Service Holes in Composite Beams
Service Holes in Composite Beams
(OP)
In the UK, when designing holes in the web of composite beams in accordance with the SCI publication, the moment capacity is obtained by the couple developed between the compression in the concrete and the tension in the steel.
Now, that tension capacity of the steel is limited to the area of steel below the hole. Which means that, giving an extreme example, if you have a 10mm hole 10mm up from the bottom flange then the tension capacity is based on the area of the bottom flange.
This seems rather unfair when there is potentially a lot of material above the hole which can carry tension.
Does anyone know of any other design methods which account for this additioal area - or does anyone have any comments?
Now, that tension capacity of the steel is limited to the area of steel below the hole. Which means that, giving an extreme example, if you have a 10mm hole 10mm up from the bottom flange then the tension capacity is based on the area of the bottom flange.
This seems rather unfair when there is potentially a lot of material above the hole which can carry tension.
Does anyone know of any other design methods which account for this additioal area - or does anyone have any comments?






RE: Service Holes in Composite Beams
www.aisc.org
RE: Service Holes in Composite Beams
https://www.aisc.org/publications/shop.asp?action=displayitem&show=one&id=221
RE: Service Holes in Composite Beams
Guide to stability design criteria for metal structures 5th ed
Galambos
also gives guide for webs with both rectangular and circular holes.
RE: Service Holes in Composite Beams
Naturally the example that you quote is not covered in this booklet.
However, what do you think of this method?
Calculate the moment capacity of the composite beam at the hole position assuming only the beam flanges and the concrete slab are acting.
Add the effect of the local bending moment (equal to shear force at opening x length of opening) across the opening assuming the moment is carried by the upper T-section only Steel and concrete slab).
Regards
RE: Service Holes in Composite Beams
If you mean carry the tension, due to the moment, in the bottom flange only, then the moment capacity is limited by the area of the bottom flange, and hence the force the bottom flange can carry.
Ok, you get a large compression flange due to combining the beam top flange and the concrete slab, but it is limited by that beam bottom flange capacity.
What I am trying to recognise is, if the neutral axis is within the depth of the concrete slab, then how can we fully utilise the area of steel below the n/a to carry tension.
RE: Service Holes in Composite Beams