Basic methods of reinforcing steel structures - Assessment and Refurbishment of Steel Structures - page 94

Figure 4.14 Reinforcement of riveted
and welded connections in the nodes:
1 auxiliary connection angle; 2
additional gusset plates; 3 reinforcing
welds
In Figure 4.14(c) there is a connected member welded all around, in Figure 4.14(d) there
are reinforcing rivets in the additional gusset plate. When reinforcing riveted connections
balanced co-operation between rigid welded joints and relatively flexible riveted joints
cannot be expected. Therefore the welds must be designed to accommodate tensional
forces that are transferred by the connection. Welding can also be used advantageously
when it is necessary to enlarge gusset plates (Figure 4.14(b), (d)). When welding is used,
reinforcement is considerably simplified because we can enlarge the cross-sections of
smooth welded profiles easily by connecting the reinforcing elements where necessary.
However, careful attention should be paid to welding techniques in particular to the
internal stresses and deformations originating during welding. For the reinforcing a
riveted connection by welds it is necessary to ensure good accessibility to all welds.
When reinforcing joints and connections, welding on riveted structures is to be
preferred. However, this assumes good weldability of the material. This should be
confirmed by appropriate tests. In many cases, especially when the joint is reinforced by
ordinary bolts or rivets, it is efficient to use high bolts.
The combination of various methods of connecting (welds, rivets, precision and thick
bolts) in one joint is not recommended. The strength of such a joint will be determined by
whether (a) the welds or (b) the rivets and precision bolts (in precision joints) has the
greater strength.