Simple beam design (Shear)
From the previous example, the section profile is:-
Maximum shear force normally occurs at the support points, i.e.
near the end of the beam. Calculation is made of the average
stress value on the web sectional area.
Using the example of 200 kN load distributed over the beam, the
maximum shear force at each end support will be 100 kN.
Therefore, the average shear stress =
shear force
web sectional area=^100 ¾^10
3
2762„56
= 36„20 N=mm^2Grade S275 steel has an allowable shear stress in the web of
110 N/mm^2. Therefore the example section of serial size: 305 mm¾
127 mm¾48 kg/m with only 36„20 N/mm^2 calculated average shear
stress is more than capable of resisting the applied forces.
Grade S275 steel has a characteristic yield stress of 275 N/mm^2 in
sections up to 40 mm thickness. This grade is adequate for most
applications, but the more expensive grade S355 steel is available
for higher stress situations.
Ref. BS EN 10025: Hot rolled products of structural steels.
Structural Steelwork---Beam Design (2)