Bolts and Welds: Welded Connection

The design strength of a full penetration butt weld, for temperatures up to 700°C, should be taken as equal to the strength of the weaker part of the connection using the appropriate reduction factors for structural steel. For temperatures > 700°C, the reduction factors given for fillet welds can also be applied to butt welds.

The design resistance per unit length of a fillet weld in fire should be determined from :

(1)

where

The variation of strength reduction factor is illustrated in Figure 1. Fillet welds are considered to have better fire performance than bolts, but are not as good as that of butt welds or the parent metals.

Figure 1: Strength reduction factors for bolts and welds at elevated temperatures