Building Design and Construction Handbook - Merritt - Ventech!

STRUCTURAL STEEL CONSTRUCTION 7.117
ricator, however, does not furnish the following items unless specified in the invitation
to bid: shims, fitting-up bolts, drift pins, temporary cables, welding electrodes,
or thin leveling plates for column bases.
The code also defines the erection practices. For example, the erector does not
paint field boltheads and nuts, field welds, or touch up abrasions in the shop coat,
or perform any other field painting unless required in specifications accompanying
the invitation to bid.
7.38 ERECTION EQUIPMENT
If there is a universal piece of erection equipment, it is the crane. Mounted on
wheels or tractor threads, it is extremely mobile, both on the job and in moving
from job to job. Practically all buildings are erected with this efficient raising device.
The exception, of course, is the skyscraper whose height exceeds the reach of the
crane. Operating on ground level, cranes have been used to erect buildings of about
20 stories, the maximum height being dependent on the length of the boom and
width of building.
The guy derrick is a widely used raising device for erection of tall buildings.
Its principal asset is the ease by which it may be ‘‘jumped’’ from tier to tier as
erection proceeds upward. The boom and mast reverse position; each in turn serves
to lift up the other. It requires about 2htomakeatwo-story jump.
Stiff-leg derricks and gin poles are two other rigs sometimes used, usually in
the role of auxiliaries to cranes or guy derricks. Gin poles are the most elementary—simply
a guyed boom. The base must be secure because of the danger of
kicking out. The device is useful for the raising of incidental materials, for dismantling
and lowering of larger rigs, and for erection of steel on light construction
where the services of a crane are unwarranted.
Stiff-leg derricks are most efficient where they may be set up to remain for long
periods of time. They have been used to erect multistory buildings but are not in
popular favor because of the long time required to jump from tier to tier. Among
the principal uses for stiff legs are (1) unloading steel from railroad cars for transfer
to trucks, (2) storage and sorting, and (3) when placed on a flat roof, raising steel
to roof level, where it may be sorted and placed within each of a guy derrick.
Less time for ‘‘jumping’’ the raising equipment is needed for cranes mounted
on steel box-type towers, about three stories high, that are seated on interior elevator
wells or similar shafts for erecting steel. These tower cranes are simply jacked
upward hydraulically or raised by cables, with the previously erected steel-work
serving as supports. In another method, a stiff-leg derrick is mounted on a trussed
platform, spanning two or more columns, and so powered that it can creep up the
erected exterior columns. In addition to the advantage of faster jumps, these methods
permit steel erection to proceed as soon as the higher working level is reached.
7.39 CLEARANCE FOR ERECTING BEAMS
Clearances to permit tightening bolts and welding are discussed in Art. 7.3.7. In
addition, designers also must provide sufficient field clearance for all members so
as to permit erection without interference with members previously erected. The