Page 218 - Urban Construction Project Management

Layouts and Surveying 173
Exhibit 7-11
1. Wind loads
Surveyors
2. Thermal expansion from the sun
corrections.
3. Contraction from cold weather
4. Shortening from the force of upper floor loading and façade
5. Possible minor settlement of the foundation
6. Any large construction equipment that is temporarily supported by the building
structure
7. Vibration caused by traffic and underground mass transit systems
8. Vibration caused by construction equipment
9. The design of the structure with potential offsets and setbacks
10. Height of the building and the curvature of the earth
11. Adjacent buildings that may be out of alignment

3. Critical operations should be accomplished when the sun is not shining, and the tem-
peratures are in the 50 to 60°F range (where possible). If these conditions do not
exist, then corrections will have to be made to the calculations.
4. The owner’s structural engineer should determine settlement calculations at various
stages of the project.
5. The owner’s structural engineer should determine potential shortening of the struc-
ture due to the loads from other floors and construction equipment.

Surveyors have used many methods to achieve their objective of constructing a straight
structure with the proper floor elevations. These have included:
1. Cutting four small holes on each floor around the core and then checking floor align-
ment and elevation at each floor via a laser beam and prism targets.
2. The use of GPS on each floor where coordinates and elevations can be determined.
3. The old standard of using a transit and measuring the angles and distance from
known benchmarks.
4. In major cities, buildings are being constructed contiguous to other buildings. Then
the surveyor places benchmarks on the existing structure. The benchmarks are then
used as reference points as the structure climbs from the first floor to the upper floors.

Whatever method is used, it is critical that the alignment and elevations of the structure
be set to the parameters established by the design team. Any deviations can create major
problems for the project. Thus, in most cases not only is the CM/GC’s surveyor
involved in the surveying process but the subcontractors who are performing the
actual work use their surveyors for confirming all calculations. See Exhibit 7-12 for the
construction survey checklist. This list should be reviewed prior to and after the survey-
ing process has begun.