Is it necessary to add a plinth beam between two columns, constructed for installing an iron gate?

Yes, It is required to install a plinth beam between two columns, which used for installing an iron gate. The reason to provide it is when the vehicle comes closer to the iron gate and passes through the gate, a load of the vehicle is acting on that beam, and the beam will be able to resist the load. If we can't install beam between two columns, the land depressed at that location and this may impact your gate and if soil bearing capacity is not enough then maybe iron gate collapse.

Plinth beam: Definition:

A Beam(usually RCC member) which is constructed in between the wall and foundation is called a plinth beam.

Purpose of plinth beam:

Plinth beam distributes load of the wall over the foundation evenly It prevents our structure from extension or propagation of cracks Plinth beam is definitely used in earthquake prone area above natural ground It maintain backfilled soil

Reason behind construction of plinth beam inbetween two columns constructed for installing an iron gate are as follows;

To distribute vehicle load evenly from plinth beam to column, from column to foundation and from foundation to ground. For high sustainability and durability of structure To strengthen the iron For protecting the iron gate against collapse To avoid the formation of cracks

If the columns and their foundations have been designed considering the loads (direct force and moment) from the iron gates then a tie beam at ground level is not necessary.

But a tie beam can help in reducing the foundation width in one direction as this beam will help to prevent overturning in one direction (if the columns are not joined by plinth beams towards wall boundaries). Another benefit of a tie beam is the extra strength provided in case of impact by a vehicle to the columns.