Plinth beams are horizontal structural elements or beam elements that are constructed between the wall and the foundation as shown in the figure.
The plinth beams distributes the load coming from the walls constructed above evenly to the below foundation elements.plinth beams are generally constructed connecting the columns of the building similar to a tie beam,plinth beam hence helps to reduce the settlement issues that are faced by the loading due to unequal transfer of load.
The unequal transfer of load will result in settlement of the building which result in cracks in the masonry wall which later propagates to the foundatio.Hence plinth beam is a better solution to prevent the extension or the propagation of cracks from the wall to the foundation.
Plinth beam concrete strength.
plinth beams are generally constructed using reinforced concrete material.The strength of plinth beam concrete shall no way lesser than 20 megapascals if the concrete is mixed manually an extra of 20 percentage cement need to be added to the mixture to compensate any sort of losses further.
Plinth beam formwork.
Formwork used for plinth beam construction should be properly installed and adequately secured prior to the concrete placement.The concrete needs to be compacted sufficiently to prevent steel bars from aggressive elements.
Plinth beam steel reinforcement
The reinforcement details of plinth beam is similar to that of a normal beam.Two bars with minimum diameter of 12 mm at the bottom of the beam and two bars with minimum diameter of 10 mm shall be provided at the top of the plinth beam.It is provided with a cover of 25 mm and it can change based on the exposure condition.
Stirrups used should be a minimum of 6 mm in diameter and the spacing of these stirrups must be minimum of 15 centimeters.
Uses of plinth beam
Plinth beams are provided in areas that are more prone to earthquake in seismic regions.
Plinth beam act as a connecting band a continuous band that can help to improve the strength of the building in dynamic loads.
The construction of plinth beam above the natural ground is another application of these type of beams.
It also helps to reduce the settlement issues that are faced by the buildings.Settlement issues that can result in wall cracks and its propagation is also resisted by the constriction of plane beams.
The use of plinth beam reduces the effective length of column that means it reduces the slenderness of the column which can further prevent the buckling issues phase by column under unexpected loading conditions.
Difference Between Tie Beam Vs Plinth Beam
Tie Beam is provided above ground level and floor level
Plinth Beam is provided at ground level
Tie beams can work as strap beams to take any stresses due to column eccentricity on footing
It retains the backfill inside the building
Tie beams can work as fixing points to reduce the unsupported length of a column
it provides the level difference between the formation to internal floor level
Tie beams can work as ground beams to support walls or partitions built above them
It distributes load to all the footings
Tie beams can work as tie elements between footings to prevent differential settlement between isolated footings according to the type of underlying soil strata.
It provides base for the block work or brick work
Tie beam resists overturning of eccentric column footings
Plinth beams can also be called as tie beam its location only distinguishes it from tie beam
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