Doubling RC Lintels

[engstructural]

If you place 1No. 215Dp. RC lintel over another and have a mortar bed between could these be considered to act compositely and have an increased effective depth therefore increased the capacity?

If not would you be able to add the 2 shear capacities together to increase shear load. (both would have to fail for collapse)?

 

[civilperson]

Add only, no composite action with mortar.

 

[cntw1953]

Don't look like a good idea. Geometric variance alone could be a big head ache.

 

[BAretired]

In order to act compositely, the two beams would have to be connected to prevent sliding on the contact surface. Dowels between beams would tend to help in this regard.

If the beams are separated by a slippery material such that there can be no horizontal shear between them, then they act as two separate beams. Their capacity is two times the capacity of one beam acting alone.

If the beams are separated by a mortar bed, some horizontal shear may exist between the two beams, but it is not reliable and should not be considered in design. If you want to develop composite action, tie the beams together with stirrups.

BA