Page 60 - Structural Steel Designers Handbook AISC, AASHTO, AISI, ASTM, and ASCE-07 Design Standards

Brockenbrough_Ch02.qxd 9/29/05 5:01 PM Page 2.22

FABRICATION AND ERECTION*

2.22 CHAPTER TWO

FIGURE 2.7 Steps in jumping a guy derrick. (a) Removed from its seat with the topping lift falls, the boom
is revolved 180° and placed in a temporary jumping shoe. The boom top is temporarily guyed. (b) The load
falls are attached to the mast above its center of gravity. Anchorages of the mast guys are adjusted and the
load falls unhooked. (c) The temporary guys on the boom are removed. The mast raises the boom with the
topping lift falls and places it in the boom seat, ready for operation.

tower, which replaces the conventional boom, and a long boom at the top that can usually accom-
modate a jib as well. With the main load falls suspended from its end, the boom is raised or lowered
to move the load toward or away from the tower. The cranes are counterweighted in the same man-
ner as conventional truck or crawler cranes. Capacities of these tower cranes vary widely depending
on the machine, tower height, and boom length and angle. Such cranes have been used with towers
320 ft high and booms 240 ft long. They can usually rotate 360°.
Other types of tower cranes with different types of support are shown in Fig. 2.9a through c. The
type selected will vary with the type of structure erected and erection conditions. Each type of support

FIGURE 2.8 Tower crane on crawler-crane base.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.