Assessment of Existing Structures and Repairs - Offshore Structures: Design, Construction and Maintenance - page 464

resistance factor design code is not recommended for design of offshore
platforms.
It is worth mentioning that API RP2A-LRFD does not mention AISC in the
main body of the code, but gives guidance on the use of AISC-LRFD in the
commentary for nontubular members.
In every edition of API RP2A-WSD, the wording has been unchanged regard-
ing increasing the allowable stresses for extreme environmental conditions:

The required section properties computed on this basis should not be less than required
for design dead and live loads but in case of considering the effect of the lateral and
vertical forces imposed by the design environmental conditions, the basic AISC
allowable stresses may be increased by one-third.

7.6 ALLOWABLE STRESSES FOR CYLINDRICAL MEMBERS
7.6.1 Axial Tension
API RP2A did not contain a recommended expression for an axial tensile check
until one was introduced in 1987 in the seventeenth edition. Until then, reliance
was on the AISC. In 1969, as now, AISC recommended that the allowable
tensile stress be given by the following equation, as presented in Chapter 3 :
F t = 0 : 6 F y (7.3)

In the seventeenth edition, API RP2A-WSD adopted this recommendation
explicitly.

7.6.2 Axial Compression
Unstiffened tubular members under axial compression are subject to the following
three failure modes:

material yield ●

Euler column (overall) buckling ●

local buckling.

●

In general, members of low D/t ratio are not subject to local buckling under
axial compression. All editions of RP2A recommend that unstiffened tubular
members be investigated for local buckling once the member D/t ratio exceeds
a limiting value.
The first three editions of RP2A (that is, until 1972), recommended that
local buckling be investigated for D/t > E/12 F y . For example, for F y =345

MPa, the limiting value is about 50.
The fourth through tenth editions of RP2A (that is, until 1979), recom-
mended that local buckling be investigated for D/t

>

22,750/F y (F y in MPa).
For example, for F y = 345 MPa, the limiting value is about 66. In later editions,
the limiting value is 60.