AD 279: Brittle Fracture
This AD gives the limiting thickness t1 (mm) for plates, flats and rolled sections for S275 JR and S355 JR material that are expected to be included in the forthcoming amendment to Table 4 (K=1) of BS 5950‑1.
The prohibition of the use of S275 JR and S355 JR material in external conditions has caused much comment since the release of BS 5950‑1:2000. Hence the code committee has been working on the issue for some time. Relaxations for t1 values in normal temperature conditions in BS 5950‑1:2000 have been proposed as shown below but they will not revert to the thickness in the 1990 standard.
Readers should remember that the forthcoming amendment must first be issued for public comment and the above values may change. However, the SCI advises that the values in Table 1 should be used for design in the interim.