· Hidden Beam, also known as Concealed Beam, is defined as the beam whose depth is equal to the thickness of the slab.
· The concept of the hidden or concealed beam originated from flat slab concept.
· Hidden beam is a means to describe the dispersion on the supporting slab.
· The hidden beams are only means to spread the concentrated load of the wall on the slab area.
· The hidden is virtual bean designed to make use of the beam free room head.
· By providing hidden beam floor height can be achieved.
· Concealed beam clears way for electromechanical duct work.
· It allows using greater span for the slab.
· Concealed beams are economical and have aesthetic appearance of the building.
Where Hidden/ Concealed Beams are used?
· Hidden / concealed beams are provided in between living and dining space right angle to each other. This gives a neat and level ceiling surface that provides a good appearance.
· Hidden beams are generally inserted within the suspended slabs where slab thickness is considerable.
· Hidden beams also provided between balcony and room to facilitate easy inclusion of balcony into room space.
· Hidden beams are provided mostly for architectural aesthetic requirements for building interiors.
· Many Structural engineers provide these hidden beams under partition walls.
Design of Hidden/ Concealed Beam:
· Hidden beams are reinforced separately from the slab, having stripped and longitudinal bars just as normal beam but its death is limited, should not be greater than the slab thickness. The depth of the beam is limit to the slab depth say 4.5” to 5”, and the width vary from 1’ to 4’, based on the load coming from the slab load including self weight, floor finish, live load and partition wall weight. The bending moment shall be calculated as wl2/10.
· The reinforcement shall normally be provided at bottom and top equally from practical consideration. Some designer may designed the beam using steel beam theory. The width is so selected that the beam should satisfy max shear stress consideration. Based on shear to be designed, the stirrups shall be provided and the spacing is limit to maximum depth of the slab.
· It saves floor height concrete.
· It gives best aesthetic interior appearance by providing greater headroom clearance.
· It is economical as it saves the cost of materials, formwork and labor.
· It clears the way for horizontal electromechanical ductwork.
· It is easier to apply a finish to the underside of the slab, often saving the time in construction process.
Disadvantages of Hidden/ Concealed Beam:
· Structurally hidden beams create a spanning problem, as spans for structural supports are at right angle to each other. This means one slab structurally rests over the other.
Hidden or Concealed beams are mostly used in Solid Slab, Ribbed Slab or Hollow Core Slab and Waffle Slab.