or more.
A pad could be constructed a little higher than that in order to avoid exceeding the load-bearing capacity of the ground.
Pad is also built with stepped shape, with its diagonal not less than 45 degrees. This may not be true when it's built with reinforced concrete.
According to standards (EN 1992-1, 2004, EN 1997-1, 2007), the pad footing must satisfy the ultimate limit state and serviceability limit state conditions.
We must design the pad footing so that it withstands.
Plain Concrete: These are pad foundations that don’t incorporate reinforcement and are used for light loads. This is the most economical option.
Reinforced Concrete: The additional reinforcement that is offered allows for wide but shallow pad foundations. It also reduces the thickness that is required for the foundation.
Combined Column Foundation: Two pad foundations are merged into a longer one which is most often used when an outer column is close to a site boundary or wall.
Continuous Pad: This is when various pad foundations are put together in order to support closely spaced columns.
Pad and Ground Beam: This is similar to a continuous pad but differs in the sense that ground beams connect the isolated pads.