Vertical strengthening ribs

The depth of the vertical strengthening ribs is related to the span between the supports. For coffered panels the web is designed using a span:depth ratio of 1:27, whereas the ribs can be designed as beams with a span:depth ratio of 1:17. Sufficient depth is often necessary to accommodate the elements of an open-drained joint (see Figs 1.21 and 1.27), especially where the profile incorporates a drainage groove or where an upstand is provided at the head of the panel. Figure 1.21 shows vertical strengthening ribs of 250 mm to coincide with the depth of a panel needed to incorporate an upstand joint.

The breadth of the rib is governed by such factors as:

- cover to vertical reinforcement;

- the dimensions of columns at panel junctions;

- the accommodation of push-pull sockets for alignment and fixing.

Additional cover will be required if open-drained joint grooves are incorporated in the edge of the panel.

Figure 1.22 shows that for panels abutting columns a breadth of 100-125 mm is normally sufficient, but when the panels occur in front of the structural columns, this may have to be increased to allow for the dimension of the column, so that panel fixing can be within the rib dimension.

Baffle groove

Drainage groove

Outside

100 mm nominal upstand

UC^Jlll UP IIU IV

accommodate upstand

Drainage groove

Outside

Baffle groove

125 mm

100 mm nominal upstand

Inside

UC^Jlll UP IIU IV

accommodate upstand

1.21 Depth of rib to accommodate upstand at head of panel,

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