Page 67 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch02.qxd 9/29/05 5:01 PM Page 2.29

FABRICATION AND ERECTION*

FABRICATION AND ERECTION 2.29

completed structure when, in fact, the two considerations are unrelated. Measurement of tolerances
requires experience. Structural steel is not static but moves due to varying ambient conditions and
changing loads imposed during the construction process. Ambient conditions can be so extreme as
to require final plumbing and span closing during nighttime hours. Making all components and
attachments fit takes skill and experience on the part of designers and craftsmen.
(“Manual of Steel Construction,” American Institute of Steel Construction, Chicago, Ill.)

2.15 COORDINATION AND CONSTRUCTABILITY

The three shop assembly methods described in Art. 2.5 result in different geometries. Some make the
pieces fit in the erected condition and others make the pieces fit in the dead-load condition. Builders
have to choose which method is right for the project. Similar decisions may have to be made for other
types of members. Project coordination is necessary in projects with complex pieces and is most effective
if done prior to assigning contracts. Methods to accommodate distortion and construction loads and
weld shrinkage, as well as use of erection aids, need to be considered and planned. All members of
the construction team are affected and need to address these items in initial project stages.

2.16 SAFETY CONCERNS

Safety is the prime concern of steel erectors. Erectors tie-off above regulated heights, install perimeter
cable around elevated work sites, and where necessary, install static lines. Lines for tying off have
different requirements than perimeter cable, so perimeter cable cannot be used as a horizontal lifeline.
Erectors are concerned with welding safety, protection around openings, and working over other
trades. Stability of the structure during construction and of each piece as it is lifted are considered by
the erector. Pieces that are laterally supported and under a positive moment in service, will frequently
be unsupported and under a negative moment when they are raised, so precautions must be taken.
Clearances for moving parts of lift equipment have to be monitored continually. Crane access and
operating areas need to be capable of supporting superimposed loads.
Small changes in member proportions can lead to significant changes in the way an erector has
to work. Long slender members may have to be raised with a spreader beam. Others may have to be
braced before the load line is released. Erection aids such as column lifting hitches must be designed
and provided such that they will afford temporary support and allow easy access for assembly. Full-
penetration column splices are seldom necessary except on seismic moment frames, but require spe-
cial erection aids when encountered. Construction safety is regulated by the federal Office of Safety
and Health Administration (OSHA). Steel erector safety regulations are listed in Code of Federal
Regulations (CFR) 1926, Subpart R. As well, American National Standards Institute (ANSI) issues
standard A10 related to construction safety.

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