How to make a trapezoidal footing?
Cuboid and truncated pyramid
Understanding Trapezoidal Footings
A trapezoidal footing is a common type of foundation element used in construction, typically supporting a column. Its shape is designed to distribute the load from the column over a wider area of soil, reducing the pressure on the ground.
Constructing a Trapezoidal Footing
Based on standard structural shapes, a trapezoidal footing can be conceptualized and constructed by combining two specific geometric forms:
- Cuboid: The bottom part of the footing is essentially a cuboid (a rectangular prism). This forms the main base that rests on the soil and provides the necessary area for load distribution.
- Truncated Pyramid: The top part, which connects the column to the wider base, is shaped like a truncated pyramid. A truncated pyramid is a pyramid with its top sliced off parallel to the base. When this truncated pyramid sits on top of the cuboid base, its sloping sides create the tapering profile characteristic of a trapezoidal footing. The column rests on the smaller top surface of the truncated pyramid.
Thus, the combination of a cuboid at the bottom and a truncated pyramid on top forms the complete structure of a trapezoidal footing, effectively transferring the load from the column down to the soil foundation.
Important Questions from Footings
For a number of columns constructed in a row, the type of foundation provided is
If p is the net upward pressure on a square footing of side b for a square column of side a, the maximum bending moment is given by
A. \({\rm{B}}.{\rm{M}} = \frac{{{\rm{pb}}\left( {{\rm{c}} - {\rm{a}}} \right)}}{4}\)
B. \({\rm{B}}.{\rm{M}} = \frac{{{\rm{pb}}{{\left( {{\rm{b}} - {\rm{a}}} \right)}^2}}}{4}\)
C. \({\rm{B}}.{\rm{M}} = \frac{{{\rm{pb}}{{\left( {{\rm{b}} - {\rm{a}}} \right)}^2}}}{8}\)
D. \({\rm{B}}.{\rm{M}} = \frac{{{\rm{pb}}\left( {{\rm{b}} + {\rm{a}}} \right)}}{8}\)
_______ is provided to support an individual column. It is circular, square or rectangular slab of uniform thickness Sometimes it is stepped or haunched to spread the load over a large area.
The minimum nominal cover to reinforcement for R.C.C. footings as per IS: 456-2000 shall be
For a proposed building, raft foundation, isolated footings and combined footings are being considered. These foundations are to be listed in the decreasing order of preference in terms of performance. Which one of the following is the correct order of listing?
