Grillage Footing Shear Force Location
A grillage footing utilizes steel beams (grillage beams) integrated with a base plate to effectively distribute heavy column loads onto the foundation concrete. The base plate plays a crucial role in transferring these loads.
Understanding Shear Force in Grillage Footings
- Grillage Beams: These beams experience maximum bending moments at their center and maximum shear forces at their ends, where they typically rest on the base plate or foundation.
- Base Plate: The base plate itself undergoes shear stresses due to the distribution of loads from the column and the grillage beams, as well as the reaction from the foundation.
Identifying Maximum Shear Location
While shear forces are maximal at the supports of the grillage beams themselves, the question pertains to the location within the grillage footing system. Considering the structural behavior and load distribution specifics related to the base plate:
The maximum shear force within the structural element of the base plate is typically found to occur at the center of the base plate. This is often associated with the location of maximum bending moment within the plate, where it acts as a primary load-distributing member transferring the concentrated loads from the column (via grillage beams) to the wider 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?
