Steels_ Metallurgy and Applications, Third Edition

186 Steels:MetallurgyandApplications

Table 2.16

applications

Design strength data for BS 4360 steels in building

BS 4360 Grade Thickness (<_ mm) Design strength (N/mm 2)

43 A, B and C

16 275

40 265

100 245

50 B and C 16 355

63 340

100 325

55 C 16 450

25 430

40 415

After BS 5950: Part 1: 1985.

Table 2.17

Tensile stress Welded Unreamed Non-welded Drilled or

due to factored location punched location reamed

load at the holes holes

location

_<100 N/mm 2 2 2 2 2

>100 N/mm 2 1 1 2 2

then the toughness/grade requirements are determined by calculation. Thus the
required impact strength at the service temperature is determined from:

Yst

Cv >

• 710k
  where Cv = Charpy V notch energy in joules
  Ys = the minimum yield strength of the material in N/mm 2
  t = the thickness of the material in mm
  k = the factor determined from tensile stress/location
  considerations

Given that the design strength is based on yield strength, then substantial benefit
is gained in building constructions from the substitution of carbon steel by higher
strength structural steels, providing excessive deflection does not occur.
As illustrated in Figure 2.22, substantial savings have been made in the cost of
corrosion protection and, in essence, this is related to the fact that paint systems
were either over-specified or, in many cases, were simply not required.
In the previous section, it was stated that the minimum Charpy energy require-
ment for steel bridges was based on the following expression for Type 1 stress
situations:

oy

Cv>_