A plinth beam is a structural member of a building made of reinforced concrete that is constructed between the walls and the foundation. The main purpose of the plinth beam is to avoid penetration or propagation of the cracks occurring in the foundation due to settlement, into the wall above. The plinth beam also assists in transferring the load of the walls and the structure above the plinth beam evenly over the foundation.
Plinth Beam Application
Plinth beam becomes an indispensable part of a building structure if the construction is taking place in an earthquake prone area. It is mandatory to include plinth beams in seismic zones and in normal areas these beams are created above the natural ground to transfer load to the foundations.
Suitable Concrete for Construction of Plinth Beam
Since the plinth beam has to withstand greater loads as compared to other structural members it should be designed to resist a minimum load of 20MPa. In case the concrete is mixed manually, approximately 20% extra cement content must be added to the mixture to compensate for any loss in binding of the mix.
Suitable Plinth Beam Dimensions
The plinth beam in a building structure should be constructed for a minimum depth of 200mm while the width should be equal to the width of the final course of the foundation.
Formwork Preparation for a Plinth Beam
The formwork needed for a plinth beam should be prepared properly after which it should be installed meticulously and sufficiently fastened before pouring of concrete. The steel bars must be prevented from aggressive and hostile elements by adequately compacting the concrete.
Suitable Reinforcement for Plinth Beams
Plinth beam design process involves the selection of appropriate reinforcement. The recommended steel bars specific to plinth beams should be a minimum of two bars with least diameter of 12mm at the bottom of the beam. In the same manner, two bars with a minimum diameter of 10mm must be provided in the top section of the plinth beam. The reinforcing bars should be protected from external elements by providing a minimum of 25mm concrete cover and the diameter of stirrups used in the plinth beams should be a minimum of 6mm along with 150mm maximum spacing.