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Steel Designers' Manual - 6th Edition (2003)
952 Fabrication
design and drawing 9%-
paint and touch-up 6%
project management 4%.
erection 10%
transport 3%.
Fig. 32.4 Cost breakdown: lattice structures
- fabrication 30%
Here fabrication is virtually the same cost as the raw steel. The designer should
work very closely with the steelwork contractor to ensure simplicity of assembly
for this form of structure, in particular checking joint capacities at the design
stage.
32.2.2 Design for production
The detailed design of any steelwork construction will have a substantial impact
on its cost of fabrication. It is therefore very important that the designer has a
basic understanding of the implications of his design on construction in practice.
Key points need to be addressed if the design is to be fabricated economically
and efficiently. This important topic is the subject of Reference 1, from which the
following key points are extracted.
Fabrication processes
• Modern computer numerically controlled (CNC) fabrication equipment is more
effective with:
(a) Single end cuts, arranged square to the member length
(b) One hole diameter on any one piece, avoids drill bit changes
(c) Alignment of holes on an axis square to the member length, holes in webs
and flanges aligned not staggered to reduce piece moves between drill times
(d) Web holes having adequate side clearance to the flanges.
• To allow efficient production of fittings:
(a) Rationalize on the range of fittings sizes – use a limited range of flats and angles
(b) Allow punching and cropping wherever possible.