Beam web openings to SCI P355
As each web opening is added it is checked against certain geometric and proximity recommendations taken from Table 2.1 of SCI Publication P355 (see below).
Guidance on size and positioning of openings
The following general guidance on size and positioning of openings is taken from Table 2.1 Section 2.6 of the SCI Publication P355
Parameter | Limit | |
---|---|---|
Circular Opening | Rectangular Opening | |
Max. depth of opening: | <= 0.8h | <= 0.7h |
Min. depth of Tee, | >= tf +30 mm | >= 0.1h |
Min. depth of Top Tee: | As above |
As above and >= 0.1 lo if unstiffened |
Max. ratio of depth of Tees: hb/ht hb/ht |
<= 3 > = 0.5 |
<=2 >= 1 |
Max. unstiffened opening length, lo Max. stiffened opening length, lo |
- - - - |
<= 1.5 ho high shear* <= 2.5 ho low shear <= 2.5 ho high shear* <= 4 ho low shear |
Min. width of web post: - Low shear regions -High shear regions |
>= 0.3h o >= 0.4h o |
>= 0.5 lo >= lo |
Corner radius of rectangular openings: | - |
ro >= 2 tw but ro >= 15 mm |
Min. width of end post, se: | >= 0.5 ho |
>= lo and >= h |
Min. horizontal distance to point load: - no stiffeners - with stiffeners |
>= 0.5 h >= 0.25 ho |
>= h >= 0.5 ho |
* A high shear region is where the design shear force is greater than half the maximum value of design shear force acting on the beam.
Symbols used in the above table:
h = overall depth of steel section
ho = depth of opening [diameter for circular openings]
ht = overall depth of upper Tee [including flange]
hb = overall depth of lower Tee [including flange]
lo = (clear) length of opening [diameter for circular openings]
se = width of end post [minimum clear distance between opening and support]
tf = thickness of flange
tw = thickness of web
ro = corner radius of opening
In addition, the following fundamental geometric requirements must be satisfied.
do <= 0.8*h for circular openings
do <= 0.7*h for rectangular openings
do < 2 * (doc - tt - rt)
do < 2 * (h - doc - tb - rb)
d2 < doc - do/2 - tt- ts/2
d2 < h - tb- doc - do - ts/2
lo < 2 * Lc
lo < 2 * (L - Lc)
Ls < 2 * Lc
Ls < 2 * (L - Lc)
where
dt= the depth of the web of the upper tee section measured from the underside of the top flange
doc = the distance to the centre line of the opening from the top of the steel section
d2 = the distance from the edge of the opening to the centre line of the stiffener
ts = thickness of stiffener [constrained to be the same top and bottom]
tt = the thickness of the top flange of the steel section
tb = the thickness of the bottom flange of the steel section
rt = root radius at the top of the steel section
rb = root radius at the bottom of the steel section
Lc = the distance to the centre line of the opening from the left hand support
L = the span of the beam