Page 217 - Urban Construction Project Management

172 Chapter Seven

Exhibit 7-10
Turnbuckle.

a transit, and then the iron worker checks each column with a plumb bob. If the sur-
veyor or the iron worker find out that the columns are out of alignment, then cables
are placed at the top and bottom of the columns and turn buckles are installed (see
Exhibit 7-10) to straighten the structure. The permissible alignment of interior
columns for the first 20 floors is 1 in., with an increase of 1/32 in. for each addition-
al floor with a maximum for the full building of 2 in. For exterior columns, the dis-
placement for the first 20 floors is no more then 1 in. inside the building line and no
more then 2 in. outside the building line. Above the 20th floor, the limits may
increase by 1/16 in. for each additional story but no more then 2 in. toward the build-
ing line or 3 in. away from the building line. However, all alignment criteria should
be obtained from the owner’s design team.

FACTORS AFFECTING THE SURVEYOR

Due to the geometry of the building, its height, construction loads, and other factors,
the surveyor has to make many corrections in order to develop reliable information for
setting benchmarks and elevations. These corrections are noted in Exhibit 7-11.

In order to avoid any problems with the setting of critical points, the surveyor must do
the following:
1. Set elevations in a “monument” (fixed object set in concrete) that will be permanent
and cannot move near the building.
2. Set benchmarks at every floor of the building.