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Effective span of beams and slabs [EC2 A§5.3.2.2]


Figure 3.1.1
Figure 3.1.1

Τhe effective span leff of a slab or beam is calculated by the expression:

l eff =l n +a left +a right

where ln is the clear distance between the lateral faces of the supports, and a=min(t/2,h/2) is the width of the support.

Notes

  • At the end support of the first slab, the width is considered to be a=t1/2=125 mm which is acceptable as in favor of the safety.

  • The width of beam-to-column supports, is taken into account more efficiently, when the analysis uses rigid bodies (see §3.1.3).

Example 3.1.1-1

Consider continuous slabs with thickness: h=150 mm, width of supports: t1=250 mm, t2=300 mm, t3=400 mm, t4 =1000 mm, clear spans: ln1=3700 mm, ln2=4000 mm, ln3=4000 mm.

The effective spans of slabs are equal to:

l1=3700+min(250/2,150/2)+300/2=3925 mm

l2=4000+300/2+400/2=4350 mm

l3=4000+400/2+min(1000/2,150/2)=4275 mm.

Example 3.1.1-2

Consider continuous beams with height: h=500 mm, width of supports: t1=250 mm, t2=300 mm, t3=400 mm, t4=1000 mm, clear spans: ln1=3700 mm, ln2=4000 mm, ln3=4000 mm.

The effective spans of beams are equal to:

l1=3700+min(250/2,500/2)+300/2=3975 mm

l2=4000+300/2+400/2=4350 mm

l3=4000+400/2+min(1000/2,500/2)=4450 mm.


 
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