What is Lintel Beam?
The beam is a structural member, to resist vertical loads acted along its longitudinal axis. Beams are supported by one or more supports. Similarly, Lintel Beam is the beam placed over the opening on the walls such as doors and windows.
When the opening is made on the walls, a concentrated load is generated over the section which should be supported. Therefore, lintel beams are introduced over the opening. The border of bricks also serves as a lintel beam.
Timber, Reinforced concrete, Bricks, stones, steel material, brick reinforced, precast beams can be used as lintels.
The material for lintel beams, size of lintel beams can be determined on the basis of the type of structure, size of the opening, and load to be carried by a lintel.
Size of lintel Beam
The dimension of the lintel beam can be determined by adopting, rule of thumb. In general, design for the lintel beams is not preferred.
- The width of the beam is taken equal to the thickness of the wall on which the lintel is being placed.
- The height of the beam is taken about L/12 to L/8 or a minimum of 100 mm
- The length of the beam is taken as the size of the opening plus bearing length at both sides of the end.
Bearing length is kept whichever is greatest among following.
- 10 cm
- Height of lintel beam
- 1/10th to1/12th of span of the lintel.
According to NBC 205:1994, the beam over the opening is let to serve as lintel and tie band. According to NBC 205:1994, the height of the band is 75 mm and thorough out the wall of the house.
The Band is provided with 2 longitudinal and 1 legged stirrup, all with a diameter of 8mm and 6mm respectively at a spacing of 150mm center to center apart.
But somehow sizes might vary according to the material chosen for the lintel.
Lintel beam design
Lintel beam is a flexural member, which should take both compression and tension forces. Reinforced concrete beams are usually being used for the lintel. The lintel should be able to take the following loads.
- Self-Weight of the lintel Beam.
- The dead load of the wall above the opening
- Dead load and live load from a section of the roof or the floor supported by the wall opening.
To determine the load acting on the lintel, one should know, how the lintel behaves on the load.
- Assume the depth of the beam, generally, it was taken, L/10. The cover is added to get the overall depth of the beam.
- The width of the beam be the thickness of the wall on which lintel is placed on,
- For the length
- L= clear span +bearing length
- L= clear span + effective depth
- Load and Moment Calculation
The load above the lintel acts as a Uniformly varying load. The uniformly varying load takes the shape of an isosceles triangle with 60 degrees as a base angle.
Check for depth.
Equate moment of resistance and Ultimate bending moment. (IS 456 Annex G) to get the required depth and check with assumed depth. Assumed depth should be greater than required depth, of not revise the depth with new depth.
Design of Tension reinforcement
Tension reinforcement is provided according to the ultimate moment on the bend. (I.S 456 Annex G1.1) Area of steel is obtained and the appropriate size of the bar is chosen.
Lintel beam reinforcement details
If the depth of the beam is requires larger section, then nos of longitudinal bars needs to be increased and strips are 2- legged in such case.
Lintel beam height
The thickness of the lintel beam is assumed to be within L/8 to L/12 which is a rule of thumb but the thickness of the beam should be able to bear both tension and compression.
I hope this article remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Rukshana Shresth