Steel connections

A moment connection transfers both shear forces AND bending moment between beam and column. Relative rotation is prevented: beam and column deform together. It is the key connection of moment-resisting frames (portal frames without in-plane bracing).

A pinned connection transfers shear only: rotation stays free. The beam is fixed to the column web with bolted angle cleats. It is the most economical and common connection for secondary beams — but the structure must then be stabilized by bracing.

The beam simply rests on a support (concrete corbel, masonry padstone or steel bracket), often via a seating plate and an elastomeric pad. Only the vertical reaction is transferred; rotation and slight expansion remain free. Common when a steel roof rests on blockwork or concrete walls — a very frequent case in Africa.

The column is welded to a thin base plate fixed with 2 anchor bolts on the column axis. The base transfers axial and shear forces but no moment: the foundation stays small and economical. Horizontal stability must come from elsewhere (bracing, frame fixed at the top).

Thick base plate, 4 corner anchor bolts and stiffener gussets: the base transfers a bending moment to the foundation. The column then contributes to horizontal stability (cantilever mast, portal). Trade-off: a significantly larger foundation block.

The gusset is the plate joining chords and diagonals at a lattice truss node. Members, loaded in pure tension/compression, are bolted or welded to it. Golden rule: member axes must converge at a single point (workline layout) to avoid parasitic moments.