Allowable stress in bolts

[tmaarleveld]

Hi there,

Does anyone know the allowable stress for bolts?
For example I use a 8.8 grade bolt yield 640 UTS 800
What is the maximum allowable tensile stress in this bolt?
And does any one of you know a code to which I can refer.

The bolts will be used in an offshore structure for the European (North Sea) market. And I have worked through lloyds and DNV rules but they do not give me an clear answer.

Regards,

 

[Ussuri]

Most of the European steel design codes are based on the ultimate limit state approach so dont use allowable stresses as such.

BS5950 (the UK steelwork code) gives the tension strength of an ordinary grade 8.8 bolt as 560 MPa. This is checked against factored loads. I'm pretty sure you would get something out of NS3472 (the Norwegian steelwork code)as well.

The old BS449 gives allowable stresses for bolts for use with unfactored loads.

Alternatively the American codes would give you a figure as well.

Lloyds and DNV are primarily ship classification societies so i'm not sure if their ship rules go into bolt detail.

 

[hokie66]

Before we moved to limit state design in Australia, permissible tensile loads for 8.8/S (snug) bolts listed by the Australian Institute of Steel Construction were as follows:

M16, 58.6 kN
M20, 91.5 kN
M24, 132 kN
M30, 210 kN
M36, 305 kN

I think these loads would have mirrored closely the British standard.

 

[rob768]

the grades work as follows:
a 10.9 quality bolt has a minimum tensilestrength of 1000 MPa, (the 10 in 10.9 times 100) and a yield strength of 90% of the tensile strength (the .9 in 10.9)
for an 8.8 bolt, the tensile strength is 800 MPA, and the yield 80% or 640 MPa.

 

[DYV1973]

Use the mentioned yield strength of 640 MPa, but check classification rules for required saftey factors on the design.