Updated: Apr 1
Why openings in Beams : Openings are required for providing pipes for plumbing and other services.
Why it cannot be under the beam: Ideally it should be under the beams.However clients and services consultants do not prefer this many times.Pipes will have to bent, Floor height will reduce.
Options: Core cutting – Drilling after the beam is concreted. This should be avoided strictly as it weakens the beam and also may affect the provided rebars.
What is a sleeve? : A planned and designed opening is called a sleeve. It is provided prior to concreting by leaving a pipe during concreting. Also structurally, the beam is designed for the opening and additional rebars are provided.
Small square or circular openings may be placed in the mid-depth of the web.Cover to main bars & links shall be satisfied all around the sleeve.Clear distance between such openings, shall not be less than 150 mm. The area of small openings shall not exceed I 000 mm2 for members with an effective depth less than or equal to 500 mm, or 0.004 d2 when the effective depth is more than 500 mm.The opening shall not be in compression face. Near columns and supports, bottom region of beam is compression zone and near span, top part is compression zone
Whenever the largest dimension of an opening exceed one-quarter of the effective depth of the member, it is to be considered large. In no case shall the height of the opening exceed 0.4 d nor shall its edge be closer than 0.33 d to the compression face of the member Main bars & stirrups shall be placed in the compression side of the web to resist one and one-half times the shear across the opening.Stirrups, extending over the full depth of the web, shall be placed adjacent to both sides of a large opening over a distance not exceeding one-half of the effective depth of the member to resist twice the entire design shear across the opening.
More info : Refer SP34